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FILE NAME: Friction Materials Standards Institute (FMS) DATE: 1972 Feb 10 DOC#: FMS017 DOCUMENT DESCRIPTION: Meeting Minutes & Attendee List Asbestos Study Committee y \r-1 or* the rssestcs sr '.':v Thursday, February 10, 1972, at 9:30 A.M. at tb i n s t i t u t e Office, -210 Route y-.cro wOr\ff Paramus, N.J. 07652 I. H. .Veaver, Chairman J. C. Henning iV. 3. Reitze M.G. Jacko (For w. Spurgeon) J . 3 . Graham ' .NOT PRESENT M M W M H MM . H. Feierabend OTHERS PRESENT . W. Drislane Raybestos-'Vanhattan, Inc. Firestone Tire 4 Rubber Co., .Vorlb osstos Division Jchns-Vanv1le Corporation oendi* Corporation Sendix Research Laboratories Carlisle Corporation Molded Materials Division bex Corporat ion * American Srakeblok Division ? Friction Materials Standards Institute The meeting vas c a lled to order by Mr. Weaver, Chairman, at 9:30 A.M. MINUTES OF PREVIOUS MgylNG The Secretary read a summary of the minutes o f the meeting held September 15, 1971. These minutes had been released, and a motion for their acceptance was entertained. Upon motion duly made, seconded and unanimously passed, it was RESOLVED* to accept the minutes of the September 15, 1971 meeting at distributed. MEETING AT DEPARTMENT OF LABOR. JANUARY 26. 1972 A brief review read of the a c t i v i t i e s at the Occupational Safety and Health Administration (0SHA) s e ss io n held in Washington on January 26, 1972. Mr. Matt Swetonic of J-M attended t h i s session, and the Secretary summarized what Mr, Swetonic had told him as follows: 0SHA previously had emphasized sa fe ty - now the emohasis is on h e a l t h - f ive - i n d u s t r i a l `substaneas^:a r t under" attack (asbestos, s i l i c a , lead, cotton dust and carbon monoxide). Our immediate 1\| U es cf* Assesses y 3* Meet i ng rtO r^i'y concern is asbes tos. CSHA is suggesting voluntary se t-uc cf ireuse-v committees working with trade associations. Industry recresen^a;svs indicated that cooperation should be based on reasoraole standards. r The croposed standard is 5 f ib e r s /c c (OSHA is apparently consider;-g recucmg tffa stanoard to 2 f i b e r s / c c ) . -- ASBESTOS' EXPOSURE STANQAPQS The prooesed standard by CSHA is now 5 fibers per co. A fiber must have a 3/1 1ergth/diameter ratio, with the length 5 microns or greater t o b e considered a fiber. This size C3n be screened with the optical microscope. Dr. Jacko noted that there were studies concerning asbestos f i b e r s in the l e s s than 5 micron length by electron microscopy. The orvtish Asbestos Regulations of 1969 were discussed. They have a ccncentrat ion of l e s s than 2 f ihers/ce. (sampled over a 10 minute period) as being s a t isf a c t o r y , with allowance on 2 to 12 fibers/cc (samoled over a L hour period) deoending on hew much the sample exceeds the 2 f i b e r s /c c limit. See copy of pages -5 of Control it Safety Guide 8. At 12 f i b e r s / c c , the plants could be shut down. r For reference: 4. The Asbestesis Research Council V ''Asbestos "Based-Fr iction Water la.ls and. Asbestos Reinforced Resinous Moulded Compounds," Controlvand'Safety Guide #3; nvironmentaliiCoht'rorrCdmni tteer'Secretar.y * 1U-Park' Street London,..England #1Y-JAS. j British faction materials council * The Secretary advised that the B r it ish Council had submitted comments to the I l l i n o i s Pollution Control Board and had indicated (through Mr. Bob Gibson of Mints* and Mr. Harry Jones of Ferodo at the SA January meeting) their interest in being informed on the status of asbestos regulations in the U.S. Upon motion duly made, seconded and unanimously passed, it was RESOLVED: to inform the B r i t i s h Council of a l l regulations known to the Friction Materials Stancaros Institute, and to forward minutes of our meetings to the Br it ish Council. LIAISON WITH ASBESTOS INPQRMATION ASSOCIATION OF NORTH AMERICA fAIA/NA) It was noted that Mr. Matt Swetonie, now with Johns-Manvi 1le, will become Executive Secretary of the AIA/NA. It wes recommenced that nusi maintain contact with the AIA/NA concerning any matters asbestos in the work-place,etc. V. of Asr =s 31- ry it tea Meeting '.'AL s a f i ~ v a>.jq h : i_t u ft m a r / A) Mr. Weaver discussed seme of the bacKgrouna for the sro3oSei Qr_i Standard^ for Exoasure to Asbestos Dust. P-ocosed rule maK,,~~~fcr these standares aoceareo in the Federal =egistsr or* Decemoer 7 '=71 and__January 2, 1972.- (Cocies were distributed by the Institute by "mail to menoers of' the Asbestos Study Committee) Mr. Weaver is the Industry rear esentat i ve on the Advisory Committee for Asbestos Standards set up under the Ccousationa 1 Safety and Health Act. He advised that while the proocsed stancards are for 5 f i b e r s /c c tme weighted average airborne concentrt ion of asbestos dust, the others on the Advisory Committee may push for 2 fibers/cc. CSHA will apparently enforce these rgult ions and i f exoerience in related safety enforcement is any c r i t e r ia , fines or plant closings may be used for enforcement purposes, ./hjle it is currently too la t e to present written comments, the'hearings are to be held on March U , 1972 in Washington. in order to be heard, a person must f i l e a notice of intention to appear no later than March 3,- 1972. The notice must state name, address, approximate time required for prsen ttion, and a statement must be included indicating the * ' position to be taken by the individual. * The Chairman and Mr. Feitze indicated that these CSHA regulations were now of prime importance to manufacturers of asbestos brake linings and clutch facings, and the Secretary was directed to inform the membership concerning the proposed standards. environmental protection aggqy <EA) The EPA's emohasis in their proposed emission standards for asbestos did not use numerical lim its on airborne asoestos, but concentrated on f i l t e r s and c ollectors - control practices'; While these are important to a ll manufacturers of asbestos brake l in i n g s , they are practices and standards which, at t h i s time, seem reasonable. The OSHA Standards are the mere immediate problem. ENVIRONMENTAL PROTECTION AGENCY - EMISSIONS FPQM ASSE3TQS 3P.AKE UNI.MGS Dr. Jacko advised that the Sendix Corporat ion1s stu dies for the EPA on em issions from brake lin i n g s may not be complete on schedule, and that 8endix had requested a time extension on t h i s work that would move th eir fin a l report barck into the f a l l of 1972. Dr. Jacko indicated that the max imum asbestos, f bar ..n.brake 1ini ng debris is r t *15. * STUDENT PAPER - ^iCLQCiCAL gpPFCTS OF ASBESTOS ON THE HUMAN CfiGANlSJj Copies of a term paper by MisV B eth 'Kru11 rChemistr y 'Junior.at. Mundelein~Ool lege* in Chicago were d is tr ibuted to the'member ship*. It would appear that t hi s papar may be an in terestin g sourcs of medical - 3- Minutes or* Asbestos Stucy Committee Meet irg "ebr-^ary \z, i r~"2 bibliography concerning asbestos; (The paoer was forwarded to th.a In stitute by Mr. J . Greenen, President of F.M.S.i.) FG'JIP^LNT r GR Jt;==roAj a; 3 f ; tcs CCMCr r s a t i ^N'S Mr. e i t z e discussed the equipment necessary for measuring asbestos concentrt ions. The test is run with a vacuum pump pulling fibers into a f i l t e r which is then examined under optical microscocy. (Mr. r .e itze discussed the equipment and procedures in more detail in an afternoon sess ion) Dr, JacUo said that the sub-5 micron asbestos fibe rs were being examined with ele ctron microscopy. He f e l t that as far as airborne fibers ware concerned, these s.uo-5 micron fibe