S P O N S O R S

H New York State Energy Research and Development Authority

US. Department of Energy, Northeast Regional Biomass Program

C O S P O N S O R S

Empire State Forest Products Association

New York Center for Forestry Research and Development

New York State Department of Environmental Conservation, Forest Products Utilization and Marketing Section

State University of New York, College of Environmental Sciences and Forestry

USDA Forest Service, State and Private Forestry

USDA Forest Products Laboratory

Increased demand for wood fiber and the need to decrease the amount of wood waste disposed of in landfills is stimulating new technologies and markets for "value added" products containing wood residue. This workshop and industry exhibition is directed at manufacturing industries in New York interested in increasing their market share and profitability by using wood residues in products that have relatively high value and proven markets. It is also directed at companies that produce, recycle, or dispose of wood waste who are looking for new uses for their wood.

The overall goal is to stimulate the development of new manufacturing activities in New York State that utilize wood residues in marketable, value-added products. Emphasis will be placed on opportunities for using urban wood waste, mill residue, and other types of wood waste in:

Traditional wood products, such as particleboard and medium-density fiberboard.

Extruded and injection-molded plastic products; and

Cement-bonded products.

This workshop represents the "next wave" of advanced technologies that increase the use of wood residue in products of relatively high value. The real-world experience of manufacturers of traditional wood products, plastic composites, and cement-bonded products that contain wood residue will be provided. The workshop will explain the status of manufacturing technologies, industry experience using the technologies, market trends for end use products, overall profitability, and lessons learned from manufacturers already in the industry. The workshop will be informative, honest, and direct about lessons learned as wood products, plastic, cement, and other companies continue to expand the range of manufacturing technologies and markets for products that add value to wood residue.

PARTICIPANTS

Wood Products Industries

Plastic Extrusion Companies

Plastic Injection Molding Companies

Industrial Development Specialists

Wood Waste Producers

Urban Wood Waste Processors

Landfill and Transfer Station Operators

Recycling Coordinators

Wood Product Development Specialists Equipment Manufacturers

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8:OO WELCOME Jeffrey Peterson, Program Manager, Energy Resources New York State Energy Research and Development Authority Albany, New York

8:15 Adding Value to Wood Waste: Opportunities for New York Industries Kevin King, Executive Director Empire State Forest Products Association, Albany, New York

8:30 Wood Waste Supply: Quantity and Problem Areas Judy Jarnefeld, Project Manager Biomass Conversion to Fuels and Chemicals New York State Energy Research and Development Authority Albany, New York

9:oo Characteristics of Wood Waste that Affect End Uses Jeffrey Fehrs, P.E., Research Director C.T. Donovan Associates, Inc., Burlington, Vermont

9:30 Value-Added Products Containing Wood Waste Brent English, Industrial Specialist USDA Forest Products Laboratory, Madison, Wisconsin

1o:oo Break and Exhibits

10:30 TRADITIONAL WOOD PRODUCTS

Demand for Traditional Wood Products in the Northeast and the Rest of the World Hugh Canham, Professor of Forestry Economics State University of New York College of Environmental Science and Forestry, Syracuse, New Y ork

Case Study: Use of Urban Wood Waste in MDF Jim McElvenny, Consultant, Beverly, Massachusetts

Case Study: Converting Wood Waste to Panelboard Christopher Carl, Executive Vice President CanFibre Group LTD, Toronto, Ontario

Agenda

Noon Lunch and Exhibits

1 :oo WOOD-PLASTIC COMPOSITES

Wood Waste Fiber in Plastics Brent English, Industrial Specialist USDA Forest Products Laboratory, Madison, Wisconsin

Case Study: New Composites Using Wood Waste to Meet Demands of Industrial Applications Michael Barrett, Marketing and Product Development Executive Strandex Corporation, Cincinnati, Ohio

Case Study: Wood Fiber/Thermoplastics Composites Dennis Meade, President Phoenix Color and Compounding, Inc., Sandusky, Ohio

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Break and Exhibits

WOOD-CEMENT COMPOSITES

FASWALL R/K-X Processes: Using Wood Waste to Manufacture Cement- Bonded Sustainable Building Products Hansreudi Walter, PresidentKEO lnsul Holz-Beton International, Inc., Windsor, South Carolina

TECHNICAL AND FINANCIAL ASSISTANCE

Doing Business in the New Empire State Bob Moppert, Regional Director, Southern Tier Empire State Development, Binghamton, New York

Recycling Means Business in the New Empire State Tom Kacandes, Market Development Specialist Empire State Development, Albany, New York

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Assistance Available from the New York State Department of Environmental Conservation - Forestry Bruce Williamson, Section Chief, Forest Products Utilization and Marketing New York State Department of Environmental Conservation Division of Lands and Forests, Albany, New York

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Assistance Available from the New York Center for Forestry Research and Development Dr. Edwin White, Dean of Research State University of New York College of Environmental Science and Forestry Syracuse, New York

Next Steps from Here: Opportunities for New York Industries Jeffrey Peterson, Program Manager, Energy Resources New York State Energy Research and Development Authority Albany, New York

Reception and Exhibits with the Empire State Forest Products Association

Organized by C.T. Donovan Associates, Inc., Burlington, Vermont

Workshop Director and Moderator: Christine T. Donovan, President Program Director: Jeffrey Fehrs, P. E.

Publicity and Finance Director: Dona L. Loso

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Michael Barrett Product Development Executive Strandex Corp. 829 Huntersknoll Lane Cinncinnati, OH 45230- (5 1 3) 624-6228

Christopher Carl Executive Vice President CanFibre Group Ltd. 6 Eva Road Suite 600 Toronto, CN

Brent English Industrial Specialist U.S.D.A. Forest Products ,aboratory One Gifford Pinchot Drrive Madison, WI 53705- (608) 231 -9393

(41 6) 695-3001

Judy Jarnefeld Project Manager New York State Energy Research and Development Authority Corporate Plaza West 286 Washington Ave. Extension Albany, NY 12203-6399 (51 8 ) 862-1 090

Kevin King Executive Director Empire State Forest Products Association 123 State Street Albany, NY 12207- (51 8) 463-1 297

Hugh Canham Professor of Forestry Economics State University of New York College of Environmental Science & Forestry 305 Bray Hall Syracuse, NY 1321 0- (31 5) 470-6694

Christine T. Donovan President C.T. Donovan Associates, Inc. P.O. Box 5665 22 Church Street Burlington, VT 05402- (802) 658-9385

Jeffrey E. Fehrs, P.E. Research Director C.T. Donovan Associates, Inc. P.O. Box 5665 22 Church Street Burlington, VT 05402- (802) 658-9385

Tom Kacandes Market Development Specialist Empire State Development Office of Recycling Market Development One Commerce Plaza Albany, NY 12245- (51 8) 486-6291

Jim McElvenny Consultant 3 Lee Street Beverly, MA 01 91 5- (508) 524-8804

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Dennis Meade President Phoenix Color and Compounding, Inc. 2520 Campbell Street Building R Sandusky, OH 44870-

(41 9) 626-1 150

Jeffrey M. Peterson Program Manager, Energy Resources New York State Energy Research and Development Authority Corporate Plaza West 286 Washington Ave. Extension Albany, NY 12203-6399

(518) 862-1090

Dr. Edwin H. White Dean of Research State University of New York College of Environmental Science & Forestry 200 Bray Hall Syracuse, NY 1321 0-

(31 5) 470-6606

Robert Moppert Regional Director, Southern Tier Empire State Development 44 Hanley Street Binghamton, NY 13901-

(607) 721-8605

Hansruedi Walter President lnsul Holz-Beton International, Inc. P.O. Box 88 Windsor, SC 29856-

(803) 642-9346

Bruce Williamson Section Chief, Forest Products U&M NY State Department of Environmental Conservation Division of Lands and Forests 50 Wolf Road Albany, NY 12233-4253

(5 1 8) 457-743 1

Exhibitors and Information Tables

Empire State Development One Commerce Plaza

Forest Products Lab. Information Services One Gifford Pinchot Drive

Room 950 Madison, WI 53705-2398

Albany, NY 12245- (608) 23 1 -9200 (51 8) 486-6291 Tom Kacandes Market Development

Specialist

lnsul Holz-Beton International, Inc. P.O. Box 88 Windsor, SC 29856-

(803) 642-9346 Hans Walter CEO

New York State Energy Research and Development Authority Corporate Plaza West 286 Washington Ave. Extension Albany, NY 12203-6399

(51 8) 862-1 090 Jeffrey Peterson Program Manager,

Energy Resources

Rotochopper 345 Willowbrook Drive Brockpoit, NY 14420-

(71 6) 637-0388 Gib Harrington Sales Manager

State University of New York College of Environmental Science & Forestry 200 Bray Hall Syracuse, NY 1321 0- (31 5) 470-6606 Dr. Edwin H. White Dean of Research

Natural Environmental, Inc. 71 8 Elk Street Buffalo, NY 1421 0-

(71 6) 824-3766 David Frost Sales Manager

NY State Department of Environmental Conservation Divison of Lands and Forests 50 Wolf Road Albany, NY

Bruce Williamson (518) 457-7431

Sorbilite, Inc. 5721 Bayside Road Virginia Beach, VA

Marc Kata bian (804) 464-3564

12334-4253

Section Chief

23455-

Sales Associate

Waste Age Magazine National Solid Waste Management Assoc. 1730 Rhode Island Avenue Suite 1000 Washington, DC 20036-

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David Ackerman President Resource Management Services NewVemon, NJ 07976-01 85 (20 1 ) 267-3306

Brian M. Arico President Mid Hudson Hardwoods, Inc. RR 1, Box 596 Clinton Comers, NY 12514- (9 1 4) 838-2 1 00

Maynard Baker Warehousing Services Representative School House Warehousing, Inc. 4500 St. & Hwy 30 P.O. Box 606 Amsterdam, NY 12010- (5 18) 843-2820

Michael Brancaleoni Supervisor Global Recycling P.O. Box 2391 Peekskill, NY 10566- (9 14) 737-901 7

Richard Buggeln Manager, TN Materials Exchange Univeristy of Tennessee Center for Industrial Services 226 Capital Blvd. Suite 606 Nashville, TN 37291 - (61 5) 532-8881

Roy D. Adams Associate Professor Penn State University 31 2 Forest Resources Lab University Park, PA 16803- (81 4) 863-2976

Sheldon Atherton Instructor Steuben-Allegany BOCES 11 26 Bald Hill Road Homell, NY 14843- (607) 324-7880

Robert M. Beaudoin C&D Project Director F.A.C.E. 75 Day Street Fitchburg, MA 01 420- (508) 345-5385

Michael Brewer Instructor Steuben-Allegany BOCES 11 26 Bald Hill Road Homell, NY 14843- (607) 324-7880

Marc Bukaty Western Region Manager New York State Electric 81 Gas 150 Erie Street Lancaster, NY 14086- (7 1 6) 65 1-5233

Kenneth Cartalemi President Global Recycling P.O. Box 2391 Peekskill, NY 10566- (914) 737-9017

David T. Damery Building Materials Marketing University of Massachusetts UMASS, Holdsworth Nat. Resources Bldg. Amherst, MA 01 003- (41 3) 545-1 770

David Donahue Fuel Procurement Manager Petrofiber Corp. 31 Old Concord Road Henniker, NH 03242- (603) 428-7044

Gary Dreibelbis Vice President Bailey Manufacturing Corp. P.O. Box 119 Walton, NY 13856- (607) 865-4380

J.W. Falk ILEC/MVATC 207 Genesee Street Utica, NY 13501-

Howard F. (Woody) Chambers, Jr. Business Manager Environmental Recycling, Inc. 8000 Hall Street St. Louis, MO 63147- (31 4) 382-7766

Edward Dina Vice President Custom Compost, Inc. 207 Milton Turnpike Milton, NY 12547- (9 14) 795-5044

John Dowd Vice President J&J Dowd Wood Products, Inc. P.O. Box 91 9 5 West Main Street Chateaugay, NY 12920- (51 8) 497-31 1 1

Annette J. Fago Program Assistant Dutchess Cty. Economic Development Commission 3 Neptune Road Poughkeepsie, NY 12601- (9 14) 463-5408

Dave Forness Cortland U&M Forester NY State Department of Environmental Conservation 1285 Fisher Avenue Cortland, NY 13045- (607) 753-3095

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Carl S. Golas Wood Products Industry Specialist Aditondack North Country Assoc. 183 Broadway Saranac Lake, NY 12983-

(5 18) 89 1-6200

Paul Gutchess President Paul Bunyan Products, Inc. P.O. Box 190 Preble, NY 13159-

(31 5) 696-61 64

Rick Handley Program Manager Northeast Regional Biomass Program CONEG Policy Research Center, Inc. 400 North Capitol St., NW Suite 382 Washington, DC 20001 - (202) 624-8454

Tim Holmes Wood Products Development Adirondack North County Assoc. P.O. Box 295 Saranac Lake, NY 12983-

(518) 891-6525

Dr. Michael Khamis President Thermo-Plastic Technology 1050 Elizabeth Street Mechanicville, NY 12118-

(5 18) 664-9550

Gary H. Gutchess President Gutchess Lumber Co. 150 Mclean Road P.O. Box 5478 Cortland, NY 13045-

(607) 753-3393

Kevin Hall Sales Manager Harbour Front Recycling, Inc. 1505 Burlington St. E. P.O. Box 3065, Depot 4 Hamilton, ON (905) 548-6900

David Hoffman Facility Manager Petrofiber Corp. 31 Old Concord Road Henniker, NH 03242-

(603) 428-7044

Mark Kenedy President Hubbard Sand & Gravel 161 2 5th Avenue Bay Shore, NY (51 6) 665-1 005

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Richard W. Krause Consultant High Technology of Rochester 5 United Way Rochester, NY 14506-

(71 6) 327-7930

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Lance Lashway Vice President Lashway Logging Inc. Box 231 Williamsburg, MA 01 096- (41 3) 268-3600

Mark Mahew Project Manager, Energy Services New York State Energy Research and Development Authority Corporate Plaza West 286 Washington Ave. Extension Albany, NY 12203-6399 (51 8) 862-1 090

Ronald J. Matre Vice President Pallet City Inc. 31 0 Grand Island Blvd. Tonawanda, NY 141 50- (71 6) 873-7700

Michael P. McHugh Supervisor of Solid Waste Town of New Castle 280 Hunts Lane Chappaqua, NY 1051 4- (9 14) 238-809 1

David Mowrey Mill Manager Lok-n-Logs, Inc. P.O. Box 613 Sherbume, NY 1 3460- (607) 674-51 1 1

Michael F. Loree Director of Recycling Modern Recycling 4746 Model City Road Model City, NY 14107- (71 6) 754-8226

Tom Martin Albany U&M Forester NY State Department of Environmental Conservation 21 South Putt Corners Road NewPaltz, NY 12561 -1 699

(914) 831-3109

Donald J. Matre President Pallet City Inc. 310 Grand Island Blvd. Tonawanda, NY 141 50- (71 6) 873-7700

Andrew E. Middleton Plant Manager Gutchess Lumber co. 150 Mclean Road P.O. Box 5478 Cortland, NY 13045- (607) 753-3393

J. Barclay Mutch Plant Manager Harden Furniture 1 Mill Pond Way McConnellsville, NY 13401 - (31 5) 245-1 000

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Edward Neuhauser Senior Research Specialist Niagara Mohawk Power Corp. 300 Erie Boulevard West Syracuse, NY 13202-

(31 5) 428-3355

David Orzel 831 5 Ericson Drive Williamsville, NY 14221-

(71 6) 633-1 256

Mike Pogue New Paltz U&M Forester NY State Department of Environmental Conservation Bureau of Private Land Services 50 Wolf Road Albany, NY 12233-5438

