DOE/[ D/12521-1 ( D E87002509)

CONVERSION OF POLYESTER/COTTON INDUSTRIAL WASTES TO HIGHER VALUE PRODUCTS

Final Report

BY Dr. David Cates

October 30, 1986

Work Performed Under Contract No. AC07-841D12521

For U. S. Department of Energy Office of Industrial Programs Washington, D.C.

BY North Carolina State University Raleigh, North Carolina

Technical Information Center Office of Scientific and Technical Information United States Department of Energy

DISCLAIMER

P

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness. or use- fulness of any information, apparatus, product, or process disclosed. or represents that its use would not infringe privately owned rights. Reference herein to any spe- cific commercial product. process. or service by trade name. trademark, manufac- turer. or otherwise does not necessarily constitute or imply its endorsement. recom- . mendation. or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily stdte or reflect those of the United States Government or any agency thereof.

This report has been reproduced directly from the best available copy.

. .

DOE/I D/12521-1 (DE87002509)

Distribution Category UC-95f

CONVERSION OF POLYESTER/COTTON INDUSTRIAL WASTES TO HIGHER VALUE PRODUCTS

FINAL REPORT

D r . David Cates

October 30, 1986

Department of T e x t i l e C h e m i s t r N o r t h C a r o l i n a S t a t e U n i v e r s i t

Raleigh, N C 27695-8302

P r e p a r e d f o r t h e U. S. Department of t Idaho Opera t ions Of f i ce , Idaho Fa l l s ! Under Contract Number DE-AC07-84IDlZE

O f f i c e o f t h e A s s i s t a n t S e c r e t a r y f c Conservation and Renewable Energy

mils uBRMw O f f i c e o f I n d u s t r i a l Programs KESYlJLmtn Washington D.C.

t i

I This book was presented by

Dr. William K - Wolch

THIS BOOK IS DUE ON THE DATE INDICATED BELOW AND IS SUB- JECT TO AN OVERDUE FINE AS POSTED AT THE CIRCULATION DESK.

1 O C T 2 4. 15 .; $

Table o f Contents

Page

i i

i i i

iv

Table o f Contents ..................................... List o f Tables ....................................... List o f Figures ...................................... Executive Summary .................................... 1

2 Introduction ......................................... Technical Feasibility ................................ 5

5 Procedures ..................................... Formulation ................................ Compaction ................................ Injection Molding .......................... Testing ....................................

Results ......................................... 14

14 16 16

Runs 1 and 2 .............................. R u n 3 ...................................... Effect of Moisture ......................... Effect of Pelletization and Injection

Molding on Cotton Component ............ 16

19 Discussion ...................................... 19 32

Role o f Cotton and Additives ............... Cotton Fiber as Reinforcing Filler .........

34 Plant Trials ........................................ 34 35 37

P1 ast i c Engi neeri ng Corp. ....................... Federal Mol ding Co. ............................ federal Molding Co., Second Trial ...............

45 Implementation Potential ............................ Conclusions ......................................... 51

Recommendations .................................... 54

55 References :. ........................................

. . .

i i

List o f Tables

Page

1 . Injection Molding Conditions (Arburg 221-55-250) ...... 8

2a . Properties 'of Standard Bar . Run No . 1 (80/20) ......... 17

2b . Properties of Standard Bar . Run No . 1 (65/35) ......... 18

3a . Properties of Standard Bar . Run No . 1 (100/0) ......... 20

3b . Properties o f Standard Bar . Run No . 1 (80/20) ........ 21

3c . Properties o f Standard Bar . Run No . 1 (65/35) ......... 22 .

4 . Heat Deflection. Hardness, and Impact Strength . Run No . 2 ........................................... 23

5 . % Moisture Regain (Relative to Bone-Dried Weight, Obtained by Heating Overnight at llO°C) ............... 24

6a . Properties of Standard Bar (Large Barbell); Mold . Temperature 75OC . Run No . 3 ......................... 25

6b . Properties o f Thin Bar (Small Barbell); Mold

7 . 8 .

9 .

10 .

11 . 12 . 13 .

14 .

15 .

Temperature 75OC . Run No . 3 ........................ Thermal Analysis o f Thin Bar . Run No . 2 ............. Effect o f Cotton and Nucleating Mixture on Percent Strain of Thick and Thin Bars . Run No . 2 ............. Cotton as Inert Tiller . Mold Temperature of 75OC . No Additive . Run No . 2 ............................... Potential Markets for PET/Cotton Reclaim Molding Compound ............................................. Cost o f Pelletization o f PET/Cotton Waste Blend ....... Estimated Compaction Costs of PET/Cotton Reclaim (CV 50)

Comparison o f Costs (Estimated). PET/Cotton Reclaim vs G . P . Polystyrene .................................... Estimated Compaction Costs of Plasticized PET/Cotton Reclaim .............................................. Comparison o f Costs (Estimated) . Plasticized PET/Cotton Reclaim vs PPO-PS .....................................

