Document rp423vLj5BebrDKj6x29dRkbq

File Name Ford Motor Company Scanned? yes Source JMA: JMA: Start Year 1970 Stop Year 1973 Contents memo, test results Notes BC notes in file 7/5/98: Ford Motor Company Nov. 1970 documents refer to Ford efforts to substitute or control asbestos in making housing units for heaters and air condHioners. Font brake tests in 1973 demonstrate asbestos emmissions in brake wear products. "Asbestos Emissions from Brake Dynamometer Tests," by A. Anderson, R. Gealer, R. McCume and J. Sprys. Env I ronmenta } Contro I Department Research <L Engineering Center November 17, '970 OoVtoaA & W. P. 01 Re 1 *'y - Cleveland Dlst. Off, cc: A. C. Smith N. W. Hendry - Asbestos 1500 H. M. Bail - GHQ W. I5. Ra I nos - Gh'Q H. G. Donovan J. Goldfield Hie 4 C FORD MOTOR COMPANY PLYMOUTH, MICHIGAN VQIJR LETTER OF NOVEMBER 13. 1970 I contacted Dr. George ftauer today In accordance with your request. We told me tha+ Ford was greatly concerned with the health hazards related to asbestos fiber usage and that he had been looking for substitute materials. Me further stated that his search had convinced him that other materials were equally, \l not more, hazardous than asbes+os Mber and ^hat instead of using a substitute, they should improve the dust cont-o: at their operations* He asked If anyone from Johns-ManvH(e could v'S't their plant and advise Ihem on dust control procedures. ' informed Dr. Bauer that J. Goldfield and * expected to be in fhe Defroit-To:edo area some hi me within the next fwo weeks and would visit their plant to review the problem with hJm and Mr. Leonard Evens, their Plant Eng\neer. EMF/ems Cleveland Office Novembe r 13 * 19 70 L.M. Fenner - Finderne cc; N.W. Hendry - Asbestos H.M. Ball - GHQ H.G. Donovan, Research W,P. Raines - GllQ File FORD MOTOR COMPANY HARDWARE 6 ACCESSORIES 14425 SHELDON ROAD PLYMOUTH, MICHIGAN DIVISION ;o This plane manufactures the Heaters and Air Conditioners for all Ford vehicles and the housing for these units is a molded poly ester premix compound. For the past three years they have pur chased from us in excess of 2000 tons of Asbestos Fiber grade 7X15 . Last month we heard through Dr. George Bauer, a chemist and their formulator for this item, that he was instructed to investigate possible substitutes for asbestos, and that if we had any comments on the subject, we, rather than he, should approach Ford about it. Last week, on the 5th of November, Noel Hendry and I visited there and brought up the matter with our contacts seeking their advice. They felt that although the subject had come uo, a presentation on our part would be premature at this time, and I believe Noel is to write them to the effect that we have such a presentation and would be glad to offer it at their convenience. I)r. bauer was not present at this meeting. Mow, on November 11th, Dr. Bauer has contacted our distributor (Mr. John Hastings of International Fibers) asking that someone from the J-M Environmental Control Department telephone him to discuss recommended asbestos dust levels. Their LCD feels the asbestos dust in their operation exceeds the allowable limits and if so, they wish to know how to reduce the dust. Dr. Bauer stated a dust level of 2 fibers per cc, which I think is a little low. At any rote, may I suggest that you or someone in your group tele phone Dr. George Bauer at Lord in Plymouth, Michigan (Phone (313) 445-0600) to discuss allowable asbestos dust levels? Then would you kindly drop a note to Noel Hendry and me informing us of what transpired? c$ < 5 - fjb'i j ,'fp/ra iVrv^nrch s Development Cantor 1 ay 22 , 1973 1 Sfex ASLE5T0S EMISSIONS FROM BRAKE DYNAMOMETER TESTS A. F, Andcrnon, R. L. Coal or, R. C, McCano and J. W, Spys, Scientific Research Staff, Ford Motor Company. (Frosentnd at the?. 197 3 SA]?J National Automobile Enginciorri.net Mooting, Detroit, May If-, 197 3) . SUMMARY by J.-.W. Axel son Dynamometer tests were made with a production disc brake and all airborne wear particles were collected on 0.45 um filters. Asbestos fibers were detected and measured by l-.ho use* of transmission electron microscopy at 40,000X and positive .identi fication was made by electron diffraction. Most of the lining asbestos (99.95 percent:) was found to be converted to a nonfibrous material by the high flash temperatures of the braking surface. Brake flash temperatures as high as 980C have been observed on a test machine. \1 * They estimate .that about 28,000 tons of asbestos are used each year by the friction materials industry in the U.S. (J-M estimates about 45,000 