rs might be targets of the regulators in the future. Mr. Graham asked whether there were any automatic ecuipment for measuring the asbestos concentrt ions - either in existence or planned. It was stated that the ?A had made a Pecuest for Prccosal for design of equipment for automatic measurement, but apparently they received no response. / As of now, oot ica l microscooy with the membrane f i l t e r is the only .. recognized method. ^ AS8S5TQS STUDY COMMUTf; - FUTUPg COURSE The members indicated that the Committee should e x is t for s c r e e n i n g and passing on information to the members. They do not feel the Committee should be used as a vehicle to comment directly on regulations proposed by the various Federal and State agencies. Further, i t is f e l t that individual company responses to CSHA or PA or others (such as I l l i n o i s Pollution Control Board) are more e f f e c t i v e , particu larly those from the smaller manufacturers. Unless directed to prepare responses to .government agencies by the general membership, the Comittee w i l l not assume t h i s respons ibility. Some members f e l t that the ''Asbestos Study Committee" would have to expand beyond asb es tos - such as into s i l i c a , resinous by-products, etc. As o f now, the prime target is to be esbesto s, but other materials, if considered of importance to the members, wi l l be studied. Another suggestion was that the Committee consider a membership survey on the methods for disposing of brake l i ni ng grinding dust. --u :r *k 55 3* - ; o e s i c sS a s Meet : r g 53.' r j r . M. Jacko requested that His race be added to the sresics Study Committee .'nailing l i s t , in addition to that or* Dr. Source-. it *e_s suggested that other manufacturers of brake linings, outside the membership', be advised of these proposed stancar-s CSi-A. Summaries of the afternoon's oresentation by Mr. Reitze will be distributed to the membership. I'oon motion duly made, seconded and unanimously passec, it was RESOLVED: to adjourn. Adjourned at 12:CC noon E. W. Dr i siane / Executive Secretary * cc: Committee Members J. Greenen L. S t i c k l e s Br i t i s h Council AIA/NA section : INTRODUCTION AND OR I OF SUC'MAJVt' The c h r v s o c i i c form of as be s t os I s a major c o n s t i t u e n t in . l ut c- r : i v brake l i n i n g s and d i s c pads, and in the f r i c t i o n ma t e r i a l s uscu ; : lutcnes. These components are expendable. In typi cal oassenger cor s e r v i c e , drum l i n i n g s wear out in about 10,000 m i l e s , di s c pads m an30, 000 mi l e s , and c l u t c h f aci ngs in aoout 70,000 mi l e s . There ar u, u: c o u r s e , wide v a r i a t i o n ? ' in the s e r v i c e l i v e s of t he s e components, w::ic depend on the n a t u r e of the f r i c t i o n m a t e r i a l s us e a , on d r i v e r h a b i t s , and on d r i v i n g c o n d i t i o n s . T.ie e xpenda bl e members of the common aut omot i ve f r i c t i o n coupl es cont ai n not only a s h e s t o s , but also v a r i o u s organic and inorganic f r i c t i o n and p r o p e r t y m o d i f i e r s . These c o n s t i t u e n t s ar e bound t o g e t h e r o>ohenolic r e s i n s . Recause of their hizh content of organic substances, suen f r i c t i o n m at eri al s are cl as s ifi ed as "organic." Asbestos-free friction, materia ls with a high content of metallic substances are c l a s s i f i e d as " s e m i - m e t a l l i c . " Over 99 p e r c e n t of the aut omot i ve f r i c t i o n m.i- : r i a l s used todav are organics. The mechanisms by which organi c f r i c t i o n maceri; Is wear can be c l a s s i f i e d under five headings: thermal, abrasive, adhesive, macrcsnear, \ and f a t i g u e . Thermal, abr as i ve , , and adhesive wear are considered to a a :*.e mes: i mp o r t a n t mechanisms, thermal wear pr edomi nat i ng above 5C*.-\ abrasive and adhesive wear predominating below 50*r (the temperature i c i n g measured by a thermocour l e in the r o t o r , about 0.030 inch from t.nu s l i c i n g i n t e r f a c e ) . The organi c c o n s t i t u e n t s pyr ol yze or o x i d i z e , ana are emitt ed to the a i r as carbonaceous s o l i d p a r t i c l e s or gaseous r e a c t i o n p r o d u c t s . The a s b e s t o s f i b e r s a r e p u l v e r i z e d i nt o smal l p a r t i - ci.es wnich a r e cr appe d i n the brake (or c l u t c h ) hous i ng, or f a l l to t..e road, or a r e e m i t t e d to t he a i r . Disc b r a k e s do not crap as much as drum br akes . Most of t h e a s b e s t o s i s h e a t e d to t emper at ur es hi gh encugu :o cause chemi cal c o n v e r s i o n , and i s t h e r e f o r e crapped or e mi t t e d as o l i vi ne or f o r s c o r i t e p a r t i c l e s . When t h e l a r g e number of e x i s t i n g c a r s and t r u c k s is c o n s i d e r e d , each with e i g h t o r a o r e p i e c e s of f r i c t i o n m a t e r i a l in the br ake system, p l u s more i n eh* c l u t c h acehani s m, i t becomes a p p a r e n t t ha t an a i r p o l l u t i o n prob l e a may e x i s t . Consi dered in a n o t h e r l i g h t , t he r e a r e perhaos one b i l l i o n p i e c es of f r i e c i o n material in vehi cles in the United States, g r a d u a l l y b e i n g p y r o l y z e d and ground to d u s t . The brake syst ems in chi v e h i c l e s u t i l i z i n g c hs s e f r i c t i o n m a t e r i a l s can thus be c o n s i d e r e d as chemical r e a c t o r s , each e m i t t i n g or gani c _nd i nor gani c compounds, i n c l u d ing a s b e s t o s and i t s d e c ompos i t i on p r o d u c t s , to the at mosphere. The comp o a i t i c n s of t he gas eous and s o l i d e mi s s i o n s have not been w e l l known, 1-1 ur.u the p a r t i c l e s u e s and shapes of the s o l i d emi s s i ons nave not :een - . --known. Because of the p o s s i b l e damage which t he s e emi s si ons tan produce in human r e s p i r a t o r y s ys t ems , i t is d e s i r a b l e to i d e n t i f y ar.c q u a n t i f y t he , wi t h p a r t i c u l a r r egar d to a s b e s t o s . That is the purpose :f me program described in this report. The amount of a s b e s t o s e mi t t e d i s a f u n c t i o n of many v a r i a b l e s : the number of v e h i c l e s on t he road, t he number of mi l es d r i v e n per year by each, vehicle size, the number of v e h i c l e s u s i n g manual c l u t c h e s , condi tions of dr ivi ng ( c i t y , expressway, mountain; driver habits, etc.), br ake system d e s i g n , and brake type (drum or d i sc ) , rotor condition (surface roughness, scoring, cracking, pitting, etc.) . rotor design ( e . g ., solid or ven tilated discs, fianta drums, e t c . ) , rotor metallurgy (cast iron or aluminum;, volume p e r c e n t o f a s b e s c o s in the f r i c t i o n m a t e r i a l , and i nhe re nt wear r e s i s t a n c e of the f r i c t i o n m a csrlal. In : n l s program a p a s s e n g e r car of medium weight ( t e s t wei ght : SCO pounos), produced i n hi gh volume, was used. I t was equi pped with a manual t r a n s m i s s i o n and c l u t c h , v e n t i l a t e d c a s t i r o n d i s c brakes on the f r o n t , and s t a n d a r d c a s t i r on drum b r ak es on the r e a r . a p a s s e n g e r c ar was s e l e c t e d f o r t e s t i n g because of the following factor: ( 1) v e h i c l e hroxlnfi cannot be s im ul at e d r e a l i s d e a d ly nn small-scale friction test-machines with the present s t a t s of cha are; ( 2) f u l l - s c a l e brake and c l u t c h dynamoaattrs provide fa- -iy good s i m u l a t i o n , and can be uaed f o r che cking out the emissions collection system; separata casta for brakes and c lu tch es would be requ ire d , however, thus increaainp program c o s t s , whertas on tha v e h i c l e , d i s c and drum brakes and clutches can be te s te d sim u ltan e o u sly ; ( 3) a i r flow in the dynamometers d i f f e r s from chat in vehicles, and em is si ons from drum brakes w i l l t h e r e f o r e be d i f f e r e n t in the two c a s e s . 