Expanded PTFE Applications Handbook. Technology, Manufacturing and Applications

283 Pages·2012·41.767 MB·English

by  Sina Ebnesajjad

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EXPANDED PTFE APPLICATIONS
HANDBOOK
TECHNOLOGY, MANUFACTURING AND
APPLICATIONS
Sina Ebnesajjad
President, FluoroConsultants Group, LLC
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Preface
I have marveled at the elegant and intricate developed for membrane manufacturing. Chapter 4
structure of expanded microporous membranes of describes processing of fine powder PTFE into
polytetrafluorethylene(PTFE)fordecades.Thanksto precursorfilmsandothershapesfortheproductionof
scanning electron microscopy, one can see the microporous membranes. Chapter 5 focuses on how
minutia of the membrane scaffolding. The beauty of expanded PTFE membranes and other shapes are
the chaoticyet ordered microporousstructure comes formedfollowedbydiscussionoftechniquestomake
in tandem with its remarkable utility. The words different shapes of ePTFE in Chapter 6.
“elegant” and “beauty” may raise eyebrows as they Chapter 7 describes the properties and character-
do in mathematics. David H. Bailey (retired Senior istics of ePTFE membranes along with a brief
Scientist, Lawrence Berkeley National Laboratory, discussion of its important applications. Chapters 8
University of California, Davis) and Jonathan M. through 12 discuss key applications of ePTFE.
Borwein (Professor of Mathematics, University of Chapter 13 discusses a number of methods for
Newcastle, Australia) wrote in a 2014 blog post treatment and modification of surfaces of micropo-
(Why Mathematics Is Beautiful and Why It Matters, rous membranes. Those superficial alterations allow
February 14, 2018, Huffington Post): all (mathe- impartation of hydrophilicity or special functions to
matical)estheticresponsesseeminparttocomefrom the membrane surface. Chapter 14 discusses the
identifyingsimplicityincomplexity,patterninchaos, manufacturers of expanded microporous PTFE
structure in stasis. I have found this description true membrane.
of microporous membranes of PTFE. This has been a difficult book to write and has
Naturally, I set out to learn all I could about this taken almost 6years to complete. Any publisher
beautiful membrane. These days there are few other than Elsevier would have long canceled my
commercial products about which one does not find contract. Now that the book is published I have two
scoresofbooksandin-deptharticles.Consequently,I hopes.First,thebook,flawedasitmaybe,wouldbe
expected to find books, at least one, and papers. To beneficial to those who seek information about
my surprise, there was little published about the expanded PTFE membranes. Second, I hope what is
fundamentals of expanded PTFE membranes and correct and what is incorrect motivates brighter
films,howtheyareformedandmade,howtheywork, minds to write their own books about this subject.
and a host of other questions. Certainly, there are The colossal impact of these membranes on human
innumerable articles about the membrane’s varied life certainly warrants such efforts. I hope to receive
applications, plenty of commercial literature and as many critiques of this book as possible, with
a plethora of patents. a promise to make corrections in the next edition.
SoIsetoutonadecadeandahalflongjourneyto Thereaderswhowishtodispensewithdiscussions
explore and learn, on my own, about this micropo- of polymer and precursor film preparation can begin
rous membrane (ePTFE). This book presents the reading the book with Chapter 5. A modest knowl-
resultsofmyePTFEeducationaljourney.Ihopeand edge of PTFE and its properties is required for
pray it offers a convenient starting point for those a deeper understanding of the discussions. The
who wish to learn about the ePTFE membranes. applications chapters can be approached without
The book begins with two short chapters reading the other chapters.
describing a short history of ePTFE and the proper-
Sina Ebnesajjad
tiesofPTFE.Chapter3discussespolymerizationand
finishing of PTFE by emulsion method (fine powder Chadds Ford, Pennsylvania
August 2016
PTFE) placing emphasis on grades specially
xi
Acknowledgment
Many people have contributed to this book Parkinson Freudenberg Sealing
including everyonewhosework has been mentioned Technologies Technologies
in this book in some shape and form. I have tried to
STM, Inc. Donaldson Corp.
acknowledgeallwhohavehelpedmewiththisbook.
