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FILE NAME: Phenolic Resins (PHR) DATE: 1972 Feb 10 DOC#: PHR050 DOCUMENT DESCRIPTION: Minutes of the Asbestos Committee Meeting; from FMSI File er vgr^iG oi* the egerrcs g^'.^y 1 Thursoay, February 10, 1972, at 9:30 A-w* at the i n s t i t u t e Offi ce, -210 Route f i , Faramus, N.J. 07652 H f o r i ? ooir^ENT I. H. .Veaver, Chairman J . C. Henning ` tf. 3. Re i t ze W.G. JacWo ( f o r W. Spurgeon) J . 3 . Graham Ray b e s t os-*Manhattan, Inc. Firestone T i r e 4 Rubber Co., .Vorld 5estos Division Jchns-Manvi1le Corporation oendix Corporation Sendix Research Laboratories Carlisle Corporation . Molded M a terials Division MfiT p a c S c ^ E. H. Feierabend ntur oq pqcScNT < . S r i . L n . 4 Abex Corporat ion _ American Srakeblok Division , - f r i c t i o n . U r i . l . S l . ~ i . r i , I f t itut* Th. meeting v , . d i e d to ord.r by - r . Chairmen, et 9:30 .. UIM1JTFS OF PQCV'CUS MEv INS The Secretary read a s u n ra ry o fih s m .n u U s Seotember 15, 1971. Thee, . . n u t . . had been released, * for th e ir acceptance wee entertained. Upon motion duly mad., seconded and unanimously pa.sad, it was RESOLVED, to aoo.pt th . m inut.s of th . S.ptsrnbar 15, 1971 m .U * t at distributed. A b rie f reviser --> r *d 0^ ` i* *C(OSHA)*sassion*hatpin ashington Safety and i! t i t t S t d o df J-M attanded th is sass.on, on January 26, 19 2. Swetonic had told him as and th . Secretary sunsmr, * * * \ "r ; . ^ * f ety - no. th . smh.s.s f o l i o . . . OSHA p r , v , o u s l y ad em on.e.d ^ ^ . U . c k (s.d.stos, i , on h M lth - fiv a ^ n d u s tr..a l.s u b s ts n e e s e . iim. d i a t . l i l i e s , le a d , c o tto n dust snd carbon m o n o s.d .). uu , : e s :* Asses*'. -sy :5rr11 .set mg a s b e s ' o s . OSHA is suggesting " ' "" ^ . ^ ' r M r e s e n t a U v c : : r i u " " *;* - - . t * . * ? r u * S i "S * on 1. nd.et*d t f t ooptf*` ^ J " i " r , / ee (OSHA ,s apparent l y c s t n w i s Ac a r e m s r x QreiQC STANS^-j I ,, e, d standard by CSHA is now 5 ,he Pr3-;* i e r st h/ di amet er r a t i o , wi h.? :: ..e , ` = ba Jonsicarad , f i b . r . ^ T h , , ^ f ^ c r o n i tr ^ an w>e screened with thire studies t h . optic al "''=r ='" f ' i e r ; ',, the l e s s the" 5 ccncernmg asbestos Hders el ec*t rron micrroossccoopryy*- . '* 5 y . h* ta W - i e M * *; !br ts { r f U Safety Guide 3. At 1 for reference: ^ ^ u -u ' . - shut da' n- 4. * tk. Ashest"*; * R*~e a ^ | CLiLu77il i a n d , Asbestos-oaseu-^ t Moulded Comoounds, Asbestos Rei'nforced Resinous Con tic l'a n d -S afe ty Guide #3. ,,Environm"en,teeli-iCpaorni+aproori'Cuoufltai t t e e r 'Secretary \ l a -Pa r k ' S t r e e t London,. England 'V-LAS.. . n . r i c u p p i m o n - T m S CTJSSli - " T d c g h Mr. the SA January " ! \ l Cu U t i o n s sUtu, of ascastas r.g u l. s" b" nS ' n' r'", d in the U.S. ^ u_ mously _ ( i , it . a s Upon n o tio n duly " da, saco f jU re la tio n s RESOLVED: U in r^ 0V " Fr'et'i o n V a t e r i a l s S U " " ' known t o the r r ' t 0f our meetings to and to forward minutes o B ritish Council. ______ rtnPA fAjA/NAj. AW efgnAi&tiriN OF iftlSeQnMw wWiITTWH *careros J.NFQPMAT-- R-- th johns-AUnville, lt . . . notad tb .t W . W H *" n , r . T - d*; ' a u . ruci CCC'JpA* ' t 1jal SiFE~v " 'ip ^v i 3*^:t iv ' z- ) Mr. Weaver discussed seme of the bac*grouna for the praoosec CSHA S t a n d a r d ^ f o r Exoosure to Asbestos Dust, P-ocosed rule .maki.?s for these standares aoseareo in the Fdrai =e gi s : s r or* Decemoer 7, 1971 and_January 12, 1972.- (Cccies were d i s t r i but e d by the I n s t i t u t e by'mail to menoers ot*' the Asbestos Study Committee) Mr. Weaver is the Industry r ear e s e n t a t i ve on the Advisory Committee For Asbestos Standards set up under the Cccusati ana 1 Safety and Health Act. He advised t ha t while the proocsed st ancards are For 5 Fi be r s / cc time weighted average airborne concentrt ion of asbest os dust, the others on the Advisory Committee may push for 2 Fibers/cc. CSHA w ill accarently enforce t h e s e regulations and if exoerience in r e la te d safety enforcement is any c r i t e r i a , Fines or plant closings may be used For enforcement purposes, ./hule it is c u rr e n tly too ' l a t e to pres en t w ritte n comments, th e'h e arin g s a re to be held on March 14, 1972 in Washington. In order to be heard, a person must File a n o t ic e of intention to appear no later than March 1972. The n o t ic e must s t a t e name, a d d r e s s , approximate time required For p r s e n t t ion, and a statement must be included in d ic a t i n g the ^ / p o s i t io n to be taken by the i n d iv i d u a l. ' The Chairman and Mr. P.eitze i n d ic a t e d that these CSHA regulations were now of prime importance to m anufacturers of asb esto s brake linings and c lu t c h Facings, and the S e c re t a r y was direc te d to inform the membership concerning the proposed standards. ENVIRONMENTAL PROTECTION AOENCV fS=A) The EPA's emohasis in t h e i r proposed emission standards For asbestos did not use numerical l i m i ts on a irborne asoestos, but concentrawed on F i l t e r s and c o l l e c t o r s - c o n t r o l practices". While these are important to a ll manufacturers of asbestos brake linings, they are p r a c t i c e s and standards which, a t t h i s time, seem reasona ble. The OSHA Standards a re the more immediate problem. ENVIRONMENTAL PROTECTION AGENCY - EMISSIONS FROM ASBESTOS SPAKE LININGS Dr. Jacko advised that the Sendix Corporat ion-s s t u d i e s for the t?A on emissions from brake l i n i n g s may not be complete on schedule, and that Sendix had requested a time extension on t h i s work that would move their final report barck in to the Fall of 1972. Dr. Jacko indicated that the max imum a s b e s t o s f iber ..m.brake 1mi ng debris is r unnThg^fiou t 15. * STUDENT PAPER - ? IHOC ICAL EEEECTS_QF .ASBESTOS QN THf HUMAN ORGANIjM Copies of a term paper by M s'B e th 'K ru llp C h e m istry ^ u n iio r..a t. Mundelein-Gollege* in Chicago were d is trib u te d to the'm embership, It would appear th a t t h is papar may be an in te re s tin g source of med ical - 3- mutes orr* Asbestos Stucy Commf.ee Meeting r e : r ,,acv bibl iography concern,ng esb.stos; (Th. paoer 5 f o r c e d to th. I n s t i t u t e by Mr. J . Greener, President of r . M . - . l . ) f "IJ | p.CKjT