Document zzE4na4GRjnMv0O7V5YjmEbXB

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 ofthe 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 1983 and the Index for SAE Transactions from 1974 to 1981. 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 Patented Ma3r.,42354, ,1999689 1 2 smaller particle si/e- There is effectively no upper limit MODIFIED 3,434,998 ORGANIC BASE FRICTION M A T E R IA L on p a rti.le sire and the enure 25*3, of semi-metallic may be comprised of a s i n g l e la r g e p a n i c l e o r i n s c r i in th e 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 ferred particle si/e range is from plus 2o lo minus 4 Delaware N o Drawing. F ile d Sept- 13. IM S , See. N o. 417,852 ' mesh la i. C l. C 08c 5 I / 0K. C 89h 3 14. F I 4d 69-02 The preferred composition of the temi metailic fric I S . C l. 240--38 5 Claim s tion m odifying panicle is as follows Constituent V o l., percent Organic re-in b in d e r ------------------------ 20 and ove- ABSTRACT OF THE DISCLOSTRE Graphite ............................................... 15-25 An organic base friction material h iv in g dispersed therein chunks of a semi-metallic friction m odifying m a Ceram ic powder _________________________ 10-25 Metal or metal oxide p o w d e r......................... .. 30-50 a terial to serve as the friction controlling means. The 1-' The processing sequence is to manufacture aemi- senti-m clalli. muddier being essentially high concentra metullic frid io n m odifying particle by combining 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 powdered graphite in ar otgani. resin hinde; of the thermosetting phenolic resin type wht.h is then cured In order to obtain the ultimate in friction characteri-- " under heat and pressure to form a blended rigid mass tics particularly high friction level for an organic type of semi metallic material Th is material i' then broken brake inline or friction material, it is necessary in add into particle- of a si/e greater than 2u me h and added to f r i.'.c - modifiers The most common of these friciion a conventional organic brake lining mix. comprising pref modi.icrs arc the cured resinous particles such as that n. erably I 1.- to 2(1'! of the vo!,,n.-. of the ttnisheJ lining derived fr-im ...-hew nut 'hell liquid The use of such * material The organic lining m atc'.ai witn semi-metalue i ..-shew re-in parti.les results in increased friction.:' ef- parti.le added t- then proce-scJ c u rcj 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- Mock The ti.id...-h ,,t .imi'iem o ' relatively-low temperatures How- arp eu 'an .c ot ttie l.mng car. best be dcs.rmed .o monied cve' sa.h use hr.' the disadvantage of decreased lade compa'ed to cor.enti.in.d linings when t` e 'cm i-m etaliic tesotar.-c (>r decre.i-ej effe.tiverie's at elevated tempera- particle m/c wutai the rre lc re d 'i/c range of p ij- 2'i t re p -.i.rc v i-v e r v . ..nd also the disadvantage ot de m f-1:- 4 rr-e-h ceased eTc.'t v e rc " s*ser Ion: le m normal tob- s -.11 : r. . c i r r i . .on-tittienr- ar. m IIjr's;ir~it-c muhue csed .. in .'s . st ;r, ivq.iiied peJai p iC"'u :. ovu lire in 1.*:1. *. ix'.c a:.x` / i:. T l: :- 0 X1,1-. iu ! t *,U112 j : c i : . i.-c !. .in-.' , o'".. 1r v 55J ! . v 'l jn i , - o; . d 'u r.i i i ; j ; m'i . f rt i. At alt.-rr ,.t. trie Use of su.h cu r.d resmou par n. ; .if. -1 n 'llllh f . nlinn..'1' ' *'e: ' i. s ' . xj ' le - ti.I . i- in, ii- c e-: n-'H-.inn materials of abrasive d ta ' - Vu- !e- ted n et.-I' an J me, Mile*' . . t ...r.'x f ?on anJ n .ic -s i..- N I nalert..!- for example alumina will n i 1r1H' \*\r!f M .* filie r !: - r v.. f 11*. deper. J .:.2 ter n ic e sec cfTecI-.mess and will also offer iirrp'oveJ II * .1 vi.pi'iv in . evieni on . y - n if i.n ox. de. f t - O . tadt- re s.'la n e tmpro-ved recovery properties, and ess ^ a vuf' sii. .u K r mci .W rj ' 'H*' l.MTi V CJim . - It wn ' be li.-.-d-.i t ipe.tai prc'si.tc increase) with extended use noli si Ih. xi: e. ni. I ; T 1- thi r : 1n binder ar.xl Su. f: luo-g.u.i, niaicrials. how e.cr. also have si-. fimtc the m. .! i- no' u x,i \u J 1.5 l 1 -. t P. I":' d ' * di-advan:, c.-s in in.reused noise characteristic- and ex- speaking, the line ot Oistii.d.ion netw eeri . : a'.llcS UTrU .e s iif w ej-ing. grooving or general dcstru.lion of the metal oxide- w hi.n car. be s.i'-'ti: ..ted Ix f i . metal con- r n . ' . . r t a . e t make dtum or d isc). ; . lent depend- <<n the abt.i.i V r-r ha rJ '1C". . r.a; actcris'te I' i- an obje.r of the prescnl invention to p rovjje a H.ake lining, m .ii.ir.icr..-.d ii a .c o td .ir.. witf. !' ; sen . n,-.: -Hi. in.-tior modifier for organic base lining to above leaching.. repre e' - a stgr.ili.ur: adv..nce o.er pin. ids in.reused (ri.tion effectiveness at both low and .or.veniioral otgani. Iir.ing- known m I'n pri, r .,'1 i.c .n e .' t. mp.