To my profound regret I may have missed some International Polymer PolyFluoro Ltd.
Engineering, Co.
names. Please accept my sincere apologies for the
oversight. A short note to the publisher or to me Adtech Polymer Diener Electronic
directlywillallowcorrectionintheelectroniconline Engineering
copyandfutureeditions.Iammostgratefultomany
OutdoorSportsCenter Henniker Plasma
companies and individuals who have contributed
data, photographs, and illustrations to this book. www.eventfabrics.com PVA TePla Co.
Authors and companies have been cited in the book
Madison Chemical Acton Technologies
or in the reference section of each chapter. Industries
I have listed the names and website of companies
REI Co-Op Enercon Ind.
wherevertheirmaterialhasbeenused.Iofferyoumy
heartfeltthanksforyourenrichingcontributionstothis Atrium MedicalCorp. Tri-Star Technologies
book. I hope the following list (in the order of
GE Life Sciences Ingenta
appearanceinthebook)isnotmissinganycompanies.
Mayo Foundationfor DeWal Industries
Ifthereisanerror,ashortnotetothepublisherorme
Educationand Res
willbeappreciatedsothattheerrorcouldbecorrected:
Clarcor IndustrialAir, ZeusIndustrialProducts
BHA Industrial Filtration
W. L. Gore & Pall Corporation
Associates Eaton Corp. MaquetCardiovascular
C. R. Bard Davol Inc. CoreflonCorp. PORTEF ePTFE Filters Porex Corporation
Willy A.Bachofen Amann & Soehne G Advantec MFS, Inc. Phillips Scientific
DuPont/Chemours Sunteca Corp.
I have used numerous illustrations and much
Buflovak, LLC WLT Dichtungstechnik,
data from W. L. Gore & Associates in this book.
e.K.
That is simply because of the paramount role
Jennings International Virginia Sealing the company has played in the development
Products
of expanded polytetrafluoroethylene (ePTFE)
QPD Inc. Teadit NorthAmerica membranes and products based on those
membranes. Rarely, if ever, a single company has
BrucknerUSA All State Gasket
playedsuchasubstantialroleinthedevelopmentof
Summit Filter Leader GT Corporation a product that has cascaded into billions of dollars
Corporation throughout the market value chains. To be sure
Marshall and Williams, RAM Gasket Solutions a number of manufacturers of ePTFE have also
Div. Parkinson made technological and applications contributions.
Technology My deepest thanks go to W. L. Gore & Associates
xiii
xiv ACKNOWLEDGMENT
and other ePTFE manufacturers for the generosity the breadth of subject matters of PDL. Ms. Nicky
they have extended to me. Carter was the production manager of this book.
I would like to thank the individuals who played Nicky’s good nature and patience, in addition to her
a key role in attainment of permission for the use of support,werevitalduringtheproductionofthisbook.
W. L. Gore illustrations and data in this book. Ms. I would like to thank my friend and soul mate
Amy E. Calhoun, the leader of Enterprise Commu- Ghazale Dastghaib for her infinite support and
nications at W. L. Gore & Associates devoted patience over the decades while I have been writing
significant time to this matter. She consulted andeditingbooks.WithoutherloveandcomraderyI
a number of people at W. L. Gore & Associates and couldhaveneverhadthewonderfulcareerIhavehad.
provided me with guidance and the needed permis- Noneoftheviewsorinformationpresentedinthis
siontousetheillustrationsandartworkinthisbook. book reflects the opinion of any of the companies
Thank you Amy. Ms. Jenny E. Maher was instru- (especially W. L. Gore & Associates) or individuals
mental in facilitating the process of obtaining thathavecontributedtothebook.Ifthereareerrors,I
permission. Thank you Jenny. own them. A note indicating the specific error to the
I would like to express my appreciation to publisher, for the purpose of correction, would be
Matthew Deans the senior publisher of William muchappreciated.Contactinformationcanbefound
Andrew imprint for his support. David Jackson, in the front matter of this book.
