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FILE NAME Manville JMA DATE 1966 Dec 19 DOC JMA239 DOCUMENT DESCRIPTION Brake Tests Manville Research mey rm ~ MANVILLE RESEARCH ae Report No. 456-2506 e te AND ENGINEERING CENTER Date December 19 1966 _ _ o Title STUDY OF WEAR DUST FROM BRAKE LINING Project 2550 SUMMARY Brake which lining wear dust was collected on a membrane filter mounted in surrounded a brake run on an inertia dynamometer In addition a box to this airborne fraction the dust that settled to the floor of the box and that which remained within the brake was also collected A total of 6-1 grams of dust was collected from 2150 stops during a total time of about 110 hours The airborne portion was 2.7 grams Most of the stops were made from 35 miles per hour at 10 secdeceleration interspersed with stops from 50 mph about 10 per cent The airborne dust was examined by light microscope electron microscope ceds . rays and other means Asbestos fiber could be detected only by the electron dan microscope which gave a maximum of 1.4 per cent fiber by weight in the wear grener dust although the lining contains 70 per cent chrysotile fiber te doe This result is accounted for by the high surface temperature and severe abrasion oserte during even the mild braking of these tests when the average temperature did not et rar exceed 200 Calculations show that the surface temperature at the true area Mdtwes e of contact 1 per cent of the apparent area can reach 2000 or more It is Wed concluded that most of the fiber is converted to an amorphous mineral by intense heat and fine grinding e e ow It is recommended that samples of the particulate matter in the atmosphere be collected at suitable distances from highways and the sample examined in the electron microscope for asbestos Contents Summary Introduction Experimental Method FFiigguurreess Appendix culations Appendix II Tables 1 and 2 Appendix III Appendix IV References I cal- 1-4 , and David David Sinclair Sinclair Reported by David Sinclair Basic Physics Section CC F. J. Solon GH a K. W. Smith MD -GH A. C. Smith S F. L. Pundsack Att S. Speil J. Dec H. G. Koch W. C. Streib H. W. Gilbert ~ , H. F. Remde D. Sinclair Library 2 Notebook 723 p 141 M. File 456 MANVILLE RESEARCH e, " a Report 456-2506 ee - centr AND ENGINEERING CENTER Page e INTRODUCTION Laboratory measurements were made to determine what type of particulate matter and gases are given off when a brake lining is worn during operation The wear of the drum usually cast iron is necessarily included Of special interest is the airborne dust expelled into the atmosphere from the moving brake Previously some observations had been made at Manville Research and Engineering Center on dust removed by hand from a laboratory brake 1 but this is the first time to our knowledge that any observations have been made on the airborne fraction oe men articles4,5 A search of the literature revealed no measurements on brake lining wear dust } although the rate of wear is sometimes given.2.3 Recently numerous have appeared calling attention to the widespread use of asbestos in materials such as brake linings floor tile roofing asbestos products etc. It is usually assumed that as these materials wear much of the asbestos fiber is dispersed into the atmosphere thereby contributing to air pollution and creating a health hazard This is understandable since the asbestos content of these republicaton materials is often high 70 per cent in the brake linings used in these tests and asbestos is commonly considered to be indestructible However we know of no measurements made to test this assumption or to observe the amount of asbestos or in urban atmospheres aistrbuion The present tests show that during the wear of brake linings very little asbestos fiber is dispersed into atmosphere Examination of the airborne dust by - light microscope electron microscope and ray diffraction showed very little general of the original chrysotile fiber Nearly all the fiber appears to have been converted to an amorphous mineral by the severe abrasion and intense heat generated for during brake operation A point made on eight electron micrographs gave an Not upper limit of 1.4 per cent fiber in the airborne dust CONFIDETAL This is not surprising when one calculates the amount of energy dissipated while operating a passenger car brake It is shown in the appendix that the heat generated raises the temperature of the surface of contact between brake lining and drum to CONFIDETAL contact.6 about 2400 This high temperature occurs on the surface of the lining at the regions of actual contact with the drum much less than the apparent area of contact.6 These regions of contact are worn away during rubbing so that the actual contact continually shifts to new regions As a result the wear particles of asbestos JM resin a Tabor etc. are heated to very high temperature for a very short time Bowden and observed many incandescent hot