1-2 Three s e r i e s of tests were ra, usin "JieTi.i. s. "- *W . c ^ S imui a t i on Friction Materials S"i<i r ^ Original Eq u i p me n t OEM1 Disc Fronc UEM Druffl Rear Class A organic o:sc Partial Reline AM2 Disc Front Used OEM Drurn" Rea rs No m e t a l l i c c h i p s ; Discs and drums r.o: turned 3 Full AM Dise Front Oise pads and seconcaries Reline AM Drum Bear c o n t a i n b r a s s c:i;,:s Discs an-, c r ur j rice This s e l e c t i o n has sever.n fe.icures. Ic provides a r e p l i c a : ... one c a s t , :hus g i v i n c an e s t i ma t e of r e p e a t a b i l i t y . I t i n c l u d e s .1 i.rim.iry/ * s econdary combinat ion tn.a: s er vos both OEM and a f t e r m a r k e t s . 1: i n c l u d e s * one c ombi nat i on (two m a t e r i a l s ) of wi del y used OEM m a t e r i a l s . 1: included one combi na t i on (two m a t e r i a l s ) from one of the l a r g e r a f t e r m a r k e t suo- p i i e r s . Ic I n c l u d e s a s e t of used l i n i n g s (about 3, 000 mi l es ) to p.ive dat a on t h e e m i s s i o n s at v a r i o u s s t a g e s of l i n i n g l i f e . It i n d u c e s two d i f f e r e n t d i s c pad m a t e r i a l s from two of the l a r g e r a f t e r m a r k e t s u p p l i e r s . Five d i f f e r e n t manufacturers were r epr es ent ed in the f r i c t i o n materia] solec t ions . The c o l l e c t i o n 0 : p a r t i c u l a t e and gaseous . . mi ssi ons from any v e d d u f ric t io n couple has never before, to the authors' knowledge,been reported in the l i t e r a t u r e . To d e f i n e the e x t e n t of these e m i s s i o n s , a comomati on s e n a r a t i o r and s t o r a g e c o l l e c t i o n system wua de vi s e d. Unique emissions c o l l e c t o r s f o r bot h d i s c and drum b r a k e s , ' and for a c l u t c n , were conce: - c u , d e s i g n e d , and b u i l t as the main embodiment of t h i s i n s t r u m e n t a t i o n . :-.u c o l l e c t o r s s e p ar at e d the wear debr is int o three d i f f e r e n t f ra ct i ons : a sump sample which i nc l uded t he wear d e b r i s on the l i n i n g s u r f a c e s , m me r i v e t h o l e s , and on the brake drum; a s u r f a c e s sample winch i n d u c e d the wear d e b r i s on th e orake and c o i l a c c o r shroud s u r f a c e s ; ana .in a i r b o r n e sample c o l l e c t e d on membrane f i l t e r s . The v e h i c l e was equipped w ith s t a n d a r d brake t e s t i n s t r u me n t a t i o n . A f r o n c d i s c b r s k s c o l l e c t o r and a r e a r drum brake c o l l e c t o r were i n s t a l l e on th e r i g h t s i d e of the v e h i c l e . The c l u t c h was s e a l e d by c l o s i n g me OEM - O r i g i n a l Equipment Manuf act ur er s 2A.M - a f t e r m a r k e t 1-3 . . ei m i t s c a s i n g . The l e f t wheel br akes were l e : in chei r -v-r-al rj_: i on and were used co moni t or :he o p e r a t i o n o; che snrouted r . < o . - e a r d e b r i s was al s o cat en from che l e f t br akes ; che a r c a r e s : or : s : -1l e e .ed and ics composicin were used co d e m n s t r a t e c.n.: - ,u' -.--. -a; r.g did noc s i gni f ica.ncly a f f e c t che o p e r a t i o n of the t u l ..salons collectors. : '-'iufcih t here a r e many a c c e p t a b l e o r i g i n a l equipment manu fa .: . r 5r. ' ; r a an.: r r i c c ion m a t e r i a l t e s t s f o r measuri ng a s p e c i f i c c a l l e : ' . . : - . .. ."i.i t; an o f e o1l er c i s , no one t e s t a d e q u a t e l y matches a r i v : - ; u . : tuns ' -inch would he r e p r e s e n t a t i v e of a l l v e h i c l e s . Consequent ly , ; : ueu.i-.u iK". o s>..iry to d e v i s e a r a t i o n a l and me ani ngf ul v e h i c l e t e s t , a t o t a l of s e v e n s chedul es were chosen and each was f ol l owed by a measuceme.nts p r o c e d u r e ( t ake emi ssi ons sampl es , measure wear , i n s p e c t systems, end r e p l a c e worn p a r e s ) . The f i r s t t h r e e s c h e d u l e s - Bur ni s h, After durnisn ( A . a . ) b a s e l i n e , and D e t r o i t T r a f f i c - Represented low-temperature t e s t i n g . The f i n a l four schedules - 10-Stop Fade, Af t er Fade (A.F.) 3aseii.-.e, 13-St op Fade, and Fi nal a s e i i * - r e p r e s e n t e d hi g h - t e mp e r a t u r e and obrus ive :s c i n g . The m i l e a g e accumul at i ons f o r each s chedul e of each v e h i c l e t e s t v e r i f : rd the p o s s i b l e t e s t mileage r e p r o d u c i b i l i t y . A c r i t i c a l component of the f r a n c d i s c brake c o l l e c t o r was a uni que r o t a t i n g s e a l . For :ne 3130 mi l es c t e s t i n g , only e i g h t r o t a t i n g s e a l s were r e q u i r e d - an t x c e s t i o n a l improvement over the a n t i c i p a t e d need at the s t a r t of the procram. P r i o r co v e h i c l e t e s t 1, a Burni sh s che dul e was performed and the t e mper at ur es f o r the r i g h t f r o n t d i s c brake wer* found to be near t 00*F. The t e mp e r a t u r e d i f f e r e n c e , IT, between the r i g h t and l e f t f r o n t brakes ranged from 200 to 250*F. This was u n a c c e p t a b l e . The a d d i t i o n of s e ve r a l thermal c o n t r o l ai ds leduced the AT to a range of 115 to 160*F. Most imp: ant was the r e d u c t i o n of the r i g h t f r o n t brake o p e r a t i n g t emperat ure from about d00*" co about 300*F. The brake s hr oudi ng d id noc p r e s e n t any pr o blems on hoc d a y s . During the D e t r o i t T r a f f i c T e s t , the AT between cne f r ont brakes remained between 100 and 140*F 'hile t hee f o r the r e a r drum orake remai ned between 10 .and 3Q*F. The r a n g e of a s b e s t o s concent in the brake e m is si on s f o r v e hi c l e t a s e s 1 and 2 went from a high of 1.65 p e r c e n t co e low of 0.03 percent for the 90 a n a l y s e e ; only three were above 1.00 p e r c e n t . The o v e r a l l average f o r v e h i c l e t e s t 1 was 0. 40 p e r c e n t end f o r v e h i c l e t e s t 2 was 0. 25 p e r e e n c . For v e h i c l e t e s t 3, the range of esbes coe concent was from a high o f 0.51 p e r c e n t to e low of 0. 003 p e r c e n t . The o v e r a l l a v e r age was 0. 07 p e r c e n t . In th i s work, a l l v a l u e s f o r hesvy-ducy (abusive) braklng-vere l e s s ehan one percent, which is s ig n i f i c e n c l y le ss than the 15 perc en t a s b e s t o s concent re p o r te d by Lynch of th e U.S. P u b li c Health Service. To p r o v i d e e s y s t e m a t i c , inde pendent check on th e a s b e s t o s a n a l y s e s , the SPA P r o j e c t O f f i c e r arranged a second c o n t r a c t f o r B a t t a l i a Columbus Laboratories co analyze twenty-four samples generated by Sendix Research 1- _ a b o r a t c r - . e s . i o h n s - t t a n v i l l e a l s o provi ded t h r e e a n a l y s e s . The Jcnns" a n v i l l e and S a c c e l l e d at a agr eed very w e l l . In 19 of the 2<* an a l y s e s , the Bendi*--r e s u l t s were s l i g h t l y hi gher t han the c or r e s pondi ng B a t t e l . r e s u l t s . The Sendi x average was 0.25 p e r c e n t , whi l e the 3 a t t e l i e a v e r a? was 0 . 