tons). hem- than half of' this,' or 12,000 tons, is estimated,to wear away. Throughout the paper they use a safety factor of 10 to make sure they are stating maximum quantities. For instance, they found that only 0.0 02'3 percent of the lining wear was released as asbestos fibers, but state this figure as loss than 0.02 percent. Likewise, the concentration of asbestos fiber? in the atmosphere from brake usage was calculated ar 0.007 x , 10"^ gms par cu meted but was reported as 10 times that or 0.07 x 10~9 gms por cu meter. Romo, of the pertinent data are given .in the These are actual values without multiplying 10 as they did in the paper. i . Background asbestos in ambient test air 'Asbestos, fiber from brake in exhaust air Total asbestos fiber in exhaust air Estimated brake asbestos in urban air* ^ . A.sbestos fiber from brake in airborn wear dust Asbestos fiber released from lining wear f o11owing t a blc. by the factor of 1.9 >: 1CT9 g/m3 1.3 x 1CT9 y/ri3 3.2 >: 1CT9 u/m3 0.007 x 10"9 y/n3 0.005 percent 0.0023 percent *Extrape1a tod ;f r om da t a on r e s idc nc a tim e s f or load partic1e s. 'May,22, 1973 B iCj-cj 2 Asbestos Emissions from Brake Dynamometer Tests Local Detroit atraor.pheric concentration ranges from 0.5 to 13.1 X- 10"^ qms per nil meter so the calculated value of O.OQ7 x 10"*5 gms per cu, meter is only a minor fraction of normal conditions accruing from all source?* inc] uding ^natural weathering of- asbestos-bearing rock and soil, min .ing, farming andexcavating. This loads to their final conclusion "Based on this upper boundr the use of brakes was judged to be not significant ns a source of atmo phoric exsbestos". cc: i J. -F. M. Hutcheson - Asbestos N. W. Hendry - 3 West H../G. Donovan - 3 West ' M. Fenner 4 North ' F, U. Solon, - 1 West W. C. Sfcrcib - Ctr S. Spoil - B&D Ctr r 't 5 4 1. n y '/ .' S(K. ' ASBESTOS EMir`''10:;S FROM BRAKE i DYNAMO! fT,TER TESTS .* * &y * \ A..E. Anderson, R. L. Gealer, R. C, McCone, J. W. Sprys Scientific Research Staff, Ford Motor Company, Dearborn, Michigan 1*8121 V- . , ASTWSTOS KMrflSlONS FROM BRAKE DifNAMOKElTiR TESTS ty '' ' . A. E. JAnderson, R. L. Gealer. R. C. McCune, J. W. i , Scientific Research Staffs Ford' Motor Company, Dearborn, .* Sprys Michigan ^8121 ( ' ABSTRACT . Dynamometer tests of. a production disc brake provided new information on asbestos fiber emissions during breakin, normal use, and high temperature ase conditions. Both ambient air and brake cool in." air were sampled isokinetically, using Oj+5 kun filters, Examination of test and background filters required a clarification process to maximize fiber detectability, the use of transmission electron microscopy (at 40,000 X) for detection, and electron diffraction for positive identification of asbestos fibers-' Most of the lining asbestos was '. 1 1 ,found to be converted to a non-fibrouc material by the high flash temperatures of the brewing surface. Less than 0.02$ of the lining wear was released as - asbestos fibers. The, concentration of asbestos fibers in the urban atmosphere, IN * 1 due1to brake usage, was conservatively estimated at less than 0.07 x 10 " grams per cubic raete^. Based on this upper-bound, the use of brakes was judged to be not significant ss source of atmospheric asbestos. INTRODUCTION Asbestos has been a. major constituent of automotive friction materials for, more than 50 years. It is.used to impart strength, ^flexibility, _t and. heat resistance to a brake lining and to enhance friction and wear proper ties.' Most present crake linings, use resin or rubber binders and chrysotile asbestos, together with organib and inorganic friction modifiers and fillers. The asbestos content varies with formulation, from a low of 25% to about 65ft by weight.. Minimum asbestos levels are found in some high performance European disc brake linings which are highly filled with metals and inorganic constituents, brake linings in the U. S, average about asbestos con tenl, (750 HXfO ' (25OfMakgt)otal U. f.3. annual asbestos consumption of 800,000 tons>)S.about 28,000 tonsjef chrysotile asbestos are purchased annually for friction materials of all types (l). Of this, it has been calculated that brake lining year ' (U Mkg) consumes about 12,CC0 tons^of asbestos per year. Roughly nn equal amount *' % remains on brake shoes at the time of replacement or is manufacturing wastage. "Recent tests have shown that densely populated urban atmospheres Often contain significantly 'higher asbestos concentrations than surrounding areas (2). Background asbestos levels in the atmosphere result from the r` natural weathering of asbestos-bearing rock end soil, as well as from mining, farming,.and excavating, The generally higher urban concentrations suggest commercial, and industAal sources. Brake lining and clutch facing wear was suggested by Thomson (^) as a possible source for hirher asbestos levels in the urban atmosphere. Lynch (4), in a study undertaken by the Public Health Service, 1 * reported the findings of several brake dynamometer and friction machine tests in which wear' debris was trapped or* a filter and subsequently examined by means.