CA1039885A - Fluoroelastomer-based composite material - Google Patents

Abstract

FLUOROELASTOMER-BASED COMPOSITE MATERIAL
Abstract of the Disclosure High modulus asperities are incorporated into a fluoro-elastomer matrix to provide a material which, when cured, exhibits high, stable coefficients of friction over a wide temperature range.

Description

Background ~r the Inv~ntlon Thlu lnventlon rclate3 to compG31te materlal~. More ~peclrlcally, thl3 lnventlon relate3 to compo~lte ~rlctlon mater-lal~ whlch e~hlblt hlgh, ~table, coerrlclent3 Or ~rlctlon over a wid~ temperature range~
The elastomerlc raaterlals herPtorore propo~ed rOr u~e a~ materlal~ have generally pr~ven to be unsatl~ractory when e~posed to hl6h a~blent worklng temperatures such a3 encountered, ror example, ln c}utch and brake applicatlons ln heaYy duty aer-~lce vehlcles. 'rypically, ~uch material~ have becn ba3ed on heat-hardenable re3ins ~uch a~ phenol-aldehyde resln3 whlch tend to heat-decompose under the hlgh pealc and bulk temperature condl-tlons created by the su3talned and/or heary loading force~ er.per-lenced ln the clutch qnd Orake ~ystem3 Or these vehlcles whlle operatlng. As a result Or this decomposltlon, the physlcal propertie~ o~ the3e materials typlcally deterlorate, and the con-sequent so~tenlng of the materlal and dlspersal o~ the produGts o~ heat decompo~ition generally lnter~ere ulth the ~unctlonlng o~ ;
the ~ictlon unlt. Furthermore, ~any tlmes a~ter frictlon mater-lal comprlslng a partlally heat-decomposed heat-hardenable resln has cooledj the material wlll exhiblt a hlgher coerriclency o~
~rlctlon than dld the orl~lnal materlal.

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These conditlon3, as well a~ other problems as~oclated wlth these and slmilar ~rlction materlal~, result ln a 1088 o~
e~rlciency ln the rriction unlt and unrellablllty in the servlce vehlcle, whlch i8 highly undes1rable.
Many attempts have been made to obviate the problems as30ciated wlth the elastomer~ ln general ~e a~ friction mater-ial basls. Many dirrerent reslns have been experlmented wlth, , . -, ln attempts to obtaln a rrlctlon material whlch po3sesAes a high, ~table coerflclent Or frlctlon oyer a wlde te~perature r~n6e. -Modl~lcatlon or the heat-hardena~le reslns wlth other polymeri¢
materlals has been attempted. Mang o~ the3e rrlction materl~ql rormulatlons have not perrormed well. Other Iinmulatlons have requlred multl-3tep procedures whlch are costly ln ter~s ~ labor and frequently ln terms Or the material used in these form-15 ulatlons. -~
Importantly, also, many o~ these Icnown rrlctlon mater-ial8 requlre a bondln~ agent to arrix them to the backing plate or ~core" portion Or the ~rlctlon element. Thls requirement severely restrlcts the scope Or the molding methods and ~old con-rlguratlons employable ln rormln~ these frlction elements. IninJectlon moldl~g, rOr example, the bondin~ agent 18 subJect to scufrlng durlng the moldlng process, which deactivate~ or destroys the bond und renders thls moldlng process useless wlth these ~rlctlon ele~ents. In general, where bondlng agents must ¦
be utillzed, only compres~lon moldlng and relatlvely slmple mold conflgurations ca~ be employed ln the process Or moldlng the ~riction element.
In order to obtaln a rrlction materlal wlth a userully hlgh coefricient o~ rrictlon which 1~ ~table over a wide tempera-ture range, the lndu~try has most u~ually used nonreslllent

