A Science and Technology Publication

Volume 11, No. 3 Fall, 2002

Role of Fiber Morphology In Thermal Bonding

Fiber Motion Near The Collector During Melt Blowing — Part 2: Fly Formation

A Comparison of Needlepunched Nonwoven Fabrics Made From Poly(trimethylene terephthalate) and

Poly(ethylene terephthalate) Staple Fibers

Linear Low Density Polyethylene Resins For Breathable Microporous Films

Fiberglass Vs. Synthetic Air Filtration Media

Patent Review ... Researcher’s Toolbox ... Technology Watch ... Director’s Corner ... The Nonwoven Web

I N T E R N A T I O N A L

NONWOVENSJ o u r n a l

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The International Nonwovens Journal is brought to you fromAssociations from around the world. This critical technicalpublication is provided as a complimentary service to the

membership of the Associations that providedthe funding and hard work.

PUBLISHER

INDA, ASSOCIATION OF THE NONWOVEN FABRICS INDUSTRYTED WIRTZPRESIDENT

P.O. BOX 1288, CARY, NC 27511www.inda.org

SPONSOR

TAPPI, TECHNICAL ASSOCIATION OF THE PULP AND PAPER INDUSTRYWAYNE H. GROSS

EXECUTIVE DIRECTOR/COOP.O. BOX 105113

ATLANTA, GA 30348-5113www.tappi.org

http://www.inda.orghttp://www.tappi.org

A Science and Technology PublicationVol. 11, No. 3 Fall, 2002

PublisherTed WirtzPresidentINDA, Association of theNonwoven Fabrics Industry

SponsorsWayne GrossExecutive Director/COOTAPPI, Technical Association ofthe Pulp and Paper IndustryTeruo YoshimuraSecretary GeneralANIC, Asia Nonwoven FabricsIndustry Conference

EditorsRob Johnson856-256-1040rjnonwoven@aol.comD.K. Smith480-924-0813nonwoven@aol.com

Association EditorsCosmo Camelio, INDAD.V. Parikh, TAPPI Teruo Yoshimura, ANIC

Production EditorMichael JacobsenINDA Director of Publicationsmjacobsen@inda.org

Role of Fiber Morphology In Thermal Bonding

Original Paper by Subhash Chand, Gajanan S. Bhat, Joseph E. Spruiell and

Sanjiv Malkan, University of Tennessee-Knoxville . . . . . . . . . . . . . . . . . . . . . . . 12

Fiber Motion Near The Collector During Melt Blowing:

Part 2 — Fly Formation

Original Paper by Randall R. Bresee, University of Tennessee-Knoxville,

and Uzair A. Qureshi, Jentex Corp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

A Comparison of Needlepunched Nonwoven Fabrics Made From

Poly(trimethylene terephthalate) and Poly(ethylene terephthalate) Staple Fibers

Original Paper by Dr. Ian G. Carson, Shell Coordination Centre s.a., Monnet

Centre – International Laboratory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Linear Low Density Polyethylene Resins For Breathable Microporous Films

Original Paper by W.R. Hale, E.D. Crawford, K.K. Dohrer, B.T. Duckworth,

Eastman Chemical Company . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Fiberglass Vs. Synthetic Air Filtration Media

Original Paper by Edward Vaughn and Gayetri Ramachandran,

Clemson University . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Editorial 4Researcher’s Toolbox 5Director’s Corner 7Technology Watch 9

Nonwovens Web 54Nonwovens Patents 57Association News 61Pira Worldwide Abstracts 63Meetings 66

NONWOVENSI N T E R N A T I O N A LNONWOVENS

J o u r n a l

DEPARTMENTS

ORIGINAL PAPERS

The International Nonwovens Journal Mission: To publish the best peer reviewed research journal with broadappeal to the global nonwovens community that stimulates and fosters the advancement of nonwoven technology.

EDITORIAL ADVISORY BOARDChuck Allen BBA NonwovensCosmo Camelio INDARoy Broughton Auburn UniversityRobin Dent Albany InternationalEd Engle FibervisionsTushar Ghosh NCSUBhuvenesh Goswami ClemsonDale Grove Owens Corning

Frank Harris HDK IndustriesAlbert Hoyle Hoyle AssociatesMarshall Hutten Hollingsworth & VoseHyun Lim E.I. duPont de NemoursJoe Malik AQF TechnologiesAlan Meierhoefer Dexter NonwovensMichele Mlynar Rohm and HaasGraham Moore PIRAD.V. Parikh U.S.D.A.–S.R.R.C.

Behnam Pourdeyhimi NCSUArt Sampson Polymer Group Inc.Robert Shambaugh Univ. of OklahomaEd Thomas BBA NonwovensAlbin Turbak RetiredLarry Wadsworth Univ. of TennesseeJ. Robert Wagner Consultant

mailto:rjnonwoven@aol.commailto:nonwoven@aol.commailto:mjacobsen@inda.orghttp://U.S.D.A. S.R.R.C.

We know you are out there becauseour website people tells us thateach issue of the INTERNATIONALNONWOVENS JOURNAL receives morethan 10,000 hits during the quarter afterpublication. Even more remarkable, theolder issues of the INJ still each get upto 5,000 hits during the same period.

Yes, we know you are out there ... andwe would like to hear from you fromtime to time.

The editors of the INJ currently haveplenty of contact with several groups.There is frequent discussion with theauthors of the technical papers and withmembers of our outstanding EditorialAdvisory Board who peer review thesepapers every issue. We also receive sig-nificant feedback and input from theINDA Technical Advisory Board, whoseMission Statement now includes theline: “Assure that the INJ remains aneffective technical vehicle.”

What we would like, in addition tothese important elements, is input fromour readers. We need to know andunderstand what you are thinking so wecan better serve you. We welcome com-ments on any aspect of the journal, eventhe stuff you don’t like about it.

Of course, the primary mission of theINJ is to publish peer reviewed researchpapers and, consequently, we considerthis the most important aspect of thejournal. Your suggestions on topics aswell as comments on the papers pub-

lished to date are always welcome andcan only serve to strengthen the journal.

Do you agree with the author’s resultsand conclusions? Perhaps you haveadditional insight to offer or commentsthat might spur further research. We’llnever know unless you tell us.

The other key portion of the INJ con-sists of the various departments whereour objective is to collect and dissemi-nate useful information pertinent totechnical professionals and others in the

nonwovens and related industries. Theregular key departments include:

• Editorials• Director’s Corner• Researcher’s Toolbox• The Nonwovens Web• Technology Watch• Worldwide Abstracts • Organization/University Focus• Patent Review• Association PageHere, again, we seek your comments

and suggestions. Are these the correctsubjects for departments to reflect yourinterests and needs? What do you like?What do you dislike? Are there topicsfor inclusion? Perhaps you have a sug-gested article that can be summarized inone of the departments. Perhaps youfeel strongly about something and wantto offer a guest editorial. Just let usknow.

You can reach us and forward yourcomments, suggestions and submissionsto Rob Johnson at rjnonwoven@aol.com.

Stealth ReadersBy Rob Johnson and DK SmithTechnical Editors, International Nonwovens Journal

EDITORIAL

4 INJ Fall 2002

INJ’s Electronic Path

It has been almost two years since we announced the online format of theINTERNATIONAL NONWOVENS JOURNAL that commenced with the Spring 2001issue. It seems that we were “ahead of the curve” at the time and it is now fullyapparent that this move was correct in that we see many journals and other pub-lications that have followed us online.

As we stated earlier, we now get more than 10,000 hits during the quarterafter publication and we feel this compares favorably with the prior hardcopypress run of 5000 copies. Further, the online format has provided several addi-tional advantages, including allowing INDA and TAPPI to make the decision tooffer the INJ free to anyone in the world with Internet access.

For another, being online offers the use of color, which increases the clarityof many tables, graphs and photos included in the journal. A good example ofthis value is a paper in the Winter 2001 issue, “Use of Infrared ThermographyTo Improve The Melt Spinning And Processing of Polyester Fibers” by GlennGibson and Mark Tincher, Eastman Chemical Company, Kingsport, TN. Thispaper obviously benefited from color, as much of the information would havebeen lost in black and white. — RJ, DKS

mailto:rjnonwoven@aol.com.

Digital Cameras for MicroscopyBecause of their convenience, flexibili-

ty, and low-cost per photo, digital camerashave gained a great deal of popularityamong the picture-taking public.Operation of the camera can be almostfoolproof as well as flexible, giving sur-prisingly good results in a wide variety ofconditions. These features, coupled withthe ability to see the results immediately,as well as a cost per shot that makes mul-tiple exposures almost mandatory, havemade the transition to digital photographyan irresistible force.

The same movement is occurring with-in photomicroscopy, the union of the cam-era and the microscope. Although pho-tomicroscopists are generally skilled pho-tographers as well, the ease, convenienceand cost are major strong drivers for thetrend. Further, the ease of storage,retrieval, transferral and quantitativeanalysis of digital photomicrographs makethis capability a significant research tool.

With the capability of 3.3+ million pixelCCD resolution, superb digital images arealmost guaranteed, even of very fine struc-tures within a specimen.

Olympus Optical Co. of Hamburg,Germany, has concentrated on the devel-opment of a line of digital microscopecameras. These cameras are fitted with auniversal C-mount thread, allowingattachment to almost any microscope.

The Olympus DP 12 is a compact digi-tal camera with 3.34 million pixel resolu-tion. The camera system is provided witha tilting 3.5” LCD monitor, which is inte-grated into the control pad. This allowsadjustable observation at the ideal angle.Real-time display of large, easy-to-seeimages allow faster, more accurate focus-ing and framing.

Date, time, shutter speed and file nameare displayed and stored together with theimage; up to 16 acquired images can be

displayed on a connected computer screenat one time for on-screen image selection.Sharp focusing, even at low magnificationsis made possible with an electronic focusindicator and a 2x digital zoom function.

