`
`Davis /Gramann /
`Osswald / Rios
`
`< aA
`
`fm
`
`>
`
`Compression
`Molding
`
`Page 1
`
`aeaie
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`i 9 >
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`iio
`
`ae
`
`a
`
`Wax;
`
`a
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`MacNeil Exhibit 2077
`
`Yita v. MacNeil IP, IPR2020-01139
`
`MacNeil Exhibit 2077
`Yita v. MacNeil IP, IPR2020-01139
`Page 1
`
`

`

`Bruce A. Davis / Paul J. Gramann /
`Tim A. Osswald / Antoine C. Rios
`
`Compression Molding
`
`
`
`
`
`
`
`Hanser Gardner Publications, Inc., Cincinnati
`
`Hanser Publishers, Munich
`
`MacNeil Exhibit 2077
`
`Yita v. MacNeil IP, IPR2020-01139
`Page 2
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`MacNeil Exhibit 2077
`Yita v. MacNeil IP, IPR2020-01139
`Page 2
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`

`

`The Authors:
`Dr. Bruce A. Davis, Dr. Paul J. Gramann, Dr. Antoine C. Rios
`all: The Madison Group, Polymer Processing Research Corp., 505 S, Rosa Rd., Suite 124, Madison, WI 53719-1265
`Prof. Dr. Tim A. Osswald, Polymer Engineering Center, University ofWisconsin — Madison, Dept. of Mechanical
`Engineering, 1513 University Avenue, Madison WI 53706, USA
`
`Printed and bound by Késel, Kempten, Germany To ourfamilies
`
`Distributed in the USA and in Canada by
`Hanser GardnerPublications, Inc.
`6915 Valley Avenue, Cincinnati, Ohio 45244-3029, USA
`Fax: (513) 527-8801
`Phone: (513) 527-8977 or 1-800-950-8977
`Internet: http://www.hanscrgardner.com
`
`Distributed in all other countries by
`Carl HanserVerlag
`Postfach 86 04 20, 81631 Miinchen, Germany
`Fax: 149 (89) 98 48 09
`Inieret: http:/Avww.hanser.de
`
`The use of general descriptive names, trademarks, etc., in this publication, even if the former are not especially
`identified, is not lo be takenas a signthat such names,as understoodby the Trade Marks and Merchandise MarksAct,
`may accordingly be used freely by anyone.
`
`While the advice and information in this book are believed to be truc and accurate at the date of going to press,
`neither the authors northe editors nor the publisher can accept any legal responsibility for any errors or omissions
`that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein.
`
`Library of Congress Cataloging-in-Publication Data
`
`Compression molding / Paul J. Gramann... [et al.].
`p.cm.
`ISBN 1-56990-346-8 (Hardcover)
`1. Thermosetting plastics. 2. Reinforced plastics. 1. Gramann, Paul
`J
`
`TP1180.TS5C66 2003
`668.4722 -de2]
`
`2003007485
`
`Bibliografische Information Der Deutschen Bibliothek
`Die Deutsche Bibliothek verzcichnet diese Publikation in der Deutschen Nationalbibliografie;
`detuillierte bibliografische Daten sind im Internet iiber <http://dnb.ddb.de> abrufbar.
`ISBN 3-446-22166-2
`
`All rights reserved. No part ofthis book maybe reproducedor transmitted in any form or by any means, electronic or
`mechanical, including photocopying or by any information storage andretrieval system, without permission in
`writing from the publisher,
`
`© Carl Hanser Verlag, Munich 2003
`Production Management: Oswald Immel
`‘Typeset by Angela Ospina-Garcia, USA
`Coverillustration by Mike Shinedling
`Coverdesign: MCP + Susanne Kraus GbR, Holzkirchen, Germany
`
`MacNeil Exhibit 2077
`
`Yita v. MacNeil IP, IPR2020-01139
`Page 3
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`MacNeil Exhibit 2077
`Yita v. MacNeil IP, IPR2020-01139
`Page 3
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`