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1039~85 inorganic friction materials such as sintered bron~e. Although the friction characteristics of this and similar metallic materials have been generally satisfactory under high temperature conditions, the high modulus or lack of resiliency of these materials and their rasultant inability during operation to conform to the friction element mating surface and absorb adequate energy result in relatively high wear rates and shortened life.
Furthermore, great care must be taken in the type of oil used in conjunction with such friction materials during use to ensure that the desired coefficient of friction is not impaired.
It is therefore an object of this invention to provide a friction material composition with a relatively high, stable coefficient of friction over quite a wide range of dynamic operating conditions. `
Brief Summary of the Invention According to one aspect of the invention there is provided an improved polymeric composition comprising a fluoro-elastomer matrix, carbon black compounded with and dispersed throughout said matrix, and particles of a vitreous or ceramic material further dispersed throughout said fluoroelastomer carbon black matrix.
According to another aspect of the invention there is provided a friction element for clutch plates and the like comprising a layer of friction material bonded to a backing plate, said layer of friction material comprising a fluoro-elastomer matrix, carbon black compounded with and dispersed throughout said matrix,and particles of a vitreous or ceramic material further dispersed throughout said fluoroelastomer `;
carbon black matrix, at least a portion of said particles being present at a portion of a friction surface of said friction element.

- 3 --, - : , : - , :, .
: : -: . : - -~0;~9~5 It is an advantage of this invention, at least in preferred forms9 that it can provide a friction material com-position with high dynamic and static coefficients of friction over a wide temperature range, and which can readily be bonded to a metal core material, compression molded, and even molded i.n con~unction with complex mold configurations. The invention, at least in preferred forms, can thus provide a conformable, long-wearing friction material composition with a high, stable coefficient of friction over a wide temperature range.
Thus, the composite friction material of this invention may comprise a fluoroelastomer compounded with minute particles of a friction-producing agent in the form of particles of a vitreous or ceramic material. The fluoroelastomer matrix has excellent properties of thermal stability, and at the same time provides a relatively low modulus resilient matrix which permits the friction material to conform readily to inherently rapid changes between it and its mating surface, thereby distributing dynamic stresses and energy absorption over a much larger true friction surface area than is permitted with high modulus metallic ~-or other non-resilient materials.
Maximum energy absorption rates of from about 3 to about 5 HP/in2 of fluoroelastomer friction material are typical.
In comparison with these high modulus materials, such a low modulus matrix significantly increases the load-carrying capabilities of the friction element of which it is a part, and further, possesses superior wear characteristics when compounded with high modulus asperities as herein disclosed.
The vitreous or ceramic particles are compounded with the fluoroelastomer in sufficient quantities to produce a relatively high concentration of these particles on the frictional surface of the fluoroelastomer matrix.

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~0~98~5 In addition to acting as the friction-producing agent in the friction material, these particles further serve to strengthen the support matrix and lessen compression set or permanent deformation under applied loads.
The compounded friction material is then applied to the core of the friction element, for example as disclosed in U.S. patent no. 4,036,668 issued on July 19, 1977, inventor William D. srandon~ and of common assignment herewith.
Description of the Drawing FIG. 1 is a photomicrograph (at 500X magnification) of the surface of material according to the invention after this surface has been "worn in". The ball and rod-like particles are clearly seen with the worn flat surfaces thereon apparent.
FIG. 2 is a photomicrograph (at 500X magnification) of another sample of material according to the invention. The particles are noted to have flattened upper surfaces produced upon "wearing in" of the material.
Detailed Description of the Invention This invention provides a fluoroelastomer based material having vitreous or ceramic particles dispersed therethrough. This composite material exhibits tensile strenghts comparable with -the fluoroelastomers alone, but however exhibits better set and stress relaxation resistance than the fluoroelastomers alone.
The fluoroelastomers useful in this invention are exemplified by Viton E60C, a copolymer of hexafluoropropylene and polyvinylidene fluoride which is commercially available from E. I. DuPont, Inc., Wilmington, Delaware, and Fluorel FG2170, commercially available from the 3M Company of Minneapolis, ~linnesota. Preferably, Viton E60C (Trade Mark) or Fluorel FC2170 are employed to form the matrix of the friction material.
To form the composite material of the invention, the .~