26

33

33

33

46

48

49

49

52

52

. L..

L

i i i

List o f Figures

Page

la. % Peak Strain and Peak Stress (psi) ................. 10

lb. F1 exural Stress at 5% Deflection; F1 exural Modulus .... 11

IC. % Strain at Zero Stress; Tensile Modulus ............. 12

2. Thermal Properties from DSC Scan ..................... 15

3. Peak Stress and Peak Strain. Run No. 2 .............. 27

4. Peak Energy and Flextural Stress at 5% Extension. Run No. 2 ........................................... 28

5. Tensile Modulus and Flexural Modulus (psi ) . Run No. 2 ........................................... 29

6. Density and Inherent Viscosity. Run No. 2 ........... 30

7 . 80/20 PET/Cotton Pellets; heated initially 2 hours at 13OoC, thereafter at 25OOC. ....................... 38

8. 80/20 PET/Cotton Pellets; Virgin: no previous heat treatment; HT: previously heated 20 minutes at 25OoC. 40

9. Infrared spectrum of water ( a ) ; distillate (b). ...... 41

10. Hourly Rates Quoted by Custom Molders ................ 42

i v

Conversion of Polyester/Cotton Industrial Wastes

to Higher Value Products

EXECUTIVE SUMMARY

A Department of Energy contract with the Department of Textile

Chemistry was undertaken to determine if polyester/cotton waste from

textile manufacturing could be used in an injection-molded plastic

application. The work was sponsored by the Department of Energy's

Office of Industrial Programs (DOE - OIP) within the Conservation and Renewable Energy organization.

Polyester/cotton waste in the primary textile industry annually

amounts to about 45 million pounds, a quantity which is only a small

fraction of the total waste, most of which goes to landfills. Our

calculations indicate that recovery and utilization of the textile

waste represents an annual energy resource of about 1OI2 BTU.

In this project, several polyester/cotton waste blends were

successfully used as feedstock to make injection molded products.

Nucleating and plasticizing additives (commonly required in the

production process) were found to be unnecessary; their functions

were fulfil 1 ed by the cotton component of the waste feedstock. The

properties of the injection molded parts were comparable general ly

to those of a great many other plastics. Cotton caused a notable

increase in stiffness (modulus) of the molded part, but failed to

produce a significant increase in tensile strength.

Plant trials revealed difficulties that were unobserved in

,,the smaller scale runs: sticking in the mold, release of water aid

other volatiles at the molding temperature, and intermittent flow.

1

" I

Sticking in the mold probably can be solved by including a small amount

of mold release compound in the formulation just prior to pelletiza-

tion. The problems of release of volatiles and intermittent flow can

possibly be solved by (a) using a molding machine with a two stage

vented plasticating unit, or (b) including plasticizer in the

formulation sufficient in quantity to lower and extend the range Over

which satisfactory melt flow occurs.

Polyester/cotton molded products would have a price advantage as

feedstock in the commodity thermoplastics market, but it is possible

that this could be dissipated by higher molding costs. The price

advantage against the higher priced reinforced thermoplastics increases

significantly, but competition in this market depends on whether the

properties o f the polyester/cotton mix can be improved. Improvement i s

viewed as a possibility since the values of the properties reported

here were obtained under conditions in which the values may have been

adversely affected by voids attributable to water and other volatiles.

INTRODUCTION

A Department o f Energy contract (DE-AC07-84ID12521) was initiated

with the Department of Textile Chemistry, N.C. State University in June

1984 to investigate using polyester/cotton waste from textile manufac-

turing as a substitute for polyester/glass in injection-molded plastic

applications. The work was sponsored by the Department of Energy's

Office of Industrial Programs (DOE-OIP) within the Conservation and

Renewable Energy organization. The contract was managed by the DOE,

Idaho Operations Office, Conservation Technologies Division. This

;document is a report of the project results.

2

The annual waste of polyester/cotton fibers is estimated to

exceed 450 X l o 6 pounds ( 6 ) . This includes about 350 x l o 6 pounds

from used clothing, approximately 60 x 106 pounds of cutting room

waste from the fabrication industry, and 45 x 106 pounds of mill waste

from the primary textile industry. Although substantial markets exist

for the separate waste materials, it is impractical to separate the

polyester and cotton components. Much of this waste is presently

disposed of as landfill. It is evident that little of value is being

derived from this huge resource.

The purpose of this project was to investigate a potential

application of the mill waste from the primary textile industry. This

wiste was chosen because it is relatively clean, containing very little

extraneous material, and could readily be obtained with industry

cooperation.