-t attires without displaying poor fade re- (icnetallv spe .king the J . a r . e is it- tern's o' increased -is-..-,.e re.overv. lor e term hutdemng. excessive wear. ,,, lii.-m- III.lio n e llc .in c u r- nr ,!c v.u io .i - .o n.li:;o r.. of or -curing operation ( om paii-on tc-'s lo -.-jl that ir,.rca-eJ etl.c- It i- another c'mect of the present invention to provide tiven.s. i. most pronour.ed under -e-erc conditions of an improved fri.tinn modifier lor organic base lining opcrjtioi. wfieie .invention,.! organ,c linm p. are the comprised of a sen t metallic particle ot chunk consisting weakest lo r example, rt.ikc fade m.f...ed " . fiiet ter o' a in--'jI powder or metallic. o x iJc powder matrix, a p c ijlu tc . c.,,.-ed f-. ireqaenr rr.->c appli..:ti >n m -ii,-t , c . u, .ornliruent and powdered graphite all bound time inter.a'- i ie-sened itom |o .- "o ', k o . o . c . ot t...e ..v r unJcr heal and pressure by a thermosetting effectiveness a ',e: tade is m .ria-e d tr ex.e-s o! 2* pnenoli. re-ir. binder. High -peed and burnish iw i-.j in i etfediver.e-- is im The tri.iio n modifier of the present invention is for proved by a sim ilar degree While to some extent ibe-e use with an organic base lining of the conventional type are ru d i.ta b le results of high friction characterist.es of consisting of a resin base with additive organic friction mel.il and ceramic particles resistant lo deterioration at modifiers aspestos and the like. high temperature, the main significance of the present in The sc.mi-nie'.alli. friction modifier or friction con- vention reside' in the fa.t that lb's improvement i- tiolhng m ejns added to the basie organic lining pref achieved without sacrificing lining wear or x o rin g the er j "'ly comprise-. I 1.- to 20f< by volume of the total lin- n;, mating brake Mir/.i.e such a- encountered witf metal tng m aietial. lfelow 11.- '"< . effectiveness is not obtained, base or m o'g -m. linings. In la d . test result- :,:-.ve Je ubo.e 20' - . ptoecssing limitations cause the addilion to monstr.ited .m inetea-e in lining life ot gi.utcr then he.ome uneconomical A functional upper lim it is 25C< 20'- computing an organic wnh I <*'< sem i-m daliic p.o- wherein tnc abrasive content c.m be expected to have tides wiih a lu ll orgum. of ttie same type deleterious effects with respect to drum or di-c wear We ilairn I lie senu-metalli. is lo he added as a particle ot thunk I A middled n.cuiii. t ... in .lio n m i.o I .onci-t M/t ere.iter ih .ir 2() mesh since the fife d tv m .i'ke.l al ing of an oi earn, I'.is, !i i : m Iin me tin ten ii .. r 1 ut'g 3 4 3,434,91/6 sfrizoemgr1eatetrot2h5a%n 2b0ymvoesluhm: seaoidf asesmcmi-mimectatalllilcicppaarrtitciclelehoafv from w ithin Vthi e lo 2 size <>*; by range o volum f plu` e ut a se 20 minus m 4 jm elallu p mesh, said ariLasenn 2in5g%a,scceoranmstiictuepnotws dbeyr vfroolmum1e0p-2e5rc*en,tagnrdapmheittealfroormme1t5al gmreatpahlliitce particle having from l < - 2 ' ' ; , as constituents bv cerjimc powder volume percent from 10- 2 * '. orexsiidne bfirnodmer5f0r-o5m0*g7rebaeteinrgthbaonunadbotuotge2t0h%er. by an organic ', agnetdhemr etbayl or metal oxide fri an organic resin .r. to o h in Jc r : being K um d to from greater than in 2c.laAimmIodwifhieerdeionrgsaanidicobrgasaenifcricretisoinn bminadteerriailsaas tchlaeirmmeod about 20% set3ti.ngApmheondoifliicedreosrignanic base friction material as claimed |,, References Cited UNIfl l> S I M Lb r.ULNlS `ineleccltaeidmfr1omwhtheereginrouspaidcocnesrisatminigc opfoswildlaemr ainsitea. cmeuralmlitirc. .VOO-'.s j^ 3.210.MH II I9M III. iv n * Klein B ig g ' ma4gneAsiummodiofxieidde,orzgiarncoicniubmaseofxriidcetioonr lminiixngturmesattehreiarleoafs. M O RRIS I If BM AN Vlf/fiJM scelaleim.tleedd ifnrocmlaimtheIgwrohuepreicnonssaiisdtinmgetoafl iorronmceotaplpoerx,idieroins I' K f L \titUIf.i I B A R O S . etunli/ir/ f i W l l l l . i r oxi5d.eAormmodixiftiuerdesotrhge.mreio,f base friction material comisting UK>--M> 0 S Cl X K of an organic base friction lining material containing 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 requirements for frictional elements used in the braking systems of m otor vehicles. Essentially, this shift in require ments has been in the direction of 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 unfortunate that the prime shortcoming of organic type materials, namely their inherent nature to change both their form and properties with tempera ture, is at complete odds with the requirement of 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 of 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 extreme 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 