Cpp V tS `-?L'^G *S3 EO'UO :\'s Mr. J U i t z e discussed the equipment necessary for measuring asoestos concentrt ions. The t es t is run with a vacuumpump pul l i ng fibers into a f i l t e r which is then examined under o p t i c a l microscccy. (Mr. P.eitze di scussed the equipment and procedures in more detail in an afternoon session) . Dr Jacko said t h a t the sub-5 micron asbest os f i b e r s *ere being examined with e l e c t r o n microscopy. He f e l t t ha t as *r f i ber s were concerned, these sub-5 micron f i b e r s might -e . r 5e t s of the r e g ul a t o rs in the future. Mr. Graham asked whether there were any automatic ecuipm-nt for measuring the a s b e s t o s concentrati ons - e i t h e r in existence or planned.8 It was s t a t e d t hat the E?A had made a J * ~ * * fc ^ T ; 9* 1 for desi gn of equipment for automatic measurement, but ap-arently they r e c e i v e d no response. . As of now, o o t i c a l microscooy with the membrane f i l t e r is the only ^ recognized method. Agarrrns study commute; - putlse coupsi The m . r b . r s i n d i c t e d t hat t h , Committ. should e x i s t far^sdrssn.ng and p a s s i n g on i nformation to t h . Berbers. T ey e -- C d l i t t e . snould b . used as a v e hi c l e to nomment r e g u l . t i o n i propob.d by the vari ous r e oe r al and St at e . r , i t is f . l t f a t individual company r e s p o n s e to CSH or w s i ; - . i : ; ; : : 1- - A - ^ .......... ^ s^ rg s3 srt szstsss& & < . Son. members f . H t h e t t h . Stu^ M rav. tc exoand beyond a sbest os - such as `n t V l i ,C \ ? `? L t other t i c ! As o r no* t h . prime ta r g e t is ti bt m a t e r i a l s , if consi dered of importance to t he members, w.i studied* Anoth.r suggsst ion . . . th st th . C o m u tt.. o o n . i * " ^ ,, d c t . surv.y on th . method. for disposing of b r.k . i i nmg grino.ng .w :r +K* 55 3* - soe s i c sS t-cv as Meet :rg sa.-.a- r j r . M, Jacko requested that His race be added to the sresics Study Committee mailing l i s t , in a d di t i on to t hat or* Dr. Sou.-g- it *^_s suggest ed that other manufacturers of brake linings, . outside the membership, be advised of these proposed st anca' - s S CShA. ' Summaries of the a f t e r n o o n ' s or e s e n t a t i o n by Mr. Reitze will be d i s t r i b u t e d to the membership, ( L'oon motion duly made, seconded and unanimously passec, it was RESOLVED: to adjourn. Adjourned a t 12:CC noon E. W. Drisiane Executive Secretary * cc: Committee Members J . Greenen L. S t i c k l e s B r i t i s h Counc i 1 Al A/NA section : - INTRODUCTION ANT) ORI l" SUTDVJtY The c h r y s o c i l c form of as be s t os Is a major c o n s t i t u e n t in iu:o-ct i v e brake l i n i n g s and d i s c pads, and i n the f r i c t i o n m a t e r i a l s uscu ... : 1 utcnes. These components are expendable. In typi cal passenger cc: s e r v i c e , drum l i n i n g s wear out in about 0, 000 m i l e s , di s c pads m !;> 30, 000 mi l e s , and c l u t c h f aci ngs in aoout 70,000 mi l e s . There nr e, e: c o u r s e , wide v a r i a t i o n ? ' i n the s e r v i c e l i v e s of t he s e components, -:; i depend on the n a t u r e of the f r i c t i o n m a ' . e r i a l s us e a , on d r i v e r n e o n s , end 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 fr-.u; i 3 anu 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 a r e bound t o g e t h e r py phenolic r e s i n s . because of t h e i r hizh concent of organic s ubst ances , suen f r i c t i o n m at eri al s are cl as s ifi ed as "organic." Asbestos-f ree ;3Pi - a t e r i a l s wi t h a hign concent of m e t a l l i c s ubs t a nc e s are c i . i s s i f i e u as " s e m i - m e t a l l i c . " Over 99 p e r c e n t of che aut omot i ve f r i c t i o n n.i- : r i a 15 used todav ar e o r y a m e s . The mechanisms by which organi c f r i c t i o n m a c e r i ; I s wear can be c l a s s i f i e d under f i v e h e a d i n g s : t h e r ma l , a b r a s i v e , a. h e s i v e , ma c r e s n e a r , In.-i f a t i g u e . Thermal , a b r a s i v e , , and a d h e s i v e wear are c ons i de r e d cn no ;.ne most i mp o r t a n t mechanisms, thermal wear pr edomi nat i ng above 50*.", acrasi ve and adhesive wear predominating below 50*F (the temperature ,,ein.g measured by a t he r moc our l e in the r o t o r , about 0.050 inch from tne 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 pvrol yze or o x i d i z e , and are emi t t ed tc 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 c . e s wnich a r e t r a p p e d i n the brake (or c l u t c h ) hous i ng, or f a l l to c..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 t rap as much as -rum br akes . Most of che a s b e s t o s i s h e a t e d to t emper at ur es hi gh encugn :o cause c h e mi c a l 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 m i t t e d as u l l vi ne or f o r s c e r i t e p a r t i c l e s . i.'hen che 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 c 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 t h e e l u e e h mechanism, 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 problem may e x i s t . Consi dered in a n o t h e r l i g h t , cher t a r e perhaps one b i l l i o n p ie c a s of f r i c t 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 t e d and ground to d u s t . The brake syst ems in the v e h i c l e s "u t i l i z i n g t h e s e f r i c t i o n m a t e r i a l s can thus be con 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 com p o s i t i o n s of che 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 ai-.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 . * . 