Document NEnK5Gke9LZGxOp44XrdaeLg

FILE NAME: Phenolic Resins (PHR) DATE: 0000 DOC#: PHR067 DOCUMENT DESCRIPTION: Report - Asbestos-Free Brakes, Bendix Patents & Other Related Material; from AS Bendix File STEPHEN L. BERGER, P.E. PATENT AGENT 4418 Pleasant Valley Court Oakland, CA 94611 (510) 622-2345 Work (510) 658-2256 Home July 31, 1998 Walter Weathers 333 Clay Street, #4440 Houston, Texas 77002 BENDIX REFERENCES AND RELATED MATERIAL Dear Walter: I have enclosed literature and patent references on Bendix (both Aldrich and Kwolek), some patents assigned to General Motors, a 1950 article by a Chrysler employee, and a 1979 general reference comparing different brake linings. Most o f the references should be self-explanatory after reading the enclosed three page report I wrote for NRDC in 1983. The report also details a telephone conversation I had with Aldrich in 1983. If you have any questions, I will gladly discuss them with you. Sincerely, Stephen L. Berger, P.E. Stephen L. Berger 6651 Saroni Drive Oakland, CA 94611 June 22, 1983 Dear Barry, Here is the report on asbestos-free brakes for NRDC. I looked through the Engineering Index from 1970 to . April 1981 1983 and the Index for SAE Transactions from 1974 to The only reference that might be of interest and which I could not locate here is a book entitled Friction Materials; Recent Advances by Louis R. Newan (it might be Newman) published in 1978. It is based on patents and mentions commercial applications. Sincerely, ASBESTOS FREE BRAKES Stephen L. Berber June 22, 1983 Possible replacements for asbestos brake linings (pads) can be divided into two groups: (1) the semi-metallic friction materials, snd (2) linings in which the asbestos fibers are replaced by other fibers, specifically Kevlar (du Pont trademark) aramid fibers. The following references describe the semi-metallic brake lir.inrs. 3AE Transactions Paper No. 710391, by F. William Aldrich from the Bendix Corp. This 1971 paper describes the advantages of semi-metallics: improved wear resistance; improved fade resistance; improved high speed effectiveness; improved frictional stability; minimal noise; and excellent mating surface compatibility. The paper seems to imply that semi-metallics are useful as both disc and drum brakes. SAE Transactions Paper No. 750874 by John F. Kwolek, at the time irom the Bendix Corp. This 1975 paper is directed to semi metallic solid rotor disc brakes in small cars. Reviewing the history of semi-metallics, the paper states that they were first developed in the 1960*s and first used on foreign vehicles. Police cars and taxicabs were also equipped with them. In 1970 in this country, semi-metallics were used for the front disc brakes of police cars. Additional costs were apparently the only reason widespread usage did not occur. "Semi-metallics are currently being produced for one domestic vehicle eouioped with solid rotors. Combinations of organic snd semi-metallic psds are being used on a domestic station wagon, luxury car and several light truck applications. The use of semimetallics has also been expanded to the larger disc brakes currently released for heavy trucks." The above paper mentions a 1974 U.S. patent 3 835118 (enclosed) to Rhee and Kwolek 8nd assigned to the Bendix Corp. This patent is the only place I found which actually describes - 2- typical semi-metallic brake pad formulations. The patent discloses coarse sponge iron particles as a friction modifier. The patent also mentions that "one of the major obstacles to the acceptance of semi-metallics as a friction material has been the poorer wear resistance of the semi-metallics (compared to organics) when operating at temperatures below 325F." (col. 3, line 66 to col. 4, line 2). The brake pad of the patent apparently overcomes this objection. SAE Paper No. 790717 (abstract only is enclosed) by Harry M. Schiefer and George V. Kubczak of Dow Corning Corp. This 1979 paper describes a Dow Corning friction modifier for semi metallic brakes and clutches to reduce squeal and wear. An article, based on the above 790717 psper, in Automotive Engineering entitled "Friction Modifiers Tailor Brake and Clutch Characteristics." This article gives more detail than the abstract and compares the oroperties of the different classes of brake linings. Semi-metallic brake linings (because of their hardness) without friction modifiers creat much noise (the saueal one hears from many European cars). A telephone call to Aldrich at Bendix in Troy, H.Y. (516 273-6550) revealed the following information about semi-metallics (1) some European manufacturers have used semi-metallics for about a decade (2) companies are very secretive about their proprietary brake formulations and, therefore, few articles giving details are published (3) semi-metallics work better than asbestos linings, but cost more (4-) more than half of GM and Chrysler disc brakes are now semi-metallics (5) brake manufacturers will soon have to stop using asbestos because it will be too expensive for them to meet the proposed OSKA standards. A telephone call to Schiefer at Dow Corning in Midland, Mich. (517 4-96-4000) did not reveal any new information, but he did confirm that brake formulations are hard to find in the published literature. I do not have information on changes in manufacturing equipment or processes for the semi-metallics. - 3- Brakes in which asbestos is replaced (the basic formulation remaining about the same) are best exemplified by SAE Transactions Paper No. 800667 by Halvsr Y. loken from du Font. iThis I960 paper suggests replacement of asbestos by a combination of "a low cost inorganic filler with higher cost reinforcing fibers added for strength snd crack resistance. This approach would in principle make it possible to continue to use the production methods that have been developed for asbestos-based friction materials." The paper presents a table which lists the advantages and potential problems of various reinforcing fibers for friction materials. The problem with Kevlar: "Cut forms...require special attention in mixing because the fibers are tough and do not break up but tend to clump together on prolonged mixing." The paper does mention that Kevlar reinforced friction materials can outperform asbestos friction materials. However, Aldrich told me that Kevlar is very expensive (shout $6.00 per pound compared to about $0.25 per pound for asbestos) and that this fact might limit the commercial applications of Kevlar. On the other hand, the formulations in the paper use only 5# Kevlar, but premium quality asbestos linings use 50-80# asbestos. Semimetallics cost less than Kevlar-based friction materials. Also enclosed is U.S. patent 4,119,591 to Aldrich and assigned to Bendix. This discloses a friction material reinforced with steel and cellulose fibers. Aldrich said that this patent is "worthless." There is also enclosed an abstract of SAE Paper No. 800979 entitled "Performance Characteristics of a Non-Asbestos Cellulose Fiber Comuosite Friction Material." No evaluation of this paper can be made by me. Lastly, there are two U.S. patents, 3,870,561 assigned to Johns-Fanville ana 4,118,528 assigned to Raybestos Manhattan, both disclosing glass fiber clutch facings. In conclusion, asbestos free brake linings can be made using either semi-metallic friction materials or by replacing the asbestos with a combination of Kevlar aramid fibers and filler. Since semi-metallics have already proven themselves in commercial applications in Europe, and recently in the U.S., and cost less than Kevlar-based friction materials, they will probably be the first choice of U.S. manufacturers when asbestos is eliminated. United States Patent Office 3 ,434,998 Patented Mar. 25, 1969 1 2 smaller particle si/e- There is effectively no upper lim it 3,434,998 o n p a r t i . le sire an d the e n u r e 25*3, o f s e m i- m e t a llic m ay MODIFIED ORGANIC BASE FRICTION M A T E R I A L be com prised of a single large p a n ic le or inscri in the F. W illiam Aldrich and Theodor E. Deane, Troy, N .Y., base organic However, to tacihtate processing. pre at*tenon to The Beadix Corporation, a corporation of f e r r e d p a r t i c l e si/e ran ge is f r o m plus 2o l o m i n u s 4 Delaware ' N o D r a w i n g . F i l e d Sept- 13. I M S , See. N o . 417,852 mesh l a i . C l. C 08c 5I / 0K. C 89h 3 14. F I 4d 69-02 The preferred composition o f the temi metailic fric I S . C l . 240-- 38 5 Claims tion m o d if y in g p a n ic le is as fo llo w s Constituent Vol., percent O r g a n i c r e - in b i n d e r ---------- ---------------20 a n d ove- ABSTRACT OF THE DISCLOSTRE A n organic base friction m aterial h iv in g dispersed therein chunks of a semi-metallic friction m odifying m a Graphite ......................... ............... .................... 15-25 C e r a m i c p o w d e r ____________________________ 10-25 M e t a l o r m e t a l o x i d e p o w d e r ............................ 