became obvious that if the technological advantages of 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 of friction material for these two types is ordinarily only a matter of 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 mseamteimriaeltsa.llCicl.ass A, Class B, and Class C, with the latter being As a general category. Class A friction materials would be represented by production materials on American made 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 omrgoanntioc mleosisnt ohfintdheerms,. oTrghaenyicarreepsirnobfraibc'tyiohnigmhloydliofiaedres,dawndith ABSTRACT-----------------------------------------------------------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 natural or synthetic rubbers or elastomers. They frequently also contain small amounts of graphite or other carbon type materials, and possibly small amounts of inorganic wear fillers slouwchinasingororguanndiclimcoenstteonnte,. pAarstiacucllaarslsy, tahneyythwinogulodfbaesguebnerally 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 temperature 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 decomposition above 600-650 F. Once having been in this "affective" temperature range, they are seldom like they were beCfolarses. B materials represent a first step major compromise 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 better fade resistance, better recovery, and overall improved frictional and thermal stability. They may give good lining life at higher temperatures (+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. attTehmepmtsotroe erexctreancttCtlhaessdCesoirrabselempimroeptealrltiicesfrfircotimoneamchateorfiatlhe 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 overdo these since it does no! want the potential hazards they offer. WEAR AND FADE RESISTANCE It has previously been noted that one of the shortcomings of organic type materials is their tendency to change form and properties at elevated temperatures. It is this characteristic which contributes substantially to highly accelerated wear as the tem perature goes up. The property of 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 comes first is problem atical, but 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. F. W IL L IA M A L D R IC H 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 temperature 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 tem perature wear capability of the Class B types, the organic materials present still cause eventual wear resis tance breakdown, even though it may 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 of substantial loss of water of 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 tem perature curves of Class A, Class B, and Class C materials, as taken from actual constant torque sample dynam om eter tests, are shown in Fig. 1. It will be noticed that the Class C semimetallic is essentially insensi tive to temperature 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. they also have minim al fade. Based on the previous fade = self-pr detrim o e tec nt. t ion In d re isc ali us ty sion the , s one emi wo met uld alli c a ht afsirast consid type o f er se t l his f-p r a o tection which 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 ore than one fade, such as SAE J843b. 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 S E M I-M E T A L L IC S 2041 Fig 2 - Vehicle fade test characteristics (5700 lb GVW) CLASSA O RG ANIC CLASSC SEM I-M ET 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 of semimetallics there is reason to believe that, in addition to the binding action o f the resin system there 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 mechanical bonding is in creased with use or duty. Early semi metallic linings showed low temperature 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 1lg 4 - Dim. 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 development, shows still further gains over the Cl type. At the other end of the duty scale. Fig. 4 illustrates 100 mph wear rate results on a full brake inertia type dynamometer 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 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 tneemssp, earsatthueres,pteheed oirngcarneiacssedh,avfreequusueanltllyy srheoqwuniripnogosroemr eefefexctteinve 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 improved. It is acknowl edged that there is still some room for additional improve 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 wiSnttaebr.ility of friction throughout the life of 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 addition, their characteristic of friction " peaking" vsith severe use. particularly in the case of Class B materials, has led to vehicle braking stability and controllability