spots during the rubbing of metals on glass EXPERIMENTAL METHOD 19 19 top A wooden box approximately a 1-1 cube with a Lucite was constructed to fit around a 1961 Ford brake mounted on the C inertia machine in the Friction Materials Research Section pilot plant Figure 1 is a photograph of the box mounted on the brake The left rear side has a conical air inlet which carries a square Flanders fiber glass on filter the entrance into the box The right front side for Gelman membrane filters These and tapers to a square opening at the outlet of the box carries two 8 x in filter holders holders are connected through flexible hoses to a 7-1 industrial vacuum cleaner not shown When the vacuum cleaner was run about 150 cfm of free air was drawn through the Flanders filter over the brake and out through the membrane filters to collect the airborne wear dust The pressure drop across the membrane filters was about cm Hg measured with the mercury manometer shown standing on the box at the right connected to a petcock on the exit side of the filters The pressure drop across the Flanders filter was about in 1120 measured with the water manometer shown on the left connected to int int - through the aide of the hov i. MANVILLE RESEARCH AND ENGINEERING CENTER S SSS | mo, | _ SSS Report No. Page 2 456-2506 < or <=< = Since the interior of the box was undera negative pressure of in H2O it was necessary to seal the joints and screw holes against entrance of dusty ambient air This was done on the outside with DUXSEAL and on the inside with contact adhesive The interior of the box and the parts of the brake and mounting within the box were painted white to show up any wear particles that settled out The stationary hubs at each end of the brake drive were sealed to the ends of the box with 16 rubber sheet and rubber cement aetn at Figure 2 shows the auxiliary equipment used to measure the relative rate of evolution of wear dust during and after braking At the left rear is seen a Sinclair e cme aerosol photometer connected to the side of the box through a petcock In the left foreground is a logarithmic amplifier connected to a Varian recorder on the right Dusty air was drawn continuously from within the box and through the photometer at a rate of about 1 cfm by means of a hp Gast pump Since this rate of air removal is about 0.7 per cent of the total air flow its reduction of the amount or dust collected on the membrane filters is negligible Minuma d Figure 3 shows the type of record obtained during stops from 35 and 50 miles per hour sec Minumannada at 10 to 12 deceleration at intervals of 2-1 minutes Two of the stops were Minumanad from 50 mph as indicated and the others from 35 mph Usually a more or less regular in pattern occurred in which the dust concentration fell to near zero between each of unaypn several stops and then remained at an intermediate level for a couple of stops ~ unaypan The marks numbered 2 3 and 4 are calibration points for the logarithmic amplifier In They are obtained by interposing neutral optical filters of known light transmission 15ust into the photometer light beam infina Figure 4 is the resultant calibration curve which shows the approximate logarithmic infina relationship between chart reading and dust concentration the latter proportional to KHUTATLIVAN scattered light intensity For example a chart readinogf 50 corresponds to a dust concentration about 100 times that for a reading of 5 KHUTALIVAN Dust was collected during 2150 stops most of it on two membrane filters The average KHUT ATALIVAN temperature of the brake lining was kept at 175-2000F and was measured with a thermo- KHUTATLIVAN couple set in a hole in the lining about 1/16 in below the surface The temperature KHUTTATALIVAN was kept low in order to simulate average braking by increasing the time between stops to 3 to 4 minutes when overheating commenced As indicated earlier this tempera- THE ture is far below the instantaneous surface temperature see Appendix I . RESULTS _ Three fractions of wear dust were collected 1. Airborne dust collected on membrane filters 2.71 gm 2 Dust removed from within brake after completion of test 3.54 gm . . > 3. Dust collected from within box after completion of test 0.214 gm be} These fractions all include some cast iron worn from the drum about 1 gm total The samples were analyzed for ignition loss by light and electron microscope ray spectrometer emission spectrograph infra spectrograph and Coulter particle size analyzer In addition air samples were withdrawn from the box during braking analyzed by the Gollob Analytical Service Table 1 shows the results obtained and fom ~ MANVILLE RESEARCH AND ENGINEERING CENTER a Report 456-2506 Page 3 Table 2 shows the composition of linings used eyemntse is about 70 per cent chrysotile fiber after the It is water seen that and other the finished lining volatiles are driven off The total weight of sample collected 6.46 gm is much less