`'Of a transmission electron microscope (TEM). He concluded that 'Tree fibers from broke lining wear ?ccta to be nn inconsequential health factor in urban air pollution.11 Lynch detected no free fiber from on automobile clutch. end a bus,drum brake, but some free fibers were found in one test of an experimental disc brake.' i ' 1 With mounting concern over air quality in general, and asbestos pollution in particular, this'study was initiated in 1970 to provide odditional lata on the asbestos emissions from disc brakes, OBSERVATIONS OF LINING WEAR The near absence of free a,sbestes fiber from lining wear has been 11 \ reported by luxon (5) using X-ray diffraction and by Lynch {K) using the TEM (transmission electron microscope). Several authors have suggested that interfacial temperatures during braking could be high enough to decompose .. the chrysotile asbestos into non-fibreus thermal degradation products. Ana-" i lytical relationships exist which permit calculation of ir.terfaciol tempera- 'tnys (6). However, several of the significant parameters arc difficult to determine accurately for heterogeneous materials such as brake linings. The asbestos crudes (larger fiber bundles) were calculated to reach their rapid i decomposition temperature during normal braking at speeds above 56 MPH ' (25 m/s) as an upper bound value and above 18 MPH (S m/*s / as a lower bound value. * An experimental approach was undertaken fo provide closer bounds. 1 Added insight into the thermal decomposition of asbestos fibers in brake lining wear was attempted by direct visualization cl the frictional process; A small laboratory friction test machine was constructed using a thermal shock resistant (Vyco^*) glare rubbing surface (replacin' the conventional cast iron) in which the friction interface was directly viewed wi-h a low power (7-5OX) 4t binocular microscope (7). Scaled rubbing velocities were 11 red to compensate for '' *t the thermophysical property differences between the glass and esct iron. -3- .\ ' Moderate scaled velocities, roughly equivalent to 12 MFH (5 m/s ), provided a view of intermittently incandescent asbestos crudes. During the ' ' ^' initial burnishing operation resinous material surrounding these asbestos .i ^ crude? vas observed to pyrolize, producing microbcods of condensation * i products around the crude. These organic products of resin degradation ond , the apparently powdered asbestos decomposition products'were seen to smear into platelets, often of such size as to be discernible to the unaided eye. ' 1 At higher rubbing velocities (over 30 MPH, or 13 m/s ) the platelets i formed a surface char layer under the action of more severe thermal and mechanical action. The larger asbestos crudes then could be seen to glow 1I with'apparent depth and for greater time durations, often several seconds. i . Ihe actual brake lining contact area was only a few percent of the total , * > '' available surface, .with contact spots moving ir. a random manner with time, irom these friction visualisation studies it appeared that local flash temperatures and .severe mechanical action could be major factors in the breakdown of asbestos fibers for most brake usage.. Examination of the lining surfaces reverted the presence of non-fibrous magnesium silicate1 in both crystalline (Frs:eritc; nnd amorphous pha.ses. Moghesiuj^ silicate is a thermal degradation produce of chrysotilc asbestos.^ Forsterite transformations have been reported to occur at bOO^C over a .period of hours!. Differential thermal analysis (DTA) studies in our laboratory indicated this transformation occurs within seconds at 620*0. ' Special brake lining formulations were then prepared and tested on the glass visualization apparatus and a Friction Assessment and Screening Test (FAST) machine.