problems. By virtue of their minimum organic content, semimetallic materi als are much more frrctionally stable over a wider range of 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 attachment 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 supplement this with additional noise when warm or hot. The effect of this characteristic is that the driver of 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 350 F). On this basis then, the driver is most apt to hear noise not under normal driving conditions, but rather during the less frequent or abnormal conditions. COMPRESSIBILITY In the disc brake, the compressibility of the lining material is a significant contributor to excessive fluid displacement. F. W IL L IA M A L D R IC H Fig 5 - Disc pad swell and crush comparison (at 5000 psi constant stress) The actual compression of the pad material is a function of both the inherent compressiblity of the pad and line pressure required, which is a function of 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 maximum in fluid displace ment. 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 of the preload. It will be noted that the Class A organic with 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. OTHER CHARACTERISTICS In the early stages of development, the increased heat conductivity of a metallic type friction material, particularly SEM I-M ETALLI 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 itnesdtiscawteitdh.ouHtoswuecvheirn, smulaantyionacftauialledvethoicplreoadnudcedyflnuaidmboomile.ter Controlled tests did indicate fluid temperatures 60-80 deg higher with semimetallics than with organic. A practical consideration, however, is that under extreme tem perature conditions or use, the wear of organic materials can be so great as to bring the actual shoe in contact with the rotor, a most critical set of 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 sthaetiisrfapcetrofroyr.maCnocme paanrdedwteoaroltehveerl,mthaeteyriaarles eevxetrnemapeplryokacinhdintgo mroatotirngmseutarfllaucregsyanodr fgineinsehr.allIyn rtehqeuciraesenoofshpeeacviayl ddurutymdorur m brakes for large trucks, they virtually eliminate drum spotting and heat checking typical of 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. Improved wear resistance, particularly at high tem pera 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 [54] SFTREICETLIOANNDMCAETLELRUIALLOSREEIFNIBFEORRSCED WITH [75] Inventor. Francis William Aldrich, Troy, N Y. [73] Assignee TMhiechB. eadix Corporation, Southfield, [21] Appl. No. 112,541 [22] Filed Jal. 5, 1977 [[5512]] IUa.tS..CCLl-............................................................................2..6..0../..1.7O.2W; L741/1/0920; 188/218BBR;; 216808//127514RC;L1;8286/205/318;A2;6206/402/1.177.4; [58] Field of Search ................................ 2602/6107/.422, 3188 [56] Reference* Cited U S PATENT DOCUMENTS .V684.0e2 8/1972 Johnson ... 188/251 R ni] 4,119,591 [45] Oct. 10, 1978 333,,.19302542.,,172014181 1941//11/1999777445 RBBhoaegrenkae.rr..e....t.....a.....l............................................................................. M226O600//1/13771.22 3,939,194 5/1976 Adelmann ................... 188/231 A APtrtiomrnaeryy,EAxgaemnti,noerr--FiErmdw--aLrdeoMH. WMocoCdobremrriyck, Jr.; Ken C. Decker [57] ABSTRACT A nfraicstbieosntoslinfrienegoorgfaanibcrbakasee. fArictcioomn bminataetrioianl foofr ufisbeearss tmeliencetreadl farnodm aragyroonupficboenrssisatinndg oaf sttheeerlm, coesleluttlionsge, grelasisns bminerdiecrmaroedicfoiemrsbainnedd iwnoirthgacnaischmewodnifuiterpsatroticplreos,duelcaestaon ocorgeaffniicciebnatseoffrfircitcitoionnmoavteerriatlhehanvoinrmg aslsoupbestraantitniagl srtaanbglee 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 IG . 15 F IG .17 FIG. 18 U . S . Patent oct. 10,1978 Sheet 4 of 5 4 , 119,591 FIG. 19 FIG .21 FIG. 2 2 FIG. 2 3 FIG. 2 4 4,119,591 FRICTION MATERIAL REINFORCED WITH dstiraepnugrsthedtotharlolouwghaoufrticatfiorinctliionninbgumnagdperoovf itdhee scuofmficpioesnit STEEL AND CELLULOSE FIBERS tiinognutnodweritnhostramnadl doypnearmatiicnglocaodnindgitsiownsi.thout deteriorat BACKGROUND OF THE INVENTION Organic friction material compositions currently used anItmishrtihteorsefforeree tohregaonbijcecftriocftitohnishinnivnegntwiointhtosupfrfoicviiednet ionf cwluitthcshtaannddinbgraskeevelrineinogpseroaftivneghitcelme*pemraintutreb*e acnapdadbyle slotraudcstuwriatlhosutrtednegttehriotoratrinepgewatheednlynewedithinstaanbdrakdeylnianminigc ntiaomnsi.c Tporespsruerveesnetxapedreietenrcieodradtiuorninign rpeeprefaotremdanacpepliacnad 10 orgItaniticanfroitchtieornobmjeactetrioafl thwiisthinvaenfotiuonndatotiopnromviadteerisanl parheysriceainlfdoecgedradbaytioansbdeustroinsgfiabnera*ppralincdaotimonly, thdeapliunninepd