`

`
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`
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`
`
`
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`
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`
`
`
`
`18 Introduction
`
`exchange membrane (PEM), which uses numerous highly conductive bi-polar
`plates that contain complex patterns of flow channels. The plates perform three
`functions: manage the hydrogen on one side and the oxygen (air) on the other,
`contain the cells where the reaction will take place, and conduct the current
`produced. Originally,
`the plates were individually machined from materials
`such as isostatic graphite, aluminum, stainless steel, and. titanium making the
`plates extremely expensive. Once again plastic was looked at to replace metal,
`and in doing so, made the product significantly less expensive while creating a
`more superior product. The final product has to have nearly exacting
`dimensions with extreme flatness and creep, thermal and corrosion resistance,
`and not leach-out contaminants. All this has to be met while processing a
`highly filled material that contained evenly mixed conductive graphite. Since
`each fuel cell contains numerous plates, the volume potential was enormous
`and processing had to be completely automated. The obvious choice for this
`operation is the injection-compression process. The current market potential
`for this application is huge. One percent penetration of the automotive market
`could consume between 50 and 100 million poundsof fiber reinforced materials
`8]. This is one example of how compression molding, or variants of it, will be
`used to mold plastic materials in the future.
`
`Soeaiewy
`
`(1972).
`
`References
`Jacobi, FLR., Kunststoffe, 55, 3, 173, (1965)
`Dubois, J.H., Plastics History U.S.A., Cahners Books, Boston,
`Northrup, F.B., U.S. Patent 1,158,830, (1915).
`Report, SMC/BMC European Alliance, Nov. 2002
`Crain’s International Newspaper for the Plastics Industry, August (2002).
`Fenichell, S., Plastic, HarperBusiness, New York, (1996).
`Application of Carbon Fiber SMCfor the 2003 Dodge - Automotive Composites
`Conference (2002).
`Composites Technology Sept/Oct (2001).
`
`
`
`NI
`
`
`Compression Molding Materials
`
`
`i
`x recipe:
`
`Compression molding materials are often comple
`m
`
`oeee -some cases, polymers make up only>ne7
`andreinforcingfibers.piemteperrilea 7oteGreece ie
`polymermaterials. This is
`followed by the aon oftievan :
`ane 5usedduringcompression molding. Here, we will eaetik
`molding P
`(s
`C), bulk molding compound (BMC),
`gl
`hermoplastics
`(GMT), and long fiber
`reinforced thersoplastics
`behavior of composites.
`apies “We Wpieseni sanmdamientals]
`[ef mechanical
`(LFT). At
`the end of the ch
`
`2.1
`
`Introduction to Polymers
`
`i
`
`As the w
`
`Hoy higoreCScSuagests polymers! are materials composed of molecules of
`pees. The ‘atteeeeene sly Soraneweectoy
`aaBrArlotomunts areeeubutedto theirmolecularoeee
`Whee
`ics of
`polymers
`ili
`ae a sanepe are processed makes them,for many applica-
`their ability to be ne ef peo today. Because of their low density and
`Beatie eeSnaP
`ane molded at relatively low temperatures compared
`FF cision when nor s ae as metals, plastics and polymers are the material
`Bpect ustally ate g several parts into a single component-—a desi
`iGitionally been
`part consolidation. Infact,partsandcomponents, whichhave
`Bastics one pa 7 le of wood, metal, ceramic, or glass are redned
`ed a
`y
`basis. Polymers can be placed into either a thermoplastic
`
`oe
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`1
`
`Fkrom the Greek,
`whi
`poli
`*k, poli which means many, and meros which meansparts
`vi
`plastics
`ibes a
`Vi
`The term plastics des
`I
`cribes d compound of polymers and arious additi es.
`
`MacNeil Exhibit 2077
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`Yita v. MacNeil IP, IPR2020-01139
`Page 4
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`MacNeil Exhibit 2077
`Yita v. MacNeil IP, IPR2020-01139
`Page 4
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`