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~0398~35 fluoroelastomer is compounded with particles of a relatively hard, vitreous or ceramic material. These particles are pre-ferably in the form of very small beads, fibers or other irregular shapes.
Although the useful size of these particles may vary somewhat according to the nature of the material and other factors, fiberglass particles of from about .OOOl" to about .005" in diameter, and preferably about 0.0005" in diameter, will yield the desired results. Such parti-cles advantageously have a length to diameter ratio of from about 3 to about lO,000. The fiberglas or other particles may also be compounded in the form of chips, fibers, spheres or other convenient shapes, although fibers are generally preferable.
The particles are compounded with the fluoroelastomer at a rate sufficient to give and maintain a high surface concen-tration of particles in the finished friction facing. Preferably, about 20 to about 50% by weight of fiberglass particles to about 30 to about 50% by weight of fluoroelastomer are admixed to provide a randomly irregular macroscopic surface finish on the friction material. It may in some instances, however, be desirable to exceed these proportions, depending on the frictional character-istics desired in the finished material.
It is contemplated that carbon black will be incorporated - into the compounded fluoroelastomer, conveniently at the same time the vitreous or ceramic particles are incorporated. This additive is preferably added in amounts of about 12 to about 30% by weight of carbon black to about 30 to about 50% by weight of fluoroelas-tomer. Additionally, accelerators, stabilizers, and curing agents, inter alia, commonly used in fluoroelastomer products, ~iill usually be compounded with the fluoroelastomer.
The vitreous or ceramic particles, carbon black, and other additives are incorporated into the fluoroelastomer by , .

~0398~35 conventional mixing technlques, for example, In a Banbury mixer.
Ideally, the vitreous or ceramic particles should be concentrated near the surface, or the frictionally active portion, of the fluoro-elastomer matrix. However, in practicality this is difficult to achieve, and satisfactory reqults are obtained by intimately in- ~
corporating the particles throughout the fluoroelastomer to obtain ~-a random orientation of the particles through the matrix.
The fluoroelastomer may be bonded to a core of steel or other metal by the process of U.S. Patent No. 4,036,668 noted above. Broadly, this process comprises incorporating CaO into the fluoroelastomer prior to curing, and then at high temperatures curing the fluoroelastomer in pressed contact with the core material. Conveniently, the CaO may be incorporated into the fluoroelastomer at the same time as are the vitreous or ceramic particles and other additives noted above.
Conventional molding techniques, such as compression transfer or injection molding, are utilized for forming the fluoro- -elastomer/backing plate friction element. In applying the friction material to the backing plate of the friction element, it is usually desirable to apply the friction material to the plate in an amount sufficient to obtain a finished thickness of friction material of from about 0.020 to about 0.250 inches, especially in applications where the material is utilized in clutches.
The friction material of this invention exhibits a high, stable, dynamic coefficient of friction through a wide range of sliding speeds and normal loads against a wide variety of opposing faces and finishes. For example, dynamic friction coefficients (~D) of from about 0.14 to about 0.06 at from `
about 2,000 to li,OOO ft/min sliding speed and from about SO to about 6BO psi of face pressure on gross area typically can be ~- - 7 _ ~.' ..
~ '..... O fl~ .
~C~39885 expected ln frlction elements comprised Or the rriction i material o~ this invention.
- Additionally, good statlc (~breakaway~') coerrlcients o~ rriction ~rom about 0.17 to about C.26 are characteristlc Or this ~luoroelastomer friction material.
The ~riction materlal o~ this lnventlon is capable o~ operatln~ agalnst matlng surraces of a Yariety Or types, ~or e~ample, hard or sort steel, cast iron, sintered metals, and ground, deburred or lapped surraces. HoNever, the mating surface rinish may adversely afrect the ~rictlon characteristlcs of the friction materlal lf this surface ls too rouehl~v or too ~inel~ ~lnished. Generally, a matln~ surface ~nish o~ about 20 to about 65 mu wlll result in satlsfactory performance Or the friction material The ~luoroelastomer rriction material o~ this inven~
tion is rurther characterized by 10N wear and dimensional 6tabilit~Y can be expected during extended dynamlc operation.
~urthermore, the material exhibits a relatively flat torque ~-curye that ~'wrings ln" about 10~25% above the dynamic torque.
The ~rictlon materlal Or this invention will respond accordln~ to test results over a wlde operating surface tempera-ture ran~e even up to about 680 F. In general, the material can be expected to malntain optimum response levels at bulk temperatures beloN about 475 F; i.e., where the average surracP
temperature Or th~ rrlction material between operations o~ the rriction element ls below about 475 F. Maxlmum peak tempera- ~
- tures, howeYer, may be as hieh as rrom about 560 F to about ~-680 F be~ore perrormance Or the ~rictlon material is -substantlally arrected.
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: ~ - . . - . . ~ : -~1~1398~5 In general, effective performance of the friction material contemplates operation of the friction element under oil cooled operating conditions. }lowever, a much wider selection of oils may be effectively employed with the fluoroelastomer friction material than with, for example, bronze.
In preparing friction elements utilizin~ tlle frictlon material of this invention, it will generally be found that after demolding, few if any of the asperities will bè present on the ~-frictional surface of the material. The thin elastomer coating covering the vitreous or ceramic particles must therefore be worn off to expose the particles and hence to obtain a stable co-efficient of friction for the element. This may either be done in situ, allowing the rubber coating to be worn off during an initial break-in period of the friction element in the service vehicle, or by pregrinding of the friction material before installation of the element. The amount of matrix material which must be removed to obtain a desirably stable coefficient of friction for the material as a whole will of course vary according to the specific formulation. However, it is generally advantageous to sufficiently expose a major portion of the underlying particles to a point where these particles are in contact with the grinding or mating surface.
During early use, these particles are ground to a point where they appear to be well-worn, as shown in FIGS. 1 and 2, to ~;
obtain a stable coefficient of friction. The particles appear to be mechanically bonded in the matrix.
The following examples are provided only to further illustrate specific friction material compositions of this invention and pertinent frictional characteristics thereof, ~;