1 ' p e r c e n t , or 63 p e r c e n t of the Sendix a v e r a g e . The 3enq;x d. :a were expec t ed to be hi g h e r f o r the f o l l o wi n g r e a s o n s : a l l f i b e r s found wt r e assumed to be c y l i n d e r s of p - o j e c t e d di a met e r and l e nt en, a f i b e r w. t h an e l l i p t i c a l c r o s s s e c t i o n was a c t u a l l y wa l l e r in v a i u . - . c.oan r e p o r t e d ; and a l l f i b e r s were assumed to be pure a s b e s t o s , oegraoed as oes tos or o li vi ne f i b e r s were mechanically reduced nc-f i b r o u s m a t e r i a l by the other a n a l y t i c a l t e c h n i q u e s , so only tne scrasoest os f i b r i l s t h a t remained were count ed). An a l y s i s of t h e gaseous e mi s s i ons was made d i f f i c u l t by the q u a n t i t i e s of water and carbon dioxi de which by-passed the gas c ono; :. ; ng t r a p and e n t e r e d through t he r o t a t i n g s e a l s . Mosc sampl es snow* t r a c e s of Cj_ to C3 hydr ocarbons onl y as lower c o n c e n t r t ions of hi gher - o l e c u l . i r we i ght gas es could not be d e t e c t e d . When the g a s e s wera c e n t r t : . d from t he fade t e s t s , C4 to Cg compounds such as b u t a n e s , ben zene, t o l u e n e , phe nol , and c r e s o l s ware d e t e c t e d in the gas t r a p s . Tne c o r r e s p o n d i n g shroud e x t r a c t s showed Cj.2 t o Cjg m a t e r i a l s , i ncl udi ng cardanoi. To compare t he g e n e r a t i o n o f a s b e s t o s emi s s i ons p r o p e r l y , i t found n e c e s s a r y to c a l c u l a t e the e mi s s i ons f a c t o r s f o r each sample m mi cr ogr ams / mi l c ( u g / m i l e ) . These v a l u e s were obt a i ne d by m u l c i p l y m me weight 0: g e n e r a t e d brake d e b r i s by the a p p r o p r i a t e a s b e s t o s per foll owed by d i v i d i n g by the m i l e s per t e s t s c h e d u l e . Thus, e i t h e r a o:gh a s o e s t o s c o n t e n t or a l a r g e sample gave a high f a c t o r . Tne f o l l o w i n g o b s e r v a t i o n s were made: As b e s t o s e mi s s i ons were h i g h e r f o r new f r i c t i o n s u r f a c e s and decreased with use. I n i t i a l l y t h e drum br a ke produced more a s b e s t o s emi s s i ons tnan t he d i s c b r a k e . The d i f f e r e n c e de c r e a s e d as the m a t e r i a l s c o n t i n u e d to be used. Heavy ( a b u s i v e ) duty di d not n e c e s s a r i l y gi ve a h i g h e r percent a s b e s t o s , however, the l a r g e amount of d e b r i s produced gave a significant rise in asbestos emissions. The o r d e r o f d e c r e s s l n g a s b e s t o s e mi s s i o n s from b r a ke s was found to bo: Fad* or heavy-duty sto p s Burnish Moderate braking f J> tj F o ^ chs d i s c pads o n l y , chere was an I ncr eas e i n a s o e s : : s emi s si on* wich inc re as ed asbestos concent in the f r i c : ; c n m a t e r i a l ( cher e was no such trend- f o r the drum oraice materials). Both the f r o n t disc pads and the drum l i n i n g s of vehi cle t e s t 3 had wear comparabl e to t h a t o f the o t h e r two vehi cl e t e s t s , yee the a s b e s t o s emi ssi ons were s i g n i f i c a n t l y lower. 3ot h pads and l i n i n g s cont ai ned b r a s s chi ps which may nave been i n p a r t r e s p o n s i b l e f o r the more complete convers::.-. of the asbestos in the brake emissions, possibly because of beccsr heat t r a n s f e r to the a s be s t o s . " or bot h d i s c and drum br akes , t he s u r f a c e s s*n.ple was t he l a r g e s t o f the t h r e e (-v92 p e r c e n t ) , the sump sample was next ("'7 p e r c e n t ) , and the a i r b o r n e sample was c.-.e sma ll es t (^1 p e r c e n t ; . Two s e r i e s of wei g h t i n g f a c t o r s were deve l ope d. The d i s t r i b u t i o n weighting f a c t o r s wart c a l c u l a t e d from the m a t er ia l r ec o v e r i e s in the shrouded and unshrouded br akes as i n d i c a t e d e e r l i e r . Es t i ma t e s were made f o r bot h d i s c and drum brcxes from the t e s e v e h i c l e f o r t he amounts u 4 t h e d i f f e r e n t samples d i s t r i b u t e d from the b r a k e s . These e s t i ma t e s were made f o r t he Bur ni s h s c h e d u l e , f o r the end of a complect v e h i c l e t e s t , and f o r the end of a l l three v e hi c l e t e s t s . For the drum brake, estimates were made up to 40, 000 mi l e s . The s e v e r i t y we i ght i ng f a c t o r s were . a i c u l a c e d from t he p e r c e n t a g e - o f d i f f e r e n t b r a k i n g modes: f o r new versus bur n i s h e d f r i c t i o n m a t e r i a l s , f o r sever e ( o r abus i ve) v e r s u s moderate b r a k i n g , and f o r the r enewal "of f r i c t i o n s u r f a c e s (A.F. B a s e l i n e ) . The t o t a l a s b e s t o s e mi s s i o n s e s t i ma t e f o r the t e s t v e h i c l e was c a l cu la te d from the asbestos emissions f a c t o r s and the s e v e r i t y weighting f a c t o r s . The a v e r a g e a s b e s t o s emi ssi ons f a c t o r f o r the d i s c brakes, drum b r a k e s , and c l u t c h were used a l o n g wi t h tha Bur ni s h (new s u r f a c e s ) , A. 's. Baseline ( s u r f a c e p r e p a ra t io n ), Detroit T r a f f i c (moderate craking), 10Scop Fade ( s e v e r e br aki ng) and A. F. B a s e l i n e ( s u r f a c e r e ne wa l ) weight ing f a c t o r s . The v a l u e obt a i ned f o r the t e s t v e h i c l e was 28. 21 ug/mile. The f a c e o f t he a s b e s t o s emi ssi ons was c a l c u l a t e d w i t h the use of the distribution veighrlng factors ts follows: Road D rop-out 8 1 . 9Z Airborne: 3.7Z enger to be Brake R eeea clo n : 1 4 . 4Z Tha annual t o t a l a s b e s t o s emi s si ons e s t i m a t e f o r 96, 400, 000 pas s v e h ic le s t r a v a ilin g an a v e r a g t of 9, 978 mi l e s per y e a r was found 60,400 pounds, d i s t r i b u t e d es follows: Road Dr o p - o u t : 49,470 lbs Airborne: 2,230 lbs Brake Ret enti on: 8,700 lbs 60,400 lbs The a n n u a l t o t a l a s b e s t o s m i s s i o n s e s t i m a t e s for Li g n : : t r u c k s (,r.d b u s e s ) , and heavy t r u c k s were fauns to 5c: Light trucks 22,300 Lbs Medium t r u c k s (and buses) Heavy t r ucks I f' , 300 Lbs 22,900 Lbs 81,500 Lbs a t r i b u t i o n of t he t o t a l a s b e s t o s emi s si ons e s t i ma t e for c -*. ated to be as foilows : Rood Drop-Out 3 7.9% Ai ro o m e : 2.9% Brake R e t e n t i o n : 9.2% " he e s t i m a t e d a s b e r t o s mi s s i ons for a l l v e h i c l e s in pour.u. -.-.ir .s summarized as follows: Total Asbestos Emissi ons (Lbs) Discr ibucion (IbsJ Drop-Out Ai r bor ne Rutvr.ii Passenger Cars Light Trucks ".cium T r u c k s (and buses) Heavy-Trucks ".isce LLaneous (notorcycles, trailers, etc.) 60,400 32,100 L6.200 32,900 L6.300 9,470 28,420 14,330 28,920 14,-330 2,230 940 170 9 50 4 70 3 ; (^ ; - ' -. , Vvu L5S ,2 00 135,470 5,060 17, 7v D is tr ib u t io n by percent: 85.62 3.2% 11. 2'" These e s t i m a t e s e r a c o n s i d e r e d to be maximum v a l u e s * / 2 . 2 . 2 Unpubl i s hed Daca Ac t he el s e of w r i t i n g of chi s r e p o r t , t h e r e were reo i'.r.O'.'ii works which had been compl et ed or were i n p r o g r e s s . The anc..-; of br ake weTr d e b r i s and es composi ci n ver*' det ermi ned on a f u i l - o r c k e . n e r t i a l dynamometer using a d u o - s e r v o drum br ake in 1968--69. determina-cien of t he amount of a s b e s t o s i n a i r b o r n e br ake d e b r i s samp Leo downwind of a d i s c brake i n s t a l l e d on an i n e r c i a l dynamometer was m p r o g r e s s . (2-3) The d e t e r mi n a t i o n of a s b e s t o s cont ent in a i r b o r n e oraka c e o r i s sampled downwind of v e h i c l e - mount e d d i a c and drum br akes va.s a l s o in p r o g r e s s . **- ' 2.3 background 2 . 