`

`
`
`Compression Molding Materials
`
`2.1 Introduction to Polymers
`
`21
`
`
`20
`
`thermoset or elastomer category. Thermoplastics in turn —s a Peeans
`tomers. However,all these material
`i
`i
`ha
`which are called thermoplastic elas
`ee
`mum!
`lecules. Some of these molecu
`on that they
`are made of huge mo
`.
`tmnerosslinked which means that each molecule can move freely ieeeto 7
`neighbors and others are crosslinked, which meansthat bridges , or Pnya
`S,
`bak
`;
`i
`i
`lecules. Thermoplastics and un-v
`s interconnect the polymer mo.
`slctomens
`are wuncrosslinked. Vulcanized rubber,
`or
`elastomers,
`and
`
`2.1.2 Thermoplastic Polymers
`
`t influence on the
`
`Durin
`
`2.1.3 Amorphous Thermoplastics
`
`there are
`if
`from monomers occurs
`The formation of macromolecules
`unsaturated carbon atoms (carbon atoms connected with double bonds), or if
`there are monomers with reactive end-groups. The double bond, say in an
`ethylene monomer,is split which frees two valences per monomer and leadsto
`the formation of a macromolecule such as polyethylene. This process is often
`referred to as polymerization. Similarly, monomers
`(R)
`that possess two
`thermosets are cross-linked.
`reactive end-groups(bifunctional) can react with other monomers (R') that also
`configuration of the polymer molecules hasa grea
`iofthe polymer component. The ale Bives the <n
`have two other reactive end-groups that can react with each other, also leading
`to the formation of a polymerchain.
`istributi
`i
`ization of
`the molecule.
`
`
`|neivihiGetSaEion it is possible to place the x groups on the ee caebout the distribution and spatial organiza On
`backbone in different directions. The order mnwhich they “esarrearsa
`the tacticity. The polymers with side
`gr
`7
`——
`ich
`ith
`side
`groups that are place
`
`Amorphous thermoplastics, with their randomly arranged molecularstructure,
`i
`de groupsare all on the same
`are called atactic. The polymers whosesi
`- me
`
`i
`i
`h regularly alternating side group
`are analogous to a bowl of spaghetti. Due to their random structure,
`the
`called isotactic, and those molecules wit
`ae
`id
`a
`characteristic size of the largest ordered region is on the order of a carbon-
`|
`ic.
`Fi
`the three different
`tacticity case
`called syndiotactic. Figure 2.1 shows
`maa
`3
`7
`
`carbon bond. This dimension is much smaller than the wavelength of visible
`ici
`i
`the
`degree
`termines
`lene. The tacticity in a polymer
`de
`elt that a polymer can reach. For example, polypropylene renig
`
`light and therefore generally makes amorphousthermoplastics transparent.
`isotactic content will reach a high degree of crystallinity and asaBeit a ae
`
`Figure 2.2 [1]
`shows the shear modulus, G', versus temperature for
`
`strong and hard. Branching of the polymer chains also AS
`polycarbonate, an amorphous
`thermoplastic that
`is
`injection-compression
`
`structure, crystallinity and properties of the polymeric material.
`molded into compactdiscs. The figure shows two general regions: one where
`
`the modulus appearsfairly constant3, and one where the modulus dropssieni-
`
`
`ficantly with increasing temperature. With decreasing temperatures,
`the
`material enters the glassy region where the slope of the modulus approaches
`
`zero. At high temperatures the modulusis negligible and the material is soft
`
`enough to flow. Although there is not a clear transition between “solid” and
`
`“liquid,”
`the temperature that divides the two states in an amorphous
`
`thermoplastic is referred to as the glass transition temperature, Tg. For the
`polycarbonate in Fig. 2.2, the glass
`transition temperature is approximately
`
`150 °C. Although data is usually presented in the form shown in Fig. 2.2, it
`
`should be mentioned here that the curve shown in the figure was measuredata
`
`constant frequency.If the frequency ofthetestis increased—reducing the time
`
`
`scale —the curveis shifted to the right since higher temperatures are required to
`
`achieve movement of the molecules at the new frequency. Figure 2.3 [2]
`
`demonstrates this concept by displaying the elastic modulus as a function of
`
`
`temperature for polyvinyl chloride at various test frequencies. A similar effect
`
`is observed if the molecular weight of the material is increased. The longer
`
`molecules have more difficulty sliding past each other, thus requiring higher
`
`temperatures to achieve “flow.”
`
`
`
`Syndiotactic
`
`ee3
`
`
`Whenplotting G' versus temperature onalinearscale, a steady decrease of the modulusis observed,
`
`
`Figure 2.1 Different polypropylene structures.
`
`MacNeil Exhibit 2077
`
`Yita v. MacNeil IP, IPR2020-01139
`Page 5
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`MacNeil Exhibit 2077
`Yita v. MacNeil IP, IPR2020-01139
`Page 5
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`