and 5uppeorcfeanctomceblliunlaotsioenfiobfeart lTeahset 3stpeeerlceanndt scteeelllufliobseer ethvrioduengcheouintdaicarteessinthmatataraixb.esHtooswliebveersr,carnecceanutsemheedaicltahl ftoibeurnsifboerimnglyddipsturribseudtetfhorrocuegsheoxuetrttehdeofnricatibornakmealtienriinagl hfiabzearrsdosf othfetthyepeluunsgesd iinn thpeermsoannsufeaxcptuosreedoftocluatacbhesatnods IS apnedatetdhedryenbaympicrebvreankte deneggaragdeamtieonnts.thereof during re btiroankeoflinthineg.suTrrhoeunhedainltgh ehnavziarrodnmisecnatuwseidthbsymtahlel ppaortri orgItanisicanforitchteiornobmjeactteroiaflthwisitihnvaenbtaiosen mfoartperrioavlidoifnsgteaenl csilteisonofinasabemstaonsudfuarcitnugritnhgefmacixiliintyg.of the friction compo 20 ffiobremr awndeacrecllhualorascetefirbisetrictooevsetarbtlhiseh ospseurbatsitnagntiraalnlygeunoif byInthaenaesfbfeosrttotsofirbeedruacnedthteheernevbiyrocnomnetinntuceomntaanmuifnaacttiuorn friTcthioenselinainndg.other objects should be apparent from isnlugrraysbpersotocesssbaisseddisocrlogsaendicinfriUc.tSio.npalitneinntgsa,ppalicwataitoenr reading this specification and viewing the drawing. Scaenr. bNeot.ra7n5s4m,4i7tt7edhatshrboeuegnheovuatluaamteadn. uTfhacetuwriantgerfascluilrirtyy 25 BRIEF DESCRIPTION OF THE DRAWING FIGS 1-24 of the drawing are graphs comparing the wwiitthhoaustbecsotonstafmibienrsa.tiHngowtheveers,ubrreofuonreditnhge ferincvtiioronnmmaetnet wmeaaterrciahlacraocmtepreisttiitciosnofmthadeenoacnc-aosrbdeisntgostoortghaisniicnvfreincttiioonn rmiaolvceadninbeorcduerredt,o tbhee awssautreerdinthtahteanslyurrreysumltuinsgt blienirneg has essentially the same operating characteristics as a 30 wiFthIGa ty2p5iciasl aastbaebslteosilolurgstarnaitcinfgricntoionn-aslibneisntgo,safnrdiction material composition made according to this invention linIinnganmoatdheerfraottmemapdtrtyo mreidx.uce the occupational health DETAILED DESCRIPTION OF THE hgaezttaerddsthinatthtehemaasnbuefsatcotsurfeibeorf lbieninrgepslaucehdaswbietehn gsluags-s fibers. lu v c x m n v : In order to evaluate the non-asbestos friction material poUsi.tSio.nPsaut.tiNlizoi.ng3,9f6ib7e,0r3g7ladsissclForsoems seevxeprearlimHennintagticoonmit ctoosmbpaosseitiforincstiodniscmloasteedriablyctohmispionsvietinotniosnw, teyrpeicuasledasbasess standard to determine the wear rate and coefficient of hacacsebpeteanbled,etheormwienveedr,thinat asdumchixilningintghecoimngproesdiiteionntss athree fiber glass tends to ball and thereby reduce the continu 40 fmriactteiroinalcwhahreanctuesriesdticins tofbtrhaeken.on-asbestos base friction ibtayseoffrtihcetiofrnicmtioantermiaaltsearirael.mIanteadddwitiitohna, swteheelnbfriabkeer rgolatossr coFmIbGinat2i5onislluosftrtahtees ftihbeersresluabtisotnitsuhtiepds fooft tahsebevsatorisouass or Ud.rSu.mP, aatn. uNnoa.cc3e,p8t9a6b,l0e75wedairsccloonsedsitiaonnoothcecrur*fr.iction composition wherein the asbestos in an organic lining is 4j diaTchloeaeindgbreydtiheinstsininvetnhteioans.bestos and non-asbestos fric tion material formulations were processed into brake qreupirlaecdetdo wreidthucbeatshaeltmfiibneerr*alBbaescaalutsientoofathfiebeprrostcaetses, trhee fdreictatiiol nforlinthinegbainsethlienefoalslboewstionsgmmaatenrniearl caosmdpesocsriitbioend Ain. uospeenofascuccehpftarincctieonascoamspuobssittiitountetofodrataesbheasstonsotbraesceedivoerd jo casThheewasnbuetstopsowfibdeerr, darnyd pshyenntohleitcicresruinb,beeqruaslcrpaapnsanodf ganLiactefrriacstiodniscmloasteedriainls.U.S. Pat. No. 4,019,912 the rein btuarreytwesaswaecrheiemviexde.dTtohgeerethaeftreru,nttihlexmhioxmtuorgeewneaosupslamciexd faocrhciienvgedoftthhreoustgrhuctthuereuosfeaorfescualrtbinognfrfiicbteirosn. lHinoinwgevwears, iwnaasmthoeldn atnradncsofemrrpeadctteod aintporeassbraiqnudetctoe.mTphreesbseridqubeyttea tlhoseepfyibroelrytsoi*a*ctaerpbroenqufiibreerdwtoourelddudceesttrhoeyrtahyeoenlaosrtocmelelru* 55 tfeomrcpeeoraftuabreouotf 5th,0e0b0ripqouuenttdeswpaesr rsaqiuseadretoinacbhouwth2i5le0*thFe. atinodni.norganic filler* found in organic friction composi tfelomwpetrhartouureg.hoTuhteth2e50m*iFxt.ucreauasneds tehsetabplhisehnoalimc amtraixinfotor SUMMARY OF THE INVENTION <0 hborilqdainegttethweasotthheernitnrganresdfeierrnetsd itno aa cfiaxreidngpoovsietinonh.avTihneg sitiIohnacvoendseisvteinlogpoefdaannaosrbgeasotoics ffrreicetifoonunmdaatteiorinalmcaotmerpiaol, aThteembprieqruateuttree wofasabthoeunt 5g0r0o*unFd. ttoo fausrptheecrifiscetsitzheecmorirne. omragtarnixicofanadthienromrgoasneitctinfgricretisoinn. mTboediafisebresstroestafirneeedfoinuna spplaocneddinogn atodysnabmraokme epteard.anTdhfirsombratbkee tepsatd pwerafaortmheedn dfiabteironanmda5tepriearlciennctlucdeellsualossaemfiibneirmaunmd oofth3eprefricbeenrst ssutecehl 63 tAhehreadonanit awvaesnegsteabcloisehffeidcitehnatt othfefrcioctmiopnosoiftio0n36Foartm45u0la* alosscearfbiboenr,s mwinheernalraannddofmibleyr golraisesn.taTtheed satenedl aunndifocremllluy F and a wear rate as illustrated by base line 20 shown in FIGS 1-9. 