1 --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 iv in g ( c i t y , expressway, mountain; driver habits , etc.), br ake system d e s i g n , and brake type (drum or d is c ) , rotor condition (surface roughness, scoring, cracking, pitting, etc.) . rotor design ( e . g ., solid or ven tilated discs, fianea 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 t 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 tha f r i c t i o n m a te r ia l. In : i s program a p a s s e n g e r car of medium weight ( t e s t wei ght : SCO pour.es), produced in 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 :he f r o n t , end 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 car 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 hraxlnfi cannot be sim u la te d r e a l l s t l c a J ly nn small-scale friction test-machines with tha present s t a t e of the are; (2) f u l l - s c a l e brake and c l u t c h dynamometers provide fa* -iy good s i m u l a t i o n , and can be uaed f o r check ing out the emissions collection system; separate testa for brakes and c lu tch es would be require d, however, thus increasing ~ program c o s t s , whertes on th e 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 that 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 l e s a s;s were run, usino r r : c : : : r , s a u r a i : (mula t i on Friction Materials :. ema r *.s Original Eq u i p me n t OEM1 Disc Front UEM Drum Rear Class A organic c :s: Partial Reline AM2 Disc Front Used OEM Drum" Rears No m e t a l l i c c h i p s ; Discs and drums no: turned Full Reline AM Disc Front AM Drum Rear Disc pads and seconcari cs c o n t a i n b r a s s c:\;,:s Di scs an-. rums i ..me r . us s e l e c t i o n has s e w r . u S e c u r e s . 1c pr ovi des a r e p l i c a : a -esc :hus g i vi nc an esti mat e of r e p e a t a b i l i t y . Ic includes . secondary c o mbi na t i on m a t s e r v e s both OEM and a f t e r m a r k e t s . 3-e 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 , ; ` OmC ' m.i rv % : nr lutics LHwi'JwCe one combi nat i on (two m a t e r i a l s ) from one of the l a r g a r a f t e r ma r k e t s e l l 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 >.i-e aca on t he e mi s s i o n s at var i ous st ages of l i n i n g l i f e . It me luces^two f f e ' e n c 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 . 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) select ions . The c o l l e c t i o n o: p a r t i c u l a t e and gaseous . m i s s i o n s from any ' - emc. u fri c t i o n couple has never before, to the authors' knowledge.been r e p o r t s ^ , . . e l i t e r a t u r e . To de f i n e the e x t e n t of these e m i s s i o n s , a corno m a : ton s e p a r a t i o n and s t o r a g e c o l l e c t i o n system wuu d e vi s e d. Unique emissions c o l l e c t o r s f o r boch d i s c and drum b r a k e s , ' and f or a c i u t c n . were concemeu - e s i a 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 whi ch 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 r i v e t h o l e * , and on the brake drum; a s u r f a c e s sample winch mc . u c e d the wear d a b r i a on th e orake and c o l l e c t o r shroud s u r f a c e s ; anc an a i r n o r - s ampIt c o l l e c t e d on membrane f i l t e r e . The v e h i c l e wee equipped wi t h 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 e d i a c brake c o l l e c t o r end e r e a r drum brake c o l l e c t o r ware i n s t a t e i n t S r i i S l . i d . of the v e h i c l e . The c l u t c h wa. s e e l e d by c l o s i n g me OEM - O r i g i n a l Equipment Man uf act ur ers 2AM - a f t e r m a r k e t fi. o. l 1-3 , e, ir: i t s c a s i n g . The l e f t wheel brak.es were l e f t m t h e i r . r a. f . , _ r n: i on and were used to moni t or the o p e r a t i o n of the snrovced u . j . ' . a r d e b r i s was al s o caxen from the l e f t br akes ; the a-cur.is o : -- a ; j l l e u ' . e d and i t s composi t i on were used to de mo n s t r a t e t - : f e 3- f . j d i d not s i g n i f i c a n t l y a f f e c t the o p e r a t i o n of the or.-*e< : c <. .SilOnS C o l l e c t o r s . ; . n.ni^h 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 ; a . re r - ' u. j - r r i c t i o n 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 co l i c : : ; : . - . -. .n.i t ; jn o f e o1len t i s , no one t e s t a d e q u a t e l y matches d n v : - ; : f u . f . o n s wi: i c h 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'..-, ; : tec.ir.e iK-ros^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 schedul es were chosen and each was f ol l owed by a measuteoents procedure (take emissions samples, measure wear, inspect systems, and r e p l a c e worn p a r t 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 Lr n. i s n (A.B.) Basel i ne, and D e t r o i t T r a f f i c - Represented low-temperature *esti.O[' . The f i n a l f o u r s c he dul e s - 10-Stop Fade, A f t e r Fad (A. F.) 3asei i n e i 15-St op Fade, *nd Fi nal Bas el ! * - 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 abrusive tasting. 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 t r d the p o s s i b l e t e s t mi leage 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 t;-.e f r o n t 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 31CC 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 ex ce p 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 ...a proaram. P r i o r t o v e h i c l e t e s t 1, a Burni sh s che dul e was performed and the temperat ures f o r the r i g h t fr ont di s c brake wer' found to be near COT. The t e mp e r a t u r e d i f f e r e n c e . AT, 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 t h e r m a l * c o n t r o l ai ds leduced the AT to a range of 115 to 160*F. Most^impo an* 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 . ro... abou' 100*" t o about 300*F. The brake s hr oudi ng di d not p r e s e n t any prai. i e-s on hot 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 i r o n : Praxes remained between 100 and 140*F - h i l e t h a t f o r the r e a r drum oroita remai ned between 10 .and 30 F. The r an g e of a s b e s t o s co n te n t in the brake em iss io n s f o r ve h i c l e : a s t s 1 and 2 went from a high of 1.65 p e r c e n t to e low of 0.03 percent for the 90 a n a l y s e s ; 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 a h i c l s t e s t 1 was 0.40 p e r c e n t and f o r v e h i c l e t e s t 2 was 0 25 s e r e c n c . For v e h i c l e t e s t 3, the range of a s b e s t o s c o n t e n t was from a high o f 0.51 p e r c e n t to a 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 e s a t . In t h i s work, a l l v a l u e s f o r hesvy-ducy (abusive) braklng-were l e s s than one percent, which is e l g n i f i c a n t l y le ss than the 15 perce nt a s b e s t o s c o n t e n t 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 a s y s t e m a t i c , inde pendent check on t h e a s b e s t o s anal yses 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 c c l l e Columbus ' a b o r a t o r i e s to analyze twenty-four samples generated by Bendix Researcn 1- ti) J _abo ra te r i e s . i o h n s - r 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 Jcr.nsa n v i l le ar.d S a r c e l l e dat a agr eed very w e l l . In 19 of the 2i ana l ys e s , :he 3 e r d i x --r e s u l t s were s l i g h t l y hi gher t han the cor r e s pondi ng b a t t e l . e r e s u l t s . The Sendi x average was 0.25 p e r c e n t , while the S a t t e l l e a v e r a? was 0 . 