acquisitions editor of Plastics Design Library (PDL)
Sina Ebnesajjad
has supported me throughout this project and others
Chadds Ford, Pennsylvania
in every possible way. He has been my energetic
August 2016
partnerintheeffortstogrowthenumberoftitlesand
1 History of Polytetrafluoroethylene and Expanded
PTFE Membrane
O U T L I N E
Part I: Discoveryof Part II: Invention ofExpanded
Polytetrafluoroethylene 1 Polytetrafluoroethylene 4
1.1 Discoveryof Polytetrafluoroethylene 1 1.4 ANew Type ofPolytetrafluoroethylene 4
1.2 Roy Plunkett’sStory 1 1.5 Early Historyof W.L. Goreand Associates 4
1.3 Commercialization of 1.6 DiscoveryofExpanded Polytetrafluoroethylene 5
Polytetrafluoroethylene 3
References 7
Part I: Discovery of newfluorinatedrefrigerantsthatweresaferthanold
gases because of being nonflammable, nontoxic,
Polytetrafluoroethylene [1a]
colorless, and odorless. He reacted tetrafluoro-
Many people around the world, regardless of ethylene (TFE) with hydrochloric acid (HCl) for
whetherornottheyhavebeendirectlyinvolvedinthe synthesis of a refrigerant, CClF2eCHF2 [2]. As he
creationandproductionofpolymer,arefamiliarwith had done on many other occasions, on the morning
the origins of fluoropolymers. Teflon®, DuPont’s ofApril6,1938,Plunkettcheckedthepressureona
trademark name for polytetrafluoroethylene (PTFE), full cylinder of TFE. He was surprised to find no
isworldrenowned.Theclassicstoryofthediscovery pressure, and yet theweight of the cylinder was the
of fluoropolymers is replete with the magical com- same as it had been the previous day. Plunkett and
binationofcuriosity,perseverance,andserendipity.It his technician removed the valve and shook the
is helpful to note the environment and context in cylinder upside down. When they cut open the gas
whichpolymersciencebegan.Thissectionplacesthe cylinder, they recovered a small amount of a slip-
invaluable discovery made by Roy Plunkett [1b] in pery white substance (Fig. 1.1). They analyzed the
the context of the times and of the events and per- waxy powder and named this new substance poly-
®
sonalitiesthatshapedscience,industry,andtheworld tetrafluoroethylene,latertrademarkedasTeflon by
in the 1930s and 1940s. Plunkett’s finding is even the DuPont Company. The rest, as they say, is his-
more impressive when viewed through the prism of tory (Fig. 1.2).
this context.
1.2 Roy Plunkett’s Story
1.1 Discovery of Roy was born into a poor farm family in New
Polytetrafluoroethylene Carlisle,Ohio.When theGreatDepressionbeganhe
was a student at Manchester College in North Man-
For those who do not already know the story, let chester, Indiana, where he shared a room with an
usbeginwiththeending.By1938,Dr.RoyPlunkett olderstudentnamedPaulFlory.Roygraduatedwitha
hadbeenworkingatDuPontfor2years,developing bachelor of arts in chemistry in 1932 and followed
ExpandedPTFEApplicationsHandbook. http://dx.doi.org/10.1016/B978-1-4377-7855-7.00001-8
Copyright©2017ElsevierInc.Allrightsreserved. 1
2 EXPANDED PTFE APPLICATIONS HANDBOOK
Paul to graduate school at Ohio State University.
Within 2years of one another, Roy and Paul both
earned Masters and PhD degrees from Ohio State
University. In 1936, Roy joined DuPont Central
Research, where Paul had been working since 1934.
Roy quickly advanced to Kinetic Chemical Co., a
joint venture that DuPont and General Motors (GM)
had set up to produce safe refrigerants to replace
ammonia and sulfur dioxide. Roy was given a
laboratory in DuPont’s Jackson Laboratory on the
shore of the Delaware River in Deep Water, New
Jersey. Roy’s laboratory was across the hall from a
laboratory run by a colleague named Charlie, whose
research focused on synthesizing new organic
compounds. Roy was trying to expand the line of
fluorocarbons, known as Freon, to meet the needs
brought on by the explosive growth of automobile
production at GM.
ExcitementeruptedinRoy’slabonApril6,1938,
when he found no pressure in the TFE cylinder and
Figure 1.1 Depiction of the discovery of polytetra-
discovered the strange new substance inside. What
fluoroethylene by Roy Plunkett and his assistant,
was this slippery white powder? Because he had
Jack Rebok [3].