One touch, automatic and manual whitebalance modes are available for optimalcolor representation, and users can choose1% spot and 30% exposure metering andautomatic or manual exposure modes.

Removable “SmartMedia” cards storeup to 138 MB of images, which can beeasily transferred to any PC. Optional soft-ware allows images to be downloadeddirectly from the camera to the PC.

This company has just introduced anew, compact digital microscope camera,the Olympus “ColorView II.” This unitincorporates Firewire Technology, whichis similar to a USB connection, but has amuch higher data transmission rate. Thecamera is wired to the LCD screen or acomputer, and transfers the photomicro-graphic image very rapidly.

For information: Olympus Optical, D-20097 Hamburg, Germany; 49+40/23-7730; www.olympus-europa.com .

Coating and Laminating EquipmentNew capabilities for studying CCL

processes (Coating, Combining andLaminating processes) in the laboratoryand plant are emerging, as new small scaleand production scale equipment is devel-oped. The following describes somerecent introductions.

American Santex has introduced theirCavitec Modular Hot Melt Coating andLaminating system. This system providesfor more than one application method inthe same process line. The Cavilex basestation can be equipped for three differentprocesses: Cavimelt engraved roll coater;Caviroll roll coater; and the Cavislot slotdie coater. All three systems provide con-siderable variability for suitable substrates

and coating formulations, along with pre-cise control of process variables.Additional details are available from:American Santex, Spartanburg, SC; 864-574-7222: www.santex-group.com .

For laboratory work, the CoatemaEasycoater discontinuous lab unit offersan economical and easy-to-operate set-upfor preparing small hand samples withconstant coating weight and thickness.The coating head in this unit is a high-pre-cision stainless steel Doctor Blade that canalso be used as an “Air Knife System.”The coating head can be adjusted to vari-ous heights and angles with a precisionscrew and micrometer gauge. This unitalso has a companion mixing set-up forpreparation of 3-5 liters of coating formu-lation. The Easymixer is fitted with anexplosion-proof motor and is scaled forsplitting batches to cover a variety of for-mula modifications. For more: CoatemaCoating Machinery GmbH, Spartanburg,SC; 846-582-1900.

Reliant Machinery, the major UK man-ufacturer of flatbed laminators, has posi-tioned its Reliant Powerbond Mark IIIseries unit into their line of powder, filmand adhesive web laminators. They claimflexibility, ease of operation, maximumproduction and improved quality.

It has special features such as a heat tun-nel that adjusts from zero to 50 millimetersfor thick and thin materials, along withstandard heat tunnels from 1.7 to 5.7meters length in 1-meter increments. Theheat tunnel can be fitted with 10-zone heatcontrols; it comes in standard width of oneto three meters. The Mark III also includestheir Synchro-Trak automatic belt trackingsystem, refrigerated cooling modules,microprocessor controls, and embeddeddiagnostics.

In the U.S., Reliant is represented byApparel Equipment, Philadelphia, PA; 215-634-2626; www.reliant-machinery.com .

Liquid Carbon DioxideIn Apparel Cleaning

The use of liquified carbon dioxide hasgenerated a considerable amount of inter-est over the past few years. The reason forthis interest is the tremendous solventpower of liquid carbon dioxide. In thisstate, the material acts as both a liquid and

RESEARCHER’STOOLBOX

INJ DEPARTMENTS

INJ Fall 2002 5

http://www.olympus-europa.comhttp://www.santex-group.comhttp://www.reliant-machinery.com

6 INJ Fall 2002

a gas, hence is able to more easily pene-trate into materials and exert its strong sol-vent action. This unique physical state isachieved at an elevated pressure and tem-perature of the carbon dioxide.

The use of the strong solvent power ofthis system has been exploited in theresearch laboratory to some extent. Also,the use of liquid CO2 in textile cleaningand scouring operations has been studiedrather extensively at North Carolina StateUniversity and the University of NorthCarolina. Joseph M. DeSimone, a chem-istry and chemical engineering professor atthe University of North Carolina in ChapelHill has done considerable research on thissystem. In 1995, Professor DeSimonefounded the company Micell Technologiesto market an apparel dry cleaning processbased on this research.

This latter company has been exploitingthe technology through a series of drycleaning establishments under the name of“Hangers” dry cleaners (16 stores inSoutheast U.S.).

In recent years almost all dry cleaningoperations have been based on the use ofhydrocarbon and chlorinated solvents, par-ticularly perchloroethylene (so-calledPerc). Such solvents have had real disad-vantages to their use including flammabil-ity and potential for causing cancer. Hence,there has been an interest in replacing suchsolvents.

Liquid carbon dioxide has none of thesedisadvantages in this application. To usethis solvent, the dry cleaning equipmenthas to be pressurized, but this has beenaccomplished fairly easily. Expanding theuse of this solvent has been accelerated bythe introduction of special boosters into thesolvent to facilitate the removal of sometypes of soil and spots. This has beenachieved by additives, generally thought tobe based on fluorine- or silicon-based sur-factants.

Such an improved solvent system basedon liquid carbon dioxide has been intro-duced to the industry under the trade name“Washpoint,” by a joint development ofICI and Linde. These two companiesjoined in product development efforts in2000, which has resulted in the proprietaryWashpoint product. This product is now

being introduced into the dry cleaningindustry.

Linde previously had entered the drycleaning business through its merger withAGA a few years ago. This earlier effortwas based on a solvent termed Dry Washfluid, which had been developed byRaytheon Environmental Systems and Los

Alamos National Laboratories. The newWashpoint solvent system is compatiblewith the Micell system.

It is apparent that these commercialactivities will expand the use of this solventsystem, and will very likely extend the usein the textiles and apparel industries, aswell as increased laboratory use. — INJ

RESEARCHER’S TOOLBOX

Laboratory Technicians

Among the numerous unsung heroes of the R&D scene, laboratory techni-cians often comprise a group that is significant in number and contribution.Generally the workhorses that get the uninteresting and tedious assignments,their suggestions and contributions can often prove critical in bringing home thesuccessful development project.

One company within the nonwovens industry makes it a practice to includelaboratory technicians as co-inventors when they honestly made a contributionto a new invention. A couple of the “Techs” within that Research Division hadmore patents to their credit than some long-time professionals, and rightly so!

Too often, however, these unsung heroes are just that — playing a significantrole, making a contribution, but always on the sidelines.

Recently, more attention has been paid to this group, and their gripes, hopesand views have been seriously noted and considered. Some scientific and engi-neering organizations have taken steps to recognize and highlight the expres-sions of this important group. Several professional societies have modified theirbylaws and clearly established membership categories for qualified technicians.This often involves a clear statement that an individual with an associate degreewith a certain minimum amount of applicable experience can join with other pro-fessionals in the society.

A study of this situation by a professor at Stanford University has identifiedthe three major “Rs” desired by laboratory technicians to clearly establish theirstatus and recognize the value their work brings to the scientific community.These three major desires include the following:

• Respect — technicians wants to be respected for the professionals they are,for the value of their experience and ability to contribute.

• Recognition — Acknowledgment of their efforts and occasional publicrecognition of their contributions and accomplishments.

• Responsibility — Commensurate with their skill and capability, the techni-cian wants and needs opportunities to do more and learn more, to take on moreresponsibility and thus experience personal grow.

The seasoned, long-time researcher who has worked with a variety of techni-cians can often recall one or more Techs that would truly be preferred on theR&D team over a lot of professionals.

When the Three Rs desired by laboratory technicians are thoughtfully consid-ered, they are not at all surprising. After all, respect, recognition and responsi-bility are consciously or unconsciously sought by all rational human beings. Adiscussion in these columns several issues ago dealt with appropriate and mean-ingful actions and recognitions that managers can arrange for deserving profes-sional researchers. Those same items can often be very appropriate for the tech-nician as well.

Beware ‘Negligent Hiring’As has been discussed in this column in

the past, the job of today’s manager isbecoming more and more complex; thetask is truly filled with hazards, potentiallawsuits and actions to be avoided. Herecomes another one.

A new employee is added to the payrollafter the usual interview and referencecheck. Very shortly, it becomes obviousthat the new hire is a discontented, ratherunbalanced individual. As a “reward” forthe baggage of associated problems, theperson is assigned to a less desirable job. Adangerous and violent nature comes to thesurface and a clash or incident occurswhere a fellow employee or worse yet, avisitor is injured. What comes next?

This could be an example of what isbecoming known as a “Negligent Hire,” alegal term that describes a violation of thebasic duty of a company or organization,the duty to exercise “care” in hiring.

In such situations, an employer can bequestioned as to whether they took all rea-sonable steps before the hiring decision toidentify whether or not the problememployee had any past misconduct orunfit behavior on the job. The referencecheck may be cited as evidence of duecare. However, everyone knows that mostorganizations are reluctant to give a for-mer employee a less-than-average rating.So, what is a manager to do?

Recent court rulings have found thatmanagers who are contacted by any com-pany doing a pre-employment check on aformer employee must reveal any seriousmisconduct by that employee.Withholding such information can putthem at risk for a lawsuit.

Almost every state now has a law whichis designed to address this problem.Invariably, former employers are legallyobligated to mention any misconduct

involving violence or acts that physicallyendangered other individuals. Failure todisclose such past misconduct by anemployee subjects the previous employerto damages the employee might inflict infuture workplaces.

Most managers who hire new employ-ees know that it is important to conductsome kind of applicant pre-screening orbackground check. This means checkingreferences, talking with previous employ-ees, and for certain jobs, conducting crimi-nal or motor vehicle department checks.Also, managers should find out if appli-cants have ever been convicted of a crime.This question is usually on the writtenapplication. It is illegal to ask about arrests,but it is okay to ask about convictions.

It is important that the manager keep achecklist in each employee’s file thatdetails who was contacted as a referenceand what was learned. It is important to tryto check each reference give. Little infor-mation may be gained, but the file mustshow that an honest and reasonable effortwas made to get such information. If youdo not try, you might be found negligent.