1 ' p e r c e n t , or 68 p e r c e n t of the Bendix a v e r a g e . The 3en.:;y. C. :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 i l f i b e r s found wt re assumed to be c y l i n d e r s of p - o j e c t e d di a me t e r and l e nt en, .--o 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 a e a l l e r in vaiu.-.- cnan r e o 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 , ( r - r : ........ cegracfed asoescos o r o l i vi ne f i b e r s were mechanically reduced nc-f i b r o - s m a t e r i a l by the ot her a n a l y t i c a l t e c h n i q u e s , so only tne s i r . - ' asoescos f i b r i l s chat remained were count ed). An a l y s i s of t h e gao*ous e mi s s i ons was made d i f f i c u l t by the ..-,,u cua r. t it ie s of water and carbon dioxide which by-passed the gas c a n o n . . ; - ; - g l T` dp 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 snoweo t r a c e s of CL t o C3 hydr ocarbons onl y as lower c o n c e n t r t Ions of hi gher -0 lecu l.ir we i ght gas es could not be d e t e c t e d . When the g a s e s were c on c e n t r a t e d from t h e fade t e s t s , C u to C3 compounds such as b u t a n e s , oencene, t c l u e n e , phe nol , and c r e s o l s were d e t e c t e d In the gas t r a p s . The 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 Cjo m a t e r i a l s , i nc l 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 : w0 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 in mi cr ogr ams / mi l e ( i g / m i l e ) . These v a l u e s were obt a i ne d by m u l t i p l y m '.re weight of 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 - : gn a s o e s c 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: Asbes.os 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 eran 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 eaiasions. The o r d e r of d e c r e a s i n g a s b e e t o s e mi s s i o n s from b r a ke s was found to bo: Fad* or haavy-ducy scops burnish Modrt braking 1-5 F o ^ c h t d i s c pads o n l y , chere was an I ncr eas e i n a s o e s : : s emission* vich increased asbestos concent in the f ciz::zr. m a t e r i e 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 , yet 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. 3och 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 b a t ea r 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 of 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 s m a l l e s t ("vl 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 te ri a l r e c 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 mads f o r bot h d i s c and drum brexes from the t e s t v e h i c l e f o r t he amounts u 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 the Bur ni s h s c h e d u l e , f o r the end o f a complete v e h i c l e t e s t , and f o r the end of a l l three v e h i cl 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 t 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 ni s hed f r i c t i o n m a t e r i a l s , f o r severe ( or abusi 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 ca l cu la t ed 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 with tha Bur ni s h (new s u r f a c e s ) , A. i. Baseline (surface preparation), Detroit T ra ffic (moderate craking), 10Scop Fadt ( s e v e r e br ak in g) and A. F. B a s e l i n e ( s u r f a c e r enewal ) weight ing f a c t o r s . The v a l u e o bt ai ned f o r the t e s t v e h i c l e was 28. 21 ug/ mi l e. The f a c e o f th e a s b e s t o s emissions 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 r op - o u t 8 1 . 9Z Airborne* 3.7Z enger to be Brake R e t e n c i n : 1 4 . 4Z The a n n u e l t o t a l asbas coa emissions e s t i m a t e f o r 96, 400, 000 v e h l e l e a t r a v e l l i n g an a v e r a g t of 9, 978 mi ls* per y e a r was 60,400 pounds, d is trib u te d es follows: pass found Road D r o p - o u t: 49,470 lbs Airborne: 2,230 lbs Brake R etention 3,700 lbs 60,400 lbs The a n n u a l t o t a l a s b e s t o s e mi s s i o n s e s t i m a t e s t o r . g - t . - i s i - i o t r u c k s u-'.d b u s e s ) , and heavy t r ucks were found to 5c: Light trucks 22,300 Lbs Medium t r u c k s (and buses) i h, 300 Lbs Heavy t r ucks 22,900 lbs 81,500 Lbs ' l i s t r t a u t i o n of t h e t o t a l a s b e s t o s emi s s i ons e s t i ma t e f ar t ru. *,-o.wu.ated to be as follows: Saab Drop-Out: 37.9% Airoome: 2.9% Brake Re 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 emi s s i ons f a r a l l v e h i c l e s m pour.ua. >r is summarized as follows: - Total Asbestos Emissions (Lbs) Discr ibucion (IbsJ Drop-Out Ai r borne Kt'. ,'!! i l Passenger Cars Light Trucks urn T r u c k s (and buses) Heavy-T r u c k s ".isce LLar.eous (no t o r c y c l e s , trailers, etc.) 60,400 32,100 16,300 32,900 16,300 158,200 49,470 28,420 14,330 28,920 14,-330 135,470 2,2 30 940 4 70 9 50 4 70 5,060 3 ' ~,* . w . , 5.,! I 7, i. 7v D is tr ib u t io n by percent: - 8 5 . 6Z These e s t i m a t t * a r t considered to be maxiaua values 3.2% 11.2"- * / 1 . 2 . 1 Unpubl i s hed Daca A t ` che 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 tr.ree , - o v n works which had been compl et ed or were in p r o m t s * . n.z-*r Qi b r a ke wear d e b r i s and i t s compos i t i on wr .- d c*f " J | a(;: f ~ lr I 1 ' /juna*nra' , r usina a duo- ser vo drum brake in 196&-0?. . e . r s ; " = - = f * . 1 * * . * * d=i r " :Q # a d l s c brake i n s t a l l e d on an i n e r t i a l dynamometer was m ->' o z " ess C2-3) The d e t e r mi n a t i o n of a s b e s t o s cont ent i n a i r b o r n e ' rake ^ o r ^ s sampled downwind of ve h i c l e - mo u n t e d d i s c and drum orakes was a i . o in progress. ( 2- ) 2.3 BACKGROUND 3 . 3 . 