20 and 21 4,119,591 In order to establish t bro3ader base for evaluating the In an attempt to smooth o4ut the wear rate ofcomposi nasobne-satsobsesftroicstifornictmioantermiaalteirdieanl ticfoiemdpaossiFtioornms,uala sBecownads t3i%onbNyov.o5luams eilolufsctraartbeodnbwyalsinaedd3e0dintoFcIoGmp5o,saitifoilnlerNoof ctoosminpoFuonrdmedu.laInAFisorrmepullaaceBdtbhye aladrdgietioanmaolucnatshoefwasfbnecs- 5 s5ittioonprNodou. c6e wcoams pmoasditeioinntNooa. 6briankTeafbrliecti1onThlienicnogmapnod atiobnrapkoewldinerinagn.dTahfeillaevreorfaggreapchoietfefipcaierntitcloesf tforipctrioodnucoef cwoheeffniceievnatluoaftefdricintiotnheofdy0n.2a8maotm4e5t0e*r Ftestw, aasnoabvtearinagede mFoormmeutlear BtesatbarsakuesepdadtomeavdaelufarotemF, oursminuglathAe swamase fdoyunnad apnrodduacwede.ar rate illustrated by line 32 in FIG 6 was tFoIGbeS.0.1305-1a9ndanthde2w2-e2a4r rate is illustrated by line 21 in 10 ganInicafiflulertrhmeroadtitfeiemrsp,tatocobmropaodseintiotnheNboaae7fsosrsthhoewinnoirn maUteproianlsinititbiaelcaemvealuevatidioenntothf atthethenorenm-aosbveasltoosf afsrbicetsitoons FmIuGm. o2f5,3%wsbsypvroodluumceedofIrnotctoenmsptoosniteiownasNaod.d7eda tmo itnhie cfrroummbthlye mstiaxlteuredulerfitngthethreemabirniiqnugetitnegrefodrimenitnsginsatadgrey. bbraaskice sltieneilnganodf cceolmluploosseitifoibnerNcoo.m7pwossistiotne.steWdhoenn tthhee Trehseinreafsorae,liiqtuwidastoneacllestshaerynoton-aadsdbepstaons ocfomthpeopshiteionnoliicn 15 d0.y3n2amato4m50e*terFanwdasanobavtaeirnaegde acnodefaficwieenatr orfatfericatsioinlluosf odlredderastoa pprroedfourcmeeadcbonmqpuoesttieti.on capable of being han traItnedorbdyerlitnoe i3m4pirnovFeigt.he7wweaasrarcahteieovfetdhe non-asbestos shoTwhen ninonF-aIGsb.es2t5oswfhriecrteiionn amciotmenbsi)nactoimonpoosfitsitoenelNfiober1 20 fmriocdtiiofinerm, aantedricaolmwphoistiintigonwNaso.se8leshctoewdnasinthFeIGino2r5gawnaics afinbder cweallsulfoosremuTliabteerdwinertehessuabmsteitumteadnneforrasthFeoramsbuelastoAs pbrraokdeucleindingWmheandethferodmyncaommopmoseitteiornteNstowa8s. arunnavfoerratghee atensdtsfowremreedpienrtfooramberda,kecolimnipnogsitWiohnenNtohe1dhyandamanomaveteerr- 25 caonedffaiciwenetarofraftreicitlilounstroafte0d.30byatli4n5e0*36FinwFaIsGob8tunweads ailgluesctroaetfefdicbieyntlinoef f2r2icitnioFnIG0 141aAt 4s5c0a`nFbeansedena,wtheearwreaater proInduacneadttempt to improve the coefficient of fnction of ara. twe haipcphroisacchuersretnhtaltyoafctcheepatsebdesbtyosthmeatveerhiaiclloefiFnodrumsturyla cliotemwpoassitiaodndeNdoth8etrheetofntcotipornodpruocdeuccoinmgpmosaitteiorinalNkroyo9- cepInabolerdfeorr tuoseesitnabalinshona-agsbroeustposoffriinctoirognanmicatefirlilaelr,staaclc- 3C stihoonwNnoi.n9FwIGas 2e5valWuahteend tihnethberadkyenlaimninogmeotfercotmespt,osain wanads csoubmsptiotusitteidonfoNr othe2 wshhoitwinng inofFcIoGmp2o5sitwioans Nesotah1 aovbetariangeed caonedffaicwieenatr oraflefniclltuiostnraotefd0b3y7liante 43580*in FFIGw.a9s hfrsohmedcoTmhpeodsyitnioanmNomoet2eirntdeisctafteodr tthheanbraankeavleinraingge mcoaedfe- 35 waCsopmropdousciteiodn No 10 shown in FIG 25 includes the iflilcuiesntrtatoefdfrbiyctilionne o2f40in30FIaGt 4520c'oFuldanbde eaxwpeecatiedraftreomas soafmtheetyaspbeesintogsrefdnicetniotsn ams aFtoerrimalulTaoBeswtaitbhlisthheberxocaedpbtiaosne thiBs eccoamuspeosoiftitohne availability of barytes and its low cost, ffonrcttihoen forifcttihoennmona-taesnbaelsatonsdmimatpernoavleththeecceolleuflfoicsieenfitboerf aopseednes of compositions including bary tes were de\el- 41 cwoams proespiltaiocnedNwoit1h0gwlaasssevfiableurateWdhbeynthtehedybnraakmeomlineitnegr latAeds sWhohwenn itnheFIbGrak2e5.lcinoimngpomsiatidoen fNroom3cwomaspofosritmioun twesats, oanbtaavineerdagaencdoeaffwiceieanrtraotfefnilclutisotnratoefd0b3y5 tlitne45400` Fin eNnot o3fwfraicstieovnaloufa0te.3d1bayt 4th5e0'dyFnawmasomobettaeirnetedstaandcoaewfficcair FthIaGt w1h0ilweagslaascshifeibveerduFhreonmadthdiesdtelsot intowna-assdbeeisetroms ifnnecd ratEeviellnusttrhaotuedghbythleinew2e6arinraFtIeGof3cwomaspporsoitdiouncedNo 45 3 toifonfnmctaiotenn,ahl ocwomevpeors,ittihoensw, deaoresraintecriesaaslesothienccoreeafsfiecdient citouwladsbfeeletxtpheacttethdetocobeeffbiceiletenrt tohfanfritchtaiotnofcoFuolrdmbuelaimA. waTshdeerveaefltoepre,dcowmitphoswitoioond fNloour 1a1ddshedowinn pilnacFeIGof th25e oprrofvibeedr mthartoeurigahl tThheroadudgihtioenxpoefnmeiethnetartiaondifitfewreanstdfeitlleerr 50 oglfacsosmfibpeorsiotifocnomNpoos1i1tiownasNeov.a1lu0aWtedhethnrtohuegbhrathkee dliynninag