`

`2.14 Semi-Crystalline Thermoplastics
`
`2.1 Introduction to Polymers
`
`23
`
`Semi-crystalline thermoplastic polymers show more order than amorphous
`thermoplastics. The molecules align in an ordered crystalline form as shown
`for polyethylene in Fig. 2.4. The crystalline structure is part of a lamellar crystal
`which in turn forms the spherulites. The formation of spherulites during
`solidification of semi-crystalline thermoplastics is covered in Chapter 3. The
`schematic in Fig. 2.5 shows the general structure and hierarchical arrangement
`in semi-crystalline materials. The spherulitic structure is the largest domain
`with a specific order and has a characteristic size of 50 to 500 um. This size is
`much larger than the wavelength of visible light, making semi-crystalline
`materials translucent and not transparent.
`However, the crystalline regions are very small with molecular chains
`comprised of both crystalline
`and amorphous
`regions. The degree of
`crystallinity in a typical thermoplastic will vary from grade to grade. For
`example, degree of crystallinity depends on the branching and the coolingrate.
`
`22
`
`Compression Molding Materials
`
`104
`
`qe
`o.
`
`108
`
`102
`
`= ©e
`
`o3
`
`3 8—
`
`3od=
`w
`
`Figure 2.4
`
`Schematic representationof the crystalline structure of polyethylene.
`
`10
`
`100
`
`-50
`
`Q
`
`50
`
`100
`
`150
`
`200
`
`Figure 2.2
`
`Temperature, T OC)
`Shear modulus of polycarbonate as a function of temperature.
`
`—— 50 Hz
`— — 500 Hz
`~~" 5000 Hz
`
`1000 |-
`
`100
`
`a2
`
`sa
`
`10
`
`0
`120
`80
`40
`160
`ou
`Temperature, T (OC)
`Figure 2.3 Modulus of polyvinyl chloride as a function of temperature at variou
`
`i
`
`.
`
`
`
`
`
`
`
`
`
`
`
` 0.736 nm
`
`
`
`test frequencies.
`
`MacNeil Exhibit 2077
`
`Yita v. MacNeil IP, IPR2020-01139
`Page 6
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`MacNeil Exhibit 2077
`Yita v. MacNeil IP, IPR2020-01139
`Page 6
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`

`

`
`
`2.1 Introduction to Polymers
`
`25
`
`the amorphous regions
`decreases below the glass transition temperature,
`within the semi-crystalline structure solidify, forming a glassy, stiff and in
`some casesbrittle polymer.
`
`104
`
`108
`
`102
`
`es
`a.
`=
`o
`§5
`
`8£
`
`3Qx=
`w
`
`
`
`Compression Molding Materials 24
`
`_
`nm
`a=0Q0.
`b = 0.492 nm
`c¢=0.254 nm
`
`Lamella
`20 to 60 nm
`
` 2.1.5 Thermosets and Cross-Linked Elastomers
`
`
`
`Figure 2.5
`
`Crystal lamella
`
`Spherulite
`~ 50 to 500pm
`
`r component
`—— Pol
`:
`mote
`i
`the general molecular
`representation of
`Schematic
`arrangementof typical semi-crystalline materials.
`
`s
`
`tructure
`
`and
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`.
`:c
`shear
`modulus versus temperature for a
`
`Figure 2.6 [1] shows tne a ° een molded semi-crystalline
`polypropylene,the te —— eens data measured at onetest frequency.
`
`
`thermoplastic, Again,
`a
`ae
`a
`he glass
`i
`t transitions: one at about
`-5 °C,th
`
`The figure clearly shows,two eaeee 165 °C, the melting temperature. Above
`|
`pny EN theshear modulusis negligible and the material will
`
`
`fomCeysalline arrangement begins to develop as the ve ee
`
`|
`below the melting point. Between the melting and oe nition
`temperatures, the material behaves as a leathery solid. As the temp
`
`
`10
`
`-100
`
`-50
`
`0
`
`50
`
`100
`
`150
`
`200
`
`!
`
`Figure 2.6
`
`Temperature, T (°C)
`Shear modulusof a polypropylene as a function of temperature.
`
`.
`.
`=r
`Thermosets, and some elastomers, are polymeric materials that have the ability
`to cross-link. The cross-linking causes the material to become resistant to heat
`after
`it has solidified. A more in-depth explanation of
`the cross-linking
`chemical reaction that occurs during solidification is given in Chapter3.
`The cross-linking usually is a result of the presence of double bonds that
`break, allowing the molecules to link with their neighbors. One of the oldest
`thermosetting polymers is phenol-formaldehyde, or phenolic. Figure 2.7 shows
`the chemical symbol representation of the reaction, and Fig. 2.8 shows a
`schematic of the reaction. The
`phenol molecules react with formaldehyde
`>
`*
`saciecalessea cuesceeeee eeeteieeeeusecd. eoue cea
`strong, The by-productofthis chemical reaction is water.
`
`MacNeil Exhibit 2077
`
`Yita v. MacNeil IP, IPR2020-01139
`Page 7
`
`ting
`
`temperature,
`
`|
`
`MacNeil Exhibit 2077
`Yita v. MacNeil IP, IPR2020-01139
`Page 7
`
`