(5 18) 457-737 1

Paul E. Schiavi Vice President Northeastern Products Corp. P.O. Box 98 Warrensburg, NY 12885-

(518) 623-3161

Joel Stopha Extension Specialist A.H.C. @ West Virginia University P.O. Box 6125 Morgantown, WV 26506-

(304) 293-7550

Tad Norton Warrensburg U&M Forester NY State Department of Environmental Conservation Hudson St. Extension Warrensburg, NY 12885-

(5 18) 623-367 1

Frank Parks Stamford U&M Forester NY State Department of Environmental Conservation Route 10 Stamford, NY 121 67- (607) 652-7364

Rodney Rogers Technical Operations Manager Cherry Creek Woodcrafters P.O. Box 267 South Dayton, NY 14138- (7 16) 988-321 1

Frank Sidari Jr. Production Manager Shomar Industries 1013 South Clinton Street Syracuse, NY 13202-3408

(3 1 5) 474-1 398

James R. Sturges Owner Pallet Corp. of America P.O. Box 21 1 Chenango Bridge, NY 13745-

(607) 648-5 1 8 1

Participants

Chris Taylor Wood Products Engineer Telescope Casual Furniture Co. 85 Church Street Granville, NY 12832-

(518) 642-1 100

Roy Turner 13 Nieman Drive Orchard Park, NY 14127-

(71 6) 662-781 6

John Warner Accounting Lok-n-Logs, Inc. P.O. Box 613 Sherbume, NY 13460-

(607) 674-51 11

Chris Works Operations Manager Allegheny Particleboard L.P. RR 1, Box 266 Kane, PA 16735-

(8 14) 778-2600

James W. Taylor Jr. Manager Taylor Recycling Facility L.L.C. 172 Neelytown Road Montgomery, NY 12549-9900

(9 14) 457-402 1

Cindy Venditti Sales Representative Clifton Recycling 3400 Court Street Syracuse, NY 13206-

(31 5) 463-1 170

James K. Waters Special Projects Manager Gutchess Lumber Co. 150 McLean Road P.O. Box 5478 Cortland, NY 13045-

(607) 753-1 08 1

James A. Yansick Vice President J.A. Yansick Lumber Co., Inc. 697 West Main Street Arcadi, NY 14009-

(7 1 6) 492-4440

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OVERVIEW

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h: Gilbert, Richard D., ed. Cellulosic polymers, blends and composites. New York: Hanser Publishers: 115-130; 1994. Chapter 6.

Lignocellulosic Composites

B m t English, John A. Youngquist, and Andrzd M. Krzysik

6.1 Introduction

"m that OOlltriRd both cellulose and lignin is a lignocellulosic. Lignoccllulosiw iachdc wood, apicultural mps, like jute or kenaf; agricultural residues, such as bagasse or

for other lignocelhdosics even though they may differ in chemical composition and matrix @logy. Wood is anisotropic (different propaties in all three growing directions of a me). It may COILtljll srpwood, heprrwood, latewood, carfywood, juvenile woo4 and abnoxrnal d o n wood Wood may also have defects such as knots, cracks, splits, rad checks and may k bent, twisted, or bowed These variations and effects occur in d i d wood or hrmba but n d not exist in wood composites. la a broad sense, a composite QO be M n s d 01 my combination of two or morc materials, in any fonn, and for any use. In the woad hdwtry, the tams composk andr#.xnrstittcd wood arc d l y usedto describe my woad product mat is 'giued" together. The composite productp in the wood industry nnge fiam fibaxhard to lrminated beams and structural components.

The objective of composite development is to produce a product with performance chnctsrirtics mat combine the positive attributes of each constituent component. Like other Iigwcellulosic materid, wood is strong, lightweight, abundant, nonhazardous, and relatively iwrrpcnuiVc. Auy lignocellulosic can be chemically modified to enbance properties such as dinrmsionrl stability and resistance to biodeterioration. This prwides incentive for prodwing a vrriety of vrlucsddtd products from d i h t raw mataids combined to provide i u p " e n t s in cost or perfonnnnce, or both.

This cbaptcr first tniw reviews various chemical treatments to wood and wood OOmPObilCg. Traditional veneer-, particle-, and fiber-based Lignocellulosic composite " i r i s md tschnology are discussed next. Then, foncasted improvements in existing

opptudjcs fix producing new types of value-added, thumofoxmabie lignocellulosic camporires using blends of diffennt materials. Cumat ztstarch in this axea is illwratcd, and

aPnst8@ gt.Mts; d other plant substances. In g e n d what is true for wood is also true

logy ate presnroed Greater detail is then presented by reviewing deve10pmg

pmpmies of selected mrtsrials uc given.

1 16 B. English, J. A. Yomgquist and A. M. I(rzyfik

6.2 Chemical Treatments

Wood is one of the few natural products that humans have used throughout history without modifying its properties. In recent years, however, several treatments have bcen developed to modify wood for special applications. Chermcal modification of wood wn be defined IS m y chemical reaction between some reactwe part of a wood cell wall component and a chermcal reagent, with or without catalyst, that results in a covalent bond f o M g between the components. Bccause the most abundant reactive chemical sites in the wood cell wall poly" arc hydroxyl p u p s , reaction involving hydroxyl reactivity has been most studied.

A USDA Forest Service, Forest Roducts Li~boramry (FPL) report by Rowell and M o l [ 1 J &sclibes five rents that alter the physical properties of wood and thus affect its stability, stifhcss, and water repellency: (1) treatment of wood with a water- soluble polymer or synthetic resin, (2) compression of wood while heating or curing with

Mung ylents, and (5) polymenzatlon of liquid monomers within wood cell lumens. These

Rerernh has demonsapted that it is possible to eliminate or substantially decreafc the * of bi- ' md the dimensional instability of wood by chemicaIly modifying iDdividual all wdl polymer components. Both f d d e h y d c cross-linkmg and acetylation nreucb being conducted at FPL and other research institutions @de an excellent

rrSin, (3) heat, (4) bonding Of wood cell wall p ~ l y m e r ~ with O ~ @ C Chemicals OT cross-

m e n u will be briefly discussed m the following sections.

omwratnily for new qxcidty pmduct developmart.

6.2.1 Ubter-Soluble Poljmer or Synthetic Resin Twtment

Poly&ylene glycol (PEG) is a white, wax-like chemical that resembles psraffin. Poly- dy lene glycol uscd for tmting wood + an average molecular weight of lo00 (small mougb to pnemte the cell wall), melts at 40 "C, dissolves easily in warm water, is noncomsive, odorless, and colorless, and has a very high flash point (305 'C).

Poiyefhylene glycol is usually used with gmn wood. Pressure is not needed because the treatment is based on difhrsion. Polyethylene glycol is dissolved in water at a concentration of 30-5OWrh. Treatment is usually done at temperatures ranging fkom 20 to 60°C. m i o n of PEG into wood can be p t l y accelerated by increasing the temp" as well as the concenuation of the aat ing solution. Polyethylene glycol is not d in the wood and rrmrins water soluble. Tbe application of PEG pnnnts the cracking that frequently occu~s in untreated wood.

6.2.2 Compmsion

Comprrnrion of wood while heating or curing witb resins greatly imprweS dimensid M@, mengrh, and s t i 5 e s s . The process consists of coxqessing the wood uudcr amditicms that cause sufficient flow of lignm to relieve the internal stresses resulting from

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6. Lignocellulosic Composites 117

comprrsrion. This process greatly reduces the tendency of the wood to swell when wet. Bdom compnrsion, thin veneers am conditioned to 3045% relative humidity. They am then prssted at high pressures at a temperonure of 17O-177OC. The wood is usually compnssed to a specific gravity of at least 1.3.

6.2.3 Heat

Heating wood in a vacuum at high temperatures causes lignin to flow and hemicellulose to dmmnpow, which produces water-insoluble polymers. This treatment increases dimensional stability but -s strength. The process is done by heating wood at temperatures between 93 and 160 "C in a bath of molten lead, tin, and cadmium alloy. This alloy does not &to the wood. Heating times range fiom a few minutes to a few hours. Because strength propdes IIZ lost in the manuftu3uing process, heat stabilization of wood using this p"hr method has not been used commercially.

6.2.4 Bonding of Cell Wall Polymers

The cell wall polymers of lignocellulosics can be permanently bonded by reacting an Organic chemical with the hydroxyl p u p s (bulking agent) or by using a cross-linking agent. These m t s macase dimensional stability but can reduce strength.

Anhydrides, epoxides, isocyanates, acid chlorides, carboxylic acids, lactones, alkyl cModdai4, rpd nitriles have been used for bullring agents. Acetylation of wood with acetic auhydride has undcxgone the most study. The greatest single application of bonded chemical bullcine of the a l l wall is in reconstituted products such as fiberboar4 fiakeboard, or puticleboard in which standard operating proceduns call for dry wood materials and small particle size.

bat& restrain the units from swelling when moisture is present. One of the most widely studied chemical systems for cross-linking is the reaction between wood cell wall hydroxyls d €i"Idchy&. Cross-linking can take place bmveen the hydroxyl p u p s on the same or diftknnt cellulose, hemicellulose, and lignin polymers. The reaction is usually tatdyzd

hrasue the wet strength of paper, commcxcial applications do not exist at pnscnt.

If'- units of the wood cell wall an Chemically bound together (a~~~-Linkeed), the

M -0 rCi&. Although formaldehyde Cross-linking ha9 bten used ~~@"tdly to

6.2.S Potperizetion of Liquid Monomers within Cell Lumens

In tbs chemical modifications described so hr, most of the chemical resides in the cell walls.

systems ae commercially available: methyl methacrylation and epoxy resin treatment. Both m t s i n u 8 ~ ~ strength pad stifiess, but neither enhances dimensional stability to any gmmt extent.

Thc hnnens (the p e s ~ ~ 1 0 s e d by the cell walls) essentially mty. TWO l~mea-611

118 8. English, 1. A. Youngquie and A. M. Krzyrik

At present the main commercial use of methyl methanylated wood is parquet floonng. Other applications include archcry bows, billiard cues, golf clubs, musical instruments, and ofice equipment. Epoxy resins arc used in boat hulls and the outer ply of plywood. Epoxy resin tratmcnts have been used to saengthen soft or decayed wood.

6 3 of Commercial Lignocellulosic Composites

T~aditional iipocellulosic composites can be placed into three main p u p s based on

subrpoups within them, arc impomnt because the smaller the size of the components, the am8llcr the miation w i t b the board becomes. For example, plywood is less lmifonn thuJ waferboard, which is less mifm thn particlebod, which is less Uniform tban fikrboud. Fibchard, whether wood-bnscd or agricUlM1-based, is made from li~occllulosic fiber. Fiberboards can be very uniform, reproducible, and consistent. A morc complete descnption of the these materials, including strength and property data, is

@cle titC: veneer-basd, particle-based, and fiber-bad materials. These -UPS, and

found in the Rbod Handbook [2].

6.3.1 Veneer-Based Materiak

Veoea is uocd to produce a number of glued wood products including s t m e panels for m u i n g applications, panels for decorative use, and components for structural lumber substmues such as beams and trusses.

63.1.1 Plywood

Plywood is a glued wood panel made up of relatively thin laym of veneer (0.5-5 mm) with the grain of adjacent layers usually at a 90 “C angle. The layers vary in number, thickness, and grade, depmding on the end-use requirements. Compared with solid wood, the chief dvmuges of plywood arc ( I ) nearly qual properties along the length and width of the panel, (2) greater resistance to splitting, and (3) capability of manufachvt into large sheets. Using plymod results in improved utilization of wood because it covers large areas witb a mini” amount of material. The properties of plywood depend on wood species, quality of veneer, order of layer placement in the panel, and type of adbesive used.

6.3.12 Veneer Lumber

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Mitakls d e by parallel lamination of veneers into boards witb thicknesses common to solid-” lumber (19.043.5 mm) arc called laminated veneer lumber (LVL). Lamimed

6. Ltgnoceiluroric Composites 119

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venar lumber represents a o w technology in wood utilization; the p" and uses for this mrtQiil are still evolviug. The industry pmmtly uses veneers 2.5-3.2 mm thick, which me hat premed with phcnol-fmmrldehyde adhesive into lengths from 2.4 to 18.0 m or more. L tyino up the individual fbr LVL manufjrchm, joints, knots, and other h w s arc stagged to avoid groar strength-reducing defects.

Some of the first applications of LVL were iuspired by rising costs and shortages of bigbpde, solid-sawn lrrmbcr fir parallel-chord trusses and sc&ld planks. Truss

defbcts are vhaully no": making possible the we of LVL in light trusses and I- #ctiaru. Tho I-Kcrionshvcawb composedofa panel procbrcs such ps plywood o r b " & glued into amrcbined groove in the L a h g e s . These I-ssction beams arc "nly being used as joists and ratters in light frame CO1WtNCtiOD.

rmSlufjEbllCrS fwnd the LVL Concept upable of opening ww Inark-. S ~ - r e d U c i n g

6.3.2 Porticlc-BaJed Materials

Tho clur of prtticl&8sed p e l nwtdals includes maLIy SubrpMlPs known as chipboard, ~~ w&bomd, oriented stmdbod (OSB), and cementboard. In final form, them pnlsl " i d s "in a fnv PFOpaties of the original mod, but because of the m d h a r h g methods, the pIlneis gaiu many n w and di&nnt Properties. Unlike solid woo4 tlmc ~ r v o o d p r o d u c b can be tailoredto satisfy the property requirements of a specific use or a brwd gmup of cnd uses.

63.2.1 Wafisrbwd and Oriented SIrsndboord

' b o aujor exterior types of paticle p e l products are waferboard and oriented rtrandboard (OSB). Particle sizcs mge from 25 to 75 mm long by 10 to 30 mm wide by 0.5 to 2 mm thidL In wrfihrbornd, thelmticlclcs am not intentionrllyoriented, andthe board is bonded with

1960s. --type resin is applied to wood strands (long and narrow &Ires) that fibnned into taut of thne to five layem. The strsnds in each layer are aligned 90 O from the ercsnt Iryer. Strand dilpwent gives OSB bending properties (in the aligned direction) that am ge"Uy supaior to those of a randomly oriented waferboard. As with my particle panel producs the propaties are bighlydependmt on the rnan*gprocess. Theplnperties of wrfaborrd and OSB uuke them suitable for many a p p l i c a t i ~ ~ now dominated by softwood Plywooa

IPL exterior* 2". oriarttcd sbrandboud emerged in the markctpla during the early

63.2.2 Partichboad

1.1

120 B. Engli& 1. A Yomgquist md A. M. Knysik

6.3.2.3 camatborrd

~ c e m c n t i s c 0 " e r C r p l * ly used as n binder for a special class of lignocellulosic particle pnncls called crmcntboards. The wood particles typically used an celled excelsior, or wood-wool, bemuse they are long (up to 250 mm) nnd Stringy. Medlum- to low-density wood @es ue reduced to excelsior, blended with cement, formed into mats, and pnssed to a dcnti of 480 to 640 kglm3. mer nOnWOOd lignoallu~osics an used in the production of amentbonrd and iaclude bn$ase. rattan, and coconut husk fiber. The processing for these ligadulosics is vuy rimilar to thnt of wood-wool. A d o n use for cementbod is roof deckmg because of its round-absmbing and fire-resistive properties. Other cement-bonded @de products include buildmg blocks and panels d e with fink= tbt can be used m doors, 500rs, lord-bearing d s , partitions, concrete forms, and exmior si-.