The primary textile industry i n 1984 produced 1.6 billion pounds

of blended polyester/cotton (PET/Cotton) yarns that are chiefly

polyester (1). The polyester component, which is almost entirely

poly(ethy1ene terephthalate) (PET) , is polymerized from petroleum

products and furnished to the texti 1 e industry as staple fiber. The

PET/Cotton bl end commercial ly avai 1 ab1 e usual ly contains polyester as

the dominant component, but blends containing up to 50% cotton are

quite common.

About 3% of the PET/Cotton production, some 45-50 mi 1 1 ion pounds,

is waste (2) , and consists 0.f waste yarn and knitted and woven fabric

pieces. Applications for the waste product have failed to materialize.

Much of the annual polyester/cotton waste is presently disposed of as

1 andf i 1 1 and the rest is processed as scrap fiber, bringing about 5

3

:S cent

cons

per pound for this purpose. An alternative is to develop an

cation for the unseparated waste, e.g., as an engineering plastic.

The annual production of engineering plastics molding compounds

sting of PET and poly( butylene terephthalate) (PBT) amounted in

1985 to 104 million pounds (3). These compounds are used for such

things as appl iance bases, power-tool housings, under-the-hood parts in

automobiles, etc. The formulations normally include approximately 65

to 70% polymer, 30 to 35% glass fiber, and 5% other additives, e.g.,

nucleating agent, plasticizer, antioxidant, etc. Glass fiber, which may

be included up to 45% by weight, adds stiffness and strength. Addi-

tives are incorporated to increase the rate at which PET crystallizes,

which by itself is rather slow, with the result that the molded part

may become embrittled.

The polyester/cotton waste can be viewed as potentially a

reinforced plastic, with polyester as the matrix and cotton as rei n-

forcing filler. The purpose o f this project was to establish the

feasibility o f utilizing PET/Cotton waste as feedstock in applications

which are met by PET/Glass and PBT/Glass injection molded plastics.

These reinforced plastics, sometimes referred to as engineering

plastics, are higher priced and have much superior strength properties

to the commodity plastics. In the event the properties of the

PET/Cotton injection molded product failed to measure up to those of

the engineering plastics, however, the feasibility of substituting

PET/Cotton for the lower valued commodity plastics was considered a

reasonable alternative objective.

In either case, considerable energy savings in feedstock cost

should be real ized and would be a primary benefit. Funding was .. .

4

Conversion of Polyester/Cotton Industrial Wastes

to Higher Value Products

EXECUTIVE SUMMARY

A Department of Energy contract with the Department o f Textile

Chemistry was undertaken to determine if polyester/cotton waste from

textile manufacturing could be used in an injection-molded plastic

application. The work was sponsored by the Department of Energy's

Office of Industrial Programs (DOE - OIP) within the Conservation and Renewable Energy organization.

Polyester/cotton waste in the primary textile industry annually

amounts to about 45 million pounds, a quantity which is only a small

fraction of the total waste, most of which goes to landfills. Our

calculations indicate that recovery and utilization o f the textile

waste represents an annual energy resource of about BTU.

In this project, several polyester/cotton waste blends were

successfully used as feedstock to make injection molded products.

Nucleating and plasticizing additives (commonly required in the

production process) were found to be unnecessary; their functions

were fulfil led by the cotton component of the waste feedstock. The

properties of the injection molded parts were comparable generally

to those of a great many other plastics. Cotton caused a notable

increase in stiffness (modulus) of the molded part, but failed to

produce a significant increase in tensile strength.

Plant trials revealed difficulties that were unobserved in

the m a l ler scale runs: sticking in the mold, re1 ease of water and

other volatiles at the molding temperature, and intermittent flow.

1

Sticking in the mold probably can be solved by including a small amount

of mold release compound in the formulation just prior to pelletiza-

tion. The problems of release of volatiles and intermittent flow can

possibly be solved by (a) using a molding machine with a two stage

vented plasticating unit, or (b) including plasticizer in the

formulation sufficient in quantity to lower and extend the range over

which satisfactory melt flow occurs.

Polyester/cotton molded products would have a price advantage as

feedstock in the commodity thermoplastics market, but it is possible

that this could be dissipated by higher molding costs. The price

advantage against the higher pri ced reinforced thermopl asti cs increases

sjgnificantly, but competition in this market depends on whether the

properties of the polyester/cotton mix can be improved. Improvement is

viewed as a possibi 1 i ty since the values o f the properties reported ,

here were obtained under conditions in which the values may have been

adversely affected by voids attributable to water and other volatiles.