~' ! ' ~, ~L039~5 r ~ ;
Nithout limiting the lnvention ln any manner;
. ~
Ineredients ~ount (Partæ by WeI~ht) Slze , ` Viton E601~Gfeh~k) lU0 parts Type E Fiberglass110 partæ 0~0005~' diameter Carbon Black 60 parts Accelerators ) . Stablli~ers )Minor amounts Curing Agents ) Ca ) 5 parts The above ingredients were compounded by mixin~ ln a Banbury mixer to acllieve an even dlspersion of the additives into the fluoroelastomer matrix, with random orientation Or the glass particles. The mixture was a~plied to a steel backing plate anG pressed to this plate into the desired pattern under about 2,500 psl. Tlle mixture then was cured for 30 seconds at 390 F. Su~ricient mixture material was applied to the plate to glve a thickness of material, when cured, o~ .050 inches/
race. The cured elastomer and backing plate, i.e., clutch disc, were then postcured at 450 F for 16 hours.
It was ~ound that the friction material possessed a Shore A Hardness of 90 - 95, and an ultimate tensile strength o~ 1,900 to 2,100 pS~ ~he clutch rriction element made by the process Or Example 1 was then sub~ected to a wear test in an earthmoving vehicle transmiss~on comprlsing 220,000 cycles, ~rom third speed reverse to third speed forward. 0 oo8 lnches of wear was observed per frictlon materlal race element at the conclusion of this test~ The rr~ct~on materlal was found to have an excellent thermal ætabillty up to 475 F ~bulk) J and 680 F (peak).
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~039885 1~

Example 2 ~
~ull Scale Clutch Te~t Results I
Frlctlon Materlul A~ in Example 1 ;
Slze O.D, - lnohés 12.25 . ;~
Area / Face - lnche~ 31 ~aces ~ Clutch 8 ~.
011 Tesperaturo 210F
Cycle Tine 30 ~econd~
Reactlon Surraces - ~round and Deburred So~t SteeI :~

Shi~t 3R ----- lF 3R ~ - 3F
Input RPM 2,000 1,8001,800 2,000 . Coe~ficlent Or Frlctlon ~xlmum 0.110 0.1100.116 0.112 Minlmum 0,065 o.o680.074 0.070 ~ .
Wrlng-ln 0,073 . 0.0750.083 0.083 .
',:
Clutch Torgue lb-ft / ln Max. Dynamlc 11.2 11.7 13.3 12.6 `, ~:
Wring-In 12.6. 13.0 14,9 14.9 Peak HP/ln23.2 2.7 1.7 1.9 .
Total BTU/ln2 o.65 0.51 0.4~ 0.73 ~:
.
Plate Temperature I :
- Ma~. F 494 443 360 390 ;`- ~
Bulk F 235 225 212 193 . ~ - .