30-50 te r ia l t o serve as the f r i c t i o n c o n t r o l l i n g m ean s. T h e 1-' T h e p r o c e ssin g seq u en c e is to m a n u f a c t u r e a aemi- senti-mclalli. muddier being essentially high concentra metullic f r i d i o n m o d if y in g particle by c o m b in in g the tions of mcia! and metal oxide powders in a base org. n L m clal or nttl.d oxide powder, ceramic powder and resin matrix pow dered graphite in a r o tg a n i. resin hinde; o f the thermosetting phenolic resin type w h t.h is then cured In order to obtain the ultim ate in frictio n ch aracteri-- " under heat and pressure to fo rm a blended rigid mass tics particularly high friction level for an organic type brake inline or frictio n m aterial, it is necessary in add of semi metallic material This material i' then broken i n t o p a r ti c l e - o f a si/e greater t h a n 2u me h and a d d ed to f r i . '.c - m o d if ie r s T h e m o st c o m m o n o f these f r i c i i o n a conventional organic brake lining mix. comprising pref m o d i. ic r s ar c the c u r e d r e s in o u s p a r tic le s such as th at n . erably I 1.- to 2(1'! o f the vo!,,n.-. of the tt nish eJ l i n i n g derived fr-im ...-hew nut 'h e ll liqu id T h e use o f such * material T he organic lining m atc'.ai witn sem i-metalue i ..-shew r e-in p a r t i . l e s res ults in in c rea sed fr ic tio n . :' ef- p a r ti.le added t- then p ro c e -s c J c u r c j and sr...pcJ into f r . t i . c n c " of the base lining or frictional material, par a fintsheJ organic brake lining segment o- M o c k The ti .id .. .- h ,,t . i m i ' i e m o ' r e l a t iv e ly - l o w t e m p e r a t u r e s H o w - a r p e u 'a n . c ot ttie l.mng car. best be d c s .rm e d .o m o n ie d c v e ' sa .h use hr.' the disadvantage of decreased lade co m p a 'e d to co r.en ti.in .d linings when t` e 'c m i-m e ta liic te s o ta r .- c (>r d e c r e . i - e j e f f e . t i v e r i e ' s at e le va te d te m p era- p a r tic le m / c w u t a i the r r e l c r e d ' i / c ran ge of p i j - 2'i t re p - . i . r c v i - v e r v . ..nd also the disadvantage ot d e m f-1:- 4 rr-e-h c e a s e d eTc.'t v e r c " s*ser Ion: l e m n o r m a l tob- s -.11 : r. . c i r r i . .on-tittienr- ar. m IIjr's;ir~it-c muhue c s e d .. i n . ' s . st ;r, i v q . i i i e d p e Ja i p i C " ' u : . o v u lire in 1.*:1. *. ix'.c a:.x` / i : . T l : : - 0X1,1-. i u ! t *,U112 j : c i : . i.-c !. .in-.' At alt.-rr ,.t. trie Use o f s u . h c u r . d r e s m o u , o'".. 1r v 55J ! . v ' l j n i , - o; . d ' u r . i i i ; j ; m ' i. f r t i. par n. ; .if. -1 n ' l l l l h f . nlin n . .'1' '' *'e : ' i. s ' . xj ' le - ti .I . i- i n , ii- c e-: n-'H-.in n m a t e r i a l s o f ab r a s iv e d t a ' - Vu- !e- ted n e t . - I ' a n J me, Mile*' . . t ...r.'x f ?on a n J n .ic-si..- N I nalert..!- for example alumina will n i 1r 1H' \*\r!f M .* f i l i e r !: - r v.. f 11*. de per. J .:. 2 ter n i c e sec cfTecI-.mess and w ill also offer iirrp'oveJ II * .1 vi . p i ' i v in . e v ie n i on . y - n i f i .n ox. de. f t - O . tadt- r e s . ' l a n e tmpro-ved re c o v e r y p ro p e rtie s , and ess ^ a vuf' sii. .u K r m c i .W r j ' 'H*' l.MTi V CJ i m . - It wn ' be li.-.-d-.i t ip e .t a i p r c 's i . t c i n c r e a s e ) w i t h ex te n d e d use n o l i si Ih. xi: e. ni. I ; T 1- thi r : 1n binder ar.xl S u . f: l u o - g .u .i , n i a i c r i a l s . h o w e . c r . also h a ve si-. fimt c the m . .! i- n o ' u x,i \u J 1.5 l 1 - . t P. I":' d ' * d i - a d v a n : , c.-s in in . r e u s e d no is e c h a r a c t e r is t ic - and ex- s p e a k in g , the line ot O is tii.d.io n netw eeri . : a'.llcS UTrU .e s i i f wej-ing. grooving or general d c stru .lio n of the m e ta l o x i d e - w h i . n car. be s.i'-'ti: ..ted Ix f i . m e ta l con- r n . ' . . r t a . e t make dtum or disc). ; . lent d e p e n d - <<n the a b t .i.i V r-r ha r J '1C". . r.a; a c t c r i s ' te I' i- an obje.r of the prescnl invention to p r o v jje a H .a k e l in i n g , m . i i . i r . i c r ..-.d ii a . c o t d . i r . . witf. !'; sen . n,-.: -Hi. in .-tio r m odifier fo r organic base lining to p in . ids in.reused (ri.tio n effectiveness at both low and above leaching.. repre e' - a stgr.ili.ur: adv..nce o.er . o r . v e n i i o r a l o t g a n i. Iir.ing- k n o w n m I'n pri, r .,'1 i . c . n e . ' t. mp.-t attires w ith o u t d is p la y in g p o o r fa de re- ( i c n e t a l l v spe .k in g the J . a r . e is it- te rn's o ' inc rea sed -is-..-,.e r e . o v e r v . lo r e te rm h u td e m n g . ex c essiv e w e ar. ,,, lii.-m- I I I . l i o n e l l c . i n c u r - nr , ! c v.u i o .i - . o n . li : ; o r . . o f or -curing operation ( om paii-on tc-'s lo-.-jl that ir,.rca-eJ etl.c- It i- an o t h e r c'mect o f the prese nt i n v e n t i o n to p r o v i d e tiven.s. i. most p ron ou r.ed under -e-erc conditions of an im proved fri.tin n m odifier lo r organic base lining o p crjtio i. wfieie .invention,.! organ,c lin m p . are the com prised of a sen t metallic particle ot chu nk consisting weakest l o r example, rt.ikc fade m.f...ed " . fiiet ter o' a in--'jI powder or metallic. o x iJ c powder m atrix, a p c i j l u t c . c.,,.-ed f-. i r e q a e n r rr.->c a p p l i. .: t i >n m - i i , - t , c . u, .ornliruent and powdered graphite all bound ti m e i n t e r . a ' - i ie-sene d i t o m |o .- " o ' , k o . o . c . ot t. .. e .. v r unJcr heal and pressure by a th erm osetting ef fe ctiv ene ss a ' , e: tade is m . r i a - e d tr e x . e - s o! 2* p ne no li. re-ir. binder. H i g h -p eed a n d b u r n is h i w i -.j in i e t fe d iv e r . e - - is i m The tri.iio n modifier of the present invention is for p r o v e d by a s i m i la r degree W h i l e to some exte nt ibe-e use with an organic base lin in g of the co n v e n tio n a l type are ru d i.ta b le results of high friction characterist.es of consisting o f a resin base with additive organic friction m e l. il a n d c e r a m i c p a r t i c l e s resista nt l o d e t e r i o r a t i o n at modifiers aspestos and the like. high temperature, the m ain significance of the present in The sc.mi-nie'.alli. friction modifier or friction con- vention reside' in the fa.t that lb's improvem ent i- tiolh ng m e jn s added to the basie organic lining p ref achieved without sacrificing lining wear or x o r i n g the er j "'ly comprise-. I 1.- to 20f< by v o l u m e o f the to t a l lin- n;, m a t i n g b r a k e M ir / . i. e s u ch a - e n c o u n t e r e d wit f m e ta l tng m a i e t i a l . lfe lo w 11.- '"< . ef fe ctiv ene ss is n o t o b t a i n e d , base o r m o ' g -m. l in in g s . In l a d . test re su lt - :,:-.ve Je u b o . e 20' - . p to e cssin g l i m i t a t i o n s cause the a d d i l i o n to monstr.ited .m inetea-e in lining life ot gi.utcr then h e . o m e u n e c o n o m i c a l A f u n c t i o n a l u p p e r l i m i t is 25C< 20' - c o m p u t i n g an o r g a n i c w n h I <*'< s e m i - m d a l i i c p.o- wherein tnc abrasive content c.m be expected to have t id e s w iih a lu l l o rg u m . of ttie same type deleterious effects with respect to d rum or di-c wear We ilairn I lie sen u-m etalli. is lo he added as a particle ot t h u n k I A m id d le d n.cuiii. t ... in . lio n m i . o I .onci-t M / t ere.iter i h . i r 2() m e sh since the f i f e d tv m . i ' k e . l al in g of an oi earn, I'.is, !i i : m Iin me t i n te n i i .. r 1 ut'g 3,434,91/6 3 4 from 1 to 25% by volume of a scmimctallic particle o f size greater than 20 mesh: said semi-metallic particle hav from V i lo 2<>*; by volume ut a s e m jm e la llu p a riL a - within the size range of plu` 20 minus 4 mesh, said senn ing as constituents by volume percent graphite from 15 metallic particle having as constituents bv volume percent 25%, ceramic powder from 10-25*, and metal or metal graphite from l < - 2 ' ' ; , cerjimc powder from 10- 2 *'. oxide from 50-50*7 being bound together by an organic , and metal or metal oxide fri .r. to o r : being Kum d to resin binder from greater than about 20%. ' gether by an organic resin h in J c from greater than 2. A modified organic base friction material as claimed about 20% in claim I wherein said organic resin binder is a thermo setting phenolic resin 3. A modified organic base friction material as claimed |,, References Cited UNIfl l> S I M Lb r.ULNlS in claim 1 wherein said ceramic powder is a ceramic .VOO-'.s j ^ II I9M Klein `elected from the group consisting of sillamanite. mullitr. 3.210.MH III. ivn* Bigg' magnesium oxide, zirconium oxide or mixtures thereof. 