3 . 1 Cr.ergy Absorpt i on bv F r i c t i o n Ma t e r i a l s 2.3.1.1 3rakes During a stop, the automobile brake converts the ki n e t i c energy of the moving v e h i c l e i nc o h e a t , abs or bs cha h e a t , and gr adual . v d i s s i p a t e s i t t o t h e at mosphere. The s l i d i n g f r i c t i o n c o u p l e in the br ake c o n s i s t s of a c a s t - i r o n r o t o r (drum or d i s c ) and a s t a t o r on winch .s mounted a f r i c t i o n ma t e r i a l or l i n i n g cons i s t i ng of a s b e s t o s f i b e r , p r o p e r t y m c c i f i e r s , and an o r g a n i c r e s i n b i n d e r . Li ni ng i s coi.<ideree expa nda bl e . Over a long pe r i od of time and many miles of s e r v i c e , muen j : i t is c o n v e r t e d to dust and g as es . Smal l er amounts of t h e r o t o r are also converted to wear debris. P a rti c u la t e debris is p a r t i a l . ; / retained and p a r t i a l l y e m i t t e d from tne v e h i c l e in normal s e r v i c e . 2 . 3 . 1.2 Clutches The " manual" aut omobi l e c l u t c h t r a n s f e r s t h e k i n e t i c energy of the en g i ne s r o t a t i n g cr anks haf t smoothly to the transmission and wheel s . Any s l i p p a g e r e s u l t s in g e n e r a t i o n of h e a t , which is aus or bed and e v e n t u a l l y d i s s i p a t e d to the atmosphere by t he c l u t c h . T'-'u.-. the c l u t c h is b a s i c a l l y a d r y - r u n n i n g s t a t i c f r i c t i o n cwuple (which s l i d e s moment ari l y dur i ng gear s h i f t s ) . The macing m a t e r i a l s are us ual T. c a s t - i r o n or s t e e l and a f r i c t i o n material or lining which is frequently organic-bound. Organic-bound f r i e t i o n materials consist of asbestos f iber r einforcemenc, property modi fiers, and ar organic r e s i n binder. The composi t i on i s q u a l i t a t i v e l y s i m i l a r to cha t of br a ke l i n i n g s . C l u t c h l i n i n g s are e ls o e x p e n d a b l e , g r a d u a l l y wearing away i n use. The wear d e b r i s can seap e from manual c l u t c h e s . Uear d e b r i s from f r i c t i o n m a t e r i a l s in autom atic transmissi ons i s retained almost completely i~ rhe transmission flu id . 2-3 2 .3 .2 Compositions of Friction Materials 2 . 3 . 2 . 1 * Generalized C'.assificacions / ^ __ Tabl e 2-1 g i v e s t y p i c a l c o mp o s i t i o n s of drum l i ni ng, c i s : p a d , ' " ! ) a n d c l u t c h f aci ng f r i c t i o n m a t e r i a l s . The f o u n d a t i o n , or major c o n s t i t u e n t , of p r a c t i c a l l y a l l organic f r i c t i o n materials is asoestos fiber , Asbestos i s chosen because of i t s thermal s t a b i l i t y , its relative.-.- mgn f r i c t i o n l e v e l , and i t s r e i n f o r c i n g p r o p e r t i e s . Si nce asbestos alone does not o f f e r a l l of the desired f r i c t i o n p r o p e r t i e s , other materials c a l l e d f r i c t i o n modi f ier s are added. Modifiers are v a r i e d in type and content to provide desired levels of e f f e c t i v e n e s s , veer, fade, recover/, and n o i s e . A r e s i n bi nder i s a l s o added to hol d the ocher ma t er i a l s together with adequate strength. 2 . 3. 2. 2 Asbestos The asbestos us ual l y used in f r i c t i o n ma t e r i a l s is chrys a c i l a from Quebec or Vermont. C h r y s o c l l e , t h e p r i n c i p a l mineral c: the s e r p e n t i n e gr oup, has Che appr oxi mat e comp o s i t i o n formula !!*3(S i20.)(CH)6 or 3MgQ.2Si02-2H20 Table 2-1 - Composition of Typical Automotive F r i c t i o n Materials (Volume Per cent ) * fi* S . - i t r * *.m ; e : n {,,r r ' i i n r * 1 - . T 4 T riief bfcanfigry 2 0 - )C ;j i r 2 5 - >1 4 JOf O n e *t<i C i i l ! <4 *<in * 4 ri c:j i H iivyO w tv 11-22 u -ii "t r 4 j o r C l - t .-, ' a - . - a . lin ea r "rJ, J. : 20-10 u jw r .,-.i .1 ; w t % ;. t ; an O htl t . * 1 1 urn* r 1 0 - 1s 5-11 1-11 o 20-21 . 0-11 0-10 C arau ni/C rapltlt* tin C M M Oi i C s* f r/lru s .'H it. A r | a i(< S u lfu r 0-1 0-1 1-10 1-2 1-2 0-1 2-1 2 -i 1-10 1-11 0-3 0-1 1 - 10 2-1 0-1 i - 1C S-lu* :* -4 1 OiTgia 0 Mattai Hua* ai'oa >0taaintaMi t0a1il co lC i a ii 'O a a u mo t/itatat aout a Ut ctt ii ot oa o a ao et tuaatvi tiiquaaiit taaieo>a cIIaCnTtiiOa Figure 2-1 - Schemacic S tr uct ur a of Chrysotil Asbestos m <m a m w ' utti it* im *> U m i a t tutti Figur 2-2 - DTA and ICA Thenaograo f o r C h r y s o c l l c Asoceos (Bendix Daca) transmission vehicles. Phenolic-bound brake lining compositions ccntaming a s b e s t o s s e r v e se one of che bese c l a s s e s of l w - c o s e expencao Le members of che f r i e c i o n couple for a l l - a r o u n d perfo rma nce , a: loo ere r e a b s o r c i n r a c e s , che cemperacure of che f r i c c i n m a t e r i a l , app r-xi.r.aca -y O mils from cha i n c e r f a c e , aay r i s e ro 3Q0*F; che i n c e r f a c e i : s e l : :s hoc ce r. Mosc of che heac i s removed from che i n c e r f a c e by c on v e c c i n and conduccin. (2-10) At high energy a b s o r p e io n r a c e s , heac i s g e n e r a r e : f a s c e r rhan i c can be d i s s i p a c e d and che cemperacure ac che s l i d i n g ; . - : e r faue reaches a poinc where chemical reactions occur rapidly. Surface te m peratures up to 1600*F have been observed or c a l c u l a t e d ; the o r e s e n c e o f o l i v i n e in Che wear d e b r i s confirms c h a t such cemper a c u r e s nave seen re acned. 2 . 3 . 3 . 2 P h y s i c a l and Chemical Changes in L in in g s During Use Figure 2-4 illu s tr a te s che heterogenous nature of a t y p i c a l f r i c t i o n m a t e r i a l composed of che f oll ow in g i n g r e d i e n t s : p h e n o l : : b i n d e r (30 volume p e r c e n t ) , asbestos f i b e r (55 volume p e r c e n t ) , and easnaw f r i c t i o n m odifier (15 volume percent). As a r e s u l t of the ener gy conversion ac the s c a c o r - r o t o r I n c e r f a c e , che c o m p o sitio n of the brake- l i n i n g s u r f a c e is a l t e r e d , a: low s e r v i c e t e m p e r a t u r e s , the phen olic r e s i n and o r g a n i c f r i c t i o n modi- 4 f i e r converc, on the s u r f a c e , to compositions with s l i g h t l y higher c a r h o p oxygen r a t i o s . At somewhat higher use t e m p e r a t u r e s , the r e s in and or g ani c f r i c t i o n m o d i f i e r co n ve r t to carbon more r e a d i l y , and t h i s in turn o x i d i z e s to ca rb on d i o x i d e . Ac the same t i m e , the a s b e s t o s wear, away s o r e r a p i d l y bec ause of t h e reduced b i n d e r s t r e n g t h and volume a: the surface. Figure 2-5 is a photomicrograph of typical wear debris c o l l e c te d 1 from 3endix Research L a b o r a t o r i e s ' dynamometer, o p e r a t e d ac 6Q0*F. As besccs f i b e r s are p r e v a l e n t in s e v e r a l of che wear d eb ris ..articles. Figure 2-6 i s a phot ograph of Che improved wear d e b r i s c o l l e c t o r designed and b u i l t f o r f r i c t i o n and wear r e s e a r c h . (2-11) At s t i l l h i g h e r t e m p e r a t u r e s , the asbestos converts from i t s fibrous form t o an o l i v i n e powder w i t h l i c c l e o r no r e i n f o r c i n g v e l u c . Figure 2-7 shows the f r i c t i o n a l - h e a c - a f f e c c e a l a y e r of l i n i n g which had experienced