For an employee with a previous con-viction, the Equal EmploymentOpportunity Commission says thatemployers must consider three factors tojustify use of a conviction record:

• The nature and gravity of the offensefor which the applicant was convicted;

• The amount of time that has elapsedsince the applicant’s conviction and/orcompletion of the sentence;

• The nature of the job in question as itrelates to the nature of the offense com-mitted.

Further, if an employers finds out thatan employee had problems with violencein the past and nothing is done about it, theemployer could be found liable for“Negligent Retention.” Also, anotherrelated employer fault is gaining accep-

DIRECTOR’SCORNER

INJ DEPARTMENTS

INJ Fall 2002 7

Workplace Greenery Reduces Stress

This Department has frequently observed the importance and interest in work-place stress. With individuals spending a major portion of their lives in theworkplace, it only makes sense to examine from time to time the factors that canalleviated or moderate the stress encountered there. Some stress-generating ele-ments cannot be eliminated, of course, but that does not excuse consideration ofanything that can help the situation.

An interesting and surprising stress-reducing factor that has received consid-eration is the use of interior plants in the work environment. It has been shownby these recent studies that such greenery can be a helpful factor. Visual expo-sure to a plant setting has produced significant recovery from stress with fiveminutes, while enhancing productivity by 12%, according to a study by TexasA&M University and Washington State University (WSU).

WSU research also confirmed that once exposed to plant settings, test partici-pants demonstrated more positive emotions, such as happiness, friendliness, andassertiveness, as well as fewer negative emotions, such as sadness and fear.

The researchers concluded that interior workplace plants signal stability andoffer employees a touch of humanity while stimulating a more productive envi-ronment. Growing plants also consume and lower the sleeping-promoting carbondioxide level within an enclosure, replacing it with more stimulating oxygen.These finding may surprising some research administrators, but most house-wives can vouch for their authenticity. For more detailed information, go towww.plantsatwork.org.

http://www.plantsatwork.org.

8 INJ Fall 2002

tance in legal circles and that is “NegligentSupervision.”

With all of these potential worries, anemployer does have some help. Alist of char-acteristics that experts in the field have identi-fied as indicative of the possibility of work-place violence has been assembled(www.noworkviolence.com/articles/prevent-ing_violence.htm ).

Studies have shown that more than 35%of job applicants lie on their employmentapplications. The courts have not ruledthat employers must verify what applicanthave written on their job applications.However, if the employer does not ques-tion about prior convictions, there may notbe a defense against Negligent Hiring.

On the other side of the coin, there is agrowing concern, especially with unionorganizations, that some employers maybe digging too deeply into the employeespast. This has been particularly true fororganizations who employ outside con-tracting firms which may not do as thor-ough a job with their employees’ past asthe company wants. There is such a thingas a company digging too deeply into anemployee’s past, as evidenced by somecurrent law suits. In some cases, thedefendant employers are claiming they areonly following government mandates. So,like a lot of elements in life, there has to bea balance in appropriate actions.

Safety ItemsThe following are a variety of safety

ideas that may be applicable to lab, plantor office environments. These items havebeen collected from numerous sources.

“Our business is in a small community,and we are serviced by a very dedicatedvolunteer fire department. Every year weinvite the officers to tour our facility sothey are aware of the layout of the struc-ture and its contents. We believe this isbeneficial to both parties and may assist ina rescue or their ability to put the fire out.”

One recommendation involves askingthe local police’s bomb squad and the localEmergency Preparedness team to join firedepartment officers in a tour of the facility.

A similar suggestion points out that inmany states, a county EmergencyManagement Agency (EMA) is mandated.

In such states, any facility possessing acertain level of “dangerous” chemicals ormaterials must report approximateamounts and locations of these substancesto the local EMA. This allows the agencyto help in many aspects, including plan-ning evacuation routes, should the needarise. Contacts with and visits from thelocal EMA should be a “must do” item forall pertinent locations.

“I am a volunteer firefighter and EMT-Intermediate, and my company under-stands that I might come in late or leaveearly if I get a call. Companies shouldencourage employees to volunteer anddesign their personnel policies to supportemployees’commitment to contributing tothe community.”

“A useful suggestion is having the localfire department help train on-site emer-gency responders. We make a generousdonation to them for their training serviceswhenever provided.”

A cautionary note regarding the sugges-tion to have the local fire department helptrain on-site emergency responders. C.J.Palmer, an EMS and fire science educatorwho has actively practiced in the field formore than 25 years, says, “I would makesure the instructors are competent in thesubject matter and that they hold aninstructor credential from an agency rec-ognized in the field. Most of us in EMSknow little about OSHArequirements, andI continuously run into well-meaningemployers who are relying on interpreta-tions from people who are not well-versedin regulatory affairs.” Enough said!

“Hearing is an invaluable sense we tendto take for granted. Hearing loss has beenfound to take place at noise levels of 85dBA and higher. An easy way to deter-mine if you are in noise levels higher than85 dBA is when you and another per-son/co-worker have to raise your voices inorder to communicate when standingabout three feet from each other.”

A very helpful Internet site for virtuallyall aspects of safety is that of the NationalSafety Council (NSC), located atwww.nsc.org .The site offers a very excel-lent First Aid and CPR training program.This program was recently offered free ofcharge for a week to commemorate the

September 11 Terrorist Attack; normally itis offered for a nominal charge. This sitealso offers a mobile field reference toemergency medical information that canbe loaded in a PDA (Personal DigitalAssistant). This reference can be loadedwith the latest medical information, andcan be undated as new information isavailable. You can even add your ownlocal protocols to the database. The sitehas a wide variety of features that containa substantial amount of interesting anduseful information. Use it!!

Science Safety, the website of theLaboratory Safety Institute (LSI) is a use-ful place for a variety of helps on variousaspects of laboratory safety. While espe-cially directed toward laboratory safety inscience education, much of the informa-tion is universal in nature.

The Laboratory Safety Institute (192Worcester Road, Natick, MA 01760; 508-657-1900) is a non-profit center for health,safety and environmental affairs. LSI indi-cates that its mission is to “make healthand safety an integral and important part ofscience education, the work and lives ofscientists and science educators.” Thatsuch a need exists is highlighted by theirstatement that “the accident rate in schoolsand colleges is 100 to 1,000 times greaterthan at Dow or DuPont.”

The “Science Safety” site offers a vari-ety of products and services includingmini-grants, audio-visual lending library, avariety of products, seminars and trainingsessions, custom training services, audits,information on regulatory compliance, anonline library with graphics andPowerPoint files, a newsletter and numer-ous other facilities - (www.labsafety.org).

By way of reducing the inventory ofchemicals and potentially hazardous mate-rials, the American Chemical Society hasprepared a publication entitled “Less isBetter.” This offers a variety of techniquesto reduce such inventories without hinder-ing the progress of research and develop-ment efforts. (American ChemicalSociety, 1155 16th Street, N.W.Washington, D.C. 20036; 202-872-4600).— INJ

DIRECTOR’S CORNER

http://www.noworkviolence.com/articles/prevent-http://www.nsc.orghttp://www.labsafety.org).

GMP and the Converting IndustrySeveral sectors within the nonwovens

converting industry pay close attentionto GMP, or Good ManufacturingPractices. These are requirements man-dated by the Food and DrugAdministration to the pharmaceutical,medical and related industries involvedin manufacturing and marketing prod-ucts that can impact human and animalhealth.

Companies that manufacture variousclasses of medical devices also mustmeet GMP standards; such standardsnot only relate to proper manufactur-ing procedures, but also cover rawmaterials, records, distribution andother elements of production and use.Some of these requirements aredesigned to provide the means to checkall aspects of a specific production lotand its use if a problem should arise inthe eventual consumption or use of theproduct.

The FDA has just begun a sizeablereview of its GMP requirements for thepharmaceuticals industry; while thecurrent review will focus initially onpharmaceutical products only, it islikely that any new aspects of GMPwill find their way into GMP standardsfor other manufacturing operations,including personal, medical and sani-tary products.

The current review will cover manu-facturing of veterinary and humandrugs, including biological productsand vaccines. The effort will strive tomake manufacturing processes consis-tent and safer, according to FDA offi-cials. Deputy FDA Commissioner

Lester M. Crawford said in discussingthe review, “Any system can beimproved upon, and with this risk-based, highly integrative GoodManufacturing Practices initiative, weintend to do just that.”

Three goals are cited for the initia-tive:

1. Focus more on processes that pre-sent actual risks to public health.

2. Establish quality standards that donot impede innovation or introductionof new technologies.

3. Enhance predictability in FDA’sapproach to quality and safety.

Over the next couple of years it isanticipated that the FDA will gatherdetailed information from the pharma-ceutical industry, and also from manu-facturing experts, academia, govern-ment and consumer groups relating tothese issues.

It is also anticipated that any princi-ples, practices and standards devel-oped from this review will be adaptedfor modifying GMP requirements inother related industries. Also, therewill undoubtedly be some internation-al implications of such review of GMPrequirements, as there is significantimportation of many of these producttypes into the U.S.; also, there is a ten-dency for such U.S. standards to be uti-lized domestically in other countries.Hence, the potential impact of thisreview may be quite significant.

Cleaning Up the OzoneOzone is one of the major targets in

efforts to clean up the air surroundingthe earth. Ozone is a important compo-

nent of smog, as it can be an importantpollutant in addition to being blamedfor a variety of reactions that increasethe smog-forming potential of variousother chemical pollutants.

To the chemist, the easiest solutionto the ozone problem would be to sim-ply convert ozone (O3) into normaloxygen (O2), which constitutes about1/5 of the atmosphere and is a vital and“good” component of air. The prob-lem, of course, is how to achieve suchconversion easily, inexpensively, andwithout any other attendant problems.