than the measured weight em loss of the brake shoes and drum primary 4.0 1 gm secondary 7.0 1 and 2 1 gm we However the accuracy of these weights is questionable because of the heaviness of mnges the shoes and the drum We feel certain that negligible loss of dust occurred during ne the tests so that we cannot account for the discrepancy eer ek ee republicaton or distrbuion genrgi es for e ee Noi e CONFIDETAL JM MANVILLE RESEARCH AND ENGINEERING CENTER mo, | Report 456-2506 Page 4 APPENDIX I Calculation of surface temperature of lining These tests simulate a front wheel brake of a 1961 Ford designed to decelerate 30.5 per cent of the car mass or 1270 pounds At a velocity of 50 mph= 73.5 sec the kinetic energy of this mass is 106,000 lb or 136 Btu At a deceleration of 10 secthis heat is generated during a stop of 7.35 seconds duration During the first second the average rate of heat generation is 34.6 Btu per second = 8.72 x 103 cal This heat is generated over a total lining area of 52.5 sq in 21 x 2-1 rubbing against cast iron Bowden and Tabor give a method which allows a calculation of the true area of contact Their experiments on metals showed that the actual area of contact is directly pro- portional to the load As the load was increased the points of contact flowed plastically until the area of contact was sufficient to support the load In the case of less ductile materials such as brake linings the points of contact would republicaton be crushed until the bearing area was large enough so that the crushing strength was no longer exceeded or For metals Bowden and Tabor found that the yield pressure is three times the tensile strength We make the same assumption for brake linings Manville Research re- distrbuion similar port 456 received from A. J. Taylor gives lining to that used in these tests The 6.87 x 105 sq ft a tensile strength of 1590 psi for a yield pressure is then Pm = 4770 psi- e gen ral According to the definition of the yield pressure Pm = L where L is the load and for a is the real area of contact The load on the lining may be calculated equating Not by the torques about the axle of the simulated car CONFIDENTIAL The torque on the tires is mR= 1270 x 10 x 32.2 CONFIDETAL Here m = mass declerated = 30.5 per cent of total mass of car = 1270 mass d = deceleration = 10 sec 32.2 JM R = rolling radius = 1.09 ft The torque on the brake lining is Mir = 0.4 x L x 0.463 . Here M = coefficient of friction = 0.4 L * load rs drum radius = 0.463 St ( bs Equating these two torques gives the load L = 2320 - force ns lining average The roughness of even the smoothest brake , microinch is about 2500 times molecular dimensions 2 Requested by J. Q. Koch 358 Summary products from brake linings were produced in a test machine in the Friction Wear products vere made and the dust from the wear Naterials Department Two runs the test machine The air borne dust vas vas collected from three locations of accumulated in the drus and box collected on Gelaun peper Samples of dust were also collected republication 607 was examined by various techniques to determine The dust from the wear products fiber is the major constituent of the nature of the products Since chrysotile undetected by ray or brake linings it was surprising to find that the fibtehrewaeslemental constituents infrared techniques Spectrographic data allows that ratio of 1 of chrysotile fiber that is silica and magnesia are present proper identified and estimated With the electron microscope however chrysotile fiber was to be 1.4 per cent in the air borne dust Sea Report or diffraction patterns A strong band Iron and magnetite were identified by ray be indicative of a phenolic material at 3.0 microns of the spectrum may probably a degradation product of phenolic resin distribution fiber is almost completely degenerated to The mechanism by which the chrysotile is not understood gmarvifor aInt aimsorbpehloiuesvepdrotdhuacttto hr isprphoadsuectosf dtuhreinignqburiarkyinigs obpeeinrgatiinovnesstigated Not A development report of the wear products 456-2506 456-2506 will be issued by D. Sinclair and other aspects of this work regarding the nature CONFIDETAL Materials Submitted Materials Submitted Sample Ident Na Laboratory Index No. SM 1 494-25-1 233 894-25-2 894-25-2 233 894-25-3 894-25-3 233 494-25-4 494-25-4 494-25-4 Description Air borne dust chmically from Gelman paper run 1 Same as sample 1 run 2 Dust from drus Dust from box separated Methods of Analysis dust vas from Gelman peper by dissolving the paper obtained Fine air borne removed run 1 The solvent vas removed and the dust solids dried and ia cold NEX and centrifugatviaorne submitted to ray spectrographic microscopic at 500 in vacuum Samples laboratories for examination In run 2 considerably more dust was collected in TUR 1 90 infrared from three locations Only air borne dust was Nambook 3433 pp 45-46-56 Results of Analysis in per cent Chemical Ignition losses at 800F Sample 