mthiannedcethllautlogsleassfibfiebre.rThhaesraefhoirgeh,erglcaosesfffiicbieerntwoafsfrsiucbtisotni ombotamineetedr atensdt,aawcoeaerffricaiteenatsoifllfunsctrtaiotend0b3y7liante45402*inFFwIGas. tsuhtoewdnfionr FtIhGe c2e5llwulaosseprofidbuecreda.ndWhcoenmtphoesibtiroankeNlioning4 c11elluualossperotydpuecefdibeFrsrowmhtehnisctoemstbiitnwedaswdietthersmteienledfibthearst oetfecromtespto, ssiticoonefNfioc.ie4nwt aosftefrsitcetdiotnhr0o.u3g5hatthe45d0y`naFmowmas 55 pternoadlucceodmpaomsiotiroensathtiasnfacwtohreyn naonsi-nagsbleesftiobserfnmctaitoennaml ais pr 4 owdaus c eadchainevdead.wUeanr forarlteu nilaltuesltyr,at ewd i tbhy tlhiinse a2m8 oinunFtI G o f useTdh.ereafter, an attempt was made to establish the golfaassrofitboerr oinr cdorummpobsriatikoen cNouo.ld4bseurefxapceecpteodlish or wear 60 owphteimnuumsedliamsitthseffoorunsdteaetli,oncemllautleorsiea,l .aonrda noothne-arsbfeibsteorss anTdhceerlelufloorsee, ftihbeeraamddoeudnttoofprgoldasusceficrboemrpwosaistiornedNuoce. d5 fFnIcGtion25mwataesriaplr.o'dTuhcues,d coImn pcoosmitipoonsitNioon. 1N2osho1w2.nthine bshyocwonmipnoFsiItGio.n2N5 oW. 5hewnatsheevraelsuualttiendgibnrtahkeedliynninagmmomadee- 65 fviobleurmeWohfencetlhluelobsreakfeibelrinwinags mdoadueblefrothmat coofmtphoesisttieoenl aterwteesatr, arcaoteeffiilcliuesntrtaotefd0.3b2yatl4in5e0*3F0. winas FobIGtaine5d wanads cNooeff1ic2iewnatsoefvaflnucattieodn tohfro0u.3g5h atthe45d0y*naFm. owmaseteorbttaeisnt,eda 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 structural strength in the6friction lining, the carbon slopsoengfiybearnsdhtohuelrdefboerer,edituwceads. determined that the cellu paIrnticalefsucrtahnerbeatrteepmlapctetdo wesittahbcliasrhboanbafisbeerfso.r the inor waTshreerdeuacfteedr,totheprcoedlluucleosceofmibpeorsoitfiocnomNpoo.si1t3iosnhoNwon 1in2 3 gthaeniscteferlicfitbioenr wmaosdiinficerresa,sethdeanvdolaummeintriimcupmervceonlutamgeetnocf FwIaGs ev25a.luAatebdrakinetlhienidnygnmamadoemferotemr tceosmt, phoasditaionnavNeor.ag1e3 pdeurcceenctoamgepoosfitiboanryNteos. w21assehsotwabnlisihnedFIaGt 1225%. Wtohepnros casoeiflfliucsiternatteodf bfnyctliinoen 4o6f 0in.32FIaGt 45103'.FT.hainsdcaomwpeoasritriaotne batreadkethlirnoinugghmathdee fdroymnamcoommpeotseirtiotne"stNoa. c2o1ewffaicsieenvtalouf wcoaesffnicoitenstpoonfgfyn,cthioown ewvaesr,reitdushceodu.ld be noted that the 10 filrliucstitoranteodf 0b.y32linate46520i'nFFiwg.as21obwtaaisnepdroadnudcead.wear rate tioTnh, ecrreyfoolritee, winaosraddedretdo tionctrheeasceotmhepocsoietifofniciNenot. o1f3farnicd voTluhmereeaafntder,sitlhaneizsetedelmfiinbeerralwfaisbemr awinatsaiandeddeadt t8o%prboy cboramkpeolsiintiinogn mNaod.e14frsohmowcnominpoFsIiGtio. n25Nwoa. s1p4rwodausceevda.luA- 13 dliuncinegcmomadpeosfirtioomn Ncoom. p2o2sisthioonwnNoin 2F2IGw.a2s5p. rAodburcaekde, actoeedffitchieronut gohf frthicetiodnynoafm0.o3m7 eatte4r50te'stF.haandd aanwaevaerrraagtee eanntd owfhfernicetivoanluoatfe0d.2in8 tahte4d5y0n"amF.o,manetdertewsteaarcoraetfeficais illuSsitnrcaetetdhebywelianrer4a5teiannFdIcGo.ef1f4ic.ient of friction of com illuFsrtoramtedthebyfolrinegeo6i4nginteFaItGit s2h2ouwldasbpereovdiudceendt.that the pthoesitoiorgnanNico m14odwifaiesrmbuacseh iwmapsroevxpedanodveedr tFhorormuguhlathBe, 20 r1a5nvgoeluomf setepeelrcfiebnetrosfhtohueldtobtael mmaiixnttuarieneHd obwetewveeer,nsi3nctoe scuobmsptiotustiitoionnoNf orott1e5nshstoownen fionr FthIGe .cr2y5oliWtehteon parobdruakcee tbheeenopetsitmabulmishreadn,gtehoerfecfeolrleu,locsoemapnodsoittihoenr Nfiob.er2s3hsahdonwont ltihnrionugghmtahdedynoafmcoommeptoesrittieosnt, aNnoave1r5agewacsoefefvicaileunatteodf 25 icnellFuIlGose 2f5ibewr awsadseivnicsereda.seIdn tcooma pmoasxitiimonumNoof. 2253ptehre iflnlucsntoranteodf b0y33linaet 45500i'nFFIwGas1o5btwaiansepdroandducaedw.ear rate ctieonnt wofhitlheeattotthale vsoamluemteimtnectpheerccaesnhteawgenoufttphoewcodmerpwosais theCsoumbpstoitsuittiioonn oNfoiron14owxiadse ffuorrththeer cerxypoalintdeetdo pthroroduugche rpeodsuitcioend Ntoo.152%3 wWasheevnalaubatreadkethlirnoiungghmthadeedfyrnoammcoomme clionminpgosmitiaodne Noof c1o6msphooswitnionin FNIoG. 1265 wWashenevaalburaatekde 30 toebrtatienset,dsancdoeaffwiceiaenrtraotef farsiciltilousntroafte0d.4b5yalitn4eW66' mF FwIGas othfr0ou3g4hatth4e50d'yFnamwoasmoebtetrainleesdt, aandcoaefwfiecaiernrtaotef afrsiciltliuosn 2m3atwchaessptrhoedwuceeadr.raAtes fsoerenc,urcroemntplyosaitciocenptNabole3asablemsotosst traCteodmbpyosliitnieon52NinoFIG14 1w6aws asstipllrodfuurctehder expanded 35 ltiunrienrgs awnidthcoouutldexbteenadcecdepqtueadlibfiycamtioosnt tveeshtiincgle Tmhaunsu,ftahce ltihterouagnhd thgelasssubfsitbiteurtioton opfrocodpupceer cpoomwpdoesritfioornthNe ocryo17 ainnddusHtreyalwthouSldtanbdeaardblse otof m19e7e5t twheithFinedethrael pCrleesacnrib.Aedir stihoonwNnoin1F7IGwhe2n5 eAvalburaatkeedlitnhirnogugmhadtheefrdoymnacmoommpeotseir