1 r r . a r g v A b s o r p t i o n bv F r i c t i o n Ma t e r i a l s 2.3 .1.1 3rakes che k i n e t i ; 0uri,,s , ,c=p. . - - * ; * . , noving" v eh ic le ^ in t o heat, absorbs the h e a t , and gradual.' energy otf ct.n.e n o v\ ii. i Sg l i d i n * f ri ec t i o n co u p l e in the / t i i . ) . -- oraKe consls:sf r i , f 3=" ^ e r . al or l i n i n g const* t i ng .of a s b e s t o s f i b e r . .s mounted a f r ------ on a t e . . a i * binder. Lining is co^ideree 2 . 3 . 1 .3 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 ^ e r e r 2v oo ft ccnhee ee nn gz ii nn ee ss -- oULt aawt i*n g5 c r a n<k s h a f t smoothly htoatt h e unt ri oanns mi s *a,u- and wheel s . Any s l i p p a g e r e s u l t s in *en***` by clutch. Tu* sorbed and e ve nt u a l l y d i s s i p a t e d to the J Cuupie (which the clutch is basically a ^ - r u n n i n g s ta tic are .. sUd es momentarily t0,, ^ i r t a l or lining which is f l u e n t l y c a s t - i r o n or s t e e l and * r lJ , organic-bound. Organic-boun . m aterials consist of asbestos lefS wd ^ organic resin binder, fiber reinforcement, property ' t0 Ch a t of b r a k e l i n i n g s . s. : : ; lnd.` " r < r : T r u ^ u. : , i * . r . " s rhe transmission fluid. u , >- 2-3 2.3.2 omosUlor.s cf Friction Materials 2.3.2.1* Generalized ClasslfIcaciona Tabl e 2-1 gives t y p i c a l compos i t i ons of drum l i ni ng, 015: p a d , ' " " and c l u t c h faci ng f r i c t i o n m a t e r i a l s . The f ounda t i on, 0: major i 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 f i b e r . Asbestos i s chosen because of i t s thermal s t a b i l i t y , i t s relative.-.nign 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"noise. A r e s i n binder is also added to hold the other materials together with adequate strength. 2 . 3 .2 . 2 Asbestos The as bes t os u s u a l l y used i n f r i c t i o n m a t e r i a l s is ch rys o t i l a from Quebec or Vermont. C h r y s o t i l e , t h e p r i n c i p a l mineral of the s e r p e n t i n e group, has the approximate composition formula " g 3 (Si 203)(CH)i r 2MS* 2SiO22h 20 Table 2-1 - Composition of Typical Automotive F r i c t i o n Materials (Volume Per cent ) - . r * | rrifisf* i f CSnf i gf ' r i l( ft<l Glut! * Stinlari c;u 1 HiivyOulv Cl` taneari eJ \ J: s.-str j s Ac : ni r `9 i i u r i 2 0 - )C 1 : s - is 11-22 1S-U 20-50 | .4 J 1 ! ijor ** JOf :*jor 1 ; wt i 1 r ' . si : :n X u t . a t urn* r :u rttn ie lifDunt/CfifOU* Cine CMS* Oii Cffr/lru* .Uth. Slfr . 10- 1s S-IS S-1S 0- 5 o-s 1-10 20-21 10-11 1-2 1-2 0-S . 0-lS 0-10 2-1 2-i S-10 S-IS 0-J O-S S-IO 2- S 1 o-s s-ic S-lu* 2-i OiTgia 0 Mattai Hua* 9 moa >0ta*ltalaMi Ql(IIcCoIa'OTiMMw<oit/|taiaasmtaiic| taitoltata0o*tetMuaivtaitouaita*a<ae0>aoHaCaaTaiOi a Figure 2-1 - Schemacic Scruccur* c: Chryaocil Aabeaios m tm *m tm >i >m > < i Kiniwi Figur* 2-2 - DTA and TCA Th*naograa* f o r Ch ry ao ci l* Aaocscos (Bcndlx Daca) tr a n s m is s i o n v e h i c l e s . Phenolic-bound brake l i n i n g compositions corta:.-.ing cbeseos s e r v e se one of che bese c l a s s e s of l w - c o s c expencao Le members o 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 energy a b s o r p e to n r a c e s , cha cemperacure of che f r i c c i n m a t e r i a l , app r-xi.r.ata .y 0 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 t s e l f :s hoc ce r. Mosc of che heac i s removed from che i n c e r f a c e by conveccin and conduccin. ( 2-10) ac high energy a b s o r p e io n r a c e s , heac is gener l e: f a s t 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 i n t e r face reaches a poinc where chemical reactions occur rapidly. Surface te m peratures up co 1600*F have been observed or c a l c u la c e d ; the oreser.ee of o l i v i n e in Che wear d e b r i s confirms chac such cemper acures rave seen re acned. 2 . 3 . 3 . 2 P h y s i c a l and Chemical Changes in L i n in g s During Lse Figure 2-4 illu s c ra c c s che hecerogenous 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 th e f oll ow in g i n g r e d i e n t s : ph en ol :: 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 easnew f r i c t i o n m odifier (15 volume percent). As e r e s u l t of the ener gy conversion ac the s t a t o r - r o t o r i n t e r f a c e , che c o m p o s i t i o n of che brake- l i n i n g s u r f a c e i s a l t e r e d . At low s e r v i c e t e m p e r a t u r e s , che phen olic r e s i n and o r g a n i e f r i c t i o n modi- . f i e r c o n v e r t , on t h e s u r f a c e , co com pos itions with s l i g h t l y h i g h e r c a r t a j ^ 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 an ic f r i c t i o n m o d i f i e r c o n v er t to carbon more r e a d i l y , and t h i s in t urn o x i d i z e s co ca rb on d i o x i d e . Ac che 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 che 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 collected from Sendix 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. Asbes: 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 the wear d eb ris a r t i c l e s . 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 end wear r e s e a r c h . (2-11) Ac 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 convsrcs from i t s fibrous form co an o l i v i n e powder with l i t t l e o r no r e i n f o r c i n g v e l u e . Figure 2-7 shevs l a y e r of l i n i n g which had experienced more 100 mph w i t h o u t s u f f i c i e n t cooling between of m a te r ia l i s about co s e p a r a t e from t h i s the frictional-heac-affectec than 10 s u c c e s s i v e scops from s c o p s . (2-12) (a Large pi ece s l i d i n g i n c e r f a c e - an example of macroshear wear, described later.) When heec I s generated ac the s l i d i n g i n c e r f a c e oetween s t a t o r and ro to r much f a s t e r chan i t can be d i s e l p e c e d , che temperature r i s e s sad My resch e p o in t whert che l i n i n g or pad components decompose, o x i d i s e , or B e lt. The s t a t o r m a t e r i a l t h e n wears r a p i d l y and the f r i c t i o n c o e ffic ie 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 t e d by SOM eo e v o l u t i o n of gas et che s l i d i n g i n t e r f a c e ; on h e a t i n g , t h e gas expands and e x a r t s * 'o rce on t h a l i n i n g or pad, tending co push i t away from cha r o t o r . ' > 1 3 ) Fade can g e n a r a l l y be e s c r i b e d to the formation, of a g aseo u s, a l i q u i d , or a l