(8). Chemical reactions were found to take place at the \ friction interface -'Which would require a flash tempernture rise of 7^0"C to initiate when an equivalent of 33 MPH (16 m/s) rubbing speed wes uned on the ': FAST machine. At this same speed melting of inorganic lining additive* and .i mot a 1 particles confirmed brake flash tempet*o turns up to Ny Based on these findings, it would not appect surprising for few asb.ostos fibers to be emitted from brakes in normal usage. However some ^1 mechanical rerpoval of fiber appeared possible during the first several brake applications with new linings. Also, high brake temperatures possibly could 1 4 , weaken the organic binders and cause increased fiber emissions. rl - JEST PROCEDURES * Complete sample collection and examination procedures, along with sample data calculations are included as Appendixes I, II, and III. briefly, the tests were performed as follows: a new Pinto disc broke assembly was installed on a single station brake dynamometer in a room which was cleaned ;j of extraneous,asbestos sources. Air from within the room was blown through a diffuser screen to provide a velocity distribution over the brake which i\ ' approximated tnat .of vehicle usage. The air stream in front of and behind the brake was sampled isokinetically, using matched 0.4? uni filters, holders, i and. air pumps. Note the system schematic in Figure 1 and the actual test setup in Figure 2, The brake exhaust air was discharged out of the building. The first pair of.filters were used during the first 82 burnish stops, to represent "breakin11 conditions. After further burnishing, a second pair of filters collected samples during 560 "normal use" braxe applications. A third set of filters then were utilized in a "high temperature use'1 test of 41 brake stops. i . All brake applications were made from a 4o MFH (lS m/s) equivalent speed. Breakin and normal use tests employed brake toroues corresponding to one-quarter Mgtf (4.9 m/sp) deceleration, This torque level was doubled for the high temperature tests. During the normal use procedure, the test filter was located for 20 i * . brake applications at each of 28 grid locations in the exhaust duct throat, to insure a representative * sampling of thc'air flow ever the brake. This test arid and filter may be seen in Figure J. ^ central collection site in the test grid \. was u;ed for the "breakin test*' end the final "high temperature" test. Samples of the three pairs of filters (breakin, normal tise, and high temperature use) were subjected to a clarification process involving low ,1 t t ' temperature ashing to oxidize all! organic material and mechanical action to "i i separate the particles. This assures maximum detectability of asbestos fiber (2), > . RESULTS AM) DISCUSSION ' * ' Transmission electron microscopy at Uo,000 magnification was used in the search for fibers. At this magnification the ultimate fibrils appear to be above one millimeter (0.0^0 inch) in diameter. Quantity, length, and apparent diameter measurements provided data for calculation of asbestos fiber mass per unit of filter area. Couuled with dimension, mass, and flew determinations from .- *' ' the dynamometer tests, this data was used to calculate the emitted asbestos fiber concentration in the collected wear dust, in the coding air stream, and from the "brake lining worn. The size distribution of collected fibers was not determined by this method, since the clarification process involved sufficient * mechanical action to reduce-most fiber bundles to the ultimate fibril size. . Additional iomple,? of the "normal use" test filters were examined ' on the i;EM without recourse to the clarification process, in an effort to determine the acbestote fiber size distribution. Roughly 10$ of the asbestos fiber was visi'ble on ti he background sample, based on the results from corresponding samples after clarification. The largest observed fiber bundle was 0. 20 um in diameter and over 1.1 u.m long. A similar direct TEM search of the $ "normal use" test filter revealed about 2% of the asbestos fibers observed after clarification. This reduced percentage of visible fiber was attributed to the greater;concentration of obscuring matter in the test filter. However, the largest observed,asbestos fiber in the test filter (0.13 urn in diameter and over > 1,1 1.P urn lenp:') wr.s about; hhe s.rnp si7f> ns wns found on- tho. h.-ickdrj.inri snjrvnl. 