Courtesy:The DuPontCo. time, knowledge, and curiosity, he paused to ask
Figure 1.2 Photograph of the notebook page in which Plunkett recorded the discovery of
polytetrafluoroethylene [3].
Courtesy:The DuPontCo.
1: HISTORY OF POLYTETRAFLUOROETHYLENE AND EXPANDED PTFE MEMBRANE 3
questions. He was not working under relentless Nazi Germany. Lieutenant General Leslie Richard
pressure to meet next month’s deadline because Groves, who led the project, made critical decisions
companies like DuPont, that funded research like to prioritize the various methods of isotope separa-
Roy’s,understoodthatsuccessinresearchrequireda tion;andheacquiredtherawmaterialsneededbythe
reasonably low-stress work environment. One won- scientists and engineers working on the project.
ders how history might have been different had Roy In the course of his search for new materials to
had been given an inflexible objective. What would meet the novel needs of the Manhattan Project,
havehappenedifRoyhad,upondeterminingthatthe General Groves came across PTFE. After hearing
foreign substance had no properties that would about the properties of PTFE and its resistance to
further his fluorocarbon research, wiped up the different chemicals, General Grove is purported to
powder and carried onwith his dailytasks? ButRoy have said that the cost, even at $100 a pound, was a
was a well-trained scientist with the freedom and bargain! Scientists working on the project badly
curiosity to investigate this unexpected finding. needed corrosion-resistant materials for the uranium
When Charlie heard the racket across the hall, he enrichment process. U-235 had to be separated from
walkedovertoRoy’slabtoinvestigate.Helatersaid, U-238 using differential diffusion of UF . UF is
6 6
“I noticed commotion in the laboratory of Roy highly corrosive to most metals, butPTFE stands up
Plunkett, which was across the hall from my own. I to it. Once the scientists involved in the Manhattan
investigated and witnessed the sawing open of a Project verified its properties, the US Patent Office
cylinderfromwhichwasobtainedthefirstsampleof placed PTFE under a national “secrecy order” and
Teflon® fluoropolymer.” This is the description of fromthenonitwasreferredtoas“K-416.”Onlyone
thatdayatJacksonLaboratorythatCharliePedersen patent, with minimal content, was issued to DuPont
sharedinhis1987NobelLecture.Pedersen(Fig.1.3) in 1941 to recognize its rights to the invention [4b].
went on to invent new crown ether compounds, for The next time anyone outside of DuPont heard of
whichhewasawardedtheNobelPrizeinChemistry. PTFE was after World War II, in 1946, under the
®
Afterloggingtheresultsofhisdiscoverythatday, now-famoustrademarkofTeflon .DuPontlearneda
Roy Plunkett continued with his research. Several great deal about PTFE during its intense efforts to
yearslater,wartimeneedsrescuedhisdiscoveryfrom produceitfortheManhattanProject.Whenresources
oblivion. The Manhattan Project was a covert pro- formerlyreservedforthewareffortbecameavailable
gramwhoseaimwastodevelopanatombombbefore again to scientists and manufacturers in the US and
aroundtheworld,itwastimetomovetheproduction
of PTFE from pilot plant to a commercial
manufacturing operationdand DuPont was ready.
Dr. Plunkett’s own words describe the impact of
his discovery: “The discovery of polytetrafluoro-
ethylene (PTFE) has beenvariously described as (1)
an example of serendipity, (2) a lucky accident and
(3)aflashofgenius.Perhapsallthreewereinvolved.
Thereiscompleteagreement,however,ontheresults
of that discovery. It revolutionized the plastics in-
dustryandledtovigorousapplicationsnototherwise
possible” [4a].
1.3 Commercialization of
Polytetrafluoroethylene
Efficient monomer synthesis methods, polymeri-
zation technologies, and various forms of PTFE had
to be developed. The fact that large-scale monomer
Figure 1.3 Dr. Charles J. Pedersen, 1987 Nobel synthesisandcontrolledpolymerizationhadnotbeen
Laureate in Chemistry (retired from DuPont). fully developed was a technical impediment to
4 EXPANDED PTFE APPLICATIONS HANDBOOK
commercialization of the new polymer. Intensive halfacentury.PTFEandePTFEhavealsogenerated
studies resolved these problems, and small-scale tens of billions of dollars’ worth of business.