4. A modified organic base friction lining material as M O R R I S I I f B M A N f Vlf/fiJM L \ t i t U I f . i I claimed in claim I wherein said metal or metal oxide is I ' K B A R O S . etunli/ir/ f i W l l l l . i r selet led from the group consisting of iron copper, iron oxide or mixtures thereof 5. A modified org.mi, base friction material comisting of an organic base friction lining material containing UK>-- M> 0 S Cl X K SAE TRANSACTIONS E. J. Manganiello/President M. J. Kittler/Treasurer Joseph Gilbert/Secretary and General Manager PUBLISHED BY jSOCIETY OF AUTOMOTIVE ENGINEERS, INC. / T W O PENNSYLVANIA PLAZA / N E W YORK, N.Y. 10001 710591 Semi-Metallics: A New Type of Friction Material F. William Aldrich Automotive Control System s Group, The Bendix Corp. THE PAST TWO decades have seen rather dramatic changes in the requirem ents for frictional elements used in the braking systems o f m otor vehicles. Essentially, this shift in require m ents has been in the direction o f greater heal resistance, greater frictional stability at a higher friction level, reduced noise, and extended durability. In general, the state-of-the-art development of friction materials has kept reasonable pace with these required changes through improved resin binder systems, improved friction modifiers and fillers, and the in creased application of scientific aids for greater uniformity Although friction material development has not been re stricted to the use of organic constituents I00a , a substantial portion of their composition has been organic type materials and they have been, thereby, subject to whatever shortcoming! these materials may have. It is u n fo rtu n a te that the prime shortcoming of organic type materials, namely their inherent nature to change both their form and properties with tempera ture, is at com plete odds w ith the requirem ent o f frictional materials to maintain maximum uniformity and stability of effectiveness over a wide range of temperatures. In the past, considerable effort has gone into a potential solution to this problem o f organic thermal instability in the form of development based on 100/f inorganic materials, namely sintered metallics. However, even these supposed ultimate materials had their shortcomings, perhaps the greatest of which was that they also had too much sensitivity to temperature. At low temperatures they weic ineffective and at high temperatures they were too effective. Their major advantage was low wear in the extrem e tem perature ranges of 1000-2000 F, which made them quite successful as aircraft linings. Sintered metallics did have, however, a potential of frictional stability, superior to the organics, if it could be controlled. It becam e obvious that if the technological advantages o f both the organic and sintered metallic friction types could be combined, then a new generation of substantially improved friction mateiials could be obtained. The result of this mar riage i- todays state-of-the-art semimetallic friction materials. Thi! paper will, as a rule, not differentiate between drum biake u:d dis^ brake applications for friction materials, since the basu characteristics remain essentially the same regardless of application. Any difference in the requirements o f friction material for these two types is ordinarily only a matter o f degree, with disc brakes, for example, generally operating at higher temperature ranges than drum brakes CLASSES OF FRICTION MATERIALS Any discussion of friction materials can be clarified to an extent, by first classifying them along general lines. For pur poses of this paper, let us assume three classes for current materials. Class A, Class B, and Class C, with the latter being semimetallic. As a general category. Class A friction materials would be represented by p ro d u ctio n materials on A m erican m ade cars over the last 5-10 year period. They would be further categorized as being fundamentally organic in nature, ex cluding. of course, their inorganic asbestos content com mon to most of them. They are probab'y highly loaded with organic lesin hinders, organic resin friction modifiers, and A BSTRA CT-------------------------------------------------------------- A new semimetallic type of friction material has been devel oped which offers improved frictional stability and high tem- peiatuie weai resistance. Having minimal organic content, these mateiials avoid the thermal sensitivity to chemical and physical clunpe characteristic of typical friction materials. 20c.`> 2040 F. WILLIAM ALDRICH natural or synthetic rubbers or elastomers. They frequently also contain small amounts of graphite or other carbon type materials, and possibly small am ounts of inorganic wear fillers such as ground limestone. As a class, they would be generally low in inorganic content, particularly anything of a sub stantially abrasive nature. Again, as a class they are reasonably quiet, give respectable durability, and under most conditions perform their frictional purpose without distinction. On the demerit side, sizeable increases in tem perature raise havoc with their efficiency, and long term use or abuse frequently lowers their effectiveness. They lose friction rapidly ai tem peratures over 450-500 F and start considerable thermal decom position above 600-650 F. Once having been in this "affective" temperature range, they are seldom like they were before. Class B materials represent a first step major com prom ise in attem pts to improve the Class A types. As a class, they ordi narily have higher inorganic and lower organic contents, a design factor to improve their thermal stability. They arc most apt to have some degree of abrasive content to help stabilize their frictional properties. Generally, as a class, they have b etter fade resistance, better recovery, and overall improved frictional and thermal stability. They may give good lining life at higher tem peratures (+450 deg), but frequently at the expense of the mating surface which suffers from excessive wear, grooving, or scoring. They are quite apt to be noisy, and in terms of frictional stabilitymay become overly effective with use or abuse, thereby in creasing their noise and reducing their controllability. The more recent Class C or semimetallic friction material attempts to extract the desirable properties from each of the Class A and Class B types. To gain maximum frictional and thermal stability it minimizes organic content, but it does not ignore it since organics do add desirable properties. It also maximizes inorganic content to gain thermal and frictional stability, but it does not o verdo these since it does no! w ant the potential hazards they offer. WEAR AND FADE RESISTANCE It has previously been noted that one of the shortcomings o f organic type materials is their tendency to change form and properties at elevated tem peratures. It is this characteristic which contributes substantially to highly accelerated wear as the tem perature goes up. The p roperty o f wear is usually considered to be an economic factor only, but to some extent it can also play a part in performance factors. In the case of a drum braked vehicle with duo-servo brakes,moderate differ ences in side-to-side lining temperature or side-to-side lining wear rate can lead to unbalanced friction levels and severe pulls or single brake burn-up. Whether the chicken or the egg com es first is problem atical, b u t the fundam ental process is the same. In a disc brake, the lack of servo action may prevent pulls for a longer time, but moderate temperatures or wear differences at the higher operating temperature range of the disc brake can result in undesirable and substantial lining life variations, side-to-side and front-to-rear. LINING TEMPERATURE-F Tig. 1 - Wear versus temperature characteristics Class A organics do have, as the temperature increases, a temporary degree of self-protection by virtue of their fade properties. By this we mean that increased tem perature de creases their effectiveness and their work output, thereby protecting them from further temperature increases and in creased wear rate. However, since fade is generally less on each successive fade condition, this protection is somewhat short lived. Some Class A materials also have such a steep wear versus temperature curve that constant surface renewal minimizes fade and also reduces or eliminates this self-protec tion. Class B organics generally have improved fade resistance and more gradual wear versus temperature curves. This better fade resistance tends to reduce their self-protection. In spite of the better high temperature wear capability of the Class B types, the organic materials present still cause eventual wear resis tance breakdow n, even though it m ay be at a level 100-150 deg higher than a Class A type. At this point, however, the asbestos fiber is reaching the tem perature range o f substantial loss o f water o f crystallization and is itself deteriorating, actually forming new materials such as olivene. Class C or semimetallic linings have a wear versus temperature curve of considerably less slope than the Class A and Class B organics. The wear versus temperature curves of Class A, Class B, and Class C materials, as taken from actual constant to r q u e sam ple d y n a m o m e te r tests, are sh o w n in Fig. 1. It will be noticed that the Class C semimetallic is essentially insensi tive to tem perature in the 250-650 F tem perature range, while the Class B starts to break at +500 F, and Class A starts to break at +400 F. Also note that up to 500 deg or so the Class B material wears at a rate somewhat greater than either the Class A or Class C types. Because of the minimal organic content of semimetallics. th e y also have m in im al fade. Based o n the p rev io u s fade = self-protection discussion, one would at first consider this a d e trim e n t. In reality th e sem im etallic has a type o f self-p ro tection w hich organics seldom have-that o f repetitive fade or considerably less tendency to antifade. This is quite evident when one looks at what happens on typical vehicle tests in volving m o re th a n o n e fa d e , su c h