6- - The similar, low fiber content of both N- ckgrounrl'nnci test filters precluded n fiber size distribution estimate, However, it appeared that the Quantity of the larger asbestos fibers on the test filter wan no greater than that of the i background filter. ' This supports the observation from the lining vryr visualization tests '| ; that normal brake wear degrades most of the asbestos fibers. A brake lining grade i' . . of asbestos appears on the TEM as in Figure 4, The fiber bundles are composed of strong, but weakly adhering fibrils of about 0.0} um (roughly 1 microinch) diameter. Mechanical action causes the larger fibers to "open11 into *mailer fibers or even fibrils, as illustrated in Figure 5, Contrast these "raw material" fibers V^ith one of the lacker fibers (Figure 6) and one of the more typical fibrils (Figure 7) from the "normal use" test filter. < The similhr, low fiber content of both background end test filters required clarification to permit an asbestos fiber count, thus providing more N accurate fiber mass determinotion, but obscuring the actual fiber size distribu tion; Therefore; '.the calculations of fiber concentration (Table 1) were expressed as asbestos mas3 per unit mass of lining wear dust and asbestos mass per unit mass .of lining worn. Asbestos fiber concentration in the ambient air (background) iv end ir trie brake exhaust air1 (test,) was calculated in units of nanogrnms (10 71 grans) per cubic} meter of air. However, the actual asbestos-emissions from brake usage t1 would be diluted substantially through nixing. The asbestos concentration in urban air due to brake/usage was estimated, based upon existing automotive exhaust lead dilution data. These calculations appear in Appendix III. All the test results in Table 1 have teen reported aa ten times the calculated test values, to allow for possible losses in collection, processing, and counting. These values, therefore, should provide upper bounds for asbestos emissions.from brake usace. For example, the local (Detroit, Michigan) atmospheric asbestos concentration ranges from 0.5 to ljji nanogrrms per cubic rector. The -7- . \ oblservedyh v:kground asbestos value was l.p iv7m3, for the normal use test, but is reported in Table 1 as 19 ng/m3. The low asbestos emissions from .. > .the test disc brake wirier "normal use" conditions is underscored by the addition of but 13 ng/m3 (1.3 ng/m^ observed) in the undiluted exhaust air stream. > ' .` f t/1ble 1 ASBESTOS EMISSIONS FROM "NORMAL USE" BRAKING Dynamometer Data for a Production Disc Brake* . Background Asbestos in Ambient Air <19 X 10' g/m'5 . .Asbestos Fiber frpm Brake in Exhaust Air <13 x 10 5 g/mJ . Total Asbestos Fiber in Exhaust Air <32 x 10"s g/'rr . Estimated fcijake Asbestos Fiber in Urban Air <0.07 x ICf3 -/m3 . Asbestos Fiber from Brake ih Airborn Wear Dust , <0.051i 1 Asbestos Fiber Released from Lining Wear <0. o^-; . * Reported values are'10 times the observed tes z * values to provide upper bounds 1I 1 The lining wear rate during the first 82 breakin stops was found 1 to be about five times above the "normal use" rate. Asbestos fiber release during breakin was also highey, an average sevenfold increase, however, since the breakin wear is less than 1$ of the total lining wear, the increase of emitted asbestos fiber resulting from this temporary sevenfold increase would be aberat 3%,, wben averaged over the life of the linings. High* temperature brMke usage ?lso increased lining wear rates, in this case,by a factor of eleven. Asbestos fiber emissions increased by less then a' factor cf three. Frequent vehicle operation under such hi>;h temperature 8- - ', 1 l '.editions would lower lining life t: levels far below present averages. However, even if all brake wear provided the' same fiber emission rate as ' ^ ' found In the'high temperature use test, the percentage fiber release to the i atmosphere would still be under 0.06$ of the lining wear. ' * , 'i Ihe remaining brake wear was a mixture of non-fib roue organic and inorganic matter. Forty-seven percent of the estimated 62 to 77$ collectable wear debris were accounted for by the test filter on the normal use test. The remaining 15 to presumably were retained on the lining- edges, the caliper, spindle, rotor, wheel, and tire. Accurate measurement of this material was not possible, due to the added retention of dust from the ambient air. r, More precise values of brake lining asbestos emissions or the determination of their particle size distributions appear possible, for these >* low fiber concentrations, only by testing brakes in an asbestos free atmosphere. This approach was used in an EPA sponsored study (9), where pre-filtcred air i wag flowed through sealed brakes at a flow rate greatly reduced from normal. CONCLUSIONS *. 