6.3.2.4 Fiber-- Panel Muerirls

"e panel nutaids arc nll made from reconrtituted wood or other lipnocellulosics like bagawe. Thc wood is fuaFeduced to fibers or fiber bundles and then put back together by apechl h of "uf.ctun into p e l s of rclntively Inrge size and moderate thickness.

plopabcs of fiber-bascd panel products an determiaed accodmg to American Nntional Standuds instiaUe (ANSI) standards, and to n considerable extent, these properlies either

into vrrious crtegories by nun- process, properties, and use. r~wa or limit their US^. In the fblIowing sections, fiber-bsed panel mMenals an divided

632.5 Insulntion B w d

"his is n gamic tam for a bomogcneous panel thnt is made from wet-foxmed, interfelted lignocellulosic f i b (usurlly wood or begme). The pnnels an consolidated under beat and pressure to a specific mty xange between 0.16 and 0.50. Thm an many diffmt types, "Cs, and uses of insulntion board.

6.32.6 Medium-Density Fibabonrd

M- ity fikrboard (MDF) is manufacad from lignocellulosic fibers usually combined with n synthetic resin or otbn suitable binder. Specific gmvity values for h4DF range from 0.60 to 0.80. The ttchnology utilized to manufacnvc MDF is a cambination of that used in the pmicleboud and hardboard in-.

The furniape "y is by fnr the dominant MDF market. Mediumdensity fiberboard fraquently takes the plrce of solid wood, plywood, md paniclebonrd for mauy fixnianr '8pplicm"r. comprrsd to particleboard, MDF has n very smooth ourface, which facilitates wood-@ printing, overbyhg with rhea mntcrinls, and vcneaing. Mediumdensity fiberboud has tight edges, which need not be bandad md CUI be routed and molded

n ii

ii

1; ii ll ll I/ l l 11 /I

I/ ii

/I

11

1

.1-1

I 1 II

: I

like solid d Wood-groin pxiatcd aud embossed, MDF is used in many fiuniture lines. "ha potentid fix MDF m othn inmior md exterior markets such as doors, moldings, exterior trim, md @let decking is cmrentdy being explored by the induay. Many industfy people expect MDF markets will expand significantly during the next decade.

6.32.7 Hudbosrd

Hmfborsrl ir a generic term fbr a panel that is manufactllrtd primarily from wet- or dry- f h d , mterkltcd lignocellulosic f i b md has been consolidated under heat and pressure to a rpccific @ty of 0.50 to 1.45. Hudbwds am classified by density, arrfa# finish, thiclmsrs, mi mini"! physical properties.

The mu forhvdborrd are diveme, but they g c n d l y can be subdivided accordiagto wes dsveloped for coamwt~ *on, furniture and fmnishiags, cabmet and store fixture work, qppliurces, and automotive and rolling stock. Much of the recent success of hardboard "ked f" the development of products for a specific use md the specifications of -t~, frbricrtion, md finiahcs for each product ?fipical hardbod producta arc prcSnishQd paneling, house siding, floor unddayment, md concrete form hardboard.

6.4 Promising Technologid Improvements

btextw cmpethion among Mlious pmduct8 bas long typised the North American n;atffials w e s . Atbough this competition is genetally recognized by those working in the mrtairls field, occasionally mricwing d c v e l ~ e n t s of the recent past is wrthwhile

anly ow or two specific examples of p i b k future changes am listed In most instances, rrrmy morc examples could be cited.

JUPIIIU they provide some pcmpcdive about the fuhm. In each of the following catcgoxies,

6.4.1 Adlruivcs

..I .

1 I

3

Thc economic health ofthe woodproducrs idustry in North America is controlled to a great cptbast by t& ntc of housing &nsmrction. which in turn is controlled by the health of the Ovenn US. economy and by demographics. Within the wood products indusl~~, the greatest uae of wood adhmivca by fju is for mmuticnxhg wood composites [3].

whu an be said about wood adhesives in the fim"? New technologies and new

"iab mom efacientty and cost dibctivsly is a possibility. Expeaations arc that urea-

rdhsrivar in the united sates. 'Rvo l" ' area6 am ths possibility of much more s&bpnt reguiUion of fbmd&hydeumtainhg pIoducts md the possibility of limitatioas or

proehrctr 8rc con tin^ being ir"d . In 8dditioq using lowquality, forestderived

fkmrldehyde md ph~l-fiormrldehydt rystanr will C ~ U C to be the domhnt wood

122 B. English, J. A. Yomgquin and A. M. Krzyoik

memapths in the supply of petrochemicals. One xcsult of these uncertainbes is that considerable rt8tltch bas been conducted ID the (VCB of developing new wood adhesive

Although “reb results bavt indicated that a number of new adhesive systems have

mcymntc adhesives. The slow adoption of this matcnal is due to the relatively high cost md toxicity concerns. This matnial does bave some definite advantages, including w i d cure at m&te temperatures, insensitivity of cure to moderately high moisture, good dunbility, and the absence of formaldehyde emissions. Another relabVC& recent LMOVatlon is the we of a nvo-prrt adhesive system that allows plywood to be bonded at 12-13% moisture content or higher compared to the previously r q d moisture content of 3 4%. ?he w of fwned adhesives for bonding plywood is also becoming more widely used. In addition, the amount of adbesive being applied can be better conwlled, leadurg to a 20-30%

systems from d l e murces.

promitt, their commercial use is currently very limlted. one example is the use of

trvings in dhcave w.

6.4.2 StcM) and Chemical Injection

A rterm injection process has bem developed that d u c e s press times for fiakeboard, pamCleborrd, urd mediumdensity fiberboard production [4]. The process begrns by coating wood flakes witb a resin and fonning them into a mat. The mat is then loaded into a press and a brrm of satuxatcd steam is injected into it through perforated platens. Within s e v d seconds, the tmrpcnnnr in the c” of the board rises to approximately 104’C. As the board is complcte(i the intcrnd pnssurr irrcrrases, dlowing the tempcram in the cater of tbe b o d to riK to behvem 138 and 157 ‘C. This high temperature accelerates the min CUIC. Sevml seconds rfter the end of the steaming period, the tcmpmavc fids to h u t 107 “c md rrrbiiizeS there for the remainder of the press cycle. A computer used to M ” 1 the l t t ~ injection scbedule also monitors the rapidly changing press option. It records time, tempau\nr, and s e v d other variables at 0.5-s intervals.

Ramcb conducted at FPL indicated that pnss time for a 13-mm-thick board can be reduced fEom 4.5 min to about 90 s. Also, the 45 min needed to conventionally press a 50- mm-thick boud can be reduced to less than 5 min with steam injection.

The DCW process uses smaller equipment and less energy than conventional pressing metbods. Steam injection also offers the possibility of injecting chemical uiditives that increase the durability and fire mistance of the board. The development of steam injection pressing md the techniques for understandmg the fundamental relations governing the chemistry md pbysics of resin cure and wood bonding during bot pressing will provide a nticwrl basis fw designing improved structural composites with controlled densities and density profiles.

6.4.3 S t “ l PopcT products

R”dIUS at FPL hive developed a sauctud fiber concept d e d Splaborrd [SI. To mrLe this the.dimentiwrl mucslnpl board, wet fibers arc press dned agamstrubbamolds

6. Lgaocdlulosic Comporites 123

T'

f; ,

with -like configurations to produce symmetrical halves. An adhesive is used to bond

te&tiqw, Sprceawd can be made as a leminate ora sandwich. It can be thin enough for rtroag, lightweight cormgated containua or thick enough fior wall sections. The result is a fsko composite stn\etural "ial that is strong in every direction.

Ldmntory tests &ow that Spaceboard is between 30 and 2Wh sbronger than "id oonulpttd fiberboard Its strmgth is due to the special canfiguration of the o~bl) urd the superior strength i x n p d by the pnss-dy"d that molds the core and

dM hrlvcr, G!W&g IIummU shaped C C b in the Centff Of the board UShg this

hciag toeahn.

6.4.4 Sqfhee h t m e n t s

Wood finishi~g d is stimulated by the lack of detailed knowledge about fi"cntal cbnmicrl md PhYricJ fictors that a t the pedormance of exterior finishes on diffmnt wood species, campsites, and new wood-bnmd products. Further complicating the problem utbewidc mage ofnew f i ~ g m o t c r i p l s being apptiedtothe abwwoOd-bp(ltd substrates. Mlms with "ate-finish durability sometimu result with these new materials. The inaayino uw ofwood treated with p " t i v e or fire retrrrdant poses special challenges to tbc u10 of d o r wood finishes. Finish durability problems may be fiatber compounded by e"mtd collarru and restrictions on traditional paint and stain systems and by rest" OLI g h t rdditivcs. The following tachnical cballenges and problems will be a i p i h u t to the fuaar of finiahed wood for exmior we:

. .

1.

2.

3. 4. 5. 6.

New wood species will be wcl, and the use of camposites and overlays will increase (Chaging-1. Use of waterborne finishes, finishes with higher solids contents, finishes incorporating tow-volrtility o w c compounds, and new multipurpose resins for new finishes will incnrare (chraging finishes). New CBcmiCrls will be used for mildew and mold control. use of hetory finishing will increase. E " m n t a l restrictions on many finish components will increase. safety md heahb collccRls will incre9se.

continuingrrreuch on wood finishingrrsdweathenn g wiU focus on demonstrating tbe

6.4,s Tirmnofonnablc Lignocellulosic Composites

f

128 B. English, 1. A. YormoqUin and A. M. I(rzyrik

The procaring began by spmying the phenolic min onto the wood fibers at a 100/0 Weight b b . The wood and p M c fibas were then mixed by p s m g them through 8 spiked dnnn, rnaOfarsd throw an airmeem to 8 moving support bed, and subsequently formed into a amhww, bdcnsity mat of intmftnncd ' fibas. The mat then weat througb a

doing, in"i tbc mtcriocking of the fibas. The xnats were 330 mm wide and of vmious

get tbe twget rpecific mty. A manually controlled, steam-heated press was used to press J1 prnslr at 1°C to a thickness of 32mm and a specific gravity of 1.0.

Pmek w m oonditioned at 65% relative humidity at 20 'C. After conditioning, the pads were cut into tea rpccimarS md tested in confonnancewitb ASTM D 1037-87 1151 (k Wtic bending, tensile, water rorL (water .baarption md thickness swell), .nd b a r

in Tkble 6.2. Tk ANSI "rnn standads arc included as a point of reference [16].

~iagpmcesswberr ~ a e e d l e s p r s s c d ttmugb the mat thickness, .n4 in (10

kI@u. Tbemrtrwffe thm cut into 330-by 330-mm rquucs. The Squareswmc Mclredto

@a. lmpOa tCrring w a ~ done b .ccordmce to TAPPI T-803 0171-88. R d k IR rbawn

camporne (10% rain)

50.6 41.1 43.2 47.8 a31.0

3.66 4.36 3.23 3.74

33.0

4.84

28.4

5.12

28.3

4.26

30.0

4.56

15.2

36. I

43.4

28.7

413

34.2

48.3

30.7 - S35.0 44.1

252 223 29.8 26.9 S25.0

025 0.46 0.65

0.21 O M 0.70

0.20 0.43 0.64

0.20 0.45 0.71

7’

J

1 ’1

II

The above composite materials exceeded the ANSI national standards for basic hardbovd shest@ properties. Except for the 80% Hem, 10% R-Pet f;ormulatioa, none of the Ipecimens met standards for water absoxption or thickness swell. Thc addition of a 1511151 ano\mt of wax (a standardpracedure in the hardboard indumy) may impnrve these values. Some debate exins about the applicability of hardboard standards for wood Bber p M c composites. Since the composites in Table 6.2 closely resemble hard- boani, ASTM testiag methods were d t o determine their properha, and ANSI standards lwm ulod for evpiurtion.

6.6.2 Additional Comments

Air-laid nut tecb1101ogy pamits the use of a wide range of lignocellulosic and synthetic fibers. ’The l i gnwl luh ic components can range from ncycled or virgin wood materials to agricultural f i h . Tbe Lignoallulosic component c811 be chemically modified to i m p m ths ptrfbnnrna ofthe composite in adverse conditions, as appropriate. Roducts a n be Mdo fipm 100% plrstic f i b , 1OO.h lignoallulosic fibers, or many di&nnt combinations of the two mrtsrirls. T h m g resins can be either coated on the lignocellulosic fibers or dded m powder form during web h d o n . Additionally, granulated plastics may be added,

6.7 Conchiding Remarks

~ e l l u l o s i c s will be ~r red in the futune to produce a wide spearum ofcamposite ranging h m vcry inexpensive, low-performance mataials to mataipls that arc relatively expasbe and have high@ormance ch” ‘cs. Taking dvantage of the wide dimrbution, d i l i t y , and recyclability of lignocellulosics, morc markets will develop br lowcost rmswrble materirrls. By chemically m0di-g the lignocellulosic cell wall to overcome some of its disadvantageous properties, new marlcets for high-performaace composites will develop.

Combining lignocellulosics with other materials provides a strategy for producing rdvcplced composites that take advantage of the enhanced properties of all types of matuials. Lignocellulosic composites allow scientists to design materials based on end-use require- mts within the fraanmodt of cost, availability, renewability, qclabil i ty, energy use, and rmvironraentll conrideratioas.’

.1‘ Acknowiedgmtnb

rl The urthon thnL George Myen, Craig Clemons, Roger Rowell, and all the USDA Fomrt Service, Farsrt PKUIUCU Lobantory emplayas for their assistance in the pnparaton of this chrpcr.

J

130 E. Engl14 1. A Ywngquin and A. M. Krryrik

References

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2.

3. 4.

5. 6.

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3 TRADITIONAL WOOD PROQUCTS

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UTILIZATION OF URBAN WOOD IN THE MANUFACTURE OF PARTICLEBOARD AND MDF

by David C. Smith

Willamette Industries, Inc.

Presented September 9, 1996 Conference: USE OF RECYCLED WOOD AND PAPER IN BUILDING APPLICATIONS

Willamette Industries began in the early 1990's to pioneer the large scale use of recycled urban wood as a raw material for particleboard. With the acquisition of the Eugene Particleboard plant from Bohemia Corp. in 1991, Willamette found itself short on raw materials to supply its Oregon mills. The company's existing facilities in Albany and Bend were already experiencing substantial price intreases due to shrinking supplies of traditional particleboard materials. Closures of sawmills and plywood plants due to timber shortages brought on by the Spotted Owl controversy were significantly reducing the availability of planer shavings, sawdust, and plywood trim.

It was clear that i f the Eugene plant was going to stay open, new sources of raw material would need to be found. Through the efforts of Tom Buglione, Dennis Adair, Alice Denham, and others, Willamette was able to arrange for the acquisition and preparation of up to 10,000 tons a month of recycled wood. Direct support and purchase contracts were made with a network of independent operators stretching from Puget Sound to Eugene.

Acquisitions by Willamette peaked in 1994 and 1995 with over 60,000 bdt (bone dry tons) of wood pulled out of the waste stream each year. Figure 1 shows that about 100,000 bdt was used at the Eugene particleboard plant from 1993 through 1995. Substantial quantities have also been used at the Duraflake mill in Albany, and KorPine in Bend, OR. By mid-I 994, Willamette was sufficiently encouraged with its recycled wood experience to reinvest in the Eugene plant. It has now been converted from the production of particleboard to MDF. However, the consumption of recycled urban wood at Eugene has not yet met projections for reasons that will be discussed later.