A fascinating approach to achievingthis conversion is being exploited in asmall way by some drivers using theirautomobiles to a greater extent. Thissounds a little incongruous, as automo-biles are considered to be a major partof the problem of ground level pollu-tion. With the right technology, howev-er, they could become part of the solu-tion.

The key to this approach is a catalystsystem that can achieve such a conver-sion at ambient or somewhat elevatedtemperatures, without any deleteriousside effects. Such a catalyst system canbe coated on the radiator of an auto-mobile. As such a car is driven, a largevolume of air is pulled through theradiator and the ground-level ozonecontained therein is converted to nor-mal oxygen.

The catalyst system has been termed“PremAir” Technology by its produc-er, the American company Engelhard.It is keeping the identity of the catalysta secret for the time being, but industrysources point out that the patent litera-ture suggests that manganese oxidesMnO2 and Mn2O3 are involved.Depending upon factors like the speedof the car, the catalyst can convert 60to 80% of the ozone flowing throughthe radiator into oxygen.

Several car manufacturers are look-ing at this technology to give them aboost in their environmental image, aswell as in meeting some governmentalrequirements that become mandatoryin the future. Volvo has had PremAirTechnology on some of its models forseveral months. Also, BMW is using

TECHNOLOGYWATCH

INJ DEPARTMENTS

INJ Fall 2002 9

10 INJ Fall 2002

the system on cars sold into certainstates in the U.S.

While the heat from the car radiatordoesn’t hurt, the reaction does notrequire the elevated temperatures nec-essary for precious metal catalysts asused in conventional catalytic convert-ers. The technology is not consideredto be a complete solution to the ozoneproblem, as it can process the ozone inonly a small fraction of the earth’satmosphere. However, to concept ofusing the automobile to do some clean-ing of the air is certainly novel.

Engelhard is looking for other appli-cations for the catalyst system in addi-tion to the use in automobiles. Use inair conditioner condensers and otherarchitectural applications may be fea-sible and advantageous.

In view of the extensive use of non-wovens in air filtration applications, itis not a wild stretch of the imaginationto think of a modification of this sys-tem to engineer nonwoven fabrics thatnot only rid air of its particulate conta-minants, but also chemical contami-nants that are not now amenable to car-bon filter media. Nonwoven fabricsthat have chemically modified fibersurfaces are being exploited in bloodfiltration by selective chemicalactions; why not a similar approach tocleaning up the IAQ (Indoor AirQuality) problem.

Also, for anyone who has a laserprinter close by, the odor of ozone maybe apparent from time to time. Somepeople claim a little ozone can be help-ful, but basically it is a poisonous gas,so elimination of an excess by such anactive ventilation system might be agood idea.

Recycling PVC PlasticPolyvinyl chloride plastic has been

under the gun from numerous environ-mental groups, who perceive the mate-rial to be a real environmental prob-lem. Recently, some favorable publici-ty was gained by the PVC industry bysome significant success achieved inrecycling waste PVC.

Earlier this year, the “Vinyloop”

recycling process went into commer-cial operation at a plant in Italy. Thisfirst industrial unit was started up at aplant of Solvay, a major chemical com-pany headquartered in Brussels,Belgium, that is a major producer ofPVC resin.

The new operation is designed torecycle 10,000 tons per year of wastePVC plastic, most of it insulationmaterial coming from electrical cable,80% of which is of post-consumer ori-gin. The plant is being operated byVinyloop Ferrara SpA, which is a jointventure of four European PVC produc-ers: SolVin Italia (a Solvay company),Adriaplast, Tecnometal, and Vulcaflex.The venture has received financialsupport from Vinyl 2010, the EuropeanPVC Industry committee devoted tothe voluntary recycling effort.

A second Vinyloop recycling plant is

being designed to recycle PVC-coatedtarpaulins and fabrics produced inEurope; Ferrari S.A. of France is amajor producer of such coated textilefabric and provided considerable assis-tance in developing the process. Thissecond unit is scheduled to begin oper-ation in 2004; other recycling units arebeing considered for Europe, Canadaand Japan.

Obviously, recycling is becoming amajor factor wherever a product rawmaterial is used in large volume.

Digital Printing of NonwovensThe company Leggett & Platt has

roots going back several years into thenonwovens industry. For many years,the Nashville company was noted as amajor producer and marketer of high-loft fabrics, needlepunch fabrics,waddings and other specialty nonwo-

TECHNOLOGY WATCH

PDAs to PocketPCs

All PDAs (Personal Digital Assistants) are not created equal. If all you wantto do is store names and phone numbers, any electronic organizer will fillyour needs. However, if you often find yourself away from your computer,whether out of the room or out of the country, you may want to consider one ofthe beefier handheld offerings that are now becoming popular.

The latest development in the digital assistant world is the introduction of the“PocketPC” – a device that is kind of a cross between a laptop computer and asimple digital organizer. Compaq’s “iPaq” was the first such device to really hitthe market a few months ago, but recently companies like Toshiba, Sony, andothers have rolled out their own version of the PocketPC.

The thing that sets these handhelds apart from the “Palm Pilot” of five yearsago is that they run much of the office software that people are already familiarwith. Most of them can run “Windows CE,” a lightweight version of Microsoft'spopular desktop operating system. The majority of them also run stripped-downversions of MS Word, Excel, Outlook, and Windows Media Player.

Several of the current models also support Java. If you get a model that isequipped for a wireless network (optional in most cases), you can also checkyour email and surf the Web on your palmtop.

Their familiar interface and inter-operability with desktop computers havemade the new generation of handheld computers very popular as a practicaloffice tool. Imagine that instead of recording laboratory data by hand and thenrecopying it to your desktop computer, you simply enter it into an Excel spread-sheet on your Pocket PC. Once the data is stored, it can either be transferred viaa wireless network connection, or through its cradle, which connects it to a desk-top computer. For more information on the various commercial models:www.compaq.com/products/handhelds/pocketpc/H3870.html; www.pda.toshi-ba.com; http://products.hp-at-home.com/products/

http://www.compaq.com/products/handhelds/pocketpc/H3870.htmlhttp://www.pda.toshiba.comhttp://www.products.hp-at-home.com/home/home.php

vens. L&P marketing activities werewell-known in the furniture, bedding,home furnishings, wipes and otherproduct areas. In the past few years, ithas been involved in several acquisi-tion and mergers.

The present L&P is actually Leggett& Platt Digital Technologies and it hasfocused on digital printing of a widevariety of substrates. Also, a majorbusiness for the company is the devel-opment and marketing of digital print-ing equipment, accessories and sub-strates for digital printing. Much of thiscurrent business, both equipment andsubstrates, is in the graphics industry,specifically for soft signage, banners,flags, pennants, point-of-purchase dis-plays and similar items.

In the digital printing equipmentarea, L&P Digital offers many modelsof industrial printing machines in awide and super-wide format (98” to138”). These units utilize piezo drop-on-demand inkjet printing heads, withas many as 8 heads on a unit for bidi-rectional printing. These units can han-dle roll-to-roll operations, as well assome models designed for discontinu-ous operation on rigid substrates, up to3-inches in thickness.

These digital printing machines arecapable of processing a variety of sub-strates, including fabric, coated papers,textiles of a variety of types, film,vinyl (film and sheet), canvas, meshand other types of soft/flexible andrigid specialty substrates. The digitalprinting can involves complex pat-terns, photos, color in an amazing vari-ety, as well as selected textures.

The company, harkening back to itsroots, recently introduced a line ofnonwoven products for the graphicsindustry. This line included 100%polyester and 100% polypropylenefabrics, along with blends in their“VirtuNonWoven” fabric line. Thesecurrent fabrics are relatively lightweight and are translucent for optimalsignage use. Within the product line,“VirtuMesh” is a durable, bright whitepolyester mesh at 8 osy. The“VirtuPoly Cotton” and “VirtuPoly

Cotton Plus” fabrics are made of poly-ester/cotton blends, and are for appli-cations requiring a softer hand.

This is certainly a specialized appli-cation for nonwovens, but it well illus-trates the synergistic combination ofnonwovens and advanced technology.(Leggett & Platt Digital Technologies,Jacksonville, FL; 904-249-1131;www.lp-digital.com). As has beenmentioned in this column in the past,other nonwoven producers are takingan active interest in the application ofdigital printing to nonwoven sub-strates. — INJ

INJ Fall 2002 11

TECHNOLOGY WATCH

http://www.lp-digital.com

AbstractThe role of fiber morphology in a thermal point bonding

operation was investigated. Primary objectives were tounderstand the changes taking place in fiber structure due toapplied heat and pressure, and the role of fiber morphology indetermining optimum process conditions and properties ofthe webs. To study fibers with varying morphology, i.e., frompartially drawn as in spunbonding to fully drawn as in staplefiber nonwovens, fibers with a wide range of crystallinity andorientation were spun and characterized, from twopolypropylene resins. Thermally bonded carded webs wereproduced, using these fibers, and characterized in order tounderstand thermal bonding behavior of fibers with differentmorphology. The fibers with different morphology differedsignificantly in their bonding behavior. The fibers with high-er molecular orientation and crystallinity tended to form aweak and brittle bond due to lack of polymer flow and fibril-lation of the fibers in the bonded regions. In general, fiberswith lower molecular orientation and lower crystallinityyielded stronger and tougher webs. Fibers with relatively lessdeveloped morphology also exhibited lower optimum bond-ing temperature. Morphological changes in fibers wereobserved during the thermal bonding process, in bonded aswell as unbonded regions of the web. As a final step to seehow the observations from staple-fiber study translate to oneof the relevant processes during scale-up, spunbond studieswere also conducted in a similar way.

IntroductionThe basic idea for thermal bonding was first introduced by

Reed [1] in 1942. Since then, there have been a number ofdevelopments in this field. Thermal bonding is now the most

popular method of bonding used in nonwovens. The mainadvantages of thermal bonding are low raw material andenergy costs, product versatility, small space requirements,cleanliness of the process, better product quality characteris-tics, and increased production rates. Of the several types ofthermal bonding such as area-bonding, point-bonding, airoven bonding, ultrasonic bonding and radiant bonding, pointbonding is the most widely used technique [2].