more chan 10 s u c c e s s i v e scoi>s from 100 mph w i t h o u t s u f f i c i e n t cooling between s c o p s . (2-12) ( a U r g e p i e c e of m a t e r i a l i s about t o s e p a r a t e from t h i s s l i d i n g i n c e r f a c e - an exampl e of macroshear wear, described lacer.) When heac i s generated ac the s l i d i n g I n c e r f a c e oecveen s t a t o r and r o t o r much f a s t e r chan lc can be d i s s i p a t e d , che cemperacure r i s e s sad M y r e e c h e p o i n t where the l i n i n g or pad eomponencs decompos e, o x i d i s e , or e l e . The s c a c o r m a t e r i a l t h e n wears r a p i d l y and che f r i c t i o n c o e f f i c i e n t , u, may d e c r e a s e . This i s f a d s . Fide has been a t t r i b u te d by so m t o e v o l u t i o n of gas at th e s l i d i n g I n c e r f a c e ; on h e a t i n g , che gas expends snd e x e r t s * 'o rce on t h e l i n i n g or pad, tending co push i t sway from t h e r o t o r . ' > 1 3 ) Fade can g e n e r a l l y be a s c r i b e d co the formation, of a g as e o u s , a l i q u i d , or a l o w - f r i c t i o n s o . i d phase ac the i n t e r f a c e , o r to s o m combination of chase phenomena. Figure 2-8 2-9 Figur 2 -7 - Photomicrograph of Croa S e c tio n of F r ic tio n Maearial T u t Speclaaa A fter Mora Than 10 Succeaalva Scop from 100 nph on Bandix Full-B rake Dynaaoaaear i I I 2-11 Mvucai OChUMCu (mmiM I c*ti monmiii im USjICMCilllMi U| |/MlACOMl|IMCaiH AMMIHNWHiKU lAMil lOMMim MMIIMiOMIMOM*!( Hit M V M lI I IlM C M l I t M M H K A t M M CHAR rM W M K M tM rtO H N M lI M OM mOUI C A M M M 6 M O IIM ltM A M im i U I A f |H fm O N M S U M I M O M O M CHAO AAlt N6M OAAOAlWfi im ( m a m iin o o n o iM a OAICHI1 r M I H W O U llf t AWO AMM I A M ft 1 Ml Figure 2-8 - Changes O ccu rrin g in the F r ic tio n M aterial as the Temperature Rises i rnt*C*| (MCn(MKA| MAI*CI CASI IMMMli ft IUMAAIIMUU mvimtutmufiMi------------------------ *-- M t W l --------- ------------------------------------------------------------------------------ WtMtl BHUIMI MftfACft 0<MIOAHI l t Figure 2-9 - Changes O c cu rrin g l Rotor as (lie Temper Rises summarizes c h t p h y s i c a l and cnemical changes which f r i c t i o n m a te ria l as the temperature r i s e s . (2-14) che p h y s i c a l and chemical changes which take pi a c e as che t e mp e r a t u r e r i s e s . ccke p i a c e ir. :r.e Fi gure 2-9 summarizes in the casc-irc.n : c ; : r 2 . 3 . 1 Brake Lining Uear Mechanisms and Ge ne r a t i on of Emissions 2 . 3 . - . 1 Types of Wear Mechanisms Emi ssi ons are gener a t ed by wear . To t he consumer, -.'ear 1: an economic c o n s i d e r a t i o n . To the e n v i r o n m e n t a l i s t , t h e s e emi ssi ons are substances to be c har act er i zed and, if harmful, to be eliminated. From the b a s i c f r i c t i o n m a t e r i a l e n g i n e e r i n g s t a n d p o i n t , wear r e s i s t a n c e is inversely rel at ed to f r i c t i o n level and other d e s i r a b l e per f or ma nce c h a r a c t e r i s t i c s . Li nings wi t h f a s t e r wear r a t e and more f r e q u e n t s u r f a c e renewal g e n e r a l l v have g r e a t e r f r i c t i o n a l s t a b i l i t y . Thi s c i r c u m s t a n c e i s used t o advant age in t he development of primary-type linin gs for duo-servo brakes, where, because of design, che s t a b i l i t y of f r i c t i o n a l p r o p e r t i e s i s o-f g r e a t e r s i g n i f i c a n c e to brake performance chan is wear r e s i s t a n c e ; use of primary i m m g s with coo much wear r e s i s t a n c e r e s u l t s in poor face r e s i s t a n c e , l ess f r i c ti o n a l s t a b i l i t y , and generally poor overall Except in the case of primary l i n i n g s , however, one of t he f o r m u l a t o r ' s o b j e c t i v e s must be to a c h i e v e the h i g h e s t p o s s i b l e l e v e l of wear r e s i s t a n c e . Cont r a r y t o che o p i n i o n of some, maximum l i f e does n o t r e q u i r e a f r i c t i o n m a t e r i e l of maximum p h y s i c a l har dnes s . What i s d e s i r a b l e i s a minimum wear r a t e i n normal l ow- t emper at ur e us e, a moderately inc re a sed r at e at elevated temperatures, and a return to che o r i g i n a l lov-cemperacure wear races a f t e r being s ubj ect ed to e l e vated temperatures. T o t a l emi s s i ons g e n e r a t i o n may be d e f i n e d as the sum t o t a l of the l o s s e s a s s o c i a t e d with five bas i c types of w e a r . (2-15) abrasive wear, e thermal wear, e adhaalva wear, f a t i g u e wear, and macroshear wear As shown i n Ta bl e 2 - 2 , t he r e a r e s e v e r a l p o s s i b l e mechanisms for each type of wear. 2 . 3 . 4 . 1 . 1 Thermal Wear Thermal wear encompasses a group of p h y s i c a l and chemi c a l r e a c t i o n s i n che cour s e of which i n t e r a t o m i c bonds a r e broken by t h e r mal e n e r g y . These r e a c t i o n s I n c l u d e p y r o l y s i s ( t h e r ma l d e c ompos i t i on) , -13 Table 2-2 - Wear Mechanisms in F r i c c i n M a t e r i a l s THERMAL WEAR PYROLYSIS OXIDATION THERMOPARTI CULATI ONMELTING EVAPORATION SUBLIMATION EXPLOSION ADHESIVE WEAR ORCANIC MATERIAL ADHESIONBINDER FRICTION DUST RUBBER INORGANIC MATERIAL ADHESION METAL PARTICLES ICE ABRASIVE WEAR TWO-BODY ASPERITIES SCORING CRACK EDGES PIT EDGES THREE-BODY WEAR DEBRIS ROAD DUST FATIGUE WEAR THERMAL CYCLINC SHOCK MECHANICAL REPEATED BRAKINC DRUMS OUT OF ROUNO DISCS OUT OF PARALLEL MACRO-SHEAR WEAR - ACROSS THE PAD AT CORNERS AND EOCES THROUGH HEAT-AFFECTED LAYERS o x id a ci n , c h e r a o p ir c lc u la c lo n , e x p lo s io n , m alting, e v a p o ra tio n , and su blim ation . Their races in crea se ex p o n en tia lly with tenqperature, and in extrema caaes they resu lt in fade. Pyrolysis probably occurs predominantly at the centers of lin in g s and pads and to a la s s e r e x te n t at the corners and edges. O xidation, on the other hand, probably predominates at the corners and ed ges end i s la s s ssvara at th s can tar. E xplosive r e a c tio n s occur under high ly abusive braking c o n d itio n s, where ths r a ts of heat input i s so high Chse so lid s ere converted to gases w ell beneath the s ur face; because thaaa g s s s s are greater in volume then the s o lid s ehey di spLacc, th ey erea to a p ressu re that ruptures th e lin in g in an e x p lo s iv e manner. Four such r e a c tio n s are represented in Figure 2-10. I t eig h t be chough.: th a t rapid therm al wear occurs on 1% at high soak tem peratures.* In fa c t, however, thermal wear probably Soak tem peratures are tem peratures measured during dynamometer or veh icle t e s t in g , u sin g a thermocouple lo ca ted in the f r ic t io n m a teria l cr in t'.e r o to r , g e n e r a lly at a d ista n c e of 20 to SO m ils from the s lid in g in ter:.:ce 0 CaC03 <) "*CjO Ul * C02 () * 0 CASHEW OUST (*) -C O j ( HjO (1 C (i) ( 0 ASBESTO S-HjO (1 OLIVINE (J ASBESTOS FIBRILS fi 0 PHENOLIC RESIN ~ C 0 2 ()< HjO () C !i> THE BRASS CHIP CONOUCTS HEAT RAPIDLY INTO THE FRICTION-MATERIAL SURFACE. IS): SOUO lGI: GAS F i g u r e 2-10 - Mechanism of Expl osi ve Thermal Uar occurs at a p p r e c i a b l e r a c e s ac low soak te m p e r a t u r e s as w e l l . I : has been shen th a t the m a te ria ls in a s l i d i n g f r i c t i o n couple contact each o t h e r at the t o p s of a s p e r i t i e s on t h e i r s u r f a c e s . There i s c o n s i d e r able evidence to indicate that tie temperature increase at these asnerl- .es for low s l i d i n g speeds i s r e p r e s e n t e d by the e ^ u a t i o n ^ " ^ ' 2-1 T - Tq ( g u v w / i a J ) ( 1 / ( k j + k j ) J where T is the " < 1 ^ te ste r ature T is the soak temperature 0 g i s t h e a c c e l e r a t i o n due to g r a v i t y u is the coefficient of frlerlon v is the sliding velocity w is the load os the asperity 2-15 a is the radius of che a s p er it y junction J i s the mechanical equivalent of heat k. i s t he t he r ma l c o n d u c t i v i t y of the d i s c <2 i - the t he r ma l c o n d u c t i v i t y of the s l i d e r .''