®
production of Teflon began in Arlington, New Jer-
sey, in 1947. In 1950, DuPont scaled up the com-
®
mercial production of Teflon in the US with the 1.4 A New Type of
construction of a new plant in Parkersburg, West Polytetrafluoroethylene
Virginia.In1947,ImperialChemicalIndustriesbuilt
the first PTFE plant outside the US, in the United W.L.Gorewasasuccessfulsmallcompany,barely
Kingdom. a decade old, when Bob Gore discovered ePTFE,
PTFE cannot be dissolved in any solvent, acid, or which the company named Gore-Tex. ePTFE trans-
base, and when melted it forms a stiff clear gel with formed W.L. Gore into a multibillion-dollar giant of
noflow.Specialprocessingtechniquesnormallyused creativity that has continued to try to find new
for molding metal powders were modified to fabri- product development opportunities in which ePTFE
cate parts from PTFE. Another process, called paste playsakeyrole.WithoutthediscoveryofPTFEand
extrusion, was borrowed from ceramic processing. fluoropolymers,DuPontwouldhavestillbeenalarge
Roy Plunkett’s discovery of PTFE was just the corporation, albeit somewhat diminished. In the
beginning. Throughout this embryonic stage of absence of ePTFE, W.L. Gore and Associates,
polymer science there was much excitement and whatever its fate, would not have been the company
curiosity and debate in scientific circles, and many that it became, thanks to Gore-Tex.
scientistsaroundtheworldbuiltuponthisdiscovery. The discovery and evolution of ePTFE is inextri-
Scientists devoted a great deal of effort, from the cably linked to the history of W.L. Gore as a com-
1940sthroughthe1960s,todevelopingtechnologies pany,andsothischaptertellsthatstory.W.L.Gore’s
to fabricate useful objects from the three forms of unique management style and structure have been
PTFE: granular, fine powder, and dispersion. Over credited for its sustained growth through innovation
time,throughthe1980s,avarietyofTFEcopolymers and creativity. Over the past five decades, the com-
were developed that could be processed by melt pany has brought the technology of Gore-Tex into a
extrusion techniques and solution processing [5]. myriad of applications. The end-use products utiliz-
ing ePTFE have enhanced people’s lives beyond
imagination. There is some controversy over which
company or individual first invented the concept of
Part II: Invention of Expanded PTFE expansion. Regardless of the answer to this
Polytetrafluoroethylene question, however, it is W.L. Gore that continues to
propel ePTFE to new frontiers.
In 2008, W.L. Gore and Associates celebrated the Over time, competitors began to produce ePTFE
50th anniversary of the founding of their company. membranesandproductscontainingthem.Thisbook
Ironically, 2008 also marked the 70th anniversary of presents the contributions of many of these com-
Roy Plunkett’s discovery of PTFE at DuPont. W.L. panies andexploresthevaluablerolethatW.L.Gore
Gore is where expanded polytetrafluoroethylene anditscompetitorsplayedintheevolutionofePTFE
(ePTFE) was discovered and perfected over the technology.
years.The discoverystories ofPTFEandePTFEare
separate yet intertwined, similar though unique.
Both discoveries were the result of the technical 1.5 Early History of W.L. Gore and
brilliance, creativity, curiosity, perseverance, and Associates
business savvy of their respective masterminds.
Foremost among the common qualities is curiosity, Wilbert (“Bill”) L. Gore was born in 1912 in
because these scientists were curious enough to Meridian, Idaho. He spent most of his formative
recognize an anomaly and pursue with vigor what years in Salt Lake City, Utah. Bill studied chemistry
many might have considered a setback or an odd and engineering and received both a bachelor of
effect. Both PTFE and ePTFE are still used in the sciencedegreeinchemicalengineering,in1933,and
development of innumerable new products that have a Master of Science in chemistry, in 1935, from the
madevitalcontributionstohumankindformorethan UniversityofUtahinSaltLakeCity.Billwasaquiet