Nonwoven fabric properties are determined by the charac-teristics of bond points and in particular by the stress-strainrelationship of the bridging fibers. During point bonding, thebond points and the bridging fibers develop distinct proper-ties, different from those of the virgin fibers, depending onthe process variables employed. The changes in fiber proper-ties have been hinted at by several authors [2-7] but have notbeen investigated. So far most of the research work [6-15] hasbeen done to study the effects of bonding conditions on fab-ric properties. Some work [12, 16-17] has been done on theeffects of fiber properties on final fabric properties. However,the role of fiber morphology and morphological changes tak-ing place in the fibers due to applied heat and pressure in ther-mal bonding has been almost untouched. This has been main-ly due to the fact that it is almost impossible to characterizethe bond points and the fibers surrounding the bonds withoutthe use of some innovative techniques.

Point bonding is used for a wide range of fibers, from thosewith less developed morphology as in spunbonding to thosewith fairly well developed morphology as in staple fibers.Thus it becomes very important to investigate the effects offiber morphology on bonding conditions and web properties.In this study, polypropylene fibers with a wide range of crys-tallinity and orientation, but with the same diameter, wereproduced. The fibers were then used in studies of their bond-ing behavior and web forming characteristics. Spunbondstudies were also done in a similar way in order to see thegenerality of the observations made in the staple fiber study.It was reported earlier that fiber morphology has a definite

Role of Fiber Morphology In Thermal BondingBy Subhash Chand, Gajanan S. Bhat*, Joseph E. Spruiell and Sanjiv Malkan,The University of Tennessee, Knoxville, Tennessee USA

ORIGINAL PAPER/PEER-REVIEWED

12 INJ Fall 2002

Subhash Chand, currently with Nylstar, Inc., Ridgeway, VASanjiv Malkan, currently with Synfil Technologies, Knoxville, TNGajanan Bhat, Corresponding Author

INJ Fall 2002 13

role on the structure and properties of the thermal bondednonwoven webs [18-20]. A summary of results from thiscomprehensive investigation is reported here.

Experimental MethodsProcessing

Fiber grade polypropylene, which had a melt flow rate of17 dg/min, supplied by Montell USA Inc. was used for theproduction of fibers. Fibers were produced using a Fourneextruder and spinning setup and a conventional two-stagedrawing machine. Extrusion temperature was kept constantat 230°C. Polymer throughput rate and take-up speed werevaried together in order to achieve the same final diameterfor all the fibers. Out of six fiber samples produced, threewere as-spun with no drawing and three were drawn afterspinning. Drawing was done at 140°C. The processing con-ditions used to prepare the fiber samples are summarized inTable 1.

Continuous fibers were chopped into staple fibers of length40 mm for carding. Staple fibers, with an appropriate level ofwater (10%) and LUROL PP-8049 spin-finish (0.4%) sup-plied by Goulston Inc., were carded on a Saco-Lowell card-ing machine to produce webs with a nominal basis weight of40 g/m2. As the fibers did not have any crimp, it was impor-tant to have sufficient finish on the fibers, and to control thehumidity of the room for successful carding. Carded webswere then bonded at several different bonding temperaturesand at a speed of 5 m/min using a Kuster point-bonding cal-ender having 15% bonding area. Speed was kept low due todifficulties in handling of small carded webs. Nip pressurewas kept constant at 350 pli for all the samples.

Spunbond studies were carried out using 35 MFR EXXONPP on the modified Reicofil-I line at the University ofTennessee, Knoxville. A schematic of the process variables isshown in Figure 1. Melt temperature and cooling air temper-ature were the main variables. Airflow rate was adjusted toachieve the same fiber diameter for all the three sets. Webswere bonded at four different bonding temperatures for eachset of fibers. Other process parameters such as bonding speedand calender pressure were kept constant. Filament samplesbefore bonding were also collected for analysis.

Characterization of the Fibers and the WebsFiber diameter and birefringence were measured using an

optical microscope. Thermal analysis of the fibers and thewebs was done using the Mettler thermal analysis systemconsisting of TC11 controller, DSC25 and TMA40 modules.The scans were done at a heating rate of 10°C/min in air.Crystallinity was calculated from the DSC scans assumingthat the heat of fusion of 100% crystalline polypropylene is190 J/g. X-ray diffraction photographs for fibers wereobtained using a flat plate camera and a Phillips x-ray gener-ator. The x-ray wavelength was 1.542 A0 in all the x-ray stud-ies. Crystal size was calculated using the Scherrer equationfrom the measured full width half maximum intensity ofreflection peaks in the equatorial scans [21]. “Duco Cement”was used as a glue for sample preparation for equatorialscans. Use of Duco Cement was helpful in sample preparationfrom bonded regions (only) and from very short fibers takenfrom unbonded regions of the web. Bonded and unbondedregions of the web were carefully separated from the webusing a sharp pair of scissors and analyzed for molecular ori-entation, crystallinity and crystal size.

Tensile properties of the fibers and the fabrics were mea-

Figure 1SCHEMATIC OF SPUNBOND

PROCESS VARIABLES

WEBS WERE BONDED AT FOUR DIFFERENT BONDINGTEMPERATURES FOR EACH OF THE SETS

Table 1PROCESS CONDITIONS FOR PRODUCTION OF FIBER SAMPLES.

Polymer NominalThroughput Rate Spinning Speed

Sample Id (G/Hole/Min) (M/Min) Draw Ratio DenierAs-spun 1 0.28 1000 Undrawn 2.7As-spun 2 0.41 1500 Undrawn 2.5As-spun 3 0.55 2000 Undrawn 2.5Drawn 1 0.42 1000 1.5 2.4Drawn 2 0.72 1000 2.5 2.7Drawn 3 0.96 1000 3.5 2.4

sured using a United Tensile Tester with test conditionsdescribed in the ASTM D3822-91 for filaments and ASTMD1117-80 for nonwoven fabrics [22]. However, for fiber sam-ples, a gauge length of 2” (5.08 cm) and an extension rate of10”/min (25.4 cm/min) were used. For webs, a gauge lengthof 5” (12.7 cm), width of 1” (2.54 cm), and extension rate of5”/min (12.7 cm/min) were used in both machine directionand cross direction.

A “Single-Bond Strip Tensile Test” was developed in orderto estimate the bond strength and the degree of load sharingbetween the fibers during tensile deformation. A schematic ofthis test is shown in Figure 2. A tiny strip of size 80 mm X 5mm was cut from the web. The strip was cut in the middle inthe width direction from two sides to leave only one bonduncut in the middle of the strip, as shown in the figure. Thestrip was then subjected to a conventional tensile test. The testwas conducted on the United Tensile Tester with a gaugelength of 1” (2.54 cm) and extension rate of 0.5”/min (1.27

cm/min). A total of twenty tests were done for each sample. SEM images of the fabrics and the tested samples were

taken using a Hitachi S-3000N electron microscope. Back-scattered images with 30 Pa gas were taken in order to mini-mize the problems due to static charge generation.

Results And DiscussionStaple Fiber Studies

Fiber diameter, crystallinity, and their mechanical proper-ties are given in Table 2. Thermomechanical responses(TMA) of the staple fibers are shown in Figure 3. The sixfiber samples covered a very wide range of morphology andproperties. Fiber diameter was kept the same in all the casesso that the differences due to change in diameter could beminimized and the role of fiber micro-morphology in thermalbonding could be analyzed. As can be expected, there was anincrease in crystallinity of the fibers with increase in spinningspeed and draw ratio. This is an expected trend and the tensiledata, i.e., increase in tenacity and decrease in elongation, isalso consistent with the development of structure. TMA(Figure 3) data also supported the morphological differencesbetween the fibers. Fibers with less developed morphologydeformed easily, compared to the well drawn fibers that

14 INJ Fall 2002

Table 2FIBER STRUCTURE AND PROPERTIES

Sample Id Diameter Crystallinity Tenacity BreakingµµM (%) GPD Extension (%)

As-spun 1 20.8 36.7 2.9 290As-spun 2 19.5 41.3 4.8 280As-spun 3 19.7 45.0 6.4 190Drawn 1 19.9 48.9 6.4 160Drawn 2 20.7 53.7 7.4 60Drawn 3 19.5 56.4 8.5 25

Figure 2SCHEMATIC OF SINGLE-BOND

STRIP TENSILE TEST

Figure 3THERMOMECHANICAL RESPONSES

OF STAPLE FIBERS

INJ Fall 2002 15

showed higher thermal stability.Tensile strength values of the webs produced from differ-

ent fibers and bonded over a wide range of bonding tempera-ture are shown in Figure 4. It was observed that web strengthdecreased with increase in fiber molecular orientation andcrystallinity. Fibers with relatively less developed morpholo-gy yielded stronger webs compared to fibers with moredeveloped morphology. Fiber to web strength realization(ratio of fiber strength to web strength) for different fibers isshown in Figure 5. Fiber to web strength realizationdecreased sharply with increase in fiber molecular orientationand crystallinity. Higher strength realization for the fibershaving lower molecular orientation and crystallinity may bepartly attributed to higher breaking extension of the fibers.Higher breaking extension of the fibers leads to greaterdegree of load sharing between the fibers during the defor-mation of the web. Optimum bonding temperature for drawnfibers was found to be higher than that for the as-spun fibers.Further, optimizing the bonding temperature did not helpmuch in the case of highly drawn fibers, as can be seen fromweb strength versus bonding temperature relationship. Webbreaking extension as shown in Figure 6 exhibited a trendsimilar to tensile strength. Wei et al. [14] and Bechter et al.

[16] have also studied the effect of fiber draw-ratio onpolypropylene nonwoven fabric properties and reported thatfibers with lower draw-ratio resulted in fabrics with highertensile strength.