as S A E J 8 4 3 b . In Fig. 2, it will be noted that for Class A and Class B organics that the second fade shows considerably less friction loss than the SEMI-METALLICS Fig 2 - Vehicle fade test characteristics (5700 lb GVW) 2041 CLASSA ORGANIC CLASSC SEMI-MET Fig. 3 Disc pad durability-city traffic test; ('lass A versus Class C first fade, while in the case of semimctalhc materials, the second fade may show almost equal friction loss. In the case o f semimetallics there is reason to believe that, in a d d itio n to the bin d in g actio n o f th e resin sy stem th e re is an inherent mechanical bonding of the metallic components. Such supplementary mechanical bonding, of course, contrib utes substantially to high temperature strength and wear resis tance and can take over at the point the organic binder fails There is also indication that the m echanical bonding is in creased with use or duty. Early semi metallic linings showed low tem perature traffic wear slightly poorer than Class A materials and more typical oi the Class B types. However, this characteristic has now been mi proved so that on normal city traffic type driving the semi metallic shows appreciably better wear. Fig. 3 illustrates 1 lg 4 - D im. pad wear at 100 mph I ull brake dynamometer. Class A versus ( lavs 10-stop test actual traffic durability test results, generally 350 F max, on four Class A production organic disc pad linings and two Class C senumetallie materials. The C2 material, a more recent developm ent, shows still further gains over the C l type. At the other end of the duty scale. Fig. 4 illustrates 100 mph wear rate results on a full brake inertia type dynam om eter using these same materials. Again, the more recent C2 material shows improvement over the C l . FRICTION Class A friction materials as a rule have the highest friction when cold and the lowest friction when hot. Class B materials are generally somewhat lower friction cold and higher friction hot compared to Class A types The senumetallie materials :042 F. WILLIAM ALDRICH have substantially different friction characteristics, in that they tend to increase with friction with both increased tem perature and increased surface speed. This characteristic has a distinct advantage for high speed effectiveness. Historically, high speed effectiveness of organic materials has been a problem. Since increased surface speed means increased temperature, the organics have usually shown poorer effective ness, as the speed increased, frequently requiring some exten sive power assist to maintain reasonable pedal efforts. In contrast to this, the semimetallic materials have temperature/ speed characteristics which tend to reduce pedal effort and stopping distances from high speeds. Also, in contrast to previous full metallic linings (sintered materials), the low speed cold effectiveness is greatly im proved. It is acknow l edged that there is still some room for additional im prove ment of this characteristic with semimetallics, but to date, there has been no serious deficiency in this area. Actual tests have been made in the subzero tem peratures of a Canadian winter. Stability o f friction throughout the life o f the lining has also been a problem with organic types. Their general charac teristics of high initial friction have frequently led to initial vehicle braking instability, and their characteristic of friction drop or loss after moderate abuse (fade) or long term light usage has frequently initiated complaints of ineffectiveness. In a d d itio n , their characteristic o f friction " p e a k in g " vs ith severe use. particularly in the case of Class B materials, has led to vehicle braking stability and controllability problem s. By virtue of their minimum organic content, semimetallic materi als are much more frrctionally stable over a wider range o f use or abuse. NOISE This nonfunctional characteristic of brake systems and friction materials has kept industry engineers "hopping" for years. The friction materials engineer may be reluctant to agree that noises are always the linings fault, but he docs have to agree that there are linings more or less prone to producing noise. Brake design or lining attachm ent not considered, class organics generally tend to produce their maximum of audible response in their cold or warming condition. Class B types usually duplicate the Class A in this respect, and supplem ent this with additional noise when warm or hot. The effect of this characteristic is that the driver o f the vehicle has the greatest odds of obtaining noise under the conditions under which he does the majority of his driving. Again, semimetallic materials tend to reverse these charac teristics. They tend to produce minimum noise cold or warming and have their maximum noise while hot (for exam ple, above 3 5 0 F). On this basis th e n , the driver is m ost apt to hear noise not under normal driving conditions, but rather during the less frequent or abnormal conditions. Fig 5 - Disc pad swell and crush comparison (at 5000 psi constant stress) The actual com pression o f the pad material is a function of both the inherent compressiblity of the pad and line pressure required, which is a function o f the materials fade resistance. This allows us to approach the compression problem from both directions; reduce inherent compressibility and/or reduce line pressures required (improve fade). Class A materials, because of their high organic content which tends to create inherent compressibility, and also to create fade, generally offer the m axim um in fluid displace m ent. Class B materials with less organic content tend to offer substantial improvement in this area. Class C semi metallic materials with still less organic content and improved fade resistance, have a potential of substantially greater im provement in reducing fluid displacement. The accurate comparison of compressibility of various friction materials under controlled laboratory conditions is difficult, due to their variable initial swell characteristics on heating. One procedure which has been used involves main taining a constant 5000 psi load on the sample and plotting, swelling, or compression versus temperature up to 800 F (Fig. 5). It will be noted that the Class A organic with high elastomer content had an initial and immediate compression prior to its showing any degree of swell. All the pad materials displayed the same basic characteristics; that is, they showed swell under initial heating-up to some point in spite o f the preload. It will be noted that the Class A organic w ith high elastomer content actually crushed at a pad temperature below 400 F, while a similar material with low elastomer content showed improvement, but still crushed at less than 550 F. The Class B material started to compress at 550 F and failed at less than 700 F, while the semimetallic material started to compress at 650 deg but would not crush at the 800 deg temperature limit of the oven used. COMPRESSIBILITY OTHER CHARACTERISTICS In the disc brake, the compressibility of the lining material is a significant contributor to excessive fluid displacement. In the early stages of development, the increased heat conductivity of a metallic type friction material, particularly SEMI-METALLI CS for disc pad use,and its effect of fluid boil was considered a potential problem. The use of a two layer, organic backed semimetallic pad with the organic acting as a heat dam was indicated. However, many actual vehicle and dynam ometer tests without such insulation failed to produce fluid boil. Controlled tests did indicate fluid temperatures 60-80 deg higher with semimetallics than with organic. A practical consideration, how ever, is that under extrem e tem perature conditions or use, the wear o f organic materials can be so great as to bring the actual shoe in contact with the rotor, a m ost critical set o f conditions. This possibility is recognized by SAE and certain vehicle manufacturers who appraise their designs for fluid boil in the bare shoe condition. Compared to organic linings, semimetallic materials have relatively low coefficients of friction against the backing plate or shoe, and a "norm al" riveted attachm ent can result in some shift or loosening and potential cracking. For this reason a roughened or grit blasted shoe surface is recom mended, preferably combined with a tapered rivet head. Alternatives to this are a higher cost organic backed pad or integrally molded or bond-molded assembly. Although the chemical composition of semimetallics varies 2043 considerably from that of normal organic friction materials, their mating surface compatibility characteristics are extremely satisfactory. Compared to other materials even approaching their performance and wear level, they are extremely kind to mating surfaces and generally require no special drum or rotor metallurgy or finish. In the case of heavy duty drum brakes for large trucks, they virtually eliminate drum spotting and heat checking typical o f most materials in use. SUMMARY A new type of friction material of improved frictional and thermal stability has been developed. This new type of fric tion material, when compared to current conventional types has the following characteristics: 1. Im proved wear resistance, particularly at high te m p era ture. 2. Improved fade resistance. 