`

`
`
`2.2 Compression Molding Material Preparation
`
`2.2 Compression Molding Material Preparation
`
`27
`
`26
`
`Compression Molding Materials
`
`Symbols
`
`OH
`
`OH
`OH H
`
`me;FsiecK
`
`Formaldehyde H
`H
`Phenol
`Phenol
`OH
`
`OH
`
`ae
`
`A wide variety of polymeric materials are compression molded. This includes
`thermosets, thermoplastics, and elastomers, of which a vast majority are fiber
`reinforced to add mechanical strength to the part. The use of these materials
`permeates many industries with 2.28 billion pounds consumedin 2002.
`Compression molding resins can be thermoplastic or thermoset plastics
`depending on the application. The resin matrix bindsall the reinforcements and
`fillers together in a structural component. The resin matrix also protects the
`different components from external factors and spreads the structural loads
`between the reinforcements andfillers.
`
`
`OH
`OH
`OH
`—CHoe
`CHs CI mo
`
`2.2.1 Thermosetting Resins
`
`2
`OH
`eT CH,
`CH,
`H,C
`onAohon CI CH,-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Unsaturated polyester (UP) is by far the most commonly used thermoset resin
`for compression molding. This material has good strength properties while
`maintaining a high resilience that is needed in many demanding applications.
`Another advantage of polyesters over other thermosetting resins is that they
`can be pigmented while in a liquid form. Vinylesters are used in more severe
`conditions where a higher strength and moreresilient material is needed. Since
`vinylesters contain fewer ester groups than polyesters,
`they exhibit better
`resistance to water and chemicals. The cure times of vinylesters are typically
`quicker than other thermosets, reducing mold time and cost to produce the
`part. However,
`the cost of vinylester
`resin tends to be higher.
`In high
`temperature applications (175 °C) and for components with thick regions,
`epoxy is a viable option. Epoxies generally exhibit higher mechanical
`properties and resistance to the environment. However,their resistance to acids
`is less than the one of polyesters and they are more expensive than polyesters
`and vinylesters. Phenolic resin systems have a clear advantage over polyesters,
`epoxies, and vinylesters in applications where fire safety is a concern. In a
`developedfire the emission of smoke is quite low. Phenolics exhibit long-term
`durability and resistance to hydrocarbon and chlorinated solvents, and show
`high strength and modulus properties similar to that of polyesters. Table 2.1
`shows properties for the various thermosetting resins discussed here.
`
`H
`
`H
`
`+ H,0
`
`OH
`
`H
`
`“H
`
`
`
`
`
`Figure 2.7
`
`OH
`
`CH»
`
`ered
`OH
`Symbolic representation of the conden
`;
`formaldehyde resins.
`
`of
`
`sation polymerization of phenol-
`
`
`
`
`
`
`
`
`
`
`OU
`
`
`+H,0
`
`
`
`
`Figure 2.8
`
`Schematic representation of the cond
`:
`formaldehyde resins.
`
`ensation polymerization of phenol-
`
`
`
`MacNeil Exhibit 2077
`
`Yita v. MacNeil IP, IPR2020-01139
`Page 8
`
`MacNeil Exhibit 2077
`Yita v. MacNeil IP, IPR2020-01139
`Page 8
`
`