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~039885 SUPPLEMENTARY DISCLOS~RE
The preferred ranges given in the principal disclosure for the vitreous or ceramic particles, fluoroelastomer and carbon black are 20 to about 50% by weight of particles, 30 to about 50% by weight of fluoroelastomer and 12 to about 30,~ by weight of carbon black. Although these ranges result in extremely useful composi-tions, it has been found advantageous to reduce the lower preferred limit of the amount of fluoroelastomer because this material tends to be the most expensive component of the composition.
Naturally, the maximum preferred amount of vitreous or ceramic particles and/or carbon black is increased to compensate for the decreased minimum amount of fluoroelastomer and it has therefore been found that preferred compositions can be prepared from the components in the following proportions:
20 to about 60% by weight of vitreous or ceramic particles;
20 to about 50% by weight of fluoroelastomers; and 12 to about 40% by weight of carbon black.
In particular, friction materials containing 27%, 25% and 20.5% by weight of fluoroelastomer have been formulated 20 and these compositions had good structural and frictional ;
properties. -It has also been found that the fluoroelastomer may be replaced in part by a polyacrylate matrix material, in which case the preferred range of the components is 20 to about 60% by weight of vitreous or ceramic particles, 20 to about 60% by weight of fluoroelastomer-polyacrylate and 12 to about 40%
by weight of carbon black.
The polyacrylates useful in this 'nvention as part of t~le matrix material are thermosetting elastomers of acrylic acid and its esters having a repeatlng structural formula -CH2 - CH (COOR) - where R is hydrogen or a low molecular :1~391~ 5 weight alkyl group having one to six carbon atoms, e.g., methyl, ethyl, or one of the propyl, butyl, pentyl, or hexyl lsomers.
Generally, the ethyl, propyl and butyl esters are preferred.
Mixed polyacryl~tes, i.e., those where some of the R groups are different than others, e.g., some are ethyl and some are butyl are quite usable. Polyacrylates wherein R is ethyl and also wherein some R is ethyl and some R is butyl have very deslrable ~ :
properties. The monomers generally polymerize easily in the presence of heat, light or catalysts, e.g., benzoyl peroxide or the like. The inclusion of acrylic anhydride, glycol esters or acrylic or methacrylic acid or acrylamide is advantageous in assuring that the resulting resin is insoluble and thermo-setting. The presence of some acrylonitrile may also be desirable to adjust resiliency.
Generally, the matrix will include fluoroelastomer and polyacrylate in weight ratio from about 1:11 to about 11:1.
The preferred weight ratio will fall within the range from about 1:5 to about 5:1. Further, such matrix will generally include at least about 5 weight per cent (of the 20-60 weight per cent total matrix) of fluoroelastomer. Thus, matrices having from about 5 weight percent fluoroelastomer and about 55 weight percent polyacrylate to matrices having from about 55 weight percent fluoroelastomer to about 5 weight percent polyacrylate-are contemplated as falling within the scope of the invention.
Generally, the friction material of the invention can be formed by high shear blending together of the solid particles ~-of the fluoroelastomer component having its appropriate ~ ;
accelerators, stabilizers and curing agents previously dispersed therethroughout with solid particles of the polyacrylatecomponent having its appropriate accelerators, stabilizers and -1~39~85 curing agents previo-lsly dlspersed therethroughout to Eorm a homo-geneous uniform intimate codispersion of the fluoroelastomer and the polyacrylate components. The carbon black, vitreous or ceramic particles and CaO components can be either previously blended with each o the fluoroelastomer component and the polyacrylate -component or can be a~ded during the step of blending together the fluoroelastomer with the polyacrylate. Usually at least the carbon black will be previously dispersed throughout both of the fluoroelastomer and polyacrylate components since each of these components are commercially available in such a form.
It should be noted that the accelerators, stabilizers and curing agents of the fluoroelastomPr are generally different than the accelerators, stabilizers and curing agents of the polyacrylate. Thus it is rather surprising that a composite friction material using a mixture of these two components is sufficiently structurally sound to exhibit good frictional and structural characteristics under beavy frictional usage. ~
Because of the considerably different accelerators, stabilizers ~-and curing agents generally used with the fluoroelastomer and polyacrylate components it is believed that at most a minor amount of cross-linking occurs between the two polymer systems. -~
Yet, the resulting friction material has both good frictional and structural characteristics as previously mentioned. The friction material further exhibits a good thermal operating range although containing significant amounts of the non-halogenated polyacrylate component.
The fluoroelastomer-polyacrylate elastomer matrix has the distinct advantage of being reboundably deflecting at normal use temperature, as for example when in use as part of a clutch plate. Normal use temperature, as discussed previously include average surface temperatures between operations of ..