3. Improved high speed effectiveness 4. Impioved frictional stability. 5. Minimal noise. 6. Excellent mating surface compatibility. ' United States Patent nq Aldrich ni] 4,119,591 [45] Oct. 10, 1978 [54] FRICTION MATERIAL REINFORCED WITH STEEL AND CELLULOSE FIBERS [75] Inventor. Francis William Aldrich, Troy, N Y. [73] Assignee The Beadix Corporation, Southfield, Mich. [21] Appl. No. 112,541 [22] Filed Jal. 5, 1977 [51] Iat. CL- ................................................OWL 1/02 [52] U.S. Cl....................................... 260/17.2; 74/190; 188/218 R; 188/251 R; 188/251 A; 260/17.4 BB; 260/17 4 CL; 260/38; 260/42.17; 260/42 18 [58] Field of Search ................................ 260/17.2, 38 [56] Reference* Cited U S PATENT DOCUMENTS .V684.0e2 8/1972 Johnson ... 188/251 R 3,04,701 3,135.118 3.922,241 3,939,194 4 /1 9 7 4 9/1974 11/1975 5/1976 B o g n a r ......................................... M O /1 7 .2 Rhee ................................. 260/31 Barker et al...................... 260/17 2 Adelmann ................... 188/231 A Primary Examiner--Edward M. Woodberry Attorney, Agent, or Firm--Leo H McCormick, Jr.; Ken C. Decker [57] ABSTRACT An asbestos free organic base friction material for use as friction lining of a brake. A combination of fibers telected from a group consisting of steel, cellulose, glass mineral and rayon fibers and a thermosetting resin binder are combined with cashew nut particles, elasto meric modifiers and inorganic modifiers to produce an organic base friction material having s substantial stable coefficient of friction over the normal operating range of the brake. 10 Claims, 25 Drawing Figures 250 300 400 500 600 700 U.S. Patent Oct. 10,1978 Sheet 1of 5 4,119,591 FIG. I FIG. 2 FIG. 3 FIG. 4 FIG. 5 FIG. 6 U.S. Patent oct. 10,1978 Sheet 2 of 5 4,119,591 FIG. 7 FIG. 8 Fl G. 9 FIG. IO FIG. Il FIG. 12 U.S. Patent Oct. 10, 1978 Sheet 3 of 5 4, 119,591 .04.03- 250 300 400 500 600 700 FIG. 13 250 300 400 500 600 700 FIG. 14 F I G . 15 F I G . 17 FIG. 18 U . S . Patent oct. 10,1978 Sheet 4 of 5 4, 119,591 FIG. 19 F I G. 21 FIG. 2 2 FIG. 2 3 FIG. 2 4 4,119,591 diapursed throughout a friction b u n g provide sufficient FRICTION MATERIAL REINFORCED WITH STEEL AND CELLULOSE FIBERS strength to allow a friction lining made of the composi tion to withstand dynamic loadings without deteriorat ing under normal operating conditions. BACKGROUND OF THE INVENTION It is therefore the object of this invention to provide Organic friction material compositions currently used in clutch and brake linings of vehicle* mint be capable of withstanding severe operating temperature* and dy an mhritos free organic friction hning with sufficient structural strength to repeatedly withstand dynamic loads without deteriorating when need in a brake lining namic pressures experienced during repeated applica It it another object of this invention to provide sn tions. To prevent a deterioration in performance and 10 organic friction material with a foundation material physical degradation during an application, the lininp up of a combination of at least 3 percent steel fiber are reinfoced by asbestos fiber* randomly dapuned and 5 percent cellulose fiber The steel and cellulose throughout a resin matrix. However, recent medical fibers being dpursed throughout the friction material evidence indicates that aabestos libers can cause health to uniformly distribute forces exerted on a brake lining hazards of the lungs in persons exposed to aabestos IS and thereby prevent degradation thereof during re fibers of the type used in the manufacture of clutch and peated dynamic brake engagements. brake lining. The health hazard is caused by the p o r It is another object of this invention for providing an tion of the surrounding environment with small parti organic friction material with a base material of steel cles of asbestos during the mixing of the friction compo fiber and cellulose fiber to establish s substantially uni sition in a manufacturing facility. 20 form wear characteristic over the operating range of In an effort to reduce the environment contamination by the asbestos fiber and thereby continue manufactur friction lining. These and other objects should be apparent from ing asbestos based organic friction linings, a water reading this specification and viewing the drawing. slurry process is disclosed in U.S. patent application Ser. No. 754,477 has been evaluated. The water slurry 25 BRIEF DESCRIPTION O F THE DRAWING can be transmitted throughout a manufacturing facility FIGS 1-24 of the drawing are graphs comparing the without contaminating the surrounding environment wear characteristics of the non-asbestos organic friction with asbestos fibers. However, before the friction mate material competition made according to this invention rial can be cured, the water in the slurry must be re with a typical asbestos organic friction lining, and moved in order to be assured that any resulting lining 30 FIG 25 is a table illustrating non-asbestos friction has essentially the same operating characteristics as a material composition made according to this invention lining made from a dry mix. In another attempt to reduce the occupational health hazards in the manufacture of linings u has been sug- DETAILED DESCRIPTION OF THE lu v c x m n v : getted that the asbestos fiber be replaced with glass In order to evaluate the non-asbestos friction material fibers. U.S. Pat. No. 3,967,037 discloses several Hning com compositions disclosed by this invention, typical asbes positions utilizing fiber glass From experimentation it tos base friction material compositions were used as s has been determined that such lining compositions are standard to determine the wear rate and coefficient of acceptable, however, in admixing the ingredients the 40 friction characteristics of the non-asbestos base friction fiber glass tends to ball and thereby reduce the continu material when used in t brake. ity of the friction material. In addition, when fiber glass FIG 25 illustrates the relationships of the various base friction materials are mated with a steel brake rotor combinations of the fibers substituted fot asbestos as or drum, an unacceptable wear condition occur*. diacloaed by this invention. U.S. Pat. No. 3,896,075 discloses another friction 4j The ingredients in the asbestos and non-asbestos fric composition wherein the asbestos in an organic lining is tion material formulations were processed into brake replaced with basalt fiber* Because of the process re friction lining in the following manner as described in quired to reduce the mineral basalt into a fiber state, the detail for the base line asbestos material composition A. use of such friction composition to date has not received The asbestos fiber, dry phenolic resin, equal pans of open acceptance as a substitute for asbestos based or jo cashew nut powder and synthetic rubber scrap and ganic friction materials. barytes were mixed together until x homogeneous mix Later as disclosed in U.S. Pat. No. 4,019,912 the rein ture was achieved. Thereafter, the mixture was placed forcing of the structure of a resulting friction lining was in a mold and compacted into a briquette. The briquette achieved through the use of carbon fibers. However, was then transferred to a press and compressed by a the pyrolysi* *tep required to reduce the rayon or cellu 55 force of about 5,000 pounds per square inch while the lose fiber to a carbon fiber would destroy the elastomer* temperature of the briquette was raised to about 250* F. and inorganic filler* found in organic friction composi temperature. The 250* F. causes the phenolic main to tion. flow throughout the mixture and establish a matrix for SUMMARY OF THE INVENTION holding the other ingredients in a fixed position. The <0 briqaette was then transferred to a caring oven having I have developed an orgaoic friction material compo a temperature of about 500* F. to further set the m in. sition consisting of an asbestos free foundation material, The briquette was then ground to a specific size corre organic and inorganic friction modifiers retained in a sponding to s brake pad. This brake pad waa then matrix of a thermosetting resin. Tbe asbestos free foun placed on a dynamometer and from tbe test performed dation material includes as a minimum of 3 percent steel 63 thereon it was established that the composition Formula fiber and 5 percent cellulose fiber and other fibers such A had an avenge coefficient of friction of 0 36 at 450* as carbon, mineral and fiber glass. The steel and cellu F and a wear rate as illustrated by base line 20 shown in lose fibers when randomly orientated and uniformly FIGS 1-9. 