Fracture mechanism of the webs was studied using bothoptical and scanning electron microscopy (SEM). Opticalmicrographs of the bonds after the tensile test are shown inFigure 7, at optimum bonding temperatures, for as-spun anddrawn fibers. The bonds did not rupture during web failure in

Figure 4WEB TENSILE STRENGTH VS. BONDING

TEMPERATURE FOR STAPLE FIBERS

Figure 5FIBER TO WEB STRENGTH REALIZATION

FOR STAPLE FIBERS

Figure 6WEB BREAKING EXTENSION VS. BONDING

TEMPERATURE FOR STAPLE FIBERS

Figure 7OPTICAL MICROGRAPHS OF THE BONDS

AFTER THE TENSILE TEST: TOP = AS SPUNFIBERS; BOTTOM = DRAWN FIBERS

the case of webs produced from as-spun fibers, for bondingtemperature at and above the optimum. Whereas in the caseof drawn fibers, web failure involved rupture of the bonds atall the bonding temperatures studied. It was observed thatbonds were very weak and brittle in the case of drawn fibers.It is further evident from the image of “elongated” bond inFigure 7 that bonds were very ductile and strong in the caseof as-spun fibers. Disintegration of the bonds during web fail-ure in the case of drawn fibers is shown in Figure 8. Fibersare pulled out from the bond one by one during disintegra-tion. A similar kind of disintegration of the bonds occurred inthe case of as-spun fibers at low bonding temperatures. In thecase of as-spun fibers, drop in web strength above optimumbonding temperature may be attributed to very severe ther-momechanical damage to the fibers in the bond vicinity athigher temperatures.

Figures 9 and 10 show SEM images of bond points of websfor as-spun-1 and drawn-1 fibers, respectively. It is evidentfrom the figures that the bond is not well formed and there is“less polymer flow” and “fibrillation of the fibers” in bondedregions of the web in the case of drawn fibers. Insufficientpolymer-flow and fibrillation of the fibers appear to be themain factors responsible for the weak and brittle nature of thebonds in the case of drawn fibers. No fibrillation wasobserved in the case of as-spun fibers. Fibrillation of the

fibers is further clear from the SEM image in Figure 11. Inthe case of drawn fibers, polymer flow could be improved byincrease in bonding temperature. However, web failureoccurred due to rupture of the bonds even at higher bondingtemperatures. A good correlation was observed between thebondability of the fibers and the TMA failure temperature ofthe fibers. The higher the TMA failure temperature, the high-er the temperature required to obtain a good bond.

16 INJ Fall 2002

Figure 8SEM IMAGE SHOWING

DISINTEGRATION OF BOND

Figure 9SEM IMAGE OF A BOND FOR AS-SPUN 1 FIBERS

Figure 10SEM IMAGE OF A BOND FOR DRAWN 1 FIBERS

Table 3RESULTS OF SINGLE-BOND

STRIP TENSILE TESTSample Id Breaking Nature Of

Load (G) Bond Failure As-spun 1 260 No failureAs-spun 2 212 No failureAs-spun 3 154 No failureDrawn 1 96 Semi-ductileDrawn 2 74 BrittleDrawn 3 73 Very brittle

Figure 11SEM IMAGE OF A BOND FOR DRAWN 1 FIBERS

AT HIGHER MAGNIFICATION (500X)

A single-bond strip tensile test was done in order to esti-mate the bond strength and the degree of load sharingbetween the fibers. The results of this test are shown in Table3. In this test also, no failure of the bonds was observed in thecase of as-spun fibers. Whereas, in the case of drawn fibers,bond failure was observed at breaking loads much less thanthat in the case of as-spun fibers. Therefore, it may be con-cluded that bonds were much stronger in the case of as-spunfibers as compared to drawn fibers. The bonds became morebrittle and weak with increase in draw ratio of the fibers.Difference in breaking loads between as-spun fibers, as therewas no failure of bonds, was attributed to the difference in thedegree of load sharing between the fibers. The degree of loadsharing between the fibers was directly related to breakingextension of the fibers. The higher the breaking extension, thehigher the degree of load sharing.

Spunbond StudiesThe morphological characteristics and mechanical proper-

ties of spunbond fibers for the three sets are listed in Table 4.WAXD photographs are shown in Figure 12. The resultsshow that the three sets differed in terms of their molecular-

orientation, crystallinity, crystallite size andother morphological aspects. Fiber diameterwas within the desired range for all the threesets. As in the case of staple fiber studies, fiberdiameter was intentionally kept the same sothat the differences due to change in diametercould be minimized and the role of fiber micro-morphology in thermal bonding could be ana-lyzed. Set I fibers had the most developed mor-phology followed by Set II and Set III, respec-tively. Diffused peaks in WAXD patterns of SetIII fibers indicate the significant presence of“smectic” phase in Set III fibers. Formation ofsmectic phase is favored at higher melt temper-ature [23], as was the case for Set III. This isprobably due to the fact that higher melt tem-peratures lead to lower stress in the spinline.This allows greater supercooling to occurbefore crystallization begins. When this tem-perature drops below about 700C, smecticphase rather than a-phase is formed [19]. Fiberbirefringence and breaking extension of spun-bond fibers did not go hand in hand. The dif-

ferences in phase structure may be responsible for lowerbreaking extension of Set III fibers, in spite of their lowerbirefringence.

Differences in the web properties for different sets weremarginal in the case of spunbond webs owing to small differ-ences in their fiber properties. Tensile strength and breakingextension of the spunbond webs from different sets of thefibers bonded over a wide range of bonding temperature areshown in Figures 13 and 14, respectively. Optimum bondingtemperature was the lowest for Set III fibers followed by SetII and Set I, respectively. Better bondability of Set III fibersmay be due to their smaller crystal size, paracrystalline struc-ture and less molecular orientation, which provide betterpolymer flow at lower temperatures. A good correlation wasobserved between the TMA failure temperature and the opti-mum bonding temperature of the fibers. Fibers with lowerTMA failure temperature, such as Set III, had lower optimumbonding temperature than the fibers with higher TMA failuretemperature, such as Set I. A similar kind of correlationbetween the TMA failure temperature and the bonding tem-perature has been reported by Zhang et al. [20]. Improvedbondability of the fibers from Set I to Set III could also be

INJ Fall 2002 17

Figure 12WAXD PATTERNS OF SPUNBOND FIBERS

Table 4STRUCTURE AND PROPERTIES OF SPUNBOND FIBERS

Sample Id Diameter Birefringence Crystallinity (%) Crystal Size Tenacity Elongation(µµM) (X x 10-3) % (Ao) (G/Denier) (%)

Set I 19.3 21.8 45.4 110 3.1 300Set II 19.3 21.2 46.5 50 2.7 280Set III 18.8 18.8 47.3 35 2.4 225

18 INJ Fall 2002

seen in terms of increase in fiber to web strength realizationfrom Set I to Set III, as shown in Figure 15. However, as canbe seen from Figures 13 and 14, the trend in web propertiesfor different sets reversed from lower to higher temperature.

Two competing factors in this case may be speculatedto be the bondability and the mechanical properties ofthe fibers. At lower bonding temperatures, bondabilityof the fibers seemed to dominate the web properties,and at higher bonding temperatures, mechanical prop-erties of the fibers were dominant. In general, bondingbehavior of spunbond fibers was similar to that of as-spun staple fibers.

Morphological Changes During Thermal Bonding

Morphological changes in the fibers were studied atmedium bonding temperature, which was 145°C in thecase of staple fiber studies, and 135°C in the case ofspunbond studies. Noteworthy changes in fiber struc-ture were observed in both the cases. The effects wereless prominent in the case of spunbond studies as com-pared to staple fiber studies due to relatively shorterresidence time in spunbonding. The changes in molec-ular orientation of the fibers during the thermal bond-ing process are shown in Table 5. Birefringence of thefibers increased as a result of annealing under con-strained length during calendering. Increase was morefor the fibers with comparatively less developed mor-phology before bonding.

The changes in crystallinity of the fibers during ther-mal bonding are shown in Table 6. A significantincrease in crystallinty was observed from virgin fibersin bonded as well as unbonded regions of the web, inthe case of staple fiber studies. Such a substantialincrease may be due to much higher residence time inthe case of staple fiber studies, which allowed suffi-cient recrystallization to occur. No significant changesin crystallinity were observed in spunbonding.However, crystal size increased during thermal bond-ing in both staple fiber as well as spunbond studies, asshown in Table 7. Here it needs to be noted that crys-tal size data for smectic phase are only reasonableapproximations. Increase in crystal size was evenmore prominant for spunbond fibers. Crystals in thecase of spunbond fibers grew bigger and fewer. Such arearrangement of crystalline structure in spunbondfibers was also indicated by WAXD equatorial scansshown in Figure 16. Change in location and width ofreflection peaks from virgin fibers to bonded andunbonded regions of the web suggested transformationof smectic phase to the more stable a-monoclinicphase during the thermal bonding process.

ConclusionsFiber morphology plays a very important role in

determining the optimum bonding conditions and themechanical properties of the web. Fibers with relative-

ly less developed morphology yielded stronger and tougherwebs as compared to fibers with more developed morpholo-gy. The fibers with high molecular orientation and crys-tallinity tended to form a weak and brittle bond mainly due to

Figure 13TENSILE STRENGTH VS. BONDING

TEMPERATURE FOR SPUNBOND WEBS

Figure 14BREAKING EXTENSION VS. BONDING TEMPERATURE FOR SPUNBOND WEBS

Figure 15MAXIMUM FIBER STRENGTH REALIZATION

FOR SPUNBOND FIBERS

lack of polymer flow and the presence of fibrillation of thefibers in the bonded regions. Fiber breaking extension wasfound to be equally important, if not more, as fiber strength,in governing the web properties. Higher breaking extensionof the fibers leads to a greater degree of load sharing betweenthe fibers during deformation, thus improving the mechanicalproperties of the web. Fibers with less developed morpholo-gy showed lower optimum bonding temperature. A good cor-relation was observed between the thermomechanical stabil-ity of the fibers as measured by TMA and the bondability ofthose fibers. Optimizing the bonding temperature did nothelp much in improving the web properties in the case ofhighly drawn fibers, i.e. fibers with very high molecular ori-entation and crystallinity.