Premise for Use This report on Willamette's experiences with recycled urban wood over the past few years will be in the context of premises that must be true to allow its successful use as a substantial raw material for particleboard and MDF. The four premises identified by Willamette as essential were:

1. Adequately free of contaminants.

n

2. Conveyable through mill systems. 3. Adequately consistent fiber characteristics. 4. Economically competitive.

Challenges with Implementation : Cleanliness Most particleboard and MDF manufacturing and end-product converting processes are very intolerant of contaminants. While this was appreciated at the on-set, ne'ither the extent of the contamination problem, nor the scope of the cleaning challenges were completly recognized.

The cleaning system must be designed to address the minimumization of all three major categories of contaminants:

Large hard contaminants, like ferrous and non-ferrous metals, rocks, ceramics, glass, and concrete. Wire and strapping can be particularly hard to handle. Soft contaminants such as plastic sheeting, rubber, silicon products, and textiles. Grit and Dirt, not only loose dirt, but dried on mud and imbedded sand.

/

It is clear now that a cleaning strategy must include the following four disciplined steps:

Good Sourcing. The cleaning process is simplified considerably by starting with clean sources. Demolition materials should be avoided. Industrial wastes from cabinet shops and other wood remanufacturing operations can be very good if not co-mingled . Construction sites are potentially good, but require careful inspection.

Sorting and Grading. Truckloads of material arriving at the collection yard must Storage areas should be designated so that clean material, suitable for board raw material, is segregated from unsuitable material. This means that the collector must have alternative outlets, such as fuel or soil amenament, for the unsuitable material. Even with the best sourcing strategy, occasional loads will arrive that are too contaminated for board making. Even with good load grading, hand picking is necessary. Before going through the size reduction process, the material should be spread out so loose contaminants can be pulled out. The best opportunity to remove soft and large contaminants is before they're ground up.

be grade inspected for cleanliness before unloading.

II / / / I

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Ferrous Metal, Fines, and Oversize Removal. The size reduction machinery should be designed t o break the fasteners out of the wood. I t is much easier to magnetically clean nails and staples from the chip

1

" 1 -1

.t ' I i

stream when they aren't still embedded. Multiple, well placed magnets are required to get all the nails, particularly if pallets are used. Most of the loose rocks, and other hard contaminants are brittle and break-up in the size reduction system. Screening, to remove and divert fines to alternative uses, will get much of the sand and grit out of the material. Oversize material , both long slivers and broad chunks, can cause material handling problems at the board plant, so must be separated

' out and re-processed.

4. Board Plant Re-Cleaning. No matter how hard the collection yard tries, the recycled wood chips will likely still be too contaminated for significant use in board making. It is important that the particleboard plant people accept this and are prepared to perform additional cleaning prior t o use. This will involve appropriate levels of screening, magnets, washing, and other separation techniques.

,

.. es of I w m e n t a t t o n : Convev- Nothing is more important to the smooth operation of a particleboard or MDF plant than material handling. It is imperative that large volumes of raw materials move consistently and continuously through the mill process. Systems at most board plants are designed t o handle conventional materials like planer shavings, sawdust, and pulp chips. Excessive fines, or a few over-sized pieces, can cause plug-ups or motor overloads that interrupt material flow. The size reduction equipment must be designed t o make uniform, chip-like particles; 1 /4" to 3/4" maximum dimensions are ideal. Even with good size control, the geometry, bulk density, and other handling characteristics of ground-up recycled wood may necessitate changes in the mill's conveying systems to allow for its significant use.

C h w s of Implementation: Consistencv Uniform and consistent size distribution, moisture content, species mix, and rot and bark content are all important to particleboard and MDF producers. Paying close attention to good sourcing, cleaning, and conveyability, goes a long ways toward addressing other consistency concerns.

. . aes of lmdementation: Economicallv Comet i t ive Even with free sources, the costs of preparing and delivering suitable recycled wood to the board plant are real and significant. This resource must compete favorably with conventional raw materials: sawmill and plywood plant residues. The price of these residual materials often does not reflect their true cost, but rather is determined by the market forces of supply and demand. When utilization demands are low, their prices can drop t o very low levels, because the mills must dispose of them if they are to continue making their primary product. In order to keep planing lumber, the sawmill must get rid of its shavings. In times of high demand, the

residuals can become significant revenue sources for the mills, and prices may increase quickly. The recycled wood supplier must be prepared to compete in this climate of high price volatility. Recycled wood is currently regarded as a lower quality raw material because it is more difficult and costly to convert into particleboard and MDF.

Results of 3 Years Ffforts: Cleanliness When we began experimenting with using recycled wood, we were enthusiastic about the opportunities offered by this new resource. We speculated optimistically, I

if not naively, about production benefits, growth possibilities, and the attractiveness of offering a "green" product. Now, after processing over 100,000 tons of recycled wood over the last 3 years, our enthusiasm has become tempered by the grim realities of how difficult it is to overcome the challenges presented by recycled wood.

Most particleboard and MDF made in North America today is sold to industrial customers who convert it into furniture, case goods, and architectural woodwork. Their converting operations often employ sophisticated cutting, machining, coating, and other finishing operations. These end-users are very intolerant of contaminants. Very small amounts of non-wood materials scattered through the board can lead to productivity, safety, and quality problems. Hard materials like metal and small rocks, glass, or sand can damage cutting tools, cause sparks to fly, starting fires in dust collection systems, or eject missiles out of machines toward operating people. Small particles of softer impurities, Ii ke plastics, rubber, caulks, or ridged foams, leave pits in sanded surfaces if they fall out, or create "shiners" or "fish-eyes" when painted over. When these issues arise, our customer's opinion about board with recycled content shifts from "green" to dirty.

These contaminants cause similar problems in the board plant as well. The use of recycled wood at Eugene lead to so many fires and problems with milling equipment that we were no longer able to continue to make our primary industrial- grade product and serve our normal customers. I t 's really tough to get recycled wood clean enough. Despite considerable efforts to improve cleanliness, Eugene had to shift its focus to more tolerant flooring grade products in order to operate with even 20% recycled wood in the mix.

Our conclusion is that cleaning efficiency, or the total contaminant loading in the mix, limits the tolerance for use of recycled wood. Without a very sophisticated cleaning strategy, this "premise for use" restricts recycled content to less than 10%.

3

Res& of 3 Years Efforts: Con . vevai l i tv and Consistency The system used to break down pallets and lumber scrape into suitable board plant raw material must be well engineered. While the biggest challenge is, of course, to build a system capable of handling a wide range of infeed sizes, considerable attention must also be paid to the particle distribution of the product. A big hog or tub grinder may be easy t o feed and maintain, but often produces a lot of material both too fine and too large for further processing.

..

Large sticks can cause enormous problems at the board plants. It doesn't take too - many broom handles or slivers longer than 6" t o bridge and plug handling and cleaning equipment. A high "fines" content causes dust control problems and complicates the cleaning process to remove grit and other small contaminants. Willamette has found it essential to establish a formal specification for particle size distribution, and to enforce it rigorously.

This means that the collection yards must be much more sophisticated than first thought. They must utilize equipment specifically designed for the purpose, and then control the size distribution by "positive" screening that ensures that only acceptably-sized particles are taken. Overs and fines must be sorted out and either reprocessed or diverted to other uses.

>

While we originally envisioned a system of multiple, small yards scattered about an urban area as the most efficient means of gleaning wood for recycling, the economies of scale for a well engineered, efficient yard now seem t o favor large, centrally located facilities. From the stand-points of capital requirement, unit cost control, and management discipline to meet quality requirement, the larger facility is favored.

Res- of 3 Years w r i e n c e : Fconomic Competitiveness Between 1988 and 1995, Figure 2 shows the average cost of raw material, less transportation, ti5 a Western Oregon board plant more than doubled. With Collection yards set-up in 1993 and 1994 finding their operating costs running below the prices of conventional material, recycled wood became attractive. Now, however, this competitive picture has changed dramatically.

. .

Supplies of traditional raw materials are again plentiful; and, as Figure 3 shows, prices have come down accordingly. A t the same time, quality demands have forced collection yards to improve their facilities and add cost to their product. Consequently, there is little short-term incentive for Willamette Industries, or other board plants in Oregon, t o continue to develop the recycled wood resource. Of the 12 collection yards that supplied us over 120,000 bdts over the past few years, we

1

continue to do business with only two. The contract prices paid for their recycled material are sufficient to allow them to keep operating, but higher than Willamette would pay for readily available, and more desirable, traditional materials. - Although recycled urban wood has presented us with substantial physical ch’allenges, and we are still learning how best to use it, Willamette Industries is confident that it is a viable raw material for making particleboard and MDF. Economically, however, the availability of traditional raw materials has a significant impact on the competitiveness of recycled wood. Without some type of cost subsidization, recycled wood is not presently attractive to Oregon board manufacturers. Whether or not this situation will change in the future will depend not only upon the availability of traditional raw materials, but upon the development of recycling technology, and the costs of disposing of waste woo&

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f m ii

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al C 0

k Y

8 0 al cn E? % a

FIGURE 3: CURRENT R I

:LATIVE I RAW MATERIAL PRICES J OREGON

Sawdust 50-70%

Ply Trim 40-60% I

Shavings 90-1 00% I

Conifer Chips 100-1 20%

Hardwood Chips 125-1 65% i

Urban Wood 100% I

. -

1 --. 3

c 3

3 3 3 3 3

3

WOOD-PLASTIC COMPOSITES

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1 1 1 4 1 1 :I :1 ’1 ._

: I . I : I i. ‘ I > I ’ 1 3 :-j

11 _I

United States Department of Agriculture

Forest Service

Forest Products Laboratory

General Technical Report FPL-GTR-91

Waste-Wood-Derived Fillers for Plastics Brent English Craig M. Clemons Nicole Stark James P. Schneider

Abstract Filled thermoplastic composites are stiffer, stronger, and more dimensionally stable than their unfilled counterparts. Such thermoplastics are usually provided to the end-user as a precompounded, pelletized feedstock. Typical reinforcing fillers are inorganic materials like talc or fiberglass, but materials derived fiom waste wood, such as wood flour and recycled paper fiber, are also effective as fillers. The goal of this project was to generate commercial interest in using waste-wood-paper-derived fillers (WPFs) to reinforce ther- moplastics. The research strategy was twofold: develop- mental research and outreach. Specific objectives were (1) to improve wastepaper fiber preparation, feeding, and compounding methods, and optimize composite perform- ance, and (2) to communicate to end-product manufacturers the advantages of WPF thermoplastics.

The research was led and supported by the Forest Products Laboratory (FPL), with input fiom a consortium of 15 fiber suppliers and plastics manufacturers. Additional funding was provided by the Wisconsin Department of Natural Resources. Equipment was leased and installed at FPL. Eight general purpose formulations were developed-they included extrusion and injection molding grades of both polyethylene and polypropylene, reinforced with WPFs.

An information packet containing performance data, appro- priate processing conditions, sample pellets, sample parts, and a questionnaire was sent to nearly 500 commercial

May 1996

English, Brent; Clemons, Craig M.; Stark, Nicole; Schneider, James P. 1996. Waste-wood-derived fillers for plastics. Gen. Tech. Rep. FPL- GTR-91. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. IS p.

A limited number of free copies of this publication are available to the public from the Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI 53705-2398. Laboratory publications are sent to more than 1,000 libraries in the United States and elsewhere.

The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin.

The use of trade or firm names in this publication is for reader informa- tion and does not imply endorsement by the U.S. Department of Agricul- ture of any product or service.

The United States Department of Agriculture (USDA) prohibits discrimi- nation in its programs on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, and marital or familial status. Persons with disabilities who require alternative means of communication of program information (braille, large print, audiotape, etc.) should contact the USDA Office of Communications at (202) 72(1-2791. To file a complaint, write the Secretary of Agriculture, U.S. Department of Agriculture, Washington, DC 20250, or call (202) 72Ck-7327 (voice), or (202) 720-1 127 (TTD). USDA is an equal employment opportunity employer.

plastics manufacturers in Wisconsin, Illinois, and Michi- gan. In response to requests for in-house trials, FPL re- searchers conducted nearly 18 site visits. The researchers ensured proper handling of the material, provided consulta- tion, and gathered information about processing and per- formance. The trials went very well, and parts were suc- cessfully manufactured at all facilities. Products included automobile trim components and housings, vacuum cleaner parts, paint brush handles, bicycle parts, cosmetic cases, and other household items. Great interest has been shown in the use of WPF thermoplastics; one consortium member is establishing a 4 million kg/yr (9 million lb/yr) facility. Total market demand is conservatively expected to exceed 45 million kg/yr (1 00 million lb/yr).

Keywords: wood fiber, plastic processing, properties of composites, recycling

Contents Page

Introduction ............................................................. 1 Background .......................................................... 1 Project Goals ........................................................ 1

Selection of Materials.. ............................................... 1 Wood-Based Fibers ............................................... .2 Plastics ................................................................ 2 Additives ............................................................ .2

Preparation and Feeding of Fillers ............................. 3 Compounding Equipment ....................................... 3 Moisture Management ........................................... .4 Processing Conditions ........................................... .4

Composite Performance.. ........................................... .4 Performance of Standard Blends. .............................. .4 Comparison of Standard and Commercial Blends. ....... .6 Study of Additives ................................................. 7

Outreach .................................................................. 8 Costs, Benefits, and Concems .................................... .9

Capital Costs.. ...................................................... 9 Material Costs.. ................................................... 10 Comparison to Unfilled Polymers., ......................... 10 Comparison to Filled Polymers.. ............................ 10 Concems ............................................................ 10

Product Applications ............................................... 1 1 Automotive Applications ...................................... 1 1 Pallets and Other Shipping Applications.. ................ 12

Environmental Impact.. ............................................ 12 Conclusions.. ......................................................... 12 Future Work .......................................................... 12 Acknowledgments.. ................................................. 13 References.. ............................................................ 13 Appendix-Examples of WPF

Thermoplastic Composite Products.. ....................... 14

Processing .............................................................. .2

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l l /I II /I !! l l I/ ll ll ll

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7 Waste-Wood-Derived I

Fillers for Plastics 1

I

1 Brent English, Forest Products Technologist Craig M. Clemons, Chemical Engineer Nicole Stark, Chemical Engineer James P. Schnelder, Materials Scientist Forest Products Laboratory, Madison, Wisconsin

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’-1 In trod u ct i on This report represents the culmination of Project 94-55 for the Solid Waste Reduction and Recycling Demonstration Grant Program of the Wisconsin Department of Natural Resources. The project was conducted from July 1, 1994 through February 29,1996.

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Background Previous research at the Forest Products Laboratory (FPL) (Myers and Clemons 1993) and elsewhere had demonstrated the benefits of using waste-wood-paper-derived fillers (WPFs) in thermoplastics. For various reasons, however, the industrial thermoplastic composite industry had been reluc- tant to accept this technology. The manufacture of thermo- plastic composites is often a two-step process: compounding or blending of the raw materials, and formation of the com- posite blends into a product. Compounders were reluctant to produce thermoplastic blends with WPFs because they were not sure about how to handle the material and were not aware of a market to justi@ production of the blends. Product manufacturers, on the other hand, did not have access to a supply of compounded pellets for producing the end product and often were not aware of performance advantages and processing limitations of the material. Moreover, few suc- cessful demonstrations of this technology had been performed on conventional commercial-scale equipment.

In response to this situation, scientists at the FPL developed a unique program that would overcome some hurdles pre- venting commercial acceptance of technology for using W F s in thermoplastics. This program was completed with the cooperation of many industrial partners selected for their particular skills, interests, and abilities.