1. Automotive brake usage provides a very small emission of asbestos fiber n tt ' (less then 0.02$ of the lining worn). y S. 2. Automotive brake)usage provides a very small asbestos fiber inuub to urban atmospheres (estimated to be below C.07 ng/n3). - * ri .* J. Intense local heating and severe local mechanical notion causes the decom position of most asbestos fiber in brake linings during typical usage, -10\. \ SAW'LE FILTER PREPARATION ' ' Microporous membrane filters with 0,^5 um pores were selected to assure \ high retention of asbestos fibrils and most of the wear dust powders. A matched pair oi Gelnan sampling pumps and 35 mm diameter holders were used. . i ft ' Thinfmetal cones of l2 included angle were fabricated and sealed to the ,filter entrance. Ihese cones increased the tip entrance velocity to that of the exhaust air duct so isokinetic sampling could be achieved. The cone tips were carefully matched in size. Flowmeters and differential pressure i indicators were installed in the system to monitor the filter airflow during each test and to set the tip entrance velocity before each test. '1 Tests were performed on the unused filters to determine their ve;ght change with variation of humidity, , Filter weights were measured on ' \' '' a inicrobalance to the nearest 10 micrograms. Filters were placed in the \ center of the designated exhaust duct grid and at a fixed portion upstream of the brake, but below the diffuser screen. This latter (background) filter was located where the upstream air velocity equalled the average over the teat grid. In this way the sampling was isokinetic with essentially equal volume flows through both filters,I | ' TEST PROCEDURE All brake ,lstops were conducted from the same speed equivalent (^0 ml, or 18 m/s) to maintain fixed air flow conditions. Burnish and "normal Use" brake applications were at 0,25 "sM (2.^5 m/s2) deceleration 'i and with a two minute time interval. .This provided a peak rotor temperature i of l80C (350F). 'The number of brake applications were selected to provide about one gram of lining wear per test. . Breakin wear was monitored for the first 82 stops. No sampling .$ . was performed for about 200 more brake applications, while the Linings and nr A ' 1* .... ... . 1 -L1- \ v The "normal use" lest van then performed on this f urnished brake assembly. Twenty brake applications were made under the same conditions with the test filter located sequentially at each of the twenty-eight grid 4 locations. The filter cone entrance velocity wan adjusted'to match the grid velocity at each relocation. .' Four grids were used to monitor exhaust velocity 'Slight adjustments were sometimes required to compensate for drift which appeared to be external wind initiated, .A thiz'd test was performed to provide an estimate of the fiber emissions from a hot brake assembly. As in the breakin test, the test filter was positioned in a central location for this procedure. Thirty-one stops wefe made at 0.5 ',gir (^.9 m/s*) and ^minimal time interval until the rotor attained 4lOgC (TT03F). (This temperature'was then maintained by adjusting the application time interval. was allowed to cool. Ten additional slops were made as the brake 's * . All filter weight determinations were performed at equilibrium conditions and then corrected for humidity. After use, the filters were individually stored in covered glass containers. Lining weights were taken after removal of we a* debrj.s but before they had cooled completely, to ' 'minimise weight changes from water absorption. Between tests the linings were stored in a dry jarJ ' The relevant test data a.re included in the foilwing table. A 1 slight pad drag caused the outboard' lining to wear above expectations on the '1 "normal use" test. Since this added.work was not included in the lining wear rate calculations, the specific wear is above the usual range for this lining. \ Mo adverse effect* on the test results would be expected to have resulted from this drag. Similar pad drag effects may occur on cars, when smooth road conditions prevent ,rp?d knockback." I Test Brcnkifl IJnrrpnl. Hre HI Tcmpcrntnrc H: Brake Speed, REM 555 (40 MHl) 555 (40 HPir) 535 (40 KPH) Brake, jecel, "gM Wheel Load, kg Brake Applications 0;25 (2.45 m/s2) ' 257 (567 lb) . 'f i 82 <' .0.25 (2.45 m/s2) 257 (567 lb)' 560 0.50 (4.Q m/s2) 257 ( 5 67 lb) 111 Total Energy, kW-h Max. Apply Temp, total Lining Wear, g lArvirvg Wear Rate, g/kW-h 0.9^3 (1.25 hp-hr) 115 (24or) 1.10 L-IT S-hr> 6.405 ( 8.54 b.p-hr) 0.469 (O.625 hp-b 115 (240F) 410 (770F) 1.60 1.07 a 0.25 (0.011 ----, ) 2.2B (0.100 y hp-nr' v hp-br i t  ' t ,; SAMPLE* EXAMINATION -35 APPENDII . 