`

`28
`
`Compression Molding Materials
`
`2.2 Compression Molding Material Preparation 29
`
`Table 2.2
`
`Table 2.1
`Thermosets Properties for Thermosetting Resins
`Glass fiberPolymer Specific “Tensile~—~«-Elongationat—__content (%)
`76
`MPa
`
`Epoxy
`1.10-1.20
`40-85
`1.5-8.0
`Phenolic
`1.00-1.25
`60-80
`1.8
`Polyester
`1,10-1.23
`30-75
`1.0-6.5
`Vinylester
`1.12-1.13
`70-81
`3.0-8.0
`
`Approximately 75% of all
`resins used in composites are payee.
`Unsaturated polyester
`is produced by condensation polymerization °
`dicarboxylic acids, glycols, and anhydrides of dicarboxylic acids [3]. Ce
`resulting polymer is dissolved ina reactive monomer, typically styrene, wi
`none
`1.13
`79
`60
`lowers the overall viscosity of the product. This decreased viscosity also makes
`13
`1.23
`97
`4.0
`the polyester easier to process in many situations. After the polymeris
`30
`1.37
`173
`3.0
`dissolved in the monomer the mixture is heated, causing the monomer to react
`Polyethylenenone+=137.£4750300.
`with the polyester. The reaction changes the liquid mixture to a high viscosity
`teraphthelate (PET)
`30
`1.56
`158
`3.0
`resin,
`* Chemically coupled: This compound uses a chemical sizing on the fiber to improve fiber-
`matrix bonding.
`
`Thermoplastics Properties of Filled and Unfilled Thermoplastic Com-
`pression Molding Resins
`
`
`Polypropylene
`none
`(PP)
`10
`30
`10*
`30*
`
`gravity
`0.89
`0.98
`1.12
`0.98
`1.12
`
`strength (MPa)
`34.
`43
`47
`50-59
`68-83
`
`break (%)
`200.0
`4.0
`2.0
`4.0
`2.0
`
`Polyamide 6
`(PA 6)
`
`Polyamide 66
`(PA 66)
`
`none
`15
`30
`
`1.12
`1.25
`1.37
`
`81
`104
`166
`
`30
`4.0
`3.0
`
`2.2.2
`
`Thermoplastic Resins
`
`Thermoplastics in general have lower weight and are tougher than thermosets.
`However, thermoplastics exhibit lower mechanical properties and higher creep
`in high temperature applications. The most common thermoplastic resins u
`;
`in compression molding is polypropylene (PP), Because of its high degree of
`crystallinity,
`the properties of PP can be greatly enhanced by the addition o
`fillers and reinforcements. For more demanding applications, such as higher
`temperatures and loads, polyamide (PA) and polyethylene terephthalate (PET)
`are more suitable. Table 2.2 shows property enhancements after adding glass
`fiber reinforcementto typical thermoplastic resins [4].
`
`2.2.3
`
`Functional Additives
`
`Additives are used to improve processing and mechanical properties of the
`compression molding materials. The most important additives for thermoset
`resins are initiators to start the chemical reaction,
`inhibitors to retard the
`reaction, and low profile additives to control shrinkage. The final compound
`used for compression molding contains up to 10% in weight of additives. Other
`additives of note are release agents (water based, calcium andzincstearate),
`pigments (titanium oxide, carbon black, others),
`thickeners (metal oxides,
`calcium oxide, others), and property-enhancing additives.
`The most common additives used for thermoplastic resins are antioxidants,
`which are used to reduce material degradation during processing, UV
`stabilizers to improve resistance to UV radiation, pigments to color the final
`part, and lubricants to aid in demolding. Thermoplastic resins can also include
`various property-enhancing additives.
`
`2.2.3.1
`
`Initiators
`
`
`
`
`
`
`
`
`
`
`
`Sheet molding compounds are polymerized by a free radical reaction where the
`double bond of the polyester molecular chain reacts with the styrene monomer.
`
`MacNeil Exhibit 2077
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`Yita v. MacNeil IP, IPR2020-01139
`Page 9
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`MacNeil Exhibit 2077
`Yita v. MacNeil IP, IPR2020-01139
`Page 9
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`This crosslinking creates a three-dimensional structure that changes the highly
`viscous liquid resin into a hard thermoset solid. The source ofthe free radicals
`are referred to as initiators since they promote the curing reaction. The free
`radicals
`are usually produced when the
`initiator
`experiences
`a high
`Selected Properties of Common Fiber Materials
`Table 2.3
`temperature,i.e., temperature during molding.
`
`
`
`
`Fiber~—~—~S*«Specific-—~‘TensileStrength—TensileModulusgravity
`
`E-glass
`2.54
`3.5
`72
`S-glass
`2.50
`4.5
`86
`Carbon
`1.77-1.80
`3.7-5.4
`33-42
`
`
`
`2.2 Compression Molding Material Preparation 31
`
`30.
`
`Compression Molding Materials
`
`matrix. The choice of size chemistry is important to balance fiber protection
`during processing andfiber-resin bonding. The choiceof size is also dependent
`on the combination of fiber and resin used.
`
`2.2.3.2
`
`Inhibitors
`
`Inhibitors are used to retard the reaction of the resin to increase the shelf life of
`the SMC. Using inhibitors can greatly enhance the time before the SMC needs
`to be used. The inhibitor acts as an agent to control the reaction rate and in
`essence works against the initiator. The inhibitor constrains the polymer chain
`Pitch precursor
`in the initial stages of polymerization preventing the rate of reaction from
`Aramid
`becoming excessively large.
`Boron
`2.49-2.57
`3.5
`400
`
`
`
`2.2.3.3 Low Profile Additives (LPA)
`The most common types of LPA are thermoplastic resins. These additives are
`used to reduce shrinkage related to the curing reaction and to improve surface
`quality. Some of the common problems related to resin shrinkage are internal
`stresses, sink marks, voids, and bubbles.
`
`2.2.4 Fillers and Reinforcements
`
`to lower shrinkage, reduce
`Fillers are mainly used as volume extenders,
`processing times, improve mechanical properties, and improvefire retardance.
`The most commonfillers are calcium carbonate, clay, and material regrind,
`such as, recycled thermosets or thermoplastics. Fillers are 30% to 70% in weight
`of the final compound. The addition of fillers also lowers the cost of the
`compound by reducing the amountof resin, fiber, additives, and colorant used
`in the final formulation - the costof thefiller is usually a fraction of the cost of
`these materials.
`Reinforcements have a higher aspect ratio than fillers. The most common
`are glass, carbon, and aramid fibers. Fibers are added to improve the
`mechanical properties of the material. The combination between the properties
`of the fibers, fiber contents, length, orientation andfiber-resin bonding greatly
`affect the final properties of the compression molded part. Table 2.3 shows
`mechanical properties and specific gravity of common available fibers.
`Fiber-resin bonding is affected by the chemistry of the fiber size or coating.
`Sizing is also used to protect
`fibers and reduce fiber breakage during
`processing. However, while protecting the fibers, sizing can hinder the wet-out
`of the fiber. Wet-outis the amountof surface contact between the fiber and the
`
`
`
`
`
`
`
`
`
`PANprecursor
`Carbon
`
`1.99-2.16
`
`1.44-1.47
`
`1,7-2.2
`
`3.8
`
`55-100
`
`62-131
`
`2.2.4.1 Glass Fibers
`
`Glass fibers account for about 90% of the reinforcement in thermosetting resins.
`These fibers are produced by drawing or blowing molten glass, a mixture of
`quartz sand and additives, through small orifices at temperatures of 1400 to
`1600 °C. Glass fibers are available as continuous (roving), short (chopped),
`fiberglass textiles, mats, and various braided patterns. The length of the fiber
`has great effect on the strength of the product; generally, the longer the fiber
`the greater
`the strength. Depending on the composition, glass fibers are
`available in different variants. The E-glass variation is the most common andit
`exhibits
`excellent
`electrical
`insulation
`properties.
`For high
`strength
`applications, S-glass exhibits a tensile strength of 40% higher than E-glass and
`can be used at higher temperatures. However, S-glass is considerable more
`expensive than E-glass. Other variants are A-glass, C-glass, which are used in
`applications requiring good chemical
`resistance, D-glass used for high-
`performanceelectrical applications, and L-glass (lead glass) used for radiation
`protection.
`
`
`2.2.4.2 Carbon Fibers
`
`
`The main advantage of carbon fibers is their lower specific gravity, about 30%
`lower than glass fibers. They also have a low linear expansion coefficient and
`excellent conductivity. However, carbon fibers are more brittle and expensive
`than glass fibers. Carbon fibers are produced by heat treating (carbonizing) the
`precursor fibers at temperatures of 1000 to 3000 °C. Therefore, the quality and
`properties of carbon fibers depend on the composition of the precursor fibers.
`
`
`MacNeil Exhibit 2077
`
`Yita v. MacNeil IP, IPR2020-01139
`Page 10
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`MacNeil Exhibit 2077
`Yita v. MacNeil IP, IPR2020-01139
`Page 10
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`