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Project Goals The overall goal was to generate sufficient commercial inter- est in WPF thermoplastics to allow large-scale commercial activity. As outlined in Figure 1, specific objectives were as follows:

1. Conduct research, development, and engineering efforts to

a. improve methods of preparing wastepaper fiber of needed quality, fiber length, and cost

b. select and develop compounding methods to optimize feeding, fiber length retention, and dispersion in the plastic

2. Communicate to end-product manufacturers the cost savings and product properties derived from using WPFs in plastic products

Selection of Materials Given the large number of processing technologies associated with thermoplastic composites, it was necessary to narrow the focus to the materials and processes with the best chance of success in light of the program objectives. For end-product manufacturing, both injection molding and extrusion tech- nologies were targeted. These are two of the four largest technologies for the production of plastic and thermoplastic composites. The others-blow molding and rotational mold- ing-are not appropriate for the materials used in this pro- gram. The study materials are described in general terms in this section; detailed information is provided in the section on composite performance.

Raw material preparation research

Identification of appropriate Process development materials and processing research technologies

Material Performance and additive development

Industrial trials of formulations

I

Objective 2 Outreach effort

Development of

for outreach effort + appropriate formulations

Information dissemination-sample

packets i

Industrial trials of formulations I

* Outcomes

Technology transfer Product identification

Commercial implementation Figure I-Research strategy.

Wood-Based Fibers The waste wood and paper fibers had previously been identi- fied for their potential as reinforcing fillers in thermoplastics. Wood flour is an economical, commercially available filler that has been used in thermoplastic composites to a limited extent. Fiber from old newspapers (ONP), another relatively inexpensive filler, has demonstrated improved performance as a reinforcing filler compared to wood flour because of its higher aspect ratio. We initially chose ONP fiber because it has a high percentage of high-yield mechanical pulps and hence short, stiff fibers. If these fibers acted as good reinforc- ing fibers, then other fibers with higher percentages of chemi- cal pulps and much longer fiber would be expected to per- form even better. In addition, ONP fiber was chosen because its fiber quality is more uniform than that of mixed waste- papers.

Plastics Polypropylene and high-density polyethylene (HDPE) were chosen as the matrix polymers. They are both widely used, are available at low cost, and have good performance for the intended applications. Their low melting points also allow processing below the degradation temperature of wood and paper.

A wide variety of polypropylene and HDPE polymers are available, and careful selection is important because extrusion

and injection molding require different material characteris- tics. For example, a critical need in injection molding is good flow of the material into the mold, whereas a critical need in extrusion is melt strength to enable handling of the hot material as it comes from the die. Choice of polymers for these technologies is therefore quite different. Injection mold- ing requires a polymer with a low molecular weight to main- tain low viscosity. By contrast, extrusion requires a polymer with a higher molecular weight for better melt strength.

Additives To lower raw material costs and thus the cost of the end products, additives such as impact modifiers and compatibi- lizers were not added to the formulations used for the out- reach portion of the project. However, ways to tailor perform- ance using additives are described in the section on composite performance. The cost increase incurred using additives may be justified when performance specifications for end products are identified.

Processing Research on processes included methods for feeding WPFs, configuration of compounding equipment, management of moisture, and determination of overall processing conditions. Care was taken to maintain quality of fillers while maximiz- ing filler dispersion, distribution, and extruder throughput.

1 1

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11 l l II ll I/ l l ll ll ll I1 I/ n

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Waste wood or paper fiber Water vapor

1 I Water vapor

t I

Preblending Compounding Pelletizing b Pelletized feedstock

0 Polymer

Figure 2 4 P L compounding line.

The FPL compounding line is shown schematically in Figure 2.

Preparation and Feeding of Fillers Conventional plastics equipment is designed to handle materials with a bulk density of approximately 500 kg/m3 (3 1 Ib/ft3). Although somewhat lower bulk densities can be handled, material with very low density is difficult to feed, requires specialized equipment, and can reduce processing rates. Because WPFs have lower bulk densities than do thermoplastics, their preparation can be a critical step in the compounding process.

No research on raw material preparation was necessary for wood flour. This material is commercially available and has a bulk density of around 112-240 kg/m3 (7-15 lb/ft3). Al- though lower in bulk density than thermoplastics, wood flour is sufficiently dense to be readily fed and dispersed. The feeding and dispersion of ONP fiber, however, required con- siderable investigation. Three different forms of ONP fiber were investigated: hammermilled newspaper fiber, crumble pulp, and Szego-milled fiber.

Hammermilled fiber is currently the least expensive dry form of newspaper fiber, and considerable fiber length is main- tained during the milling process. This fiber has an ex- tremely low bulk density (16-32 kg/m3 (1-2 lb/ft3)) and is available through a number of insulation manufacturers. Crumble pulp is made by densiQing and briquetting damp hammermilled paper and then crumbling the resulting dried briquettes into coarse paper pellets. It has a bulk density of around 192 kg/m3 (12 lb/ft3) and is available commercially in the form of bagged absorbent products. Szego-milled paper is paper that has been cut into platelets in a Szego mill. The platelets that we used were about 40 mesh in size, had a

consistency and texture not unlike graphite, and had a bulk density of around 224 kg/m3 (14 lb/ft3). This material is currently available only on special order.

Although hammermilled paper is inexpensive and compos- ites made from it perform well, the low bulk density makes it difficult to feed without specialized crammer-type feeders. Budgetary constraints limited us to noncrammer-type feeders. We used both an Acrison (Moonachie, NJ) Model 75-E volumetric feeder and an AccuRate (Whitewater, WI) Model 8000 loss-in-weight feeder. Both of these feeders were very effective for processing wood flour, crumble pulp, and Szego- milled paper.

Unfortunately, the high density of the individual paper pel- lets that formed the crumble did not readily break apart and disperse in the plastic. Research is being conducted on a crumble pulp compacted to a lower initial density and on a crumble pulp containing waxes as a dispersion aid; signifi- cant progress is being made in this area. Because Szego- milled fiber could be fed and dispersed easily and because composites made with it performed at least as well as those made with wood flour, the Szego-milled fiber was chosen for the bulk of the research.

Compounding Equipment The development of compounding technology, evaluation of feeding of raw materials, and manipulation of formulations required the construction of a small-scale industrial com- pounding line on site. A search was initiated for a com- pounding line that used conventional technology and was cost-effective and flexible. Based on the results of this search and previous experience with different compounders, coopera- tor input, budgetary considerations, and plant trials, we decided that a twin-screw extruder would be most beneficial to the program.

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Processing Conditions The compounding pf WPF with thermoplastics is also limited by the thermal degradation temperature of the wood or paper fiber. Typically, melt temperatures (temperature of molten material) were kept below 204°C(4000F). Above this limit, signs of degradation (smoke, odor. discoloration) were readily apparent with ONP thermoplastics. Strand quality from the extruder rapidly decreased with attempts to raise this limit by as little as 1’ or 2’.

Figure 34ompounding and pelletizing equipment at FPL.

A leasing agreement was arranged with the Davis Standard Corporation (Pawcutuck, CT), and a twin-screw extruder manufactured by them was installed at FPL (Fig. 3). The extruder has 32-mm (1.26411.) co-rotating, intermeshing segmented screws with a length-to-diameter ratio of 32: 1. There are eight electrically heated, water-cooled barrel sec- tions, two of which have vents for removing volatile materi- als. Power is supplied by a 15-hp DC drive, and a four-hole strand die is fitted to the discharge end. The machine’s capacity is 45 kg ( I 00 Ib) of unfilled polypropylene per hour.

To cool the compounded strands discharged by the extruder, FPL staff constructed a waterslide cooling trough similar to that manufactured by Conair Jetro (Franklin, PA). After cooling, the strands were fed into an older model Cumber- land (Providence, RI) pelletizer for cutting into pellets.

Moist u re Ma nag em en t Processes for manufacturing plastics tolerate little or no water. Removal of moisture is critical because any moisture remaining in the WPF-plastic blend tums to steam and manifests itself in the form of foam. This can disrupt proc- esses and lead to unacceptable finished parts.

During compounding, moisture was managed by a combina- tion of predrying the fibers from their ambient moisture content of 6-8 percent to 2-3 percent; vacuum was then applied to the vent zones in the extruder barrel during com- pounding to remove the remaining moisture. Properly done, pelletized feedstock with a moisture content of < 0.1 percent could be manufactured. At that level, the pellets were ready for injection molding or extrusion in unvented conventional systems. Using hot, predried wood and paper fiber also tended to increase throughput.

Wood-flour-filled strands were somewhat more forgiving. At 204OC (400°F), some discoloration was apparent, indicating some degradation, but strand quality was still sufficient for pelletization. At around 2 1 O°C (4 1 OOF), smoke and exces- sive odor were apparent, and strand quality began to rapidly deteriorate.

In general, we found that polyethylene-based formulations could be successfully compounded at 182OC (360’F) or less, whereas polypropylene-based formulations seemed to work well at around 193°C (380OF). These temperatures were typically used regardless of the type of WPF selected.

Several variables could be adjusted to keep melt temperatures at these levels. First, as mentioned previously, one reason for selecting polyethylene and polypropylene was their low melt temperatures and their ability to be effective in these tempera- ture ranges. Two other variables were similarly connected: the intensity and speed (r/min) of the screws.

In general terms, the more mixing elements in the screw configuration, the more intense the mixing action of the fibers into the plastic matrix. This extra mixing increases the mechanical work imparted to the material, thus increasing melt temperature. Screw speed has a similar effect: the higher the rotationdminute, the more mechanical energy imparted, and thus the higher melt temperatures.

We found that a fairly low number of mixing elements was sufficient for satisfactory compounding with wood flour and Szego-milled ONP fiber. Screw speed could also be kept reasonably moderate, at around 240 r/min. Under these conditions, compounded material was routinely produced at 75-1 00 percent of rated machine capacity.

Composite Performance Performance of Standard Blends In support of the objectives of the outreach portion of the project, eight “standard” blends were compounded (Table 1). Melt flow indices are summarized in Table 2. These blends were formulated with ease of processing by the end user as the primary criterion. Since it was likely that many different

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Table I-Mechanical properties of standard blends'

Tensile Tensile Tensile Flexural Flexural Notched Unnotched strengthb modulus elongation strengthb modulus lzod lZOd

Blend (MPa) (GPa) (%I (MPa) P a ) (JW ( J m

PP-w-x

PE-W-X

PP-WF-1

PE-WF-I

PPSZ-x

PE-SZ-X

PP-sz-1

PE-SZ-1

29.7 10.31

[o .31

l0.51

19.7

27.0

18.7 [0.21]

29.2 [0.31]

23.4 [O. 31

26.3 [0.06]

18.7 [0.21

4.10 [0.23]

2.69 [0.09]

2.92 [O. 141

2.43 [0.09]

4.34 [0.21]

[O. 1 I] 3.27

3.28 [0.09]

2.21 P.11

58.6 (0.41

10.71

~.31

w.51

[0.51

l0.41

w.31

[0.51

35.8

51.9

32.4

57.2

40.2

51.1

32.4

4.06 [0.13]

2.43 [O. 131

3.07 [0.06]

2.13 [0.14]

4.24 [O. IO]

2.88 [O. 151

3.41 [O. 1 I]

2.13 [O. 131

20.8 105 [0.91] [Ill

v.91 161

16.2 109

26.7 66

[0.63] [91

[0.45] [41

10.911 [71

[0.74] 131

[0.67] (71

[0.78] 131

17.8 52

19.1 103

22.2 65

14.2 89

14.7 53

'Bracketed numbers are standard deviations. PP is polypropylene; PE, high-density polyethylene: WF, wood flour; SZ, Szego-milled newspaper; X, extrusion grade; and I, injection molding grade.

bMaximum values.

Table 2-Melt flow indices (MFls)'

Polymer Polymer Composite Filler Filler MFI at MFI at MFI at

Blend (%I tY Pe 230°C 190°C 190°C

PP-WF-x

PE-WF-X

PP-WF-I

PE-WF-I

PP-SZ-x PESZ-X

PP-sz-I

PE-SZ-I

40 WF

40 WF

30 WF

30 WF

40 sz 40 SZ

30 sz 30 SZ

4

- 35 - 4

- 35

2 0.4 4 0.7 18 4.2 44 8.8 2 0.3 4 0.3 18 2.0 44 5.4

'See footnote to Table 1 for definitions of terms. Unit of measurement for MFls is gramsll0 min. f°F = 1.8 foc + 32.

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products with different performance requirements would be molded or extruded, we recognized at the outset that the standard blends would not represent an optimal formula- tion. Optimization of formulations for a given product is an iterative process involving the specific product, product manufacturer, and compounder, and, as such, lay outside the scope of this project. The work on standard formula- tions promised to fulfill the requirements of the outreach portion of the project in that such formulations would allow processors some initial hands-on experience with the proc- essing of this class of materials and a rough idea of perform- ance.

Polymers The polypropylenes for the extrusion and injection molding grades were Fortilene 9200 and Fortilene 3907 ho- mopolymers, melt flow 4 and 36.5 g/10 min, respectively (Solvay Polymers, Inc., Deer Park, TX). The high-density polyethylenes for extrusion and injection molding grades were LS 6402-00 and LS 3420-00 polyethylene copoly- mers, melt flow 4.2 and 44 g/10 min, respectively (Quantum Chemical Corporation, Cincinnati, OH).

Fillers The wood flour was a standard 80-mesh pine (#8020) from American Wood Fibers (Schofield, WI). When appropriate, a standard 40-mesh pine (#4020) was also used. The ONP fiber selected for the outreach portion of the project was Szego-milled paper (American Wood Fibers) because of our early success with handling and processing this material. The newspaper was milled at General Communition, Inc. (Toronto, Ontario) to a -40 mesh.

The materials were premixed and compounded in a twin- screw extruder as described in the section on processing. ASTM standard test specimens for mechanical testing were molded at 190'C (374'F) in a 33-t reciprocating screw injection molder (Cincinnati Milacron, Batavia, OH). Izod impact, flexural, and tensile properties were then measured according to ASTM D 256, D 790, and D 638, respec- tively (ASTM 1990a-c). As a rough measure of viscosity, the melt flow indices (MFIs) of the blends were measured at 19OOC (374'F) and 2.16 kg (4.76 lb) plunger weight.

Melt Flow Indices The addition of filledreinforcements to thermoplastics can greatly reduce the flow properties of a polymer. This reduc- tion in flow properties becomes especially important in highly filled blends. To provide processors with blends with appropriate flow properties for the processes, targets for MFIs for the injection molding and extrusion grades were identified.

Targets for MFIs of the composite formulations were 4-10 g/10 min for injection molding grades and fiactional

(< 1 g/10 min) for extrusion grades. As a general rule, WPF-thermoplastic blends are kept below 204OC (400'F) during processing to prevent degradation. Because of the low processing temperatures, MFI was measured at 190'C (37OF). This is particularly important to consider with the polypropylene blends since the MFI of polypropylene is usually measured at 23OOC (446'F). This difference in temperature has a significant effect on the MFI.

These temperature and filler effects must be taken into account when choosing an appropriate polymer for a par- ticular application. Consequently, high MFI (low viscos- ity) base polymers were chosen as a starting point for the injection molding grades. The MFIs of the base polymers and standard blends are shown in Table 2. All of the tar- geted MFIs were obtained except for the injection molding grade of polypropylene that contained ONP, which was a little low. The HDPE blends had higher MFIs than the polypropylene blends, which was not surprising consider- ing that the base resins had lower MFIs when measured at 190 "C (374 OF). Wood-flour-filled blends had higher MFIs than did blends containing ONP fibers.

Mechanical Properties The mechanical property data are summarized in Table 3. For most properties, the polypropylene blends performed better than the HDPE blends, undoubtedly because of the relative performance of the base polymers. Extrusion-grade blends performed better than injection molding grades. This was not surprising considering that the extrusion grades contained higher molecular weight polymers with better mechanical performance. Few differences were seen between the wood flour and Szego-milled blends. These results contradict those of previous studies in which ONP fibers performed better than wood flour as a reinforcement in polypropylene (Myers and others 1992, Gonzales and others 1992). This reduction in ONP fiber performance as a reinforcement can be attributed to the reduction of fiber length in the Szego mill. Work on ONP preparation methods is in progress.