o a - f r i c c i o n s o . i d phase ac the i n t e r f a c e , o r to io m combination of th e se phenoaens. Figure 2-8 Sliding Surface Unchanged Material Flaur 2-7 - Photoaieroiraph of Croee Section of F ric tio n Material Test Spociaon A ftar Mora Than 10 Suceeaaive Scopa from 100 aph on Bandix Full-Brake Dynaacaacer i l I 2-11 f**M*l OACMCftKAiCMAMfit ( M l U K toM lilft U S ) K A lC lfll M C M O M I c*n,iMMawiiiai(iiMH A M IIM N M U CII H A W AIMIIM4MilOMMllfl IMfl *AlU| 1MI 1 M(MMA> fMCMiiia m MMMK At AM (HAA m M IM tK M M >tO *M ll fit M O AM M I CAAHM M b MCA OAW lltM MMlimtUlwMIA *M MMA CHAU AMASA N 6 M ONlOtIMC (M( MM UMAOli! MHOCaIaHfMMJOiMAUAWPtMMM F igure 2-8 - Changes O ccurring in the F ric tio n M aterial as the T e m p e r a tu r e Ki&es rnl(t(A| (MCH(MtCA4 MAI*CI F igure 2-9 - Changes O c c u rrin g in t |,e Rotor as (lie T e m p e ra tu re Rises l su-r-arlzes eh p h y s i c a l and cntmical changes which r i: tio ri"matrial as the temperature rl ses . ( 2 -U ) che p h y s i c a l and chemical changes which cake p l a ce as crhe t erm. cpeerratt u r e r i s e s , ccke p l a c e in :r.e r i g u r e 2-9 summarizes in che c a s c - i r c n : c : : : 2 . 3 . 1 Brake Li ning Wear lechanlsms and Cer.eraci.on of m i s s i o n s 2 3 . 1 . 1 Tvpes of Wear Mechanisms E m is s i o n s are generaced by w ear . To che consumer, . e a r i s an economic c o n s i d e r a t i o n . To th e e n v i r o n m e n t a l i s t , t h e s e emissions are substances to be c h a ra c te riz e d and, If harmful, to be eliminated. F-om 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 , u t , r r e s i s t a n c e U m v . r . t l y r . l . t . C to n o t i o n l . v . l anO o t h . r O . s t r s t h n a B a c n . r . c t e r l s t i c a . U n l n ,, n t h r . a t a r y n . r r a t a 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 y have g r e a t e r f r i c t i o n a l sea ! ^ i , c irc u m s ta n c e i s used to advantage in ch, d . v e opment^of Irimarv-cype lin in g s for duo-servo brakes, where, because of des.g... cne 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 rtie s is of g r e a t e r s ig n if i c a n c e to brake performance than is wear r e s is ta n c e ; use of P r i o r y ` too 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 , .e s s . . . . cional s t a b i l i t y , and generally poor overall perrormance. Except in the case of primary l i n i n g s , however, one of che 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 . e l e v e l o T w e e r r e s i s t a n c e . Contrary to th e o p i n i o n of some l < ` 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 a l of maximum p h y s i c a l h ar d ne s s . I * d e s i r a b l e i s a minimum wear r a t e in normal low-te mp era tu re us e, a moderately increased rate at elevated temperatures, and a return to ^ 'o r d i n a l ^ t e m p e r a t u r e wear rates . i t e r being subjected to e le vated cemperatures. T o t a l em iss io n s g e n e r a ti o n may be d e f in e d the l o s s e s a s s o c i a t e d w it h f iv e b a s i c ty p e s of. w e a r . ^ che SuK o: a i abrasive wear, e thermal waar, e adhasive wear, ' f a ti g u e wear, and macroshaar wear shown I n T * b U 2 - 2 . t h . r . . r . . . ! j o . . l b l . c h . n l , o r . , c h type of wear. 2 . 3 . 4 . 1 . 1 Thermal Wea_r Thermal wear encompasses a group of p h y s i c a l and chemi- i H a R < i n the co u rs e of which i n t e r a t o m i c bonds a r e broken by t.,e. `" n-! t i i . ? . t o n , Inelud. yyroly.l. (th .m .1 d .. p ..U io n > , \ -13 T *blt 2-2 - Wear Mechanisms in F r i c c i n l e e r a i s THERMAL WEAR PYROLYSIS OXIDATION THERMOPARTICULATI ONMELTING EVAPORATION SUBLIMATION EXPLOSION ADHESIVE WEAR ORCANIC MATERIAL ADHESION BINDER 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 CYCLING SHOCK MECHANICAL REPEATED BRAKINC DRUMS OUT OF ROUND DISCS OUT OF PARALLEL MACRO-SHEAR WEAR - ACROSS THE PAD AT CORNERS AND EDCES THROUGH HEAT-AFFECTED LAYERS o x i d a c i n , c h e r m o p a r t i c u l a t i o n , e x p l o s i o n , m a lt i n g , e v a p o r a t i o n , and s u b lim a ti o n . T h eir r a te s i n c r e a s e e x p o n e n t i a l l y with t e n ^ e r a t u r e , and in extreme catses they result in fade. . Pyrolysis probably occurs predominantly at the cencars of li n i n g s and pads and to a l e s s e r e x t e n t a t the co rn ers and edges. O x id a tio n , on th e oth er hand, probably predominates a t the corners and edges and i s l e s s severe at the e s n ta r . Explosive r e a c tio n s occur under highly abuslvm braking co nditions, where the r a te of heat input i s so high th a t solids are converted to gases well beneath the surface; because thssm g s s s s ere g r e a t e r in volume than the s o l i d s they dispLacc, th e y c r e a t e m p r e s s u r e t h a t r u p tu r e s t h e l i n i n g in an e x p l o s i v e manner. Four such re a c tio n s are representad in Figure 2-10. " i t s i g h t be thought t h a t ra p id th e rm a l wear occurs on i> at high soak t e ^ e r a t u r a s . * In fact, however, thermal wear probably *Soak t e m p e r a t u r e s are tempera ture measured during dynamometer or vehi cle t e s t i n g , u s i n g s thsrmocouple lo c a te d i n th e f r i c t i o n m a t e r i a l or in the r o t o r . g e n e r a l l y at a d i s t a n c e of 20 t o 50 mils from th e s l i d i n g i nter:, -:. \ fr ic tio n . m a t er ia l FRICTIONAL HEAT 0 CaC03 <) - C j O (i ) C 0 2 1) * 0 CASHEW OUST (1) - C 0 2 (9) * HjO (> C (i) 0 ASBESTO S --HjO ( |l O LIVIN E It) ASBESTOS F IB R IL S (1 0 PH EN O LIC R E S I N - C 0 2 () * H j (9) C (1) THE BRASS CHIP CONOUCTS HEAT RAFIOLY INTO THE FRICTION-M ATERIAL SURFACE. (S): SOUO ' F i g u r 2-10 - Mechanism of Expl osi ve Thermal Wear occurs at a p p r e c i a b l e r a c e s at low soak te m p e r a t u r e s as w e l l . I : has been shown t h a t t h e m a t e r i a l s in a s l i d i n * f r i c t i o n couple c o n t a c t eacr, 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 is c o n s i d e r able evidence to indicate chat tie temperature increase it t h e ? ? ' t i e s for low s l i d i n * speeds i s r e p r e s e n t e d by the e q u a t i o n ' ' T - T0 ( * u v w / ^ a J ) ( l / ( k .