20 and 21 4,119,591 3 4 In order to establish t broader base for evaluating the In an attempt to smooth out the wear rate of composi non-asbestos friction material compositions, a second tion No. 5 as illustrated by line 30 in FIG 5, a filler of asbestos friction material identified as Formula B was 3% by volume of carbon was added to composition No compounded. In Formula B the large amount of asbes 5 to produce composition No. 6 in Table 1 The compo tos in Formula A is replaced by additional cashew fnc- 5 sition No. 6 was made into a brake friction lining and tion powder and a filler of graphite particles to produce when evaluated in the dynamometer test, an average a brake lining. The average coefficient of friction of coefficient of friction of 0.28 at 450* F was obtained Formula B a brake pad made from, using the same dyna and a wear rate illustrated by line 32 in FIG 6 was mometer test as used to evaluate Formula A was found produced. to be 0.35 and the wear rate is illustrated by line 21 in 10 In a further attempt to broaden the baae for the inor FIGS. 10-19 and 22-24 ganic filler modifiers, a composition No 7 ss shown in Upon initial evaluation of the non-asbestos friction FIG. 25, wss produced In composition No. 7 a mini materials it became evident that the removal of asbestos mum of 3% by volume of rotten stone was added to the from the mixture left the remaining ingredients in a dry basic steel and cellulose fiber composition. When the crumbly stale during the briquette forming stage. 15 brake lining of composition No. 7 wss tested on the Therefore, it was necessary to add pan of the phenolic dynamometer and an average coefficient of friction of resin as a liquid to all the non-asbestos composition in 0.32 at 450* F was obtained and a wear rate as illus order to produce a composition capable of being han trated by line 34 in Fig. 7 was achieved dled as a preformed bnquette. In order to improve the wear rate of the non-asbestos The non-asbestos friction m i tens) composition No 1 20 friction material whiting was selected as the inorganic shown in FIG. 25 wherein a combination of steel fiber modifier, and composition No. 8 shown in FIG 25 was and cellulose Tiber were substituted for the asbestos produced When the dynamometer test was run for the fiber was formulated in the same manner as Formula A brake lining made from composition No 8. an average and formed into a brake lining When the dynamometer coefficient of friction of 0.30 at 450* F was obtuned tests were performed, composition No 1 had an aver- 25 and a wear rate illustrated by line 36 in FIG 8 was age coefficient of friction 0 14 at 450` F and a wear rate produced illustrated by line 22 in FIG 1 As can be seen, the wear In an attempt to improve the coefficient of fnction of rate approaches that of the asbestos material of Formula composition No 8 the fnction producing material kryo- a. which is currently accepted by the vehicle industry lite was added thereto to produce composition No 9 In order to establish a group of inorganic fillers ac- 3C shown in FIG 25 When the brake lining of composi cepable for use in a non-asbestos friction material, talc tion No. 9 was evaluated in the dynamometer test, an was substituted for the whiting of composition No 1 average coefficient of fnction of 0 37 at 450* F was and composition No 2 shown in FIG 25 was estah obtained and a wear rale illustrated by line 38 in FIG. 9 hshed The dynamometer test for the brake lining made was produced from composition No 2 indicated than an average coef- 35 Composition No 10 shown in FIG 25 includes the ficient of friction of 0 30 at 450' F and a weai rate as same type ingredients as Formula B with the exception illustrated by line 24 in FIG 2 could be expected from of the asbestos fnction material To establish broad base this composition for the friction matenal and improve the coefficient of Because of the availability of barytes and its low cost, fnction of the non-asbestos matenal the cellulose fiber a senes of compositions including bary tes were de\el- 41 was replaced with glass fiber When the brake lining oped composition No 10 was evaluated by the dynamometer As shown in FIG 25. composition No 3 was formu test, an average coefficient of fnction of 0 35 tt 450` F lated When the brake lining made from composition was obtained and a wear rate illustrated by line 40 in No 3 was evaluated by the dynamometer test a coeffici FIG 10 was ac hieved From this test it was deiermined ent of friction of 0.31at 450' F was obtained and a wcar 45 that while glass fiber uhen added lo non-asbestos fnc rate illustrated by line 26 in FIG 3 was produced tion matenal compositions, does increase the coefficient Even though the wear rate of composition No 3 of fnction, however, the wear rate is also increased could be expected to be belter than that of Formula A. Thereafter, composition No 11 shown in FIG 25 it was felt that the coefficient of friction could be im was dev eloped with wood flour added in place of the proved through the addition of either a different filler 50 glass fiber of composition No. 10 When the brake lining or fiber material Through expenmentation it was deter of composition No 11 was evaluated through the dyna mined that glass fiber has a higher coefficient of friction mometer test, a coefficient of fnction 0 37 at 450* F was than cellulose fiber. Therefore, glass fiber was substi obtained and a wear rate as illustrated by line 42 in FIG. tuted for the cellulose fiber and composition No 4 11 uas produced From this test it was determined that shown in FIG 25 was produced. When the brake lining 55 cellulose type fibers when combined with steel fibers of composition No. 4 was tested through the dynamom produced a more satisfactory non-asbestos fnction ma eter test, s coefficient of friction 0.35 at 450` F was tenal composition than when a single fiber matenal is produced and a wear rale illustrated by line 28 in FIG used. 4 was achieved. Unfortunately, with this amount of Thereafter, an attempt was made to establish the glass fiber in composition No. 4 surface polish or wear 60 optimum limits for steel, cellulose, and other fibers of a rotor or drum brake could be expected when used as the foundation material .or a non-asbestos Therefore, the amount of glass firber was reduced fnction material. 'Thus, composition No. 12 shown in and cellulose fiber added to produce composition No. 5 FIG 25 was produced In composition No 12. the shown in FIG. 25 When the resulting brake lining made volume of cellulose fiber was double that of the steel by composition No. 5 was evaluated in the dynamome- 65 fiber When the brake lining made from composition ter test, a coefficient of 0.32 at 450* F. was obtained and No 12 was evaluated through the dynamometer test, a a wear rate illustrated by line 30 in FIG 5 was coefficient of fnction of 0.35 at 450* F. was obtained achieved. and a wear rate as illustrated by line 44 m FIG 12 wav U . S . Patent Oct. 10, 1978 ORGANIC FRICTION M ATERIAL COM POSITION "TYPICAL A SB EST O S FRICTION M ATERIAL FORMULAS NON--A S B E S T O S FRICTION M ATERI A L F O R M U L A S IN G R E D IE N T S A A SB EST O S FIB ER 52 ST EE L F IB E R B i 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 2 0 21 2 2 2 3 2 4 43 5 5 8 8 8 8 8 5 5 8 8 8 8 8 8 8 8 8 15 5 8 8 8 8 CELLU LO SE FIBER 7 7 10 7 7 10 10 10 16 10 13 13 13 13 13 25 15 G LA SS F IB E R WOOD FLOUR PHENO LIC DRY 25 R ESIN LIQ UID (o) O R G A N IC M O D IF IER S 2 2 (b) IMNOODR GI FAI ENRICS 1 533 10 3 10 16 15 15 17 2 0 2 0 2 0 2 0 17 2 0 2 0 18 2 0 25 2 0 2 0 2 0 2 0 2 0 2 0 2 0 2 0 17 2 0 18 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 10 34 0 0 0 0 0 0 0 0 <2t 0 6 & fit 0 0 <7 0 0 0 0 0 a 47 4 7 4 5 4 7 4 5 42 45 4 3 4 0 4 5 4 8 4 0 4 0 4 0 4 0 4 0 4 0 4 0 45 45 4 5 4 0 17 25 0 ) (2) (3) (4) (3) () (T) () (9) fo) 00 9?) 03) 4) () () W 4 0*) * 4 NO ttt) 1) (*4) 7 21 21 2 3 15 12 15 12 2 0 2 3 12 II II 12 12 14 14 14 II 15 2 5 2 2 30 25 2 4 W C A S H E W NUT POWOER, NATURAL RUBBER, SY N T H ETIC RU BBER SCRAP, LATEX, CRUDE M O LA SSES, ASPHALTIC B A S E MATERIAL, ETC. (BARYTES, W HITING, TALC, ROTTEN STO NE. CA RBO N P A R T IC L E S, Q RAPHYTE ~OPPER POWDER. W OLLASTON ITE, K R Y O L IT E . ETC. A L L P E R C E N T A G E S G IV E N IN. VO LU M E OF T O TA L C O M P O S IT IO N PA RTICLES, CRY O LIT E, IRON OXIDE, 0 AT L E A S T (DAT LEAST 16% (2) AT L E A S T 1 6 % (3)AT L E A S T 10% (4) AT L E A S T 1 5 % (5) AT L E A S T 1 2 % 6) AT L E A S T 3 % 7)AT L E A S T 3 % 6) AT L E A S T 11% ;9)AT L E A S T 3 % (IO)AT L E A S T 1 2 % (H U T L E A ST 11% (12)AT L E A S T 11% 2 9 % OF WHICH IS C A SH EW NUT OF WHICH IS W H ITIN G OF WHICH IS T A LC OF WHICH IS B A R Y T E S OF W HICH IS B A R Y T E S OF WHICH IS B A R Y T E S OF WHICH IS C A R B O N OF W H ICH 13 R O T T E N S T O N E OF WHICH IS W H ITIN G OF WHICH IS K R Y O L IT E OF WHICH IS B A R Y T E S OF WHICH IS B A R Y T E S OF WHICH IS B A R Y T E S POWDERS (13) AT (14) AT (15) AT (16) AT (17) AT (18) AT ( I AT (20) AT (21) AT (22) AT (23)AT (24)AT LEAST LEAST LEAST LEAST LEAST LEAST LEAST LEAST LEAST LEAST LEAST LEAST 12% OF WHICH IS B A R Y T E S 3 % OF W HICH IS C R Y O L IT E 3 % OF WHICH IS ROTTEN STONE 3 % OF W HICH IS IRO N OXIDE 3 % OF W HICH IS COPPER POWDER 11% OF WHICH IS B A R Y T E S 5 % OF W HICH IS W O LLA STO N E 5 % OF WHICH IS CA RBO N 12% OF WHICH IS B A R Y T E S 10% OF WHICH IS SILANIZED MINERAL FIBER 2 5 % OF WHICH IS B A R Y T E S 1 0 % OF WHICH IS C A R B O N Sheet 5 of 5 4,119,591 FIG. 25 produced Unfortunately, composition No 12 was 6 structural strength in the friction lining, the