In general, findings with spunbond studies are also similarto that in staple fibers. In addition, it was observed that crys-talline structure and crystal size do affect thermomechanicalstability and, thus, bondability of the fibers. Less perfect andless stable structure, such as smectic phase with smaller crys-tals in the case of Set III, led to lower thermomechanical sta-bility and, thus, better bondability of the fibers. In general,bonding behavior of spunbond fibers was found similar to

that of as-spun staple fibers. It wasobserved that fibers do undergosome structural changes in bondedas well as unbonded regions of theweb during the thermal bondingprocess. The extent of change infiber structure would depend uponthe structure of original fibers andthe process variables employed.

AcknowledgementsThis project was funded from

Nonwovens Cooperative ResearchCenter, NCSU, Raleigh, NC.Authors would like to thankMontell USA Inc. and ExxonMobilCorp. for providing the polymers.Support from TANDEC for provid-ing the Spunbond equipment timeis also appreciated.

References1. Reed R., U.S. Patent 2277049,

assigned to Kendall Company,1942.

2. Dharmadhikary R. K., GilmoreT. F., Davis H. A. and Batra S. K.“Thermal Bonding of Nonwovenfabrics”, Textile Progress,1995(26), No. 2, pp. 1-37.3. Warner S. B. “Thermal Bonding

of Polypropylene Fibers”, Text.Res. J., 1989(59), pp. 151-159.

4. Kwok W. K., Crane J. P.,Gorrafa A. and Iyengar Y.“Polyester Staple fibers for

INJ Fall 2002 19

Table 5CHANGE IN MOLECULAR ORIENTATION

DURING THERMAL BONDINGSample Id Birefringence Birefringence

Of Virgin Fibers In Unbonded(X x 10–3) Region (X x 10–3)

As-spun 1 19.0 23.3As-spun 2 20.4 23.4As-spun 3 17.8 25.0Drawn 1 23.8 26.6Drawn 2 29.4 29.6Drawn 3 31.4 30.6Set I 21.8 21.6Set II 21.2 22.3Set III 18.8 22.4

* In bonded regions, molecular orientation was estimated in terms ofchange in bond- dimensions when heated up to 160 oC.

Table 6CHANGE IN CRYSTALLINITY (%) DURING THERMAL BONDING.

Sample Id Crystallinity Crystallinity Crystallinity Of Virgin In Unbonded In Bonded Region

Fibers (%) Region (%) (%)As-spun 1 36.7 41.9 50.1As-spun 2 41.3 47.8 55.1As-spun 3 45.0 48.3 58.8Drawn 1 48.9 52.6 53.5Drawn 2 53.7 54.2 54.3Drawn 3 56.4 56.9 56.1Set I 45.4 45.0 48.6Set II 46.5 44.8 46.3Set III 47.3 45.8 47.1

Table 7 CHANGE IN CRYSTALLIZE DURING THERMAL BONDING.

Sample Id Crystal Size Crystal Size Crystal SizeFor Virgin For Unbonded For Bonded RegionFibers (A°) Region (A°) (A°)

As-spun 1 140 160 185As-spun 2 185 215 245As-spun 3 150 170 180Drawn 1 140 165 190Drawn 2 155 160 170Drawn 3 135 145 160Set I 110 145 170Set II 50 130 145Set III 35 90 160

Thermally Bonded Nonwovens”, Nonwovens Industry, June1988, pp. 30-33.

5. Gibson P. E. and McGill R. L. “Thermally BondablePolyester Fiber: the Effect of Calender Temperature”, TAPPIJ., 1987, No. 12, pp. 82-86.

6. Drelich A. “Thermal Bonding with Fusible Fibers”,Nonwovens Industry, Sept 1985, pp. 12-26.

7. Muller D. H. “How to Improve the Thermal Bonding ofHeavy Webs”, INDA J. Nonwovens Res., 1989(1), No. 1, pp.35-43.

8. De Angelis V., DiGiaoacchino T. and Olivieri P. “HotCalendered Polypropylene Nonwoven fabrics”, Proceedingsof 2nd International Conference on Polypropylene Fibers andTextiles, Plastics, and Rubber Institute, University of York,England, 1979, pp. 52.1-52.13.

9. Bechter D., Kurz G., Maag E. and Schutz J. “ThermalBonding of Nonwovens”, Textil-Praxis, 1991 (46), pp. 1236-1240.

10. Malkan S. R., Wadsworth L. C. and Devis C.“Parametric Studies of the Reicofil Spunbonding Process”,Third TANDEC Conference, Knoxville, 1993.

11. Malkan S. R., Wadsworth L. C. and Devis C.“Parametric studies of the Reicofil Spunbonding Process”,International Nonwovens Journal, 1992, No.2, pp. 42-70.

12. Wei K. Y., Vigo T. L. and Goswami B. C. “Structure-Property Relationships of Thermally bonded PolypropyleneNonwovens”, J. Appl. Polym. Sci., 1985(30), No.4, pp. 1523-1534.

13. Phillipp P. “Thermal Bonding with Copolyetster MeltAdhesive Fibers”, Nonwovens World, Nov 1986, pp. 81-85.

14. Beyreuther R. and Malcomess H. J. “SpunbondedNonwovens-Linking Innovative Polymer, Technological andTextile Research”, Melliand Textilberichte, 1993(74), No. 4,pp. E133-135.

15. Winchester S. C. and Whitwell J. C. “Studies ofNonwovens-I: A Multivariable Approach”, Text. Res. J.,1970(40), No.5, pp. 458-471.

16. Bechter D., Roth A., Schaut G., Ceballos R., KleinmannK. and Schafer K. “Thermal Bonding of Nonwovens”,Melliand Textilberichte, 1997, No. 3, pp. E39-40.

17. Wyatt N. E. and Goswami B. C. “Structure–PropertyRelationships in Thermally Bonded Nonwoven Fabrics”, J.Coated Fabrics, 1984(14), pp. 100-123.

18. Zhang D., Ph.D. Dissertation, The University ofTennessee, Knoxville, December 1995.

19. Lu, F. M. and Spruiell, J. E., J. Appl. Polym. Sci., 34,1541 (1987).

20. Dong Zhang, G. S. Bhat, Sanjiv Malkan and LarryWadsworth, “”Evolution Of Structure And Properties In ASpunbonding Process,” Textile Research Journal, 68(1), 27-35 (1998).

21. Cullity B. D., ‘Elements of X-ray Diffraction’,Addison-Wesley Publishing Company Inc., Massachusetts,1978, p. 284.

22. Storer R. A., ASTM, Easton, MD, USA, 1986.

23. Ahmed M., ‘Polypropylene Fibers, Science andTechnology’, Elsevier Science Publishing Company, NewYork, 1982, p. 194. — INJ

20 INJ Fall 2002

AbstractOn-line and off-line measurements were obtained to gain

an understanding of fly production during multi-hole meltblowing at commercial speed. These measurements allowedus to describe the effects of common processing parameterson fly production and develop a model for fly formation thatbegins to account for experimental measurements.

IntroductionIn a previous paper [1], we reported results of experiments

conducted to obtain a general understanding of fiber motionsnear the collector of the basic multi-hole melt blowing (MB)process operating at commercial speed. In the current paper,we address the problem of fly formation. Fly particles arefibers that have been broken and released from the fiberstream during MB. The phenomenon of fly formation haspractical importance to web producers and knowledge of flyformation is important for understanding the MB process. Flyis undesirable and its formation is sometimes used to identifya processing limit during commercial MB. That is, prelimi-nary processing conditions are determined, primary air pres-sure is increased until fly is produced and then air pressure isdecreased until little fly is produced.

In this paper, we will report numerous experimental mea-surements related to fly formation during multi-hole MBoperating at commercial speed. Measurements include flyparticle mass, fly particle length, total fiber length in fly par-ticles, fiber bundle size in webs, air speed in the direction nor-mal to the collector surface, air speed in the direction of col-lector motion and the direction of fiber flow near the collec-tor. While obtaining these measurements, we varied primaryair pressure, die-to-collector distance (DCD), collector speedand collector vacuum. These measurements were used to for-mulate a conceptual model of fly production based on aero-dynamic drag and fiber entanglement.

Experimental ProceduresWe processed PP-3546G polypropylene resin (1259 MFR)

supplied by ExxonMobil Chemical Company on three differ-ent multi-hole MB lines in TANDEC at the University ofTennessee. These were a 180-hole (15 cm) horizontal linehaving a 47 cm diameter rotating drum collector, an AccurateProducts 600-hole (51 cm) horizontal line having a 55 cmdiameter rotating drum collector, and a Reifenhauser 601-hole (61 cm) vertical bicomponent fiber line having a flatendless belt collector. Commercial speed processing condi-tions generally were used.

A high-speed camera and pulsed laser were used to acquireimages of fibers on-line. Procedures used to obtain fibervelocity from these images have been reported previously [2].Air speed measurements were obtained using processing con-ditions similar to those used for fiber measurements but withno resin throughput. Air speed was measured on-line using aPitot tube and anemometer. Fiber bundle size in webs wasmeasured off-line using WebPro [3]. Fly particles were cap-tured during MB using wire screens and analyzed off-line

. Results and Discussion

Figure 1 provides optical images of fly particles collectedwhile processing polypropylene with a die temperature of232O C, air temperature of 243O C, resin throughput rate of0.42 ghm, primary air pressure of 2.5 psi and DCD’s of 76,30 and 15 cm using a 55 cm rotating drum collector. This fig-ure qualitatively shows that the size of fly particles variedover a large range. Figure 1 also shows that fly particles pro-duced with a particular set of processing conditions exhibitedsimilar sizes. Finally, Figure 1 shows that DCD significantlyinfluenced the size of fly particles.