1 PREPARATION AMT) EXAMINATION OF ASBESTOS CARRYING SAMPLES "ROM TEST FlliTERG* * * 1. All slides, dishes, scalpels, and other utensils used in the following tt * preparations were cleaned in acetone, followed by rinse in 200 proof ietha nol, - 2. An area of measured dimension was selected at random from the test filter, * "cut end placed particle side down on a clean glass slide. JV Several drops of acetone were placed on the filler segment to partially* dissolve and secure it jto the plate. k. The, samples were ashed for a.period of two hours by using a low tempers Lure asher at a chambei pressure of C.5' torr (TO Pa) oxygen end. power cf 200 watts. .< 5 Several drops of a 1\$ solution of nitro-cellulose in amyl acetate were i placed on the residue, and a clean watch glass was used to grind the mixture for a period of five minutes. , 6. A second clean glass Jlide v;as then placed over the mixture of nitre-cellulose and residue, and a "smear" obtained by pressing the two slides together and o. . then sliding them apait. 7. The films thus formedlwere permitted to dry andthen removed by scoring the . edge of the slide with a scalpel and "floating" the film free from the slide in ?.distilled water bath. It was found that the film was most easily removed from the \ slide introduced in Steom 6. Sample preparation techniques outlined below are similar to those reported by Selikoff', et al. in Reference 2. * XT - *8. Approximately. 10 -ell jtrail mtcrosccr ; grids (5 nrn, finder grids) V* . 1 \^ were placed at rnndora on the floating film, and the film was lifted by putting a .clean slide on ton of the film and drawing the slide down through . >. . i the water -so as to trap the grids between the slide and the film (which should now cling to the slide). V*. . i 11 i 'i 4 q, A carbon layer of approximately Q.06um was deposited on the film to t _ . 1 orevent charging during examination in the transmission electron microscope (TSM Direct examination specimens were prepared by depositing a carbon layer bn the dust side of the test filter and dissolving the filter in acetone. Electron microscope grids were used, both to support the sample and to provide grid location reference tnarks. TEH EXAMINATION AND COUNTING `ROOFDUKES 1i Approximately ten electron microscope grids were prepared for eacn of the five filter samples analyzed. Four grids were arbitrarily selected i i from each cample and two grid squares on each grid were sconned for asbestos. The individual grid squares are approximately 9^ M-n on each side and -were examined at a TFM magnification of about h0,000. Tor each grid ares scanned, photographs were taken where possible of the first, 'last, and one randomly Ji * chosen fibril 'for the purpose of determining an average fibril diameter accurately. Measurements were ihep mede visually; that is each fibril, fiber, or asbestos bundle was compared to known calibration marks on the electron microscope screen .i 'to estimate the lengths. The length could*be estimated to within 20J, as .\ determined by vhe photographic measurements. The marks on the screen arc 0.5 cm apart corresponding to 0.125 um when a magnification of >0,000 is used. 1Is7 This approach was taken because it was impractical to photograph all the fibrils l and, furthermore, length measurements were not as critical as diameter measure- .i ments in'determining fiber volume. Wher* both measurement methods ^ere used, 1. c the values providing the greatest indicated brake shoes to:; levels were chosen. Spjnple i. i \) C' D 'E f' '5- \ ASBESTOS CONCL'Nl'H ATION ON FILTERS Sample Identification . Concentration (ng/c;xP of filter) Test-normal stop-new brakes 15*32 Background for A i Test-normal stbp-burnished brakes 1.06 7-9^ . Background for C 4.64 Test-high temperature stop-burntshed brrkes 5*37 Background for E - not used, insufficient sample Blank - unused filter 0.33 1 From photographic measurements of 120 chrysotiie fibrils, the. asbestos fibril average diameter was determined to be 0.0337 ^m w^h distributions similar to that observed by other workers (10). From 45 fibrils of triple jet- milled chrysotile' the average diameter was determined to be O.C316 with a standard deviation of O.OO63 ASBESTOS IDENTIFICATION . .. Asbestos can be identified in the transmission electron microscope .1 n in one of two ways. The first nnd absolute method is by electron diffraction. 5 Such a diffraction pattern is presented as Figure 8. Measurement of diameters and correlation of these measurements with a known standard gives the interplanar *1 spacings of. the material. Comparison of these spacings with the ASTM file identifies the material as clir.o-chrysotile (asbestos). . 