carbon spongy and therefore, it was determined that the cellu particles can be replaced with carbon fibers. lose fiber should be reduced. Thereafter, the cellulose fiber of composition No 12 In a further attempt to establish a base for the inor ganic friction modifiers, the volumetric percentage of was reduced to produce composition No. 13 shown in 3 the steel fiber was increased and a minimum volumetnc FIG 25. A brake lining made from composition No. 13 percentage of barytes was established at 12% to pro was evaluated in the dynamometer test, had an average duce composition No. 21 shown in FIG 25. When s coefficient of fnction of 0.32 at 450' F. and a wear rate brake lining made from composition" No. 21 was evalu as illustrated by line 46 in FIG 13. This composition ated through the dynamometer test a coefficient of was not spongy, however, it should be noted that the 10 friction of 0.32 at 450' F was obtained and a wear rate coefficient of fnction was reduced. illustrated by line 62 in Fig. 21 was produced. Therefore, in order to increase the coefficient of fric Thereafter, the steel fiber was maintained at 8% by tion, cryolite was added to the composition No. 13 and volume and silanized mineral fiber was added to pro composition No. 14 shown in FIG. 25 was produced. A duce composition No. 22 shown in FIG. 25. A brake brake lining made from composition No. 14 was evalu- 13 lining made from composition No 22 was produced, ated through the dynamometer test had an average and when evaluated in the dynamometer test a coeffici coefficient of friction of 0.37 at 450' F. and a wear rate ent of friction of 0.28 at 450" F., and wear rate as illustrated by line 45 in FIG. 14. illustrated by line 64 in FIG 22 was produced. Since the wear rate and coefficient of friction of com From the foregoing teat it should be evident that the position No 14 was much improved over Formula B, 20 range of steel fiber should be maintained between 3 to the organic modifier base was expanded through the 15 volume percent of the total mixture However, since substitution of rotten stone for the cryolite to produce the optimum range of cellulose and other fibers had not composition No 15 shown in FIG. 25 When a brake been established, therefore, composition No. 23 shown lining made of composition No 15 was evaluated in FIG 25 was devised. In composition No. 23 the through th dynamometer test, an average coefficient of 25 cellulose fiber was increased to a maximum of 25 per fncnon of 0 33 at 450' F was obtained and a wear rate cent of the total volumetnc percentage of the composi illustrated by line 50 in FIG 15 was produced. tion while at the same time the cashew nut powder was Composition No 14 was further expanded through reduced to 15% When a brake lining made from com the substitution of iron oxide for the cryolite to produce position No. 23 was evaluated through the dynamome composition No 16 shown in FIG. 25 When a brake 30 ter test, s coefficient of friction of 0.45 at 4W' F was lining made of composition No 16 was evaluated obtained and a wear rate as illustrated by line 66 m FIG through the dynamometer lest, a coefficient of friction 23 was produced. As seen, composition No 3 almost of 0 34 at 450' F was obtained and a wear rate as illus matches the wear rate for currently acceptable asbestos trated by line 52 in FIG 16 was produced lining and could be accepted by most vehicle manufac Composition No 14 was still further expanded 35 turers without extended qualification testing Thus, the through the substitution of copper powder for the cryo industry would be able to meet the Federal Clean .Air lite and glass fiber to produce composition No 17 and Health Standards of 1975 within the prescribed shown in FIG 25 A brake lining made from composi time set for compliance. tion No 17 when evaluated through the dynamometer To substantiate the results of composition No 23 test had a coefficient of fnction of 0.34 at 450" F and a 40 another composition No. 24 shown in FIG 25 was wear rate as illustrated by line 54 m FIG 17. prepared by reducing the percentage of cellulose fiber Composition No 14 was still further expanded while increasing the resin content and substituting car through the addition of fiber glass to the base material bon in powder form for a portion of the barytes There tc produce composition No 18 shown in FIG 25 A after, when a friction bring made from composition No brake lining made from composition No 18 when eval- 45 24 was evaluated through the dynamometer test, a coef uated through the dynamometer test had a coefficient of ficient of friction of 0.28 at 450' F was obtained and a fnction of C.37 ai 450' F and a wear rate as illustrated wear rate as illustrated by line 68 in FIG 24 was pro by line 56 in FIG 18 duced In order to establish relationship between steel fiber From the foregoing compositions it was determined and cellulose fiber in the non-asbestos fnction matenal, 50 that while steel and cellulose fiber produce an accept tnt cellulose fiber was eliminated from the basic compo able non-asbestos fnction material, when combined smon and composition No 16 shown in FIG 25 was together with inorganic modifiers, which can include produced In an attempt to provide composition No. 19 glass, mineral and carbon fibers produce a friction mate with an adequate coefficient of friction, at least 5% by rial with a substantially uniform wear rate throughout volume of Wallastonite was added to the composition 55 the operating range of most brake linings A brake lining made from composition No 19 when I claim. evaluated through the dynamometer test, had a coeffici 1. An organic friction material for use as a fnction ent of fnction of 0 32 at 450' F. and a wear rate illus lining consisting of a mixture o f trated by line 55 in FIG. 19. 8-50% by volume of a combination of non-asbeatos As seen in FIG. 19, the wear rate for composition No. 60 fibers selected from a group conmsting of fiber glass, 19 was not as good as asbestos Formula B Thus, the mineral fiber, at least 3% by volume of steel fit rs, steel fiber in composition No. 19 was reduced and car and at least 5% by volume of cellulose fibers, bon particles were added to produce composition No. 12-35% by volume of thermoaetting phenolic resin, 20 as shown in FIG. 25. When a brake lining made of 5-35% by volume of cashew nut particles: composition No. 20 was evaluated through the dyna- 65 3-20% by volume of elastomeric modifiers; and mometer test, a coefficient of fnction of 0.37 at 450' F 10-55% oy volume of inorganic modifiers, said thermo was obtained and a wear rate illustrated by line 60 was setting phenolic resin being responsive to heat to produced. In some applications in order to achieve form a matrix for holding said non-asbestos fibers. 4,119,591 7 cashew nut particles, elastomeric modifiers and inor S. 8 The organic base friction material, a* recited in ganic modifiers in a fixed relationship, said non-asbe claim 4, wherein said inorganic modifiers are selected stos fibers and phenolic resin matrix providing struc from a group consisting o f barytes, whiting, talc, rotten- tural strength for allowing the friction lining to with S stone, wollastonite. pumice, iron oxide powder, copper oxide powder, carbon and silanized mineral particles. stand dynamic repeated engagements with a rotating 4. The organic base friction material as recited in member and providing a substantially uniform wear claim 1 wherein said non-asbestos fibers include up to rate up to 600* F. during a dynamic engagement. 10% fiber glass fibers. 2. The organic base friction material, as recited in 7. The organic base friction material, as recited in claim 1, wherein said phenolic resin includes at least 10 claim 1, wherein said non-asbestos fibers include up to 12% dry phenolic resin powder. 10% wood flour fibers. 3. The organic base friction material, as recited in claim 2, wherein said phenolic resin includes up to 18% liquid phenolic resin to attenuate segregation of said elastomeric and inorganic modifiers prior to the appli cation of heat to the mixture 4. The organic base friction material as recited in claim 3, wherein said elastomeric modifiers is selected t. The organic base friction material, as recited in claim 1 wherein said non-asbestos fibers include up to 10% silanized mineral fibers. 9 The organic base friction material, as recited in claim 1 wherein said non-asbestos fibers include up to 10% carbon fibers. 10. The organic base friction material as recited in claim 1 wherein said phenolic resin includes at least S% from a group consisting of natural and synthetic rubber 20 liquid resin scrap, natural latex, crude molasses, and asphalt 25 30 !< 40 4? M'. 