yl~ - 14 -'' - - ~- , . .

~0~8~5 generally below abo-lt 475F. Cenerally, normal use t~mpera-tures will be at least about 180 F in frictional operation.
Thus, the matrix is reboundably deflecting and resilient in the temperature range from about 180 F to about 475 F. The term reboundably deflecting as used herein means that the asperities particles which are at the surface of the material are pushed or deflected thereinto durlng contact with a mating reaction plate as in a clutch but then rebound back as the material resumes its natural or unstressed state when the mating reaction plate is removed from contact therewith. It is clearly of great advantage to have a friction material that is reboundably deflecting at its use temperature yet is not easily or quickly worn away (due to the vitreous or ceramic particles) since this allows for a controlled and relatively smooth change in friction as pressure is applied between the material and a mating reaction plate plus long wearing characteristics.
Description of the Additional Drawings Figure 3 illustrates in greatly enlarged view a ;~ -section through the improved friction material disposed adjacent - `
20 a substantially flat reaction plate with a relatively thin -energy absorbing oil film therebetween and with a metal backing ' plate bonded thereto. , Figure 4 illustrates in greatly enlarged view the surface of the improved friction material after this surface has been "worn in". The vitreous or ceramic particles are noted to have flattened upper surfaces produced upon "wearing in" of the material.
The structure and operation of the friction material may be still better understood by reference to the figures of the Additional Drawings wherein like numbers denote like parts throughout. A friction material 10 in accordance with the present invention is illustrated as including a matrix 12 of , - 15 .... . -- . . .
,: . :......... -.. . . ., . - ~ .
. :. ~ . . . . - i - ~13988~
previously mentioned composition with particles 14 suspcnded mechanically therein in non-bonded relationship thereto. The friction material 10 is bonded to a metal backing plate 16. In operation, the surface of the friction material 10 removed from the backing plate 16 faces a mating plate 18 with a fluid layer 20 generally therebetween. ~n operation in a clutch, the mating plate 18 and the facing surEace of the friction material 10 are forced towards one another while rotating relative to one another. Thus, a high shear is introduced in the fluid layer 20 whereby a substantial amount of the energy of clutch engagement is absorbed. On contact, a top portion 22 of each protruding one of the particles 14 touches the mating plate 18 and the particles 14 thus tend to flatten as illustrated in Figure 4. Also, due to the reboundably deflecting character of the matrix 12 at use temperature the protruding particles 14 are pushed down against the matrix 12. On release of pressure, as when the mating plate 18 is moved away from the friction material 10, the particles 14 spring up under the impetus of the resilient matrix 12 and return generally to their original 20 protuberance above said matrix 12. Thus, relatively smooth ;~
clutch engagement occurs 9 first via the fluid 20 shear, then via particles 14 during their partial retraction into the matrix 12 and finally via the direct supported contact of the particles 14 with the mating plate 1~.
The following additional Example is provided only to further illustrate specific friction material compositions ~ , and pertinent frictional characteristics thereof, without limiting the invention in any manner:

`- - 16 -, .. , : . . -. :
- ~

~039885 Additional Example Ingredients Amount (Parts by Weight) Formula I Formula II
l~ Viton E6o(r~ac/e~d~/~J 50 Parts 70 Parts Polyacrylate 50 Parts 30 Parts Fiberfrax 30 Parts 110 Parts Carbon Black 50 Parts 57 Parts Accelerators ) Stabilizers ) Minor amounts Minor amounts 10 Curing Agents) CaO 5 Parts 5 Parts The clutch plate having Formula I affixed thereto exhibited dynamic coefficients of friction of 0.114 at 7000 fpm -~
(feet per minute) and 50 psi, 0.086 at 5000 fpm and 250 psi and 0.071 at 7000 fpm and 250 psi. The failure point of this clutch plate was above 11,000 fpm. The wear of the friction material on this plate at 7000 fpm and 250 psi was 1 mil. Wear i, was measured by a screening test comprising 120 to 200 cycles of break in at 5000 fpm and 100 psi.(until the dynamic co- -efficient of frictlon stabilized) followed-by a cycle of 15 clutch engagements each at 50 psi, 150 psi and 250 psi at 3Q00 fpm, then a cycle of 15 clutch engagements each at 50 psi, 150 psi and 250 psi at 5000 fpm, and then a cycle of 15 cIutch engagements each at 50 psi, 100 psi, 150 psi, 200 psi and 250 psi at 7000 fpm. The clutch was periodically checked at 5000 fpm and 100 psi to assure that no significant change in dynamic coefficient of friction had occured. Wear values obtained were ;~
generally good to about + 0.3 mil.
The clutch plate having Formula II affixed thereto 30 exhibited dynamic coefficients of friction of 0.089 at 7000 fpm and 50 psi, 0.088 at 5000 fpm and 250 psi and 0.081 at 7000 fpm .. . , . . ..................... , , , ~ . . : -:
- - - ~ -... . ... .

~L;)398~5 and 250 psi. The failure point of this clutch plate was not measured. The rate of wear of the friction material on this plate at 7000 fpm and 250 psi was 0 mil.
In each case the Formulas were compounded by mixing in a Banbury mixer to achieve an even dispersion of the additives into the matrix and of the two components (the fluoroelastomer and the polyacrylate) of the matrix into one another with random orientation of the asperities (Fiberfrax) particles.
Each ~ormula mixture was applied to a steel backing plate and pressed to this plate into the desired pattern under about 2,500 psi. Formula I then was cured for 30 minutes at 335 - 340 F and Formula II for 10 minutes in the same tem-perature range. Sufficient mixture material was applied to each p'ate to give a thickness of material, when cured, of .050 inches/face. The cured elastomer and backing plate, i.e., clutch disc, were then postcured at 450 ~ for 3 hours.
The friction material possessed a Shore A ~ardness of 90 - 95, and an ultimate tensile strength of 1,900 to 2,100 psi. The friction material was found to h~ve an excellent thermal stability.
While the invention has been descrlbed in connection with specific embodiments thereoE, it will be understood that it is capable of further modification, and this application is `~
intended tc cover any variations, uses or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as fall within the scope of the invention and the limits of the appended claims.

Claims (22)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An improved polymeric composition comprising a fluoroelastomer matrix, carbon black compounded with and dispersed throughout said matrix, and particles of a vitreous or ceramic material further dispersed throughout said fluoro-elastomer carbon black matrix.

2. The polymeric composition of Claim 1 wherein CaO is further admixed with the matrix.

3. The composition of Claim 1 wherein the fluoro-elastomer matrix is a copolymer of hexafluoropropylene and polyvinylidene fluoride.

4. The composition of Claim 1 wherein the particles are glass.

5. The composition of Claim 1 wherein the particles are ceramic.

6. The composition of Claim 1 wherein fluoroelastomer is present in about 30 to 50% by weight, vitreous or ceramic material is present in about 20 to 50% by weight, and carbon black is present in about 12 to 30% by weight of the polymeric composition.