'The second method of identification is by appearance. Figure 9* \ represents an image of asbestos obtained ir. the TEM. Fine lamellae are observed within the fibril which are parallel to the long axis, This appearance , . is characteristic o1 f chrysotile asbestos fibrils. * Because of the nature of the N electron beam, radiction and heat damage enn occur in the material markedly -16- i i changer in asbestos are represented in Figure 9b, the fibril of Figure 9a has been changed to a v A*a and calculated . Temo Use Calculation >st BK/rrd Hasi s 564 0.564 Measured .27 0.00 Measured yt 0,12* Measured 33 0.33 Measured .62 9.62 Measured .48' 1.07* r(3)-(4)] x (5) 96 1.90* (6) * (1) ,1 Mt) 7.4 (8) x (1) 255 From Meas. > .0586 070 .0055* (9) x (10) Measured (11) T (12) X ICC . 27v {* A(2) 33 .018% XKX (10) x (14) (11; - (15) x ice (15) * (12) :: ICO to insufficient sample -18- ! ;i V T/uTIMATION OF DRAKE LINING ASBESTOS Dj J.UTION IN UKNAN ATMOSFITEHE . The concentration of asbestos fiber from the broke lining wear debris . i . is assumed to bo the same as was found in the "normal usage" dynamometer test and to be dispersed and have the'.same residence times as the lead emitted from 1f the engine. Assume an average mileage of 15 MPG from cars which emit 75$ of the lead to the .atmosphere. When gasoline averaged 2.52 grams of lead per gallon, the typical lead concentrations in urban atmospheres were about 2 ng/nr3 (JAVCA, Sep. 19^9 19, p, 684). Typical U. S. cars wear 202 grams of lining per year and drive 10,000 miles per year. * The 11 normal use1' dynamometer tests provided asbestos fiber amounting to 0.0025$ (2.3 x 10"") of the brake lining worn. ' Allowing a factor of ten to provide an upper bound in this determina tion, the asbestos concentration in urban atmospheres from brake wear should be less than , C 2C2 r, ~2 ng Fb/'tn3(15M?G)~! 0.07 ruz 10 (2.5 x 10* ^ vicjooo ni' L0 (.75) J or i?" 2.52 gal Urban atmospheres vary in asbestos fiber concentration freo city to i, city , within a city, and from one time to another. This variation does r.ot correlate with expected automobile-brake usage. The concentration has been reported to reach 100 (2). Thus it appears thot the wear of brake lining produces, at most, a'small fraction of the asbestos fiber in urban air. This is not surprising when one considers that brake lining wear involves only 1.5$ of J. S. asbestos usage and that brake usage converts over 99*95$ of this to non*-fibrous dust. v . CALCULATIONS 0? '')LLECTICN EFFICIENCY LINING COMPOSITION ESTIMATE FROM LABORATORY ANALYSIS S1O2 ' MgO. .1 16.5^ 17.8 Fe203 Alg03 . h2o 2.5 0.5 | J Chrysotile Asbestos CaCOs 15.1 Zn Organic 5.9 ^X- Total 100,C$ i ij - WEAR DEBRIS ESTIMATE Decomposed Asbestos 36-9%. Decomposed Limestone 8.6$ Zinc Metal '. liStk Inorganic ORGANIC J * i Volatile Uncertain Low Volatility Organic Collectable Total Collectsble Collected on Filter Collectable Material t* r*'.'v'i 10.5$ 15 7$ ' 12.1$ 12.1$ to 27.8;t . 61.5$ to 77.27; hTl, . to >0.2*' \ RE!ERKNCEE 1. Sullivan,' R. J. et al., "Preliminary Air Pollution Survey of Asbestos," * I H.A.P.C.A. publication AfTD 69-21, (1969). 1 2, Selikoff, E. J., et el., "Asbestos Air Pollution," Arch. Environ. .' r 1 ' r Health, Vol. 25, (July 1972). .. 3- Thomson, J. G. , "Asbestos and the Urban Dweller," Ann. N. Y. Aced. Set., ' 132:196 (1965). I. h. Lynch, J. P., "Brake Lining Decomposition Products," .T. Air Pollution Control Assoc. 18:1^ (1968). 5. Utxon, S., "Technical implementation cf the New Asbestos Regulations," Arm. Cccup. Hyg. (Brit.) Vol. 1} (1970). 6. Rabinowicz, E., 'lT?riction and Wear of Materials, " John Wiley, (1565)* 7. Anderson, A. K., "Wear in Brake'Materials, M ACME Wear Conf. , (1969). 8. Anderson, A. E., et al.) "A New Laboratory Friction and Wear Test for the Characterization of Brake Linings," SAE Trans., pp. 56I-9, (is68). 1 9. ;Tacko, M. 0., et al., "brake and Clutch Emissions Generated During > Vehicle Operation," SAE Preprint 730548, (1973). 10. Yada, K., "Study of the Microstructure of Chrysotile Asbestos by High 1 Resolution Electron Microscopy," Acta Crystal, Vol. A, 27, (I97I). Figure 1 Dynamometer tor,l schematic. Figure 2 Dynamometer test setup. ' Figure 5 i >igur k i Figure 5 View'of brake assembly and test grid. i ,( TEM image of chrysotile asbestos fibers. TEM .image of partially opened fiber bundles. . F3 gure 6 TEM image of fiber bundle on "normal use" filter. 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