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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
Sponsored By
Journal NotesAll links are active but invisible
As the cursor passes over a link it will change to a pointer
Links include: Article names on cover www references E-mail
addresses Table of contents
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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
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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 [email protected].
[email protected]
Association EditorsCosmo Camelio, INDAD.V. Parikh, TAPPI Teruo
Yoshimura, ANIC
Production EditorMichael JacobsenINDA Director of
[email protected]
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:[email protected]:[email protected]:[email protected]://U.S.D.A.
S.R.R.C.
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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 [email protected].
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:[email protected].
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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
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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.
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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.
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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