* + k,).] where T i s t h e "1*10*1 te m p e ra t u re T0 i s t h e s o a k te m p e r a t u r e * 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 che c o e ffic ie n t of friction V is che s l i d i n g v elo city w i s the load on th e asp erity 2-15 a is che ra d iu s 'of che a s p e r i t y j u n c t i o n J is che mechanical equivalent of heat it. i s th e th e rm al c o n d u c t i v i t y of the d i s c 'itj i t the th e rm al 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 . Experiments i n d i c a t e t h a t the f l a s h te m p er at u r e nay be as high -s U0G*F ( 760' C) i f th e soak te i^ s er a tu r e i s 650*F ( 3 4 3 * 0 . This f l ash temperature is high enough to cause rapid lo c a liz e d p y r o ly s is of the o r g a n i c compounds used i n f r i c t i o n m a t e r i a l s , as v e i l as co n v er s io n o: f i b r o u 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 m a t i o n of p e a r l i t e to martensite in the c a s t-iro n mating surface. 2 . 3 . 4 . 1 . ? Abr as i ve Wear A o r a s iv e wear i s of two t y p e s : evo-body wear ( F i g ure 2-11) and c h t e e - b o d y wear (F ig u re 2 - 1 2 ) . Plwving 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 plowing by edges i n rough-machined, s c o r e d , cracks or c-orroced ( p i t t e d ) r o t o r s are examples of two-body wear. C rin d in g by wear 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 an d , c l a y , mud, or s a l t the slid in g in te rfa c e is three-body wear. A brasive wear would be e x p ec te d to i n c r e a s e w ith tem perature. It in c re a s e s a lso with t h t braking load and with t h t 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 electron photomicro graph of a d y n a m o m e te r - te s te d f r i c t i o n m a t e r i e l showing the a b r a s i v e wea t r a c k s on the s u r f a c e . S e v e r a l ad her en t 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 to che vear track widths. 2 . 3 . i . 1. 3 Adhesive Wear Adhesive wear, i l l u s t r a t e d i n Figur e 2-14, i n v o l v e : ch adhesion of o r g a n ic and/or inorganic m a teria ls to the ro to r and che sub sequen. te arin g o r s e p a r a tio n of these m ateria ls from the lin in g or pad. Organic c o n s t i t u e n t s of f r i c t i o n m a t e r i a l s i n c l u d e che 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. Inorga nic c o n s t i t u e n t s in clude s i n e powder, b r a s s c h ip s, and a s b e s to s . L i t t l e i s b w n about che te n de n cy of ehese m a t e r i a l s to adhere t o th e c a s t i r o n u,ed i n to d a y ' s d n J M end d i s c s , Chough e x p e r i e n c e w ith hoc e l a s t o m e r i c com pounds suggests thsc elastomers are very likely to s t l e k . Experiments at Bcndlx Research L a b o ra to rie s i n d i c a te chat brass chips w i l l alloy with c e r t a i n n o n f e r r o u s r o t o r a l l o y s . (2-18) whan t h i s o c c u r s , me tal is tr a n s f e r r e d from che r o t o r to che lin in g , s co iin g che su rface of the -ocor and in c u m s u b j e c t i n g che l i n i n g t o a high r a t e of cwo-boay ab ra vt wear. . - 4 ---------------------------------- OIRECTION OP R ELA T IV E MOTION F i g u r e 2-11 - Mechanism of Two-Body Abrasi ve Uear DIRECTION OF RELATIVE MOTION F i g u r e 2 -1 2 - Mechanism of Three-Body Abrasive Wear 2-17 OIRECTION OF RELATIVE MOTION ROTOR ,//// C ttd F lgurt 2-14 - Mchini* of Adhtilv Utr 1 I Adhesive wear probably i n c r e a s t s with temperature, b r a k i n g l o a d , and the c o n c e n t r a t i o n of a d h e r e n t components In sha f r i t : m a t e r i a l . .--I s i s a l s o causad by th pr a s a nc a i n cha f r i c t i o n ma t e r i a l of met al p a r t i c l e s capable of s ol uci n in or r e a c t i o n wish she rosar a ' l o v i n c r - a s l n g wi t h the s i z e and c o n c e n t r a t i o n of such p a r t i c l e s . Because t h i s t y p e of waar can cause s t i c k - s l i p , i t may be a s s o c i a t e d with brake noise. 2 . 3 . A. 1 . 4 Fat i gue ^ e a r Fat i gue wear (Figure 2-15) i s most commonly observed i n s a l b e a r i n g s . However, i t 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 two forms, t h e r ma l and w c n a n i c a . . Thermal f a t i g u e is caused by r e p e a t e d h e a t i n g and nnLine Such r e p e a t e d t e mper at ur e changes i npos e c y c l i c s t r e s s e s on cne s u r f a c e m a t e r i a l , which h e a t s and c ool s more r a p i d l y than the bulk m a r . r i a l and t h u s 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 hermol 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 cnose in metals. Th e rm a l-s h o c k c r a c ki ng may be t hought of as a s p e c i o . 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 load ing. Mechanical f a t i g u e is caus ed by r e p e a t e d mecnanical s e r e s s t 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 r e p e a t e d l y to bot h compression and s h e a r f o r c e s . Adc. t i o n a l s t r e s s e s a r e al so a p p l i e d r e p e . t . d l y i f drums ere out -o - r o u n d , i s c s are o u t - o f - p a r a l l e l , or i f r otor thi ckness is 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 arounc the l a r g e c a s u e v p a r t i c l e . Thi s ma t e r i e l s w e l l s when h e a t e d and thus the surface wears. After cooling, the p a r t i c l e contracts, cracks, p u l l s away from t he edges. ^han the p a r t i c l e i s compl et el y loose, i . can f a l l out. 2 . 3 . 4 . 1 . 5 Macrosheer Wear Three t ypes of ma t e r i e l removal f e l l i n the cat egor y of me c r os ne e r w e a r , -which i s i l l u s t r a t e d i n F i g u r e 2-16. A f r a c t u r e , i n s h e e r , may oc c ur a c r os s the e n t i r e br ake oad u n d e r e s t r e - e l v 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 has M . n * .< 1 by ! > . . m i . 1 . " " * i ' " " *1 type of year. F r a c t u r t a t th . i l l " and cor rv.r. oi a p l a t . of f r i ct i on m atarlal 1. anothar typ. of . . C r o a t i a . , w a r . Oxidation o( o .,.n ic cocr- sonants walkana th . fric tio n . a t . r i a l t h . . . lo catio n .. 2-19 Figur* 2-15 - Mechanism of Fat i gue Wear DIRECTION OF RELATIVE MOTION ROTOR GENERALIZED!* failure through; t kDIRECTION OF heataffecteo ZONE \ friction m aterial NORMAL FORCE '\\W < ^ NS' vv s\ N\ \ \ ^ ^ \ \ ^ ^ \ \ \ \ \ V ' ` LOCALIZED FAILURE AT EDGE WEAKENED BY OXIOATION F i g u r e 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 l i t e r i a l i s a not her type of macroshear wear. Ox i d a t i o n of orqa.