.edifications of this equation have also been developed for high sliding s peeds . Exper i ment s i n d i c a t e chat the f l a s h t e mp e r a t u r e nay be as high -s U0G*F ( 760' C) i f t h e soak t e i ^s er a t ur e i s 650*F ( 3 4 3 * 0 . This f l ash temperature is high enough to cause rapid l o c a l i s e d p y r o l y s i s of the o r g a n i c compounds used i n f r i c t i o n m e t e r a i s , as v e i l as conve r s i on o: f i br ou s a s b e s t o s to p w d e r y o l i v i n e and t r a n s f o r ma c i n of p c a r l i t e to martensite in the c a s t - i r o n mating surface. 2 . 2 . 4 . 1 . ? Abr as i ve Wear Aor a a i ve wear i s of two t y p e s : cuo-body wear ( F i g ura 2--LI) and c h t e e - b o d y wear ( Fi gur e 2 - 1 2 ) . Plowing by a s p e r i t i e s on the r o t o r s u r f a c e and pl owi ng by edges i n rough-machined, s c o r e d , cracked, or c-orroced ( p i t t e d ) r o t o r s are examples of two-body wear. Cr i ndi ng by -ear d e b r i s and by f o r e i g n p a r t i c l e s such as s a nd, c l a y , mud, or s a l t i:i the s l i d i n g i n t e r f a c e i s t hree-body wear. Abr as i ve wear would be e xpe c t e d t o i n c r e a s e wi t h tem p er at ur e. I t i n c r e a s e s a l s o with the braking load and with the concen t r a t i o n , s i z e , and h a r d n e s s of f o r e i g n p a r t i c l e s . I t may be accompanied < by n e g a t i v e f a d e . Figure 2-13 is a Sendix scanning electr on photomicro graph of a d y n a mo me t e r - t e s t e d f r i c t i o n m a t e r i a l showing t he a b r a s i v e wear t r a c k s on toe s u r f a c e . S e v e r a l adher e nt wear d e b r i s p a r t i c l e s a r e s i mi l ar in s i z e t o che vear track widths. 2 . 3 . 1 . 1 . 3 Adhesive Wear Adhesive wear, i l l u s t r a t e d In Figure 2-14, i nvol ve: the adhesion of o r g a n i c and/ or inorgani c ma t er i a l s to the r ot or and the subsequen. t ear ing o r s e p a r a t i o n of chtss macarais from the Lining or pad. Organic c o n s t i t u e n t s of f r i c t i o n materials include the b i n d e r , f r i c t i o n m o d i f i e r s end e l a s t o m e r i c compounds. I nor ga ni c c o n s t i t u e n t s i nc l u d e s i n e powder, b r a s s c h i p s , and a s b e s t o s . L i t t l e i s known about t he t e nde nc y of ehese m a t e r i a l s to adhere t o t he c a s t i r o n u.ed i n t o d a y ' s d r u s a end d i s c s , chough e x p e r i e n c e wi t h hoc e l a s t o m e r i c com pounds suggests t h a t elastomers are very likely to s t i c k . Experiments at Bcndlx Resear ch L a b o r a t o r i e s i n d i c i e s thee b r a s s chips w i l l a l l o y wi t h c e r t a i n n o n f e r r o u e r o t o r a l l o y s . (2-18) y^n Chi * o c c u r s , me t al is t r a n s f e r r e d f r o a the r o t o r to the l i n i n g , s cor i ng the s ur f ace of the acor and i n c u m s u b j e c t i n g t h s l i n i n g t o a hi gh r a t e of cv*boay abr a- v* wear. OIRECTION Of RELATIVE MOTION \ V a sper it ies in teractin g TO FORM WEAR DEBRIS CTION MATERIAL ^ \ \ \ s ' s N\ \ \ \ \ \ \ W ' F i g u r e 2-11 - Mechanism of Two-Body Abrasi ve Uear ROTOR W6 Afl OEBRiS DIRECTION OF RELATIVE MOTION F igure 2-1 2 - Mechanism of Three-Body A brasive Wear 2-17 OIRECTION OF RELATIVE MOTION ROTOR ,/ / / / C t t d F lg u rt 2-14 - Mch in i* o f A dh tilv Utr 1 I Adhesive wear probably i n c r e a s e s with temperature, b r a c i n g l oa d, and che c o n c e n t r a t i o n of adhcrenc eompontnes in :he f r i c t i c r . m a c e r i a l . I t i s a l s o eaused by ch< pr e s e nc e i n che f r i c c i n ma t e r i a l of metal p a r t i c l e s capable of solution in or reaccin with the rotor a l l o y , i n c r e a s i n g wi t h the s i z e and c o n c e n t r a c i n of such p a r t i c l e s . Because t h i s t y p e of wear can cause s t i c k - s l i p , l c may be a s s o c i a t e d with brake noise. 2 . 3 . A. 1 . 4 Fat i gue Wear Fat i gue wear (Figure 2-13) I s most commonly observed i n me t a l b e a r i n g s . However, i c may a l s o be e x p e r i e n c e d by organi c f r i c t i o n m a t e r i a l s , o c c u r r i n g i n cwo forms, t h e r ma l and mecnant cai . Thermal f a t i g u e is caused by repee ced h e a t i n g and c o o l i n g . Such r e p e a t e d t e mper at ur e changes l npos c c y c l i c s t r e s s e s on t he s u r f a c e m a t e r i a l , which heacs and c ool s more r a p i d l y than the bulk m a t e r i a l and chus expands and co n t r a c t s to a g r e a t e r e x t e n t . Because of t h e i r low t h e r m a l c o n d u c t i v i t i e s , the t h e r m a l g r a d i e n t s and r e s u l t a n t t he r mal s t r e s s e s I n or gani c f r i c t i o n m a t e r i a l s may he h i g h e r than t hos e in metals. Thermal-shock cr acki ng may be t hought of as a s p e c i a l case of thermal f a t i g u e , o c c u r r i ng as a r e s u l t of a s i n g l e abusive loading. Mechani cal f a t i g u e is ca us e d by r e p e a t e d mecnamcal s t r e s s i n g . Because of the frequency of b r a k e use, f r i c t i o n ma t e r i a l s are s u b j e c t e d repeat edl y to both compression and shear forces. Addi t i o n a l s t r e s s e s ar e al so a p p l i e d r e pe a t e dl y i f drums are o u t - o f - r o u n d , if d i s c s are o u t - o f - p a r a l l e l , or i f r otor t hi ckness i s not uniform. Figure 2-13 shows the i n i t i a t i o n of f a t i g u e wear arcunc the l a r g e castiew p a r t i c l e . Thi s ma t e r i a l s w e l l s when heat ed and thus the s ur fa c e w e a r s . After c o o l i ng , the p a r t i c l e c o n t r a c t s , cracks, and p u l l s away from t he edges, J hen the p a r t i c l e i s compl et el y loose, i t can f a l l out. 2 . 3 . A. 1 . 5 Macroshear Wear Three t ypes of ma t e r i e l remove1 f a l l i n the cat egor y of macrosnear w ea r, which i s i l l u s t r a t e d in Figure 2-16. A f r a c t u r e , i n s h e a r , may oc c ur a c r os s the e n t i r e br ake pad u n d e r e x t r e a e l y heavy l o a d i n g , e s p e c i a l l y i f t he f r i c t i o n m a t e r i a l bar. p r e v i o u s l y bean weakened by h e s t . This i s a sudden r a t h e r than a gradual type of year. Fr act u r e at t he edges and c o m e r s of a piece of f r i c t i o n m a t e r i a l i s a n o t h e r type of macroshear we a r . Oxi da t i on of organi c com ponents weakens the f r i c t i o n material at these locations. 2-19 Figur* 2-15 - Mechanism of Fat i gue Wear DIRECTION OF RELATIVE MOTION ROTOR GENERALIZED!