INTRODUCTION

A Department of Energy contract (DE-AC07-84ID12521) was initiated

with the Department of Textile Chemistry, N.C. State University in June

1984 to investigate using pol yester/cotton Waste from texti 1 e manufac-

turing as a substitute for polyester/glass i n injection-molded plastic

appl ications. The work was sponsored by the Department of Energy's

Office of Industrial Programs (DOE-OIP) within the Conservation and

Renewable Energy organization. The contract was managed by the DOE,

Idaho Operations Office, Conservation Technologies Division. This

" document is a report of the project results. i

2

c

The annual waste of polyester/cotton fibers is estimated to

exceed 450 x 106 pounds ( 6 ) . This includes about 350 x l o 6 pounds

from used clothing, approximately 60 x l o 6 pounds o f cutting room

waste from the fabrication industry, and 45 X l o 6 pounds of. mill waste

from the primary textile industry. Although substantial markets exist

for the separate waste materials, it is impractical to separate the

polyester and cotton components. Much of this waste is presently

disposed of as landfill. It is evident that little of value is being

derived from this huge resource.

The purpose of this project was to investigate a potential

application of the mill waste from the primary textile industry. This

waste was chosen because it is relatively clean, containing very little

extraneous material, and could readily be obtained with industry

cooperation.

The primary textile industry in 1984 produced 1.6 billion pounds

o f blended polyester/cotton (PET/Cotton) yarns that are chiefly

polyester (1). The polyester component, which is almost entirely

poly( ethylene terephthalate) (PET), is polymerized from Petroleum

products and furnished to the textile ,industry as staple fiber. The

PET/Cotton blend commercially available usually contains polyester as

the dominant component, but blends containing UP to 50% cotton are

quite common.

About 3% of the PET/Cotton production, some 45-50 million pounds,

is waste ( 2 ) , and consists of waste yarn and knitted and woven fabric

pieces. Applications for the waste product have failed to materialize.

Much of the annual polyester/cotton waste is presently disposed of as

1 andf i 1 1 and the rest is processed as scrap fiber, bringing about 5

3

CI L

E ' I' I cents per pound for this purpose. An alternative is to develop an i

1 application for the unseparated waste, e.g., as an engineering plastic.

~ The annual production of engineering plastics molding compounds consisting of PET and poly( butylene terephthalate) (PET) amounted in

1985 to 104 mi 1 1 ion pounds (3). These compounds are used for such

things as appliance bases, power-tool housings, under-the-hood parts in

automobi 1 es, etc. The formul ati ons normal ly incl ude approximately 65

to 70% polymer, 30 to 35% glass fiber, and 5% other additives, e.g.,

nucleating agent, plasticizer, antioxidant, etc. Glass fiber, which may

be included up to 45% by weight, adds stiffness and strength. Addi-

tives are incorporated t o increase the rate at which PET crystallizes,

which by itself is rather slow, with the result that the molded part

may become embrittled.

The polyester/cotton waste can be viewed as potentially a

reinforced plastic, with polyester as the matrix and cotton as rein-

forcing filler. The purpose of this project was to establish the

feasibility of utilizing PET/Cotton waste as feedstock in applications

which are met by PET/Glass and PBT/Glass injection molded plastics.

These reinforced plastics, sometimes referred to as engineering

plastics, are higher priced and have much superior strength properties

to the commodity plastics. In the event the properties o f the

PET/Cotton injection molded product fai 1 ed to measure up to those of

the engineering plastics, however, the feasibility of substituting

PET/Cotton for the lower valued commodity plastics was considered a

reasonable a1 ternative objective.

In either case, considerable energy savings in feedstock cost

should be realized and would be a primary benefit. Funding was

4

Industrial Programs of the U.S . Department of Energy to

feasibility of using PET/Cotton as feedstock for inject

thermopl asti cs.

therefore sought, and subsequently obtained, from the Office

study

ion mo

Assuming 45 mil 1 ion pounds of polyester/cotton waste can

f

the

ded

be

substituted on a pound for pound basis for an engineering plastic with

a feedstock energy cost of 1.5 x lo3 BTU/in3 (based on heat content)

(4), and taking the density of aggregate polyester/cotton as 0.051

1 b/in3, the energy savings per year i s calculated as 1.3 x 10l2 BTU/yr:

45 'x lo6 " 1 b x 1 in3 x 1.5 x lo3 BTU = 1 . 3 x 1 O 1 2 ~ yr 0.051 lb inj Yr

The report which follows is divided into sections which discuss i n

turn: (a) Preparation and evaluation o f injection molded products from

the polyester/cotton waste (Technical Feasibility); (b) Plant Trials;

(c) Economics, market potential , and energy savings of the waste blends

(Implementation Potential); (d) Conclusions; (e) Recommendations.

TECHNICAL FEASIBILITY

Procedures

Formulation. The compositions of polyester/cotton waste that are

available from the textile industry tend to vary with the relative cost

of the polyester and cotton components. When polyester is cheap, 80/20

(polyester/cotton) blends are more plentiful; when cotton is cheap,

50/50 blends tend to be more plentiful. The 65/35 blend is ordinarily

the most abundant.

5