Comparison of Standard and Commercial Blends Although a large body of literature is available on the properties of thermoplastics filled with minerals, no direct comparisons could be found to WPF thermoplastics. The project study plan did not include the comparison of stan- dard and commercial blends. The comparison of various reported data is inconclusive because the polymers selected for study significantly affect performance. Comparison of the extrusion-grade and injection molding polypropylenes will show how properties can vary in apparently similar ho- mopolymers fiom the same manufacturer. (See section on future work.)

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Table 3-MechanicaI properties of additives' Additive Tensile Tensile Tensile Flexural Flexural Notched Unnotched

Additive amount strengthb modulus elonga- strengthb modulus lzod lzod Blend type (%I (MPa) (GPa) tion (%) (MPa) (GPa) ( J W (JW PP-w-x -

Nucleating agent

EPDMI

EPDM2

MAPP

PP-SZ-x -

Nucleating agent

EPDMl

EPDM2

MAPP

0.15

5.5

5.5

1.8

-

0.15

5.5

5.5

1.8

3.93 [0.26]

4.02 [0.07]

3.53 (0.1 I]

3.62 [0.24]

4.17 (0.341

5.41 [0.58]

4.96 [0.35]

4.27 [0.47]

4.48 [O. 121

5.59 [o .71

3.86 (0.1 I]

3.79 [ O . l l ]

3.20 [0.08]

3.54 [0.09]

3.86 [0.10]

[ O . l l ]

[0.02]

4.36

3.65

2.94 [0.05]

3.26 (0.151

4.12 (0.201

19.3 (4.71

18.8 (1.41

10.41

w.31

10.91

22.5

21.6

16.9

17.6 [0.81

16.7 (0.41

27.1 (2.01

22.3 (0.61

(0. 61 16.8

a4 I1 21

94 171

1141 123

96 (81

95 (61

89 [71

109 [161

163 (241

142 11 61

142

'Additives were added as part of polymer content. Bracketed numbers are standard deviations. bStrength at yield.

Study of Additives A brief study on additives was undertaken to demonstrate how some common additives can be used to tailor mechani- cal properties of composite blends. The purpose of this investigation was not to recommend an optimized formula- tion but to demonstrate how manipulation of the formulation can lead to better balances of properties. Specific parts with specific mechanical requirements would have to be identified to justify the use of these additives; otherwise, even small additional costs would be prohibitive. The additives and their level of addition are somewhat arbitrary without a mechanical property target; they were chosen at supplier- recommended levels or were based on previous experience, with a concem for cost. The extrusion grade of polypropylene was used for all blends (Fortilene 9200, Solvay Polymers, Deer Park, TX). The additives used in the investigation were a coupling agent, impact modifiers, and a nucleating agent.

Coupling Agent Hydrophilic WPFs are not chemically compatible with the hydrophobic polypropylene polymers. To improve bonding between the two components, a maleated (MA) poly-

,propylene was added as a coupling agent (MP 880, Aristech Chemical Corporation, Pittsburgh, PA). In previous investi- gations (Sanadi and others 1994), the addition of a similar MA polypropylene G-3002 (Eastman Chemical Products, Inc., Kingsport, TN), which has a relatively high molecular weight and acid number, to these types of composites mark- edly improved performance.

Impact Modifiers Elastomers or rubbers are often added to filled and unfilled thermoplastics to improve impact performance. At low lev- els, these modifiers often form a separate phase in the poly- mer matrix. Applied stresses can be transferred to the softer elastomeric phase rather than accumulate in unfavorable locations, which may lead to failure. Ethylene-propylene- diene copolymers (EPDMs) are commonly added to poly- propylenes as impact modifiers. Several EPDMs have also been chemically modified to improve compatibility of the WPF with polypropylene. Two EPDMs were used in this study-Fusabond 227D and Fusabond 280D, both fiom Dupont Canada, Inc. (Mississauga, Ontario); they are referred to as EPDMl and EPDM2, respectively.

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Nucleating Agent Nucleating agents can be added to a formulation to affect the crystal growth of the polymer during cooling. By affecting the crystal structure, these nucleating agents can improve such properties as transparency and stiflhess. The effect of Millad 3988 (Milliken Chemical Company, Inc., Spartan- burg, SC) on mechanical properties was investigated.

Summary of Additives Study The materials were blended in a I-L (1.06-quart) thermoki- netic mixer (K mixer, Synergistics Industries Inc., St. Remi de Napierville, Quebec). The thermokinetic mixer, a high- intensity batch mixer, was used because of its ability to handle formulation changes quickly and to accurately control the small additive concentrations. The blends were then injection molded and tested in the same manner as were the standard blends.

Table 3 summarizes the results of the study on additives; Table 4 shows the increases in property values of blends with additives compared to baseline blends. The nucleating agent had very little effect, if any, on the mechanical proper- ties of the composite blends, despite its reported effectiveness in unfilled polypropylenes (Giichter and Muller 1990). One possible explanation is that the WPFs themselves act as nucleating sites for the polypropylene and, therefore, addition of a nucleating agent does not have a great effect on crystal- line development. The effects of cellulose fibers on crystalli- zation of polypropylene were reported by Quillen and others (1993).

The EPDM effects on mechanical properties of the WPF- filled polypropylenes were typical of elastomer-modified composite blends. The tradeoff between increases in impact performance and decreases in moduli with addition of elas- tomer has been well documented. Impact performance of these ternary composites is affected by many factors, includ- ing weight fraction of the components, EPDM type (e.g., EPDMs with different ethylene/propylene ratios, chemically modified EPDMs), processing parameters (e.g., intensity), and polymer matrix properties (e.g., viscosity, compatibility with fillers or EPDM). Manipulation of these variables will depend on considerations related to finished parts, processes, and cost.

The effects of addition of MA polypropylene on composite performance were similar to those found in previous studies (Sanadi and others 1994). Improved bonding of the WPF component resulted in improved tensile/flexural and un- notched Izod impact strengths. Better transfer of applied stresses because of better bonding allows higher stresses to be reached (higher strength properties) and makes it more difficult for cracks to be initiated at stress concentrations such as fiber ends (higher unnotched impact strength). Since the initial modulus of the composites is a result of the moduli of

Table &Effects of various additives on mechanical properties of 4-MFl polypropylene with 40% filler

Change (%) compared to base blenda

Tensile Flexural Notched Unnotched Additive strength modulus lzod lzod

Nucleating LTP LTP LTP 18 agent, 0.15%

EPDMl. 5.5% LTP -25 35 65

EPDM2, 5.5% LTP -1 7 20 37

MAPP, 1.8% 27 LTP LTP 37

I ‘Average value of both fillers. LTP refers to e1 0% property change.

the components, not the bonding between them, flexural and tensile moduli are not affected.

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Outreach An information packet (Fig. 4) containing general informa- tion on the material, performance data, appropriate processing conditions, sample pellets, sample extruded and injection molded parts, and a questionnaire was sent to nearly 500 commercial plastic product manufacturers in Wisconsin, Illinois, and Michigan. Response rate to the questionnaire exceeded 16 percent; half the respondents requested materials for in-plant evaluation.

The outreach effort was part of the informational activities prescribed by the Wisconsin Department of Natural Re- sources for this project. Other informational activities have included the wide distribution of this report to the general public as well as presentations at conferences and technical workshops, the first for the “Progress in Wood Fibre- Plastics Conference” in Toronto, Canada, on April 29, 1996.

Manufacturers who had submitted favorable responses to the questionnaire were contacted for trials at their manufacturing facility. A total of 18 site visits were conducted; scientists from FPL ensured proper handling of material and gathered information from the manufacturers on processability, per- formance, and potential end-uses.

The FPL supplied between 20 and 200 kg (44 and 440 Ib) of pelletized material for each trial (Fig. 5) . Material was always redried before the trial to remove any moisture absorbed by the pellets. All the trials were conducted at injection mold- ing facilities; a straight 193OC (380OF) temperature profile was used for polypropylene formulations and a straight 182°C (360°F) temperature profile for HDPE formulations.

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Figure 4-WOOD-COM marketing and information package.

Table !+Estimated capital costs of 4 million kglyr (9 million Iblyr) wastepaper fiber-reinforced thermo- plastic compounding facility

Item c o s t

2 acre lot, 6,000 ft2 building, $ 240,000

Handling and drying of WPF 150,000

Compounding system (extruder, 600,000

Handling and packaging of 80,000

Total $1,070,000

office furnishingsa

feeders, pelletizer)

finished materials

al acre = 4.046 x I O 3 m2. 1 ft2 = 0.0929 m2.

Figure &Examples of pelletized thermoplastic feedstock (left to right): virgin unfilled feedstock, feedstock reinforced with waste wood fiber, feedstock reinforced with waste newspaper (ONP) fiber.

Mold temperature varied between 15OC and 55OC (60’F and 1 3 0 O F ) . Injection pressures and times were usually reduced for the wood-flour-filled formulations and occasionally re- duced for the ONP-filled formulations. All other conditions were also well within normal operating range.

All manufacturers were impressed with the moldability of the formulations, and parts were successfully made at all trials. Depending upon the type of processing, the part being made, and the material currently being used, the use of WPF ther- moplastics resulted in shorter cycle times, superior perform- ance or appearance, or environmental benefits.

A producer of cosmetics cases liked the natural appearance of cases molded with wood-filled polypropylene. A manufac- turer of home repair tools thought the recycled content af- forded by WPF would give his products a market edge in the “green” products section of some major home repair supply stores. Several manufacturers stated that the reduced cycle times will significantly increase profits and make them more competitive. Automotive suppliers envisioned the WPF- thermoplastics as being able to replace higher cost resins

following section.

Costs, Benefits, and Concerns Successful adoption of WPF thermoplastics by the conven- tional plastics industry will depend upon costs and real and/or perceived benefits. Several resolvable concerns also need to be addressed.

Capital Costs A 4 million kgiyr (9 million Ibiyr) facility has been sug- gested as the minimum size for a successful commercial compounding venture. Such a facility would employ 13 persons: 8 production workers, 1 production supervisor, 1 engineer, 1 salesperson, 1 clerical worker, and 1 general manager. Total sales would be approximately $4-$5 mil- lion, based on the assumptions described in this section. At 45 million kg/yr (100 million Ib/yr), total employment would probably approach 100, with total sales of $50-$60 million. The estimated capital costs of a 4 million kg/yr (9 million Ib/yr) facility are shown in Table 5.

Additional employment and economic activity would be created in the existing wastepaper recovery and processing infrastructure, and through product changes.

1 9

Material Costs To fully discuss the cost benefits of WPF thermoplastics, several assumptions will need to be made. For this discus- sion, we will assume a cost of $0.50/lb for thermoplastic polymer and $0.1 O/lb for prepared (hammermilled) wastepa- per fiber.' We will also assume that compounding can be profitably conducted at $0.20/lb at maximum throughput. This figure is derived from the capital cost, operating cost, assumed 80-percent operating time, and requisite return on investment. Based on these assumptions, the cost per pound of precompounded pelletized feedstock can be determined using the following formula:

t p(0.50) + f(O.10) + 0.20 e

$x/lb =

where p = polymer weight (percent) f = filler weight (percent) e = throughput efficiency at assumed

80-percent operating time

As an example, a 50150 formulation compounded at 100 percent efficiency would have a price of

(0.50)(0.50) -t (0.50)(0.10) + 20 1 .oo $x/lb = ' = 0.50

This scenario was selected as an example because the cost of the compounded feedstock equals that of the virgin resin. As the formula indicates, increasing the filler content decreases cost; either increasing the polynier content or decreasing the efficiency increases cost.

In general, most manufacturers contacted during the indus- trial trials thought that the costs were reasonable. Most manufacturers lowered their operating temperature when molding the materials, resulting in significant energy sav- ings. Some manufacturers did not routinely process filled materials, while others did. Because filled and unfilled ther- moplastics have different purposes and uses, comparisons to WPF thermoplastics are discussed separately in the follow- ing sections.

Comparison to Unfilled Polymers One obvious justification for using WPFs is improved performance. From a product standpoint, the improvements may allow the user to manufacture products in a higher performance category, to reduce overall material use through better engineering, and to increase the life of the product. Some users contacted in the technology transfer activity also

anticipated replacing higher priced, higher performing resins like ABS, which currently costs about $l.OO/lb.

A less obvious advantage, but one with great significance, is reduced cycle time. During the technology transfer stage of the research, most users of unfilled thermoplastic were able to reduce product cycle times, some in excess of 25 percent. The resultant savings far outweighed a 5- to 10-percent cost premium. Cycles can be reduced because WPF can be used to displace a considerable volume of polymer, thereby reduc- ing the amount of polymer to be chilled to solid form. In addition, and perhaps more important, the WPF helps to dimensionally stabilize the part at elevated temperatures, allowing it to be removed from the mold at a higher tempera- ture without fear of distortion.

Comparison to Filled Polymers One the greatest benefits of using WPFs as opposed to inor- ganic materials is weight savings. Fiberglass has a specific gravity of 2.5; talc or calcium carbonate, around 2.8. When used as a reinforcing filler, WPF has a maximum specific gravity of about 1.4. Equal volume loadings will result in a molded part that weighs less, which means the user will be able to buy less material to mold the same part (Fig. 6). This is particularly important in large volume applications where even minute weight reductions in parts provide huge cumulative savings.

The lower specific gravity of WPFs also means that on a weight basis, they will displace roughly twice the volume of polymer as will an inorganic filler (Fig. 7). Therefore, higher loadings are possible without weight gain. These savings in weight also allow many wastepaper fiber formulations to be made with a higher specific stifhess than are formulations using minerals; that is, they are stiffer on a weight com- parison basis.

For some users contacted in the technology transfer activi- ties, cycle time was reduced compared to the time required for filled resins, particularly polypropylene filled with talc and calcium carbonate. This was probably due to the higher polymer displacement afforded by the WPF formulations. Anecdotal information also indicated that WPF is less abra- sive to processing equipment than are inorganic fillers, par- ticularly fiberglass.

Concerns The greatest concem raised by manufacturers involved the rate of moisture uptake by the dried feedstock. As mentioned previously, for most applications >O. 1 percent moisture content resulted in foaming. Articles made of WPF plastic have an equilibrium moisture content of 1 to 2 weight per- cent. Pelletized feedstock is no exception, which means that

' 1 lb = 0.454 kg.

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1.0r a Waste wood fiber filled 0 Inorganic filled

10 20 30 40 50 Filler level (%)

Figure "Relative volumes of thermoplastic composites reinforced with inorganic fillers compared to WPF-reinforced composites.

Waste wood fiber filled 0 Inorganic filled

2.5

n

0 10 20 30 40 50 100 Filler level (%)

Figure 'I-Specific gravity of thermoplastic composites reinforced with inorganic fillers compared to WPR-reinforced composites.

4.5 '"1 n . 6 0 % P P l 4 O % W F a t 6 5 % R ~ 60% PP 140% ONP at 65% RH

3.5

A 60% PP140% ONP at 90% RH A 60%PPl4O%WFat90%RH

0 60% PP 140% ONP at 30% RH WO PP 140% WF at 30% RH

3.0 8 a 2.5 d

E .- V 1.5

1 .o

0.5

h

Y

-Y

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P 3

0 2 4 6 8 1012 14 16 18 20 22 24 262830 Days

Figure &Moisture uptake of ovendried polypropy- lene (PP) pellets reinforced with wood flour (WF) or newspaper (ONP) fiber at various humidities.

dried feedstock will have a working life before it needs to be redried.