7. A friction composition comprising a fluoroelastomer matrix, carbon black admixed with said matrix, and particles of a ceramic or vitreous material dispersed randomly in said matrix.

8. The friction composition of Claim 7 wherein said particles are of a vitreous material.

9. The friction composition of Claim 7 wherein the particles are of a ceramic material.

10. The friction composition of Claim 7 wherein said particles are in the form of beads, fibers and irregular shapes.

11. A friction element for clutch plates and the like comprising a layer of friction material bonded to a backing plate, said layer of friction material comprising a fluoro-elastomer matrix, carbon black compounded with and dispersed throughout said matrix, and particles of a vitreous or ceramic material further dispersed throughout said fluoro-elastomer carbon black matrix, at least a portion of said particles being present at a friction surface of said friction element.

12. The friction element of Claim 11 wherein said high particles are distributed throughout the layer of friction material.

13. The friction element of Claim 11 wherein the fluoro-elastomer is a copolymer of hexafluoropropylene and polyvinylidene fluoride.

14. The friction element of Claim 11 wherein the particles are glass fibers from about 0.0001 to about 0.005 inches in diameter and have a length to diameter ratio of from about 3 to about 10,000.

15. The friction element of Claim 11 wherein said layer comprises about 30 to 50% by weight fluoroelastomer, about 12 to 30% by weight carbon black, and about 20 to 50% by weight glass.

16. As a article of manufacture a friction material formed of a matrix comprising from about 30 to about 50 percent by weight of a copolymer of hexafluoropropylene and vinylidene fluoride, and from about 12 to about 30 percent by weight of carbon black; and said friction material further containing from about 20 to about 50 percent by weight of vitreous or ceramic particles of from about 0.0001 inch to about 0.005 inch in effective diameter intermixed with and dispersed throughout said friction material in mechanically held nonbonded relation to provide a friction surface of said article of manufacture including the said matrix and said particles.

17. A friction material composition consisting essentially of a matrix having from about 30 to about 50 percent by weight of a copolymer of hexafluoropropylene and vinylidene fluoride, and from about 12 to about 30 percent by weight of carbon black;
and said friction material further consisting of from about 20 to about 50 percent by weight of vitreous or ceramic particles having a minimum size of 0.0001 inch which are dispersed through-out the copolymer matrix in mechanically held non-bonded relation and assuring a relatively high surface concentration of the particles to provide a friction surface of said friction material including said matrix and said particles.

18. The friction material composition of claim 17 wherein said particles are glass fibers of a size from about 0.0001 inch to about 0.005 inch in diameter and having a length to diameter ratio of from about 3 to 10,000.

CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE

19. The composition of claim 1 wherein the fluoroelastomer is present in about 20 to 50% by weight, the vitreous or ceramic material is present in about 20 to 60% by weight, and the carbon black is present in about 12 to 40% by weight of the polymeric composition.

20. As an article of manufacture a friction material formed of a matrix comprising from about 20 to about 50% by weight of a copolymer of hexafluoropropylene and vinylidene fluoride, and from about 12 to about 40% by weight of carbon black; and said friction material further containing from about 20 to about 60% by weight of vitreous or ceramic particles of from about .0001" to about .005" in effective diameter inter-mixed with and dispersed throughout said friction material in mechanically held nonbonded relation to provide a friction surface of said article of manufacture including the said matrix and said particles.

21, A friction material composition consisting essentially of a matrix having from about 20 to about 50% by weight of a copolymer of hexafluoropropylene and vinylidene fluoride, and from about 12 to about 40% by weight of carbon black; and said friction material further consisting of from about 20 to about 60% by weight of vitreous or ceramic particles having a minimum size of .0001" which are dispersed throughout the copolymer matrix in mechanically held nonbonded relation and assuring a relatively high surface concentration of the ceramic particles to provide a friction surface material including said matrix and said particles.

22. A friction material composition as in claim 21 wherein said particles are glass fibers of a size from about .0001"
to about .005" in diameter and having a length to diameter ratio of from about 3 to 10,000.