60 65 TRANSACTIONS Rodger F. Ringham/President M. J. Kittler/Treasurer Joseph Gilbert/Secretary & General Manager P U B LISH E D BY: S O C IE T Y OF A U T O M O T IV E E N G IN E E R S , INC./400 Commonwealth Drive/Warrendale, Pa. 15096 750874 Friction Materials for Small Car Solid Rotor Applications John P. Kwolek Automotive Control Systems Group, Bendix Corp. WITH CONSUMER INTEREST in lower priced vehi cles and improved fuel economy on the increase, domestic vehicle manufacturers are giving more serious thought towards producing sub-compacts (vehicles having curb weights less than 3600 lbs.). Foreign vehicle manufacturers have pro duced vehicles equipped with solid rotor disc brakes in this weight category for over a de cade, but most American manufacturers have b e e r hesitant to use the solid rotor disc brake systems found on a majority of these lighter weight cars due to several factors. From the brake engineer's point of view, while solid rotors offer lower cost, the ven tilated rotor offers substantial improvement in brake cooling over solid rotors thereby lowering the brake lining temperatures encoun tered during usage. The front brake tempera ture profile for a durability test of a 1973 Domestic Disc-Drum Station Wagon is illustrated in Figure 1. This vehicle had standard venti lated rotors, which weigh 27 lbs. each; the brake test weight was 5860 lbs.; operating tem peratures generally ranged between 15 0 and 3U0F. The same durability test was also con ducted on a 1973 European made vehicle equipped with U-wheel disc brakes. Brake test weight of this vehicle was 2800 lbs., with the solid rotors weighing only 6 lbs. each. A comparison of the front brake temperature profile for this vehicle (see Figure 2) with that of the 5860 lbs. Station Wagon test indicates the average brake lining temperatures increased 75 F, with peak temperatures I 5O0 hotter than those experi enced on the heavier station wagon. Several differences can explain these re- Fig. 1-Average front brake tenperature pro file, 1973 station wagon 5860 lb G. V. W. , ventilated rotors, 11 cycles suits with the most influential factor being rotor weight and design. The purpose of dis cussing these temperature profiles is to empha size the fact that the lighter weight vehicles equipped with solid rotors require linings which can successfully operate at higher temperatures than those experienced on the heavier domestic vehicles presently produced with ventilated rotors. ABSTRACT Semi-metallic friction materials recent ly developed offer significant improvements in lining life, rptor compatability and noise over organic friction materials on small cars equipped with solid rotors. Improvements originally predicted from full brake inertia dynamometer tests have been verified on ve hicle durability and fleet tests. 2369 2370 J. P. KWOLEK CLASS A - CONVENTIONAL ORGANIC--CLASS B - HEAVY DUTY ORGANIC----- Fig. 3-Average wear versus temperature charac teristics, inertia dynamometer, 1740 lb wheel load, ventilated rotor Fig. 2-Average front brake temperature pro file, 1973 sedan 9 2800 lb G.V.W., solid rotors, 11 cycles TYPES OF FRICTION MATERIALS Friction materials are designed for speci fic applications, with the composition and method of manufacture determining the particu lar properties of any specific material. The primary function of the friction material is to produce a relatively high constant coeffi cient of friction under the conditions antici pated in use. The friction material must also exhibit excellent resistance to wear and opposing surface compatability under these same conditions. A previous classification of friction materials (1 )* gives some insight into the fundamental compositional differences and how these differences affect friction and wear in brake lining presently used by vehicle manufacturers. The organic friction materials presently used on domestic passenger cars equipped with ventilated rotors, which are referred to as Class A materials, are fundamentally organic in nature excluding their inorganic asbestos content. "As a class, these materials are reasonably quiet, give respectable durability and, under most conditions, perform their frictional purposes ..." namely, maintain ac ceptable friction and fade resistance. Class A type friction materials are not generally found on solid rotor applications because: ' 1. Lining wear rates increase exponential ly at the higher operating temperatures (Fig ure 3 ). Numbers in parentheses designate References at end of paper. 2. They exhibit more fade and over recovery when compared to Class B organics or semi-met- allics (Figure U ) . Organic friction materials designed for heavy duty (Class B) generally have higher in organic contents to improve their high tempera ture wear resistance and fade resistance. A b rasives are generally added to achieve higher friction. Historically, these types of mate rials have been used on solid rotor applica tions because they are more suited to higher operating temperatures than Class A type or ganics (Figure 3) and the fade performance (Figure 1+) demanded by this class of vehicles. FADE RECOVERY STOP NO. Fig. 4-Green fade and recovery, 1973 sedan 9 2600 lb G.V.W., 4 solid rotors, (fade 60 tnph, 15 fpsps, 35 second interval), (recov ery 30 mph, 10 fpsps, 1 mile interval) FRICTION MATERIALS But, as so commonly found in friction material development, improvements in one area usually results in losses in other areas. Class B materials generally exhibit higher low tempera ture wear rates, and frequently either groove, score or wear the mating rotor surfaces. They are also quite prone to generate objectional noise. The success of sintered metallic-ceramic friction materials for specialized applications such as Jet Aircraft Brakes, Heavy Duty Clutch Facings and Police and Racing Car Brakes sug gested metallic composites would some day find usage in Automotive Braking Markets if refine ment could be made. Semi-metallics, the third class of materials, rely heavily on iron, steel and graphite substitutions for the organic and asbestos materials usually found in the Class A materials. But, unlike the sintered metallics, semi-metallic3 can use organic components to add desirable properties. As in all friction materials, the use of abrasives must be mini mized in order to maintain acceptable mating surface compatability. HISTORY OF SEMI-METALLICS The semi-metallic formulations developed in the 6 0 's for heavy duty ventilated rotor applications were first released on foreign vehicles equipped with solid rotors. These vehicle manufacturers released semi-metall ic formulations for police cars and quickly ex panded their usage to taxi cabs ar.d a few vehicles sold to the general public. In 1970 domestic manufacturers released semi-metallic formulations for the front (ven tilated rotors) disc brakes of police cars based on the success of these materials in meeting Los Angeles Police Dept. Braking Stan dards. (2) By this time the advantages of semimetallics over conventional organics were clearly understood: 1. Improved friction stability. 2. Improved fade resistance. 3. Excellent high temperature wear resis tance. L. Minimal speed spread. 5. Excellent compatability with rotors. 6. High performance with minimal noise. Even these with advantages, widespread usage could not be anticipated on domestic ' vehicles sold to the general public because of the additional costs. Raw material mix cost represents the major factor in the pre mium prices of semi-metallics. These compounds generally weigh approximately twice as much as Class A organics and use materials which cost more per pound than those found in con ventional Class A organics. The smaller sized pads used in small ear solid rotor application drastically reduce the affects of raw material mix cost and semi-metallics can be competitive with many of the higher priced heavy duty 2371 (Class B) organics on small cars. With the advent of FMVSS 105-75 testing, it became apparent that, while semi-metallics showed excellent friction stability from 2nd through Lth effectiveness, the pre-bumished friction had to be improved. Still another area of concern was initial wear (referred to by some as low temperature wear). One particular type of dynamometer test procedure, a wear versus temperature schedule, indicated higher wear rates than those experi enced with conventional organics at low tem peratures. Subsequent dynamometer tests and microscopic examination of the materials proved this to be an initial wear problem and that conditioning of the lining at higher tem perature and by extended usage dramatically iii5>roves lining life at low temperatures (see Figure 5 ). The analysis of numerous vehicle tests conducted confirmed that the wear rate of semi-metallic formulations improves with usage (see Figure 6 ). PREVIOUSLY CONDITIONED TO 250*F PREVIOUSLY CONDITIONED TO 400*F - PREVIOUSLY CONDITIONED TO 550*F <.020 g . 0 1 0 1 . 0 0 0 TOTAL STOPS AFTER PRECONDITIONING Fig. 5-Effects of preconditioning semi-metal lic on subsequent low temperature incremental wear, inertia dynamometer, 1740 lb wheel load, ventilated rotor, all stops from 50 raph, 12 fpsps deceleration Fig. 6-Incremental mileage projections for Detroit Durability of Semi-Metallic, 1973 domestic sedan, 5560 lb G.V.W. Even with this knowledge, the development program for semi-metallics concentrated on im proving pre-burnished friction and initial wear characteristics. The program led to sig nificant improvements and resulted in the issuance of a patent (3) for this new type of material. Pre-bumished front torque was in creased 20% and initial low temperature wear rates were decreased to levels comparable to those obtained with conventional Class A or-