`
`2.2 Compression Molding Material Preparation 33
`32 Compression Molding MaterialsNeEEE
`
`
`
`Precursor fibers are usually polyacrylonitrile (PAN) or pitch based. The heat
`treating temperature also affects the properties of the carbon fiber. High
`strength (HS) carbon fibers are heat treated at temperatures of up to 1700 °C and
`high modulus (HM) carbon fibers are heat treated at temperatures of up to
`3000 °C.
`
`2.2.4.3 Aramid fibers
`
`Aramid fibers, also known as Kevlar®, are based on aromatic amides resulting
`from the reaction of carboxolic acid and amine groups. Thesefibers generally
`have comparablestrength to thoseof glass fibers, but up to twice the modulus
`and a specific gravity of about 45% lower than glass fibers. Aramid fibers
`exhibit high thermal
`stability,
`low conductivity, and good resistance to
`chemicals, except strong acids and alkalies. Aramid fibers can be used at
`temperatures up to 200 °C, any prolonged used above 175 °C will degradeits
`mechanical properties. Aramid fibers must be coated to protect them from
`moisture and UVlight over a long period of time.
`
`2.2.5
`
`Compounded Materials
`
`The compounded material is the product that will be placed in the compression
`molding mold. This compoundis a mixture of the resin matrix with numerous
`additives,
`fillers, and reinforcements. Depending on the type of
`resin,
`thermoplastic or thermosetting, and onits delivery form,it can be divided into
`four main compounds: SMC and BMC for thermosetting resins and LFT and
`GMTfor thermoplastic resins.
`
`2.2.5.1 Sheet Molding Compound (SMC)
`
`Table 2.4
`
`Inhibitor traces
`Initiator
`
`Wetting agent
`
`Release agent
`Filler
`
`Formulation for a Typical SMC [5]
`
` Ingredient
`
`Weight %
`Ingredient
`Weight %
`
`Polyester resin
`Vv
`Styrene
`15
`
`LPA
`30
`Styrene
`2.0
`LPA
`14
`Thickener
`8.0
`
`
`
`
`Color pigment
`Filler
`
`1.0
`46
`
`0.5
`
`1.0
`
`15
`
`The compounding of the resin recipe into a paste is performed before it
`reaches the combination line where the SMC sheet is produced. Thepaste is
`then metered into a Doctor Box where the resin is applied to a polyethylene
`carrier film, At the same timefibers are choppedto lengths of 25 to 50 mm and
`sandwiched between twocarrier films to form the SMC sheet. The typical fiber
`content varies between 25 and 40 vol%. The sheet is then compacted to ensure
`the impregnation of the fiber. A schematic of this line is shownin Fig. 2.9. After
`completion the sheetis rolled and stored to mature for a period of 2 to 5 days.
`
`Continuous
`strand roving
`
`Resin/filler
`paste
`
`Carrier film
`
`
`
`The production of SMC generally involves two distinctive steps: compounding
`of the resin and additives, and the fabrication of the SMC sheet. During
`
`Chainlink
`compounding all ingredients, except fibers, are mixed together to formapaste.
`
`compaction belt
`Various thermosetting resins can be used for the paste, including, unsaturated
`polyester, vinyl ester, epoxy, phenolic, to name a few.
` Coneo96TOOCO(Resin/filler O
`In the compounding process, the resin ingredients are pre-mixed in two
`different batches, referred to as A-side and B-side, as presented in Table 2.4 [5].
`The B-side formulation includes the thickener, low profile additives, and some
`fillers. The A-side formulation also includes low-profile additives (LPA), as
`
`well as the chemical reaction initiator and inhibitor, wetting agents, and mold
`release. The A and B side formulations are mixed in a predetermined ratio,
`Figure 2.9
`SMC productionline.
`typically in the range of 10/1 to 20/1 to formapaste.
`
`
`
`paste
`
`Carrier
`film
`
`
`
`
`Take-up roll
`
`MacNeil Exhibit 2077
`
`Yita v. MacNeil IP, IPR2020-01139
`Page 11
`
`MacNeil Exhibit 2077
`Yita v. MacNeil IP, IPR2020-01139
`Page 11
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`