The length of the working life depends on several factors, including relative humidity, filler content, and storage tech- niques. To better determine the working life of the feedstock, several formulations were oven dried and placed in various temperature- and humidity-controlled rooms at FPL. Rates of moisture uptake are shown in Figure 8.

Another concem was shrinkage rates. Plastic shrinks as it solidifies; in response, molds are made oversize by a

prescribed amount. The thermal coefficient of expansion of most plastics is 250 to 400 times greater than that of wood. Therefore, plastics filled with WPF do not shrink as much as their unfilled counterparts, and they are thus somewhat larger than those made in the same molds fiom unfilled material. For parts that are not components of an assembly, this is not much of a problem. For parts that are components of an assembly, either the mold or the mating parts may need to be modified. The problem may not occur with molding equipment designed for filled materials because shrinkage rates are already reduced. Filler content can also be manipu- lated to give equivalent shrinkage rates. Of course, physical and mechanical properties will change correspondingly.

Product Applications A list of all applications for this class of materials is beyond the scope of this report. The following description of two product areas may provide some indications of usage.

Automotive Applications Recycling is a high priority research area for the automotive industry. The motivation for this is twofold: one from customer demand, the other from existing and anticipated government mandates. Thermoplastics reinforced with postconsumer wastepaper fibers are very attractive for these reasons. However, the adoption of W F thermoplastics for automotive applications may rest on cost and performance. The automotive industry uses much ABS; for nonimpact sensitive applications, filled polypropylenes can offer per- formance similar to that of ABS for reduced cost. Parts made

11

using WPF-filled polypropylene also weigh less than those made with mineral fillers, and weight savings economize fuel expenditure.

Pallets and Other Shipping Applications Another potential high volume use of WPF thermoplastics is for pallets and other related shipping containers. Plastic pallets and other retumable plastic containers have already made significant in-roads to this huge market, which has traditionally been dominated by wood pallets and containers. As an example, the Postal Service purchases 2.5 million plastic pallets each year. For many applications, however, plastic pallets do not perform as well as wood pallets. Typi- cally, plastic pallets suffer fiom a lack of stiffness. Perform- ance is enhanced by using thick plastic components or fiber- glasdmetal reinforcement. The added weight cantributes to both the purchase price and the shipping costs, which are incurred every time the product is used. Using WPF as a reinforcing filler can significantly improve performance with- out significantly adding weight.

Environmental Impact Reasons for using WPF thermoplastics extend beyond per- formance and cost advantages to far-reaching environmental impact.

The technology described here provides a high volume outlet for both postindustrial and postconsumer waste wood and paper fibers. From the paper perspective, the fibers do not require the cleaning methods needed for paper-to-paper recy- cling. No sludge is produced, no waste water needs to be treated, and there is no need for deinking. Although most of our research has focused on old newspapers, many other grades of paper, like mixed office waste and bulk mailings, could also be used.

Because of the thermoplastic component, the composite material itself is recyclable, and previous research has shown that recycling can be accomplished with little loss in per- formance (Youngquist and others 1993). Recycled plastics can also be used in these systems, diverting this valuable material from landfills.

The products made from these materials will often have long life cycles. Life expectancy for most automobiles exceeds 10 years, and automobile recycling technology is among the most advanced. Plastic pallet manufacturers also recycle their products. In fact, the buy-back of damaged plastic pallets for raw materials is one of their major selling points.

Recycling is not a fad, nor is the use of WPF as a reinforcing filler in thermoplastics. The WPF thermoplastics will help make automobiles lighter and more fuel-efficient, increase the shipping efficiency of a wide class of goods, and reduce the

demand on landfills. These materials use a renewable resource to extend the life of a nonrenewable one, and in so doing, retain their recyclability.

Conclusions The overall goal of the project has been met. At the time of this writing, one cooperator is undertaking tasks to establish 'a commercial facility of the scale described in this report. Customers identified during the outreach phase of the project will form the basis for this commercial endeavor.

Both study objectives have been met. Quality feedstocks can be produced using the guidelines described in this report. The plastics industry is receptive to pelletized feedstocks reinforced with fillers derived from waste wood and paper fiber. Users of unfilled plastics have found the feedstocks attractive for their combination of high performance and low cost, as well as reduced molding cycle times. Users of filled resins have found similar advantages, as well as weight savings. No advantages on a strict cost-only basis have been identified.

The formulations developed for the outreach effort were gen- eral purpose ones. While all manufacturers who tried the formulations were able to mold parts successfully, each application would benefit from a more tailor-made formula- tion. Research presented in this document shows how per- formance can be tailored, and continued work by the FPL will address that issue and others related to material science.

Future Work Future work concerns both old and new problems. An old problem remains: feeding low-bulk density, fiberized waste- paper into an extruder, while making good use of the fibers present. Ongoing work at FPL is directed toward examining medium-density crumble pulp with a preapplied wax disper- sant. Researchers will also examine several grades of Szego- milled paper to determine which size yields the best perform- ance.

New problems include development of formulations for specific end-uses. This work will include various recycled fiber types, virgin and recycled plastics, homopolymers and copolymers, and additives. A formal study has also been initiated to make a direct comparison of WPF and mineral fillers. This new project will use the injection molding grade polypropylene used in the work reported here. The materials will be compared on the basis of equal weights and volumes of filler.

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1 Acknowledgments The success of a large project like this does not happen without the efforts of many people. We thank the following industha1 cooperators (in alphabetical order): Chris Anderson and Mike Ford, Badger USA, for development of the mailing list, help with the marketing packet, and assistance during plant trials; Mark Berger and Tom Forcey, American Wood Fibers, for prompt deliveries of wood flour and Szego-milled paper as well as technical assistance; Mark Billian and Mike Dahl, Eaglebrook Products, for allowing us to conduct trials and for loan of the Cumberland pelletizer; Jim Giatras, Be- mis Manufacturing, for allowing us to conduct plant trials and for valuable insight about the possibilities of wood fiber- plastic composites; Kevin Gohr, Sheboygan Substrates, for consultation, valuable contacts, and loan of the Acrison feeder; Bemie Kieman and Mark Lindenfelder, Davis Stan- dard Corporation, for lease of the extruder, excellent startup service, and continuing technical advice; Mike Killough, Solvay Polymers, for generous donations of polypropylene, guidance, and advice; Paul Koch, Penn State-Erie, for sample production and insight; Dennis Kopcha, Perm Pro Manufac- turing, for backup supply of crumble pulp; John Kraus, Lamico, for being an early supporter and helping with appli- cations; Terry Laver, Strandex, for allowing us to conduct trials and for technical assistance; Milt Risgaard and his entire staff at Tee1 Plastics, for continuing support, assis- tance, and willingness to try new things; George Tedder, Conair Reclaim Technologies, for arranging trials; and Jim Van Hulle, Quantum Chemical Co., for timely donations of HDPE, advice, and guidance.

A complete listing of all the FPL staff who contributed to the project would be quite lengthy, but we would like to single out several people. In no particular order, we would like to thank Jerry Saeman and George Myers (both retired) for their pioneering promotion and research that led to this project; John Youngquist for excellent facilitation; John Bachhuber and Pat Brumm for negotiating contracts and shortening red tape; and finally, Gary Lichtenberg and his entire mainte- nance staff for prompt and excellent service.

References ASTM. 1990a. Standard test method for impact resistance of plastics and electrical insulating materials. ASTM D 256, Annual book of ASTM Standards, Vol. 08. Philadelphia, PA: American Society for Testing and Materials.

ASTM. 1990b. Standard test method for flexural properties of reinforced and weinforced plastics and electrical insulat- k g materials. ASTM D 790, Annual book of ASTM Standards, Vol. 08. Philadelphia, PA: American Society for Testing and Materials.

ASTM. 1990c. Standard test method for tensile properties of plastics. ASTM D 638, Annual book of ASTM Standards, Vol. 08. Philadelphia, PA: American Society for Testing and Materials.

Giichter, R; Muller, H. (eds.). 1990. Plastics additives handbook-Stabilizers, processing aids, plasticizers, fillers, reinforcements, colorants for thermoplastics. 3d ed. Munich; Vienna; New York: Hanser Publishers.

Gonzates, C.; Clemons, C.M.; Myers, G.E. 1992. Effects of several ingredient variables on mechanical properties of wood fiber-polyolefm composites blended in a K mixer. In: Proceedings of the Materials Research Society; 1992 April; San Francisco, CA.

Myers, G.E.; Clemons, C.M. 1993. Wastepaper fiber in plastic composites made by melt-blending: Demonstration of commercial feasibility. Final report for solid waste reduction and recycling demonstration grant program, project 9 1-5, FPL Agreement FP-91-1572, Wisconsin Department of Natural Resources. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory.

Myers, G.E.; Clemons, C.M.; Balatinecz, J.J.; Wood- hams, R.T. 1992. Effects of composition and polypropylene melt flow on polypropylene-waste newspaper composites. In: Proceedings, Antec ‘92; 1992 May 3-7. Detroit, MI: Society of Plastic Engineers.

Quillen, Daniel; Caulfield, Daniel F.; Koutsky, James A. 1993. Crystallinity in the polypropylene/cellulose system.-I. Nucleation and crystalline morphology. Journal of Applied Polymer Science. 50: 1 187-1 194.

Sanadi, A.R.; Clemons, C.M; Rowell, R.; Young, R.A. 1994. Recycled newspaper fibers as reinforcing fillers in thermoplastics. Part I. Analysis of tensile and impact proper- ties in polypropylene. Journal of Reinforced Plastics and Composites. 13: 54-67.

Youngquist, J.A.; Myers, G.E.; Muehl, J.H.; Krzysik, A.M.; Clemons, C.M. 1993. Composites from recycled wood and plastics. Final rep. for U.S. Environmental Protec- tion Agency, project IAG DDW 12934608-2. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory.

13

Appendix-Examples of WPF Thermoplastic Composite Products

Vacuum cleaner beater bars and battery terminal covers (wood flourlpolypropylene).

Lawn tractor seat trim piece and castors (wood flourlpoly propy lene).

.. , I _ ’ . . ’,, . .

Grill piece for Marda (newspaperlpolypropylene).

14

Brackets for curtain valance (colored wood flourlpoly propy lene).

Flower pots (wood flourlpolypropylene).

Mudtrays for plaster (wood flourlpolypropylene).

Chime boxes for Chrysler (wood flour or newspaperlpoly propy lene).

Bicycle bottle holders (wood flour or newspaperlpoly propy lene).

Paint roller handles (wood flou rlpoly pro py lene).

Cosmetic case covers (wood flourlpolypropylene).

Scissor handles (wood flourlpoly propylene).

Flashlight cases and coat hangers (wood flour or newspaperlpoly propy lene).

15

3 -

3’ WOOD-CEMENT COMPOSITES

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DRAFT

Cement-Bonded Wood Composites as an Engineering Material

Ronald W. Wolfe, Research Engineer Agron Gjinolli, Structural Engineer

USDA Forest Service Forest Products Laboratory

Madison, Wisconsin

October 1996

For Publication in: Proceedings of “Use of Recycled Wood and Paper in Building Applications,” Forest Products Research Society, September 9-1 1, 1996

Keywords: cement, composites, engineering

The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright.

Abstract

This paper discusses the potential for developing engineered materials from recycled wood in the form of cement-bonded wood composites. Wood-cement composites have been used in the fabrication of building materials for more than 60 years. Uses have focused primarily on the advantages of these composites-resistance to decay and insects, acoustical properties, and thermal insulating properties. Recent studies of the strength, stiffness, toughness, and durability of wood particle and fiber based cement composites project expanded use in applications that require a durable material that exhibits consistent bending and shear stiffness and strength along with a ductile, energy-dissipative failure mode. While most research in this area has dealt with “clean” fiber from roundwood, it appears that recycled pulp and solid wood waste could be used with acceptable tolerance for product variability. In this study, we report results from basic research on interactions between wood and cement and their effect on strength and durability of wood-cement composites. The results provide a solid basis for refining product fabrication processes. Although this effort focused on fiber-reinforced cements, many results can be applied to wood particle-cement composites. Using a larger quantity of woodfiber waste in a less refined form adds to the attraction of wood particle-cement composites as environmentally friendly materials. It also adds to the challenge of defining them as an engineering material.

Introduction

Cement-bonded wood composites have the potential to provide a wide range of products for building applications and an outlet for a wide range of recycled wood-based materials. Recycled newsprint and magazines, old pallets, construction waste, and small-diameter tree stems have been used for both experimental and commercial products. The value of these products could be improved by a better understanding of the fabrication process and resulting material properties.

The development and use of cement-wood composites over the past 60 years attest to their attraction as building materials. In addition to their resistance to fire, these materials have a special attraction for use in warm humid climates where termites and decay are a major concern for wood use. The cement binder provides a durable surface as well as one that can easily be embossed and colored for an attractive, low-maintenance finished product. The raw materials used are compatible with a range of processing methods to provide a variety of products that are easily machined with conventional woodworking tools. Preliminary research results suggest that these composites can also be manufactured to exhibit a range of unique energy-dissipating properties, which are advantageous in areas subject to seismic andor heavy wind loads. These attributes appeal to engineers, architects, and contractors for use in public and multifamily residential buildings.

To extend the acceptance and use of these materials in the area of structural applications, we need more information on their strength, stiffness, toughness, and reliability. Private industry has taken the lead in research to develop and use cement-wood composites in building construction.

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Cement-bonded wood-excelsior panels have been in use for more than 60 years, but the emphasis has been on acoustics, fire resistance, and aesthetics, rather than strength and stiffness. More recently, industry has focused on the development of fiber-reinforced cement cladding products. These products normally use 8%-10% wood by weight compared to 20%-40% for wood particle composites, and they rely on appearance and durability rather than on strength and stifiess for their acceptance.

Material resource and recycling demands suggest that the time is right for research to characterize the unique problems and properties associated with these composites and to attempt to expand their use to structural applications in residential structures.

0 bjective

Basic research is needed to assess the feasibility of developing engineered products that will exploit the unique properties of cement-wood composites. The purpose of this paper is to summarize what we know about these materials and to recommend a course of action that will provide the basis for developing engineered composites from low-value wood resources.

History

Cement is perhaps the most widely used and versatile composite matrix material. In its most common form, cement is combined with stone aggregate to improve compressive strength and durability and with steel reinforcing bar to improve bending capacity and resistance to cracking. Fiber reinforcement has also been used to improve fi-acture toughness. The best known and widely used material of this type is cement asbestos board, which has been used as a roofing and siding material throughout the world for nearly 80 years.

Wood-cement composites are generally placed in one of two categories: wood particle-cement composites (WPCC) and wood fiber reinforced cement (WFRC). WPCCs have been in use as architectural, fire-resistant, and acoustic panels for more than 60 years. WFRC products were developed primarily as a substitute for asbestos-cement and are relatively new, developed and promoted mostly in the last 25 to 30 years. These composite materials have been developed primarily by private companies and thus have received relatively little attention in published technical literature.

The W C C s have a slightly longer history as commercial products than do WFRCs, but they have received far less rigorous research attention. These composites generally have densities in the range of 300 to 1,300 kg/m3. Their maximum bending strengths are often limited to less than 10 MPa. Research in Europe in the 1920s led to the common practice of using wood chips in cement to make building blocks. By 1940, there were a number of manufacturers producing a cement-bonded wood composite commonly called woodwool, which uses a wood:cement ratio in the range 0.4 to 0.6 by weight. Woodwool is made with a ribbonlike particle called excelsior.