timTeosestufbosrtacnotimatpeliathncee.results of composition No 23 twesetarhardatea casoeiflfluicsiternatteodfbfyncltiinoen5o4fm0.3F4IGat 41570." F and a 40 apnreopthareerdcboymrpeodsuitcioinng Nthoe. p2e4rcsehnotawgne oinf cFeIlGlulos2e5 fwibaesr thrCooumghpotshietioanddiNtioon o1f4fibwearsglastsislltofuthrtehebraseexmpaatnedrieadl bwohnilienipnocrweadseirngfotrhme froersianpcoorntitoenntoafntdhesubbarsytitteustinTghcearer tbcrapkeroldinuicneg cmoamdpeofsriotimoncoNmopo1s8itisohnowNno in18FwIGhen2e5vaAl- 45 a2f4tewr,aswehveanluaaftreidcttihonroburgihngthme addyenafrmomomceotmerptoessitt,ioancoNeof funactetidonthroofuCg.h37thaei 4d5y0n'amFomanedtear wteestarhardatea caoseiflfliucsiternatteodf fwiceiaerntraotfefarsictiilolunstoraft0e.d28byatli4n5e0'68F inwFasIGobt2a4inwedasanpdroa byInlinoerd5e6rintoFeIsGtab1li8sh relationship between steel fiber duFcerodm the foregoing compositions it was determined atnndt cceelllluulloosseeffibibeerrwinastheelimnoinna-taesdbefsrotoms fthnectbioasnicmcaotmenpaol, 50 athbalet wnhoinle-assbteeesltoasndfnccetlilounlosme afitbeeriralp,rowdhuecne acnomacbcienpedt spmroodnucaendd IcnomanpoasttietimonptNtoo pr1o6vsidheowconmipnoFsiItGion2N5ow. a1s9 tgolagsest,hmerinweriathl ainndorcgaarbnoicn mfiboedrisfiperrso,duwcheicahfrcicatnioninmcluadtee vwoiltuhmaen oadf eWquaalltaestcooneiftfeicwieanst aodfdferdicttioonth, eatcloemaspto5s%itiobny 55 rthiael owpiethratainsgubrsatnagnetiaollfymuonsitfobrrmakewleianrinrgaste throughout Aevabluraakteedltihnirnogugmhatdhee dfryonmamcoommeptoesritteiosnt, hNaod a1c9oewffhiecni I1.claimA.n organic friction material for use as a fnction etrnatteodf bfnycltiinoen5o5fi0n 3F2IGat. 41590. ' F. and a wear rate illus l8i-n5in0g%cobnysisvtoinlugmoef aofmaixtcuorme boifnation of non-asbeatos 19AwsasseennotinaFsIgGo.o1d9,atsheaswbeesatrosratFeofromrucloamBposTihtiuosn, Nthoe. 60 fmibineresraslelfeibceterd, aftrolmeasat g3r%oubpycovnomlusmtinegooffsfteibeelrfgitlasrss,, sbtoenelpfaibrteirclienscwomerpeoasidtdioend Ntoo.pr1o9dwucaes rceodmupceodsitainodn cNaor. 12a-n3d5%at blyeasvtol5u%mebyofvtohleurmmeoaoeftctienlglulpohseenfoilbicersr,esin, 2co0masposshiotiwonn NinoF. I2G0. w2a5s. Wevhaelunaatedbrathkeroluignihngthme addyenoa-f 65 53--3250%% bbyy vvoolluummee ooff eclaasshteowmenruict mpaortdiicflieesr:s; and mwaosmoebtetarinteesdt,aancdoaefwficeaiernrtaotef finllcutsitoranteodf 0b.y37linaet 46500w' aFs 10s-e5t5ti%ngoyphveonluomlice orefsiinnorbgeainnigc mreosdpiofniesrisv,esatiod thheeartmtoo produced. In some applications in order to achieve form a matrix for holding said non-asbestos fibers. 4,119,591 cashew nut particles, ela7stomeric modifiers and inor S. The organic ba8se friction material, a* recited in gstaonsicfibmeorsdiafniedrspihnenaofliixcedrerseinlamtioantrsihxipp,rosaviiddinnogn-satrsubce cfrloaimma4g,rwouhperceoinnsissatiidnginoofrbgaarnyitcesm, wodhiiftiienrgs,atarelc,serloetctetend- tural strength for allowing the friction lining to with stone, wollastonite. pumice, iron oxide powder, copper stand dynamic repeated engagements with a rotating member and providing a substantially uniform wear S ox4id.eTphoewdoergr,anciacrbboanseanfdricstiiloannizmedatmeriinael raasl praerctiitceldes.in claim 1 wherein said non-asbestos fibers include up to rate up to 600* F. during a dynamic engagement. 2. The organic base friction material, as recited in 107%. Tfihbeerogrlgaassnifcibberass.e friction material, as recited in c1l2a%imd1ry, wphheenreoilnicsraeisdinpphoenwodleicr. resin includes at least 10 c1l0a%imw1o, owdheflroeuinr fsiabiedrsn.on-asbestos fibers include up to cla3i.mT2h,ewhoergreainnicsabidaspehefrniocltiiconremsinatienrcialul,deass urpectiote1d8%in clati.mT1hewhoergreainnicsabidasenofnr-iacstiboenstomsaftiebreiarsl, ianscluredceiteudp tion elilqausitdompehreicnoalnicd riensoirngatnoicatmteonduiaftieerssepgrrieograttoiotnheofapspaliid 10% 9 Tsihlaeniozregdanmicinebraaslefifbreicrsti.on material, as recited in claim 1 wherein said non-asbestos fibers include up to cation of heat to the mixture 4 The organic base friction material as recited in 101%0.cTarhbeonorfgibaenrisc. base friction material as recited in claim. 3, wherein said elastomeric from a group consisting of natural modifiers is selected and synthetic rubber 20 clilqauimid 1rewsihnerein said phenolic resin includes at least S% 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 cade, but this most b e e r weight category for over a de American manufacturers have 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 150 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 file, 1973 station wagon t5e8n60perlbatuGr.Ve .Wpr.o, 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 1.000 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-