To obtain quantitative information about fly, we collectedfly particles while varying processing conditions and mea-sured the mass and length of individual particles and the

Fiber Motion Near The CollectorDuring Melt Blowing:Part 2 — Fly FormationBy Randall R. Bresee, The University of Tennessee, Knoxville, Tennessee USAand Uzair A. Qureshi, Jentex Corporation, Buford, Georgia USA

ORIGINAL PAPER/PEER-REVIEWED

INJ Fall 2002 21

22 INJ Fall 2002

diameter of fibers inparticles. From thisdata, we computed thetotal length of fiber con-tained in individual flyparticles. Measurementsfor individual particlescollected with each pro-cessing condition were

averaged and are summa-rized in Figure 2.

Figure 2 shows that pri-mary air pressure, DCD

and collector speed influenced the structure of fly. Increasingprimary air pressure 20% increased particle mass, particlelength and total fiber length in particles, although the increas-es were relatively small. Increasing DCD reduced particlemass, particle length and total fiber length in particles.Increasing collector speed increased particle mass, particlelength and total fiber length in particles.

We are aware of no phenomenological model for fly for-mation in the published literature. In the following pages,we will propose a basic model for fly formation based onaerodynamic drag and fiber entanglement and will show thatthis model begins to account for the experimental data inFigure 2.

Mechanism of Fly FormationWe believe that fly formation is controlled primarily by

aerodynamic drag and fiber entanglement. That is, fly parti-cles are released when (i) a drag force exists that is strongenough to break fibers and (ii) fiber entanglement is insuffi-cient to retain broken fibers within the forming web.

Drag ForceFibers must be broken to release fly particles from the fiber

stream during MB. We previously showed that only tworegions of the basic MB process are likely to produce a largedrag force on fibers [1]. These regions are located near the dieand near the collector where differences between air and fiberspeeds are large. Consequently, these two regions are mostfavorable for producing fly whereas most of the regionbetween the die and collector is less favorable for fly produc-tion because drag forces are smaller.

Figure 2 showed that fly production is greatly influencedby two collector parameters - DCD and collector speed.Figure 2 also showed that individual fly particles contained asmuch as 150 m of fiber length. These observations suggestthat fly is most likely released near the collector rather thannear the die. Consequently, we will focus our discussion onfly formation near the collector although we recognize thepossibility that fly also may be produced near the die.

In a previous discussion of the basic MB process, weremarked that aerodynamic drag forces acting on fibers sud-denly increase near the collector since fiber speed decreasesto zero during laydown but air continues to flow at relativelyhigh speed [1]. Recognizing this phenomenon allows us to

Figure 1FLY PARTICLES COLLECTED WITH 76 CM (LEFT), 30 CM (MIDDLE) AND 15

CM (RIGHT) DCD; EACH IMAGE AREA = 9.0 CM X 6.7 CM (BAR = 3.0 CM)

Figure 2EXPERIMENTAL FLY DATA FOR VARIOUS

PROCESSING CONDITIONS

qualitatively explain experimental observations in Figure 2that show fly formation apparently was reduced when prima-ry air pressure was decreased or DCD was increased. That is,fiber speed decreases to zero during laydown for any pro-cessing condition so the aerodynamic drag force available tobreak fibers near the collector is determined mostly by thespeed of air in the laydown region of the collector. Decreasingprimary air pressure at the die or increasing DCD reduces thedrag force near the collector since the speed of air arriving atthe collector is reduced. Consequently, we expect less fiberbreakage to occur and less fly to be produced when primaryair pressure is decreased or DCD is increased.

To learn more about drag force near the collector, we mea-sured the distribution of airflow over a collector surface. Thespeed of air traveling in the direction normal to a flat collec-tor belt was measured near the airflow centerline as well asplus and minus 7.5 and plus and minus 15.0 cm from the cen-terline and 1.5, 4.0, 6.6, 9.1 and 11.6 cm from the collectorsurface. The general measurement region is identifiedschematically in Figure 3 and specific measurement locationsare denoted by vertical arrows in Figure 4.

Figure 5 provides air speed measurements in the directionnormal to the collector surface. Near the airflow centerline,air speed decreased as the collector surface was approached.Slowing was observed as far as 11.6 cm from the collectoralthough air slowed more rapidly as it traveled closer to thecollector. This effect would be expected to slow fibers nearthe airflow centerline as far as 11.6 cm from the collector and

slow fibers more rapidly as they traveled closer to the collec-tor surface. This conclusion is consistent with fiber speedmeasurements that showed fiber speed decreased as far as 9cm from the collector but decreased more rapidly within 3 cmof the collector [1].

In contrast to air traveling near the centerline, air 7.5-15 cmfrom the centerline traveled faster at locations closer to thecollector surface. Faster moving air would be expected toincrease the speed of some fibers approaching the collector inthis region. This may seem to contradict the general conceptthat fiber speed must decrease to zero during laydown.However, we need to recognize that fibers near the collectorof a commercial MB process are entangled with numerousother fibers to form an extensive network. Fibers near the air-flow centerline that slow as they approach the collector helpslow fibers traveling far from the airflow centerline. It isimportant to note, however, that Figure 5 provides evidencethat a drag force exists far from the airflow centerline thatmay accelerate and break fibers. This suggests that fly is mostlikely produced in laydown regions far from the airflow cen-terline rather than laydown regions near the centerline.

The interior of MB webs generally result from fiber lay-down in the vicinity of the airflow centerline whereas lay-down far from the centerline produces the collector-side anddie-side of webs. Figure 5 provides evidence that aerody-namic drag may reduce the speed of fibers forming the webinterior at a different rate than fibers forming the collector-side and die-side of webs. This leads us to expect that the inte-rior of a MB web may exhibit a slightly different structurethan the collector-side and die-side of the web. However,experimental measurements of web structure that could testthis hypothesis have not been reported.

Figure 2 provided experimental evidence that fly formationwas influenced by collector speeds of 10-35 m/min. To learnmore about this, we acquired air speed measurements similarto those of Figure 5 but using three collector belt speeds (0,21 and 61 m/min) at each measurement location. These mea-surements are provided in Figure 6. This figure clearly shows

INJ Fall 2002 23

Measurement Region

Figure 3MEASUREMENT REGION NEAR

A FLAT BELT COLLECTORFigure 5

AIR SPEED IN THE DIRECTIONNORMAL TO THE COLLECTOR

Figure 4MEASUREMENT LOCATIONS

NEAR THE COLLECTOR

-15.0 -7.5 0 7.5 15.0

24 INJ Fall 2002

that collector belt speed had little influence on the speed of airtraveling in the direction normal to the collector belt at dis-tances as close as 1.5 cm from the belt surface.

We also evaluated the influence of collector belt speed onthe speed of air traveling parallel to the direction of beltmovement at various distances from the collector surface.Horizontal arrows in Figure 4 denote our specific measure-ment locations. Measurements were recorded only at the air-flow centerline and 15 cm from the centerline to save time.Figure 7 provides measurements obtained at the airflow cen-terline whereas Figure 8 provides measurements obtained 15cm from the centerline.

Figures 7-8 show that collector belt speed had little influ-ence on the speed of air traveling in the direction of beltmovement at distances as close as 1.5 cm to the belt surface.Overall, Figures 6-8 lead us to conclude that the influence ofcollector speed on fly formation reported in Figure 2 did notoccur as a result of collector motion affecting air speed.

Figures 7-8 also show that air flowing in the direction ofcollector motion traveled fastest at locations far (15 cm) fromthe airflow centerline. This implies that some fibers may beswept during laydown toward the direction of belt movementby large drag forces. Since belt motion proceeds in the MD,Figures 7-8 support our previous claim [4] that fiber orienta-tion is markedly changed during laydown from CD to MD. Inaddition, fast moving air in the MD would be expected toincrease the speed of some fibers which, in turn, increases theprobability of fiber breakage and fly formation.

Next, we attempted to learn more about the influence of avacuum applied to the collector laydown area on fly forma-tion. To help understand this, we acquired air speed measure-ments that were similar to Figure 5 but while using a vacuumand combined these measurements to produce Figure 9. Thisfigure shows that a vacuum applied to the collector signifi-cantly influenced the speed of air traveling in the directionnormal to the collector belt. The vacuum influenced air speed

Figure 6AIR SPEED IN THE DIRECTION NORMAL TOTHE COLLECTOR FOR THREE COLLECTOR

BELT SPEEDS (SEE FIG. 5 LEGEND FOR DISTANCES FROM COLLECTOR SURFACE)

Figure 7AIR SPEED IN THE DIRECTION OF COLLECTOR

BELT MOVEMENT AT THEAIRFLOW CENTERLINE

Figure 8AIR SPEED IN THE DIRECTION OF COLLECTOR

BELT MOVEMENT 15 CM FROM THE AIRFLOW CENTERLINE

Figure 9AIR SPEED MEASUREMENTS NORMAL

TO THE COLLECTOR BELT

as far as 6.6 cm from the collector surface, although air trav-eling closer to the collector was influenced more.

It is important to note that the vacuum increased air speednear the airflow centerline but decreased air speed in areas far(5-15 cm) from the airflow centerline. Since practical MBexperience has demonstrated that fly is reduced when a vac-uum is applied to the collector, Figure 9 suggests that fly ismost likely released from regions located far from the airflowcenterline and near the collector surface (where air speed wasreduced most by the vacuum). That is, the vacuum ought toreduce aerodynamic drag and thus fiber breakage most sig-nificantly far from the airflow centerline and near the collec-tor surface.

Figure 9 also suggests that fiber laydown with a vacuum isdifferent than laydown using the same MB equipment butwithout a vacuum since the distribution of air speeds in thelaydown area are different. For example, Figure 9 shows thatthe vacuum increased air sp