3

These ribbons are coated with cement and pressed into panels that have densities in the range of 300-500 kg/m3. Woodwool is attractive for use as noncombustible and sound-absorbing ceiling and wall panels. In 1973, a company called Durisol in Switzerland was among the first to produce a building panel consisting of small wood flakes bound in a cement matrix. In this case, the composite is roughly 20% wood by weight and has a density closer to 1,300 kg/m3.

Interest in WFRCs was sparked by the post-World War I1 shortage of asbestos fibers, which caused some private companies to consider cellulose fiber as a substitute for asbestos in fiber- reinforced cement. This interest faded as asbestos supplies recovered in the I950s, but it regained strength by the mid-1970s with growing concern over the health risks linked to asbestos. The controversy over asbestos led a number of companies in Australia, Europe, and Scandinavia to develop processes for fabricating fiber-reinforced cement boards using cellulose and other mineral fillers. Over the past 25 years, the American Concrete Institute has also sponsored research to develop high-performance fiber-reinforced cement composites that use discrete fibers, including steel, glass, synthetic polymers, and cellulose.

Today, cellulose fiber is used in a wide variety of fiber-reinforced cement products, many of which were originally developed using asbestos fiber. These materials use only 5%-15% cellulose fiber by weight, have densities ranging from 1,100 to 1,800 kg/m3, and have bending strengths ranging up to 30 MPa. The primary function of fibers in these cement composites is to increase the energy of fracture. By bridging gaps, the fibers prevent stress concentrations at crack tips, thus retarding brittle fracture mechanisms and dissipating energy in the form of fiber pullout or rupture.

Engineering Properties

Many studies have evaluated various aspects of cement-wood composite fabrication and material properties (4,7,10-14,15, I B) , but few have directly addressed issues of importance to their use in structural applications. The majority of these studies have been concerned with wood-cement compatibility, methods of gaining rapid cure, and effects of fiber type and mass on strength stifhess and toughness (5,18). While these studies have provided a necessary foundation for developing composite products for specific applications, they have lacked the sample size and load conditions needed to derive reliable design values. We need a basis for assessing what are the strength and stiffness distribution parameters and how they vary with changes in raw material properties, processing variables, long-term load, and environmental exposure.

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Bending Strength and Stiffness

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The majority of the work on bending strength of wood-cement composites was part of an effort to develop high-strength fiber-reinforced cement products. Concrete is used primarily in compression, developing strengths of 20 to 35 MPa, 68 MPa for high-strength fiber-reinforced concrete. In bending, strengths may range from 7 to 20 MPa. The addition of wood particles or cellulose fiber improves fracture toughness by blocking crack propagation. This permits the composite to carry load to a higher strain limit. Figure 1 shows a typical load deformation plot measured for a cement-wood composite. The initial portion of this plot (zone I) is fairly linear and represents the strength of the cement matrix. When the matrix begins to fail, the plot becomes nonlinear. At this point, the fiber or particle content begins to contribute by blocking fracture propagation. This action may permit the composite to take a slightly higher load or to exhibit a ductile failure, deflecting until a strain limit is reached for the fiber reinforcement. Normally, the strain-at-failure for the wood may range from 40 to 400 times that of cement.

Coutts ( 5 ) and Soroushian (1 8) reported WFRC bending strengths of 7 to 30 MPa, depending on fiber mass, moisture content, and type of fiber. Figure 2 shows how these parameters affect bending strength. Coutts attributed the drop in strength past 8% to a tendency of the fibers to pack less efficiently as fiber mass increases beyond this point. Moisture tends to reduce flexural strength, making the fibers more flexible and less likely to inhibit cracking in the cement matrix. Data presented by Coutts also showed that high-yield, thermomechanical pulps (TMPs) do not give as high a strength as do chemical pulps. He attributed this result to damage to the fiber as well as :‘poisoning” of the cement by extraction of polysaccharides and wood acids. These substances, left behind by mechanical pulping, are removed during the chemical pulping process.

Coutts also compared autoclaved cure to air seasoning (Fig. 2). Autoclaved composites included a portland cement and fine sand mix with wood fiber that was subject to steam heat for 8 h at 170°C to 180°C. This curing process resulted in a decrease in strength with fiber content when high-yield thermomechanical pulps were used, but gave maximum strength of over 20 MPa when Kraft pulp was used. Air curing, which took 14-28 days, gave a composite bending strength of 30 MPa when composites were made from an 8% Kraft pulp mix.

The WPCCs cover a wide range of material configurations as well as a wide range of bending strengths. Dinwoodie and Paxton (6) presented information on a number of cement particleboards consisting of 20% wood by weight in which the wood was in the form of flakes 10-30 mm long and 0.2-0.3 mm thick. The authors reported densities in the range 1.2 to 1.3 g/cc and bending strengths from 10.1 to 12.9 MPa.

Karam and Gibson (9) presented information on several commercially produced composites (Fig. 3), which included fiber-reinforced cement particleboard as well as a WPCC containing 20% wood flakes by weight. In a study by Moslemi and Pfister (1987), wood content had little effect on bending strength of cement-bonded particleboard for wood:cement ratios between 1.3 and 2.3.

5

I I For composites made from lodgepole pine flakes with an average thickness of 0.6 mm and a portland type I binder, there was no significant difference in strength at 90% confidence on the mean. Tests conducted at the Forest Products Laboratory (FPL) by Wolfe and Geimer (20) yielded values ranging from 2 to 4 MPa for composites containing 40% to 50% wood particles by weight and densities ranging from 0.5 to 1.2 g/cc. The commercial excelsior board referenced in Figure 3 was made from 0.38-mm-thick southem pine excelsior with a width:depth ratio of 4:5. The poplar excelsior used for the FPL boards was slightly thicker than these boards, but the width:thickness ratios of the FPL boards bracketed that of the commercial board. The wastewood board was made from southem pine chunk-type particles that varied in size from fiber bundles to 12 mm diameter by 1.5 inches long. Within each sample, the ratio of wood to cement was the same; variation in density resulted from variation in void volume.

Coutts (5 ) also compared autoclaved cure to air seasoning (Fig. 2). The autoclaved composites include a portland and fine sand mix with the wood fiber, which is subject to steam heat for 8 h at 170°C to 180 “C. Air curing is normally done at ambient temperatures or in a hydration kiln at 80°C and takes 14 to 28 days. The strength of autoclaved composites increased with fiber content when kraft pulp was used but not when thermomechanical pulps were used. Air curing resulted in strength increase with fiber content up to 8% by weight for both thermomechanical and krafl pulps, but strengths were still greater for the kraft pulp mix. The maximum strength at 8% fiber content was due to a “balling” of the wood fiber at higher concentrations, reducing effective cement coating.

Compressive Strength

The compression characteristics of cement-wood composites vary depending on the wood:cement ratio and the type of particles used. Sorfa (1 7) reported that bricks developed for use as mining supports exhibited compression properties similar to compression perpendicular to the grain in wood. These bricks were fabricated using pine planer shavings and had densities ranging from 0.5 to 1.32 g/cc, depending on the bulk density of the wood fiber and the wood:cement ratio.

Sorfa (1 7) reported compression curves in which the load increased linearly with deformation up to apoint of matrix cracking (Fig. 5). The initial slope increased with density or drop in the wood:cement ratio. Beyond this point, load continued to increase with increased compression but at a slope that was similar for all the cement:wood mixes used. An actual point of failure was never reached in a 15-mm displacement equal to 20% of the depth of the test specimens.

Compression tests conducted at the FPL on cement-wood particle composites were different than those reported by Sorfa in that the height of the test samples was greater than their width and failure resembled a buckling type of failure more than pure compression. In this case, the load deformation plot resembled that shown in Figure 1, except for a slight initial stiffening zone caused by compaction of the material. After the matrix began to fail, the samples began to crack; the load fell 30% to 50%, then decreased gradually as displacement continued to increase. As was

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the case with the bending tests, wood:cement ratios for the FPL samples were on the order of 1:2.

Toughness

Toughness has been defined and characterized in different ways by different authors and different standard test procedures. In essence, toughness is a measure of the energy absorbed by the test sample during the test. It is determined as the area under the load deformation curve. Coutts reports toughness as energy per unit area (Joules/m2). These units normally refer to fracture toughness in which a test specimen fracture initiates at a notch and the toughness is the energy per generated crack area (length times width). This terminology is commonly found in discussion of the fiacture toughness of paper tested in tension.

In the concrete industry, the ASTM C 1018 standard (1) defines a set of toughness indices for fiber-reinforced cement, which is reported as the area under the load deformation curve up to deformations of 3, 5.5, and 10.5 times the deformation at first crack as multiple of the area to first crack. Concrete has a toughness index of 1 as the first crack normally defines failure strength.

The FPL study (2 1) evaluated both bending and compressive toughness following the procedures given in ASTM C 101 8 (1). Toughness indices (Table 1) were evaluated using the index derived as the area (A3R) under the load displacement curve between zero and three times the displacement at the point where the cement matrix cracks ( 6 ~ ) (Fig. 1, I and 11) divided by the area under the curve between zero and 6R (I in Fig. 1). For cement, this index is designated I5 because 5 is the average value obtained for fiber-reinforced cements. In these tests, the composite consisted of wood particles rather than individual fibers and the wood:cement ratio was close to 50%. Test results indicated a toughness index of more than 6.5 for both bending and compression.

The different approaches to defining toughness make it difficult to compare values across studies. However, the energy-dissipating properties of cement-wood composites make toughness a valuable measure of the advantages of adding fibers and or wood particles to cement. Soroushian (18) showed an almost linear increase in toughness with fiber mass content (Fig. 6) and an increase in toughness with fiber moisture content. Coutts (5) also demonstrated these same relationships.

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Potential Applications

From a structural viewpoint, toughness appears to be the primary advantage of cement-bonded wood composites. These materials are not particularly strong, having roughly only 5% to 30% of the strength of wood. Strength limitations can be accommodated to some extent through use of increased section properties or reinforcement. However, the premise that wood-cement composites can be designed to give a characteristic ductile failure is attractive. In cases where it is not feasible for design to resist the maxi" possible load, a material that dissipates a lot of energy as it fails can save lives. Examples include buildings in areas prone to heavy wind, particularly tornadoes; highway crash barriers; break-away walls in surge zones; and mine supports. With the proper mix of materials, these composites could also be used to develop a structural fuse whose failure could serve as an indicator of a structural system overload or weakness.

Research Needs

Cement-bonded wood composites have been proven economically feasible as cladding materials. Preliminary research has shown that these materials can be fabricated to resist cyclic moisture and temperature effects (6,9,21), but there is a need for further research and development to evaluate shear strength, toughness, connections, and creep under constant load.

These materials have been developed to the point where we need an organized effort to establish standard evaluation procedures to simplify recognition of the influences of additives and processing variables on mechanical properties. Test specimen sizes should be selected with some recognition of the effect of particle size. Standard tests are needed for evaluation of toughness, creep, and shear. Standard methods should also address the reporting of properties such as moisture content, fiber content, density, wood species, geometry, orientation, and alignment.

Conclusions

There are many advantages to combining wood and cement that benefit the use of such composites in construction. Preliminary studies suggest that some wood-cement composites also have attributes that could qualify them as engineered structural materials. On the basis of available test results, the most prominent attribute of this nature appears to be toughness. The adoption of standards for fabrication and structural performance evaluation would help to promote research needed to gain acceptance of these composites as engineered materials and encourage their development as a use for recycled wood-based material.

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Lite rat u re Cited

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11.

ASTM. 1989. Standard test method for flexural toughness and first crack strength of fiber-reinforced concrete. ASTM C 101 8-89, vol. 4.02. American Standards for Testing and Materials, Philadelphia, PA.

ASTM. 1990. Standard test method for resistance of concrete to rapid freeze-thawing. ASTM C 666-90, vol. 04.02, American Standards for Testing and Materials, Philadelphia, PA.

ASTM. 1992. Methods of static tests of timbers of structural sizes. ASTM D 198-84, American Standards for Testing and Materials, Philadelphia, PA.

Biblis, E.J. and Chen-fan Lo. 1968. Sugars and other extractives: Effect on the setting of southern pine cement mixtures. Forest Products J. 18(8):28-34.

Coutts, R.S.P. Wood fibre reinforced cement composites. Concrete technology and design, vol. 5. Natural fibre reinforced cement and concrete. Department of Mechanical Engineering, University of Shefield, UK.

Dinwoodie, J.H. and B.H. Paxton. 1991. The long term performance of cement-bonded wood particleboard. In proceedings, Inorganic bonded wood and fiber composite materials. Forest Products Society, Madison, WI, pp. 45-54.

Hachimi, M. and A.G. Campbell. 1989. Wood-cement chemical relationships. In proceedings, Fiber and particleboards bonded with inorganic binders. Forest Products Society, Madison, WI

Japanese Concrete Institute. 1984. JCI standards for test methods of fiber reinforced concrete. Report No. JCI-SF, pp. 68.

Karam, G.N. and L.J. Gibson. 1992. Evaluation of commercial wood-cement composites for sandwich-panel facing. Journal of Materials in Commercial Engineering 6( 1): 100-1 16.

Lee, A.W.C. 1984. Physical and mechanical properties of cement bonded southern pine. Forest Products J. 34(4):30-34.

Lee, A.W.C. 1985. Bending and thermal insulation properties of cement-bonded cypress excelsior board. Forest Products J. 35(11/12):57-58.

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Figure 1-Load deformation c w e for cement-bonded wood composite showing bimodal failure. Zone I shows initial linear portion up to point where cement matrix begins to crack. Load continues to increase to maximum load, then drops 30%-50% to the point that wood particles are left to resist stress.

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Resources for Further Information

NEW YORK STATE

Empire State Development Central Office One Commerce Plaza Albany, New York 12245 (51 8) 474-41 00

Empire State Development Office of Recycling Market Development One Commerce Plaza Albany, New York 12245 (5 1 8) 486-629 1

Empire State Forest Products Association 123 State Street Albany, New York 12207 Contact: Kevin King, Executive Director (51 8) 463-1 297

New York Center for Forestry Research and Development State University of New York 200 Bray Hall, SUNY Syracuse, New York 1321 0 Contact: Dr. Edwin H. White, Dean of Research (3 1 5) 470-6606

New York State Department of Environmental Conservation Division of Lands and Forests 50 Wolf Road Albany, New York 12233-4253 Contact: Bruce Williamson, Section Chief Forest Products and Utilization (51 8) 457-7431

New York State Department of Environmental Conservation Bureau of Waste Reduction and Recycling 50 Wolf Road Albany, New York 12233-401 5 (51 8) 457-7337

New York State Energy Research and Development Authority Corporate Plaza West 286 Washington Avenue Extension Albany, New York 12203-6399 Contact: Jeffrey M. Peterson Program Manager, Energy Resources (51 8) 862-1 090 Ext. 3288

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Resources for Further Information I 1

REGIONAL AND NATIONAL

Northeast Regional Biomass Program CONEG Policy Research Center, Inc. 400 No. Capitol Street, N.W. Suite 382 Washington, D.C. 20001 Contact: Rick Handley, Program Manager (202) 624-8454

U.S. Department of Agriculture Forest Service Forest Products Laboratory One Gifford Pinchot Drive Madison, Wisconsin 53705-2398 Contact: Information Services (608) 23 1 -9200

American Forest and Paper Association 11 11 Nineteenth St., N.W. Suite 800 Washington, D.C. 20036 (202) 463-2700

American Plywood Association 701 1 S. 19th St. P.O. Box 11700 Tacoma, Washington 9841 1-0700 (206) 565-6600

National Particleboard Association 18928 Premiere Court Gaithersburg, Maryland 20879 Contact: Mike Hoag, Technical Director (301 1 670-0604

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