* fa ilu r e through; t kDIRECTION OF h ea t a ffec t eo ZONE \ fric tio n m a t er ia l NORMAL FORCE '\\W < ^ NS' vv s\ N\ \ \ ^ ^ \ \ ^ ^ \ \ \ \ \ V ' ` LOCALIZED FAILURE AT EDGE WEAKENED BY OXIOATION Figure 2-16 - Me.iianlsa of Hacroehear Wear Fr act ur e at che edges and corners of a piece of f n o t i o n j i t e r i a l i s a n o t h e r type of macroshear wear. O x i d a t i o n of orsjar. : components weakens the f r i c t i o n material at these l o c a t i o n s . A t h i r d type of macr oshear wear can o c c u r when a f r i t cion m a t e r i a l such as chat shown in Fi gur e 2-15 is s u b j e c t e d to heavy ' l adi ng f o l l o w i n g thermal a b u s e . The h e a e - a f f e c t e d l a y e r i n die ma t e r i a l p i c t u r e d i s about 100 mils d e e p , and from t h i s l a yer o r g a n i c m a t e r i a l has been removed by p y r o l y s i s . If s u f f i c i e n t l y weakened, such a l a ye r can be s h e a r e d away by a s i n g l e , heavy b r a k e a p p l i c a t i o n . Whatever t he mechanism, macroshuar wear i s promoted by .lonuniform l o a d i n g and by o x i d a t i o n and charmai d e g r a d a t i o n of the b i n d e r . I t Is most l i k e l y to occur a t el avaced t e mp e r a t u r a s and under s e v e r e b r a k i n g c o n d i t i o n s . I t s end p r o d u c t s are t y p i c a l l y Large f r a g ments of . f r i c t i o n m a t e r i a l chat leave t he s u r f a c e rough. These f r a g ments s u b j e c t t h e remaining f r i c t i o n m a t e r i a l to plowing or a b r a s i v e wear, and whi l e they are p r e s e n t in the i n t e r f a c e , f r i c t i o n behaviour w i l l be e r r a t i c . 2 . j .4 .2 Predominant Wear Mechanisms The predomi nant wear o r e m i s t l o n s - g e n e r a t i o n mechanisms may be summarised simply ( F i g u r e 2 - 1 7 ) : C2--19j Below 450*7: Abrasive and a d h e s i v e wear. Above 450*F: Thermal wear. Figure 2-13 i l l u s t r a t e s the wear loss of t h r e e d i f f e r e n t kinds o: f r i c tion materials as a function of temperature, i l l u s t r a t i n g these predomi nant wear mechanisms. 2 . 3 . 4 . 3 Wear Equation Recent work a t Bendlx Research that each f r i c t i o n material wears according to t i o n . ( 2- 20) Laboratories has a u n i v e r s a l wear indicated equa W k pa Vb cc or l o g (AW) log k * a log P b log V + c l og c 2-21 >10'>(nai Fi gure 2- 17 - Predomi nant ' Jeer Mechanisms of F r i e s i a n M a t e r i a l s MMMU MU Figure 2 - 1 8 - V a r i a t i o n of F r i c t i o n M a t e r i a l Wear w ith Temperature ' 2 wittre i'.v t s t h e weigh: l o s t k i s che wear factor < i s che load is the sliding velocicy c i s Che cime of s l i d i n g , and a , b , c are conscancs c h a r a c t e r i s t i c of a given f ri cc i on c.r-n.e. Uhen f ur c he r devel opei , t i l l s equa t i on w i l l be u s c f . . p r e d i c t i n g wear (and emissions) under var ious driving conditions. 2 . 3 . 5 Emissi ons of P a r t i c u l a t e and Caseous Cmiss: on s 2 . 3 . 5 . 1 Drum Brakes Caseous decomposition products ir d r u r brakes arc from two a r e a s : The space between che r o c a e i n g drum and the s t a t i c s backing place, Die s n a i l hol es in che backi ng p l a c e i c s e i f ( e . > ; . t clearance holes, brake adjusting sloe, etc.) P a r t i c u l a t e s are e m i t t e d from the same two a r e a s , ale. on Iv s mal l p a r t i c u l a t e s would come chrough che hol es i n che backi na ?'. in or urn b r a k e s , some p a r t i c l e s are noc e m i t t e d but r ema i n in che r o t a : d run. 1c i s e x p e c t e d chat some of t h e s e p a r t i c l e s woul d evencuai l v m e - : t : ed chrougii che space oeeween t.ne r o t a t i n g drum and scacicr,ary d e - ;1S Pl a t e . Al s o, some l a r ge p a r t i c l e s would be "ground up" ana e m c e e as a number of s m a l l e r p a r t i c l e s i f they a r c crapped between che f r i c i mat or cal and drum on s ubs e quent br aki ng o r i f they ar e crapped between t i e r ocacing drum and s t a t i o n a r y backing p l a t e . If the brake shoes a/ uf r : w e e d c o n s t r u c t i o n , then some p a r t i d e s ' c a n be cr apped in the r: ivj 1us and t hus r e t a i n e d in che brake. I f convect i ve c e d i n g o f drum brakes i s improved in :: f u t u r e , as Is d e s i r a b l e for s a f e r o p e r a t i o n and longer dr i v i n g l i f e , : is l i k e l y that, fewer p a r t i c l e s will remain crapped. Die p ar ti cl es o m i t t e d , how ever, w i l l pr obabl y be l a r g e r , as they w i l l be s u b j e c t e d t o g r i n d i n g a c tio n for s n o r t e r periods of cime. 2 . 3 . 5 . 2 Disc Brakes As the d i s c br a ke is e s s e n t i a l l y an open braking s v s t v i t is expected chat a l l p a r t i c u l a t e and gaseous decomposition product-, -ill ba e m i t l t d . However, a smal l amount of p a r t i c u l a t e s c o l l e c t ; - c. r i v e t h o i * of r i v e t e d d i s c brake pads and on some area.* o: cne cal i per . * 2.3.3.3 Clutches In the dry c l u t c h e s commonly i n use on " s t t c k - s h ; : t " cars t here a r e very few openi ngs for gas es and p a r t i c l e s to escape. The ruo aain areas are: `Die a r ea around t he c l u t c h f o r k , which genera i l v -.as a rubber boot on i t for p r o t e c t i o n ot the clutcr. iron road spray, sand, etc. A s mal l openi ng a t t he lower f r o n t of the c.'utcn ca d r a i n any o i l , w a t e r , e t c . , which may get i nt o cne clutch, Because. of the c o n s t r u c t i o n , many p a r t i c u l a t e s remain in the cluccn housing. 2 . 3 . 6 D i s t r i b u t i o n and Changes In Brake and Clutch Emissions Entrapped gases and p y r o l y s i s gases r el e as ed during braking or c l u t c h s l i p p i n g w i l l be hoc enough t o mix r a p i d l y wi t h thp surrounding a i r and become p a r t of the a i r wake of t he c a r . The h i g h e r mol ecul ar weight v a p o r s w i l l condense and e v e n t u a l l y s e t t l e t o the ground. The low molecular weight gases w i l l dis per se es part of the loeal atmosphere. Some of t h e c o n d e n s i b l e vapors may, of c o u r s e , s e t t l e on s ma l l , a i r - bnr ne dust p a r t i c l e s and coul d be c a r r i e d i n t o t he r e s p i r a t o r y syst em as par: of the breat hin g a i r . The p a r t i c l e emi s s i ons w i l l d i s p e r s e i n d i f f e r e n t wavs dscd ing on t h e i r s i z e , s h a p e , and d e n s i t y . S ubml c r omet er - s i ze p a r t i c l e s , re gardless of shape, w i l l o r di nar i ly remain a i r- b o r n e u n t i l they are scrubbed o u t by r a i n f a l l or some o c h e r s e p a r a t i n g a c t i o n . In e f f e c t they became a l o n g - t i m e p a r t of the at mosphere. S p h e r i c a l p a r t i c l e s i n the 1.0 -m to 10 .m di a me t e r range w i l l s e t t l e , under g r a v i t y and in s t i l l a i r , a t v e l o c i t i e s from 12 :o 1000 c m/ hr , a c c o r d i n g to St okes ' l aw. I r r e g u l a r l y shaped p a r t i c l e s of s i m i l a r s i z e and i n t u r b u l e n t a i r w i l l s e t t l e a t much s l ower v e l o c i t i e s and coul d remain a i r - b o r n e f or heurs or days. These p a r t i c l e s cause cne g r e a t e s t aggravaclon i n the human r e s p i r a t o r y syst em because they c o l l e c t i n the tracheobronchial r egi ons end, to some e x t e n t , In t he a l v e o l i . P articles from 20 um t o 100 vm In di a me t e r w i l l s e t t l e as p a r t of the duet tr a il l e f t by cha c a r or w i l l c o l l e c t with any l a r g e r p a r t i c l e s i n mechanical t r a p s i n t h e c a r . Event ual l y t h t e l a r g e r - s i z e p a c t ) c it s w i l l f a ll or be shaken ou t of the car and become p a r t of the road dust. INFERENCES ( 2 - 1 ) J. Lynch, " B r a k e Li n i n g Oecompos 1 c i on i'rodui . ' 3 , ' . . . r " P o l l . C o n t r o l As s o c . , <1_3, .'.'o. 12, 324 ( 9 o 3 n ._.2--2 5 S. 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