-.i; 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 c cin m a t a r i a l such as chat shown in F i gur e 2-15 is s u b j e c t e d to heavy ' l a d i n g f o l l o w i n g thermal a b u s e . The h e a c - a f f e c c e d l a y e r in die ma t e r i a l p i c t u r e d i s abouc 100 mils d e e p , and f r o 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, a a c r o s t u a r wear i s promoted by .lonunlform l e a d i n g and by o x i d a t i o n and t he r mal d e g r a d a t i o n of the b i n d e r . I t i s raost l i k e l y to occur a t e l e v a t e d t e mp e r a t u r e s and under sever e b r a k i n g c o n d i t i o n s . I t s end pr o d u ct 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 t h a t leave t h e 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 while they ara p r es 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 . u . 2 Predominant Wear :!echanisms ~ The predomi nant wear o r e m i s i i 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 ) : ( 2 - 1 9 ; e Below 45Q*F: Abrasive and a d h e s i v e wear. Above 5D*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 of 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 . 1 . 3 Wear Equation Recent work a t Bendix Research that each f r i c t i o n material wears according to ti o n . (2-20) Labor ator ies has a u n i v e r s a l wear indicated equa a b c CM k p V C or l o g (AW) log k * a log P + b log V + e l og t 2-21 Fi gure 2-17 Predominane Wear Mechanisms of F r i c c i n M a t e r i a l s Figure 2 -1 8 Variation of Friction Material Wear wich Teap.rac ure '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 velocity c i s Che cime of s l i d i n g , and a , b , c are constants c h a r a c t e r i s t i c of a given f r i c t i o n c.r-n.e. Uhen f u r t h e 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 in d r u r brakes arc : from two a r e a s : The space between t h e r o c a e i n g drum and the s t a t i o n backing plate, Die s n a i l hol es in t h e 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 , a l t . on Iv s mal l p a r c i c u l a t e s would come t hr ough t he hol es i n che backi na p in or urn b r a k a s , some p a r t i c l e s are not e m i t t e d but r ema i n in che r a t a : d run. I t i s e x p e c t e d t ha t some of t h e s e p a r t i c l e s woul d e v e n t u a i l v m e - : t : ed chrougii che space oeeween :na r o t a t i n g drum and s t a t i o n a r y d e ? l 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 n i t : 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 the f r i c i .-.at or l a l 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/ o f r: vu ted 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 entiling o f drum brakes i s improved in :: f u t u r e , as Is de sirab le for s a f e r o p e r a t i o n and longer dr i vi ng l i f e , : is l i k e l y that, fewer p a r t i c l e s will remain trapped. Die p ar t i c l e s e m i t t e d , however, 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 grinding a c t io n f o r s n o r t e r peri ods 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-, ' i l l b t e m i t t e d . However, a s a a l l amount of p a r t i c u l a t e s co l le c r i v e t h o l e s of r i v e t e d d i s c brake pads and on some area. of .-.e sr. 2.3.3.3 Clutches In the dry c l u t c h e s commonly in use on "s c 'k-sw :-.ere are very few openings for gases and p a r t i c l e s to escape aain areas are: ` ' "-V-a - s '* The area around the c l u t c h f o r k , which genera ilv -,as a rubber boot on I t for p r o t e c t i o n ot the clutcr. irzr road spray, sand, etc. . A small opening a t th e lower f r o n t of the c.' utcn to . d r a i n any o i l , w a t e r , e t c . , which may get in to t n e 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 clutcn 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 ele 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 to mix r a p i d l y with ch* surrounding a i r and become p a r t of the a i r wake of the c a r . The h i g h e r molecular 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 to the ground. The low molecular weight gases w ill disperse as part of the local 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 m a l l , ai r- b n r n e 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 the r e s p i r a t o r y system as par: of the breathing a i r . ' ' The p a r t i c l e em iss io ns w i l l d i s p e r s e in d i f f e r e n t wavs deoe: mg on t h e i r s i z e , s h a p e , and d e n s i t y . Submicromecer-size p a r t i c l e s , re gardless of shape, w ill ordinarily remain air-borne u n ti l they are scrubbed o u t by r a i n f a l l or some o t 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 becone a long-time part of the atmosphere. ` S p h e r i c a l p a r t i c l e s i n the 1.0 -n to 10 _m d ia m et 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 to 1000 cm /hr, a c c o r d i n g to S t o k e s ' law. 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 In 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 slower v e l o c i t i e s and could remain a i r - b o m e for heurs or days. These p a r t i c l e s cause tne g r t s t e s t aggravation i n tha human r e s p i r a t o r y syscam because they c o l l e c t In the tra c h e o b ro n c h ia l regiona and, to some e x t e n t , in th e a l v e o l i . A r t i c l e s from 20 um t o 100 urn in d le m e te r w i l l s e t t l e as p a r t of eh d u a t t r a i l l a f t by th# 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 rticle In aachanlcal traps in tha ear. Eventually thee larg cr-size p a r t i c l e s w ill f a l l or be shaken ou t of the c a r and become p a r t of the road dust. INFERENCES ( 2 - 1 ) J. Lynch, " Br ake Li ning Oecompos 1c ion i'rodui.' 3 , ' . . . r " P o l l . Co nt r ol Assoc. , <1_3, .'.'o. 12, 324 ( 9 o 3 n ._.2--2 5 ' S. S p i e l , lohns-Mansvi 1l e Research am! ; nsi revr comnunicat i c r t , L971 (2-3) Privat e Communication, 1972. (2-4) J. Moran, Envi ronmental P r o t e c t i o n Agency, p r i v a t e cu;:.-;..-:__ tion, 1972. (2-3) (2-6) 3. W. 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