`i|
`
`|
`
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`| | |
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`
` 34 Compression Molding Materials 2.2 Compression Molding Material Preparation 35
`
`During the maturation period the compound thickens to a moldable
`The compounding of BMCstarts with the productionof a paste. Thepasteis
`iscosity. The SMC sheetincludes all the components needed for molding the
`prepared by mixing the resin with the different additives. This paste is then
`final
`‘ (resin, reinforcement filler, catalyst, low profile additives, etc.) in a
`mixed on a batch mixer with the fillers. After this mixture is homogeneous,
`caailecole end non-tacky chest, Its characteristics allow it to fill a mold when
`towardsthe end of the mixing cycle, fibers are added. A schematic of this
`subjected to the molding temperature and pressure.
`process is shown in Fig. 2.10. The BMC compound can be further extruded to
`form cylindrical batches to facilitate placing in the compression mold.
`.
`Fibers
`
`Paste
`
`.
`2.2.5.2 Bulk Molding Compound (BMC)
`The advantage of BMC js in its short fibers that allow the material to be used
`for injection molding as well as for compression molding. However,
`the
`shorter fibers in general give BMC lower mechanical properties. BMCis
`producedin bulk form or as extrudedcylinders, which eliminates theuse ofthe
`polyethylene carrier film used in SMC. Because BMC has lower reinforcement
`content, higher
`filler
`loadings can be used with a consequent economic
`advantage. Anotheradvantageis that BMC does not require a maturation stage.
`The most common form of BMC contains a paste based on unsaturated
`polyester, low profile additives, catalyst, inhibitors, pigments, release agents,
`filler (calcium carbonate), and thickener. Thefibers typically are 6 to 25 mm in
`length. The typical fiber content for BMCis 10 to 25 vol%. The proportions of
`these components and otheradditives depend on the properties required and
`type ofapplication. A typical BMC formulation is shown in Table 2.5 [5].
`Table 2.5 Typical Formulation of BMC [5]
`[%]
`Paste compound ingredient
`a
`Polyester resin
`0-50
`ges
`LPA
`7
`Fibers
`
`o
`Styrene
`2.2.5.3 Glass Mat Thermoplastic (GMT)
`1-2
`Catalyst
`atalys
`
`Glass mat thermoplastics are semi-finished sheets produced by combining a
`oa
`Release agent
`
`thermoplastic resin with continuous, woven or chopped fiber mats. The most
`50-300
`;
`
`sas
`:
`.
`.
`7
`Filler
`common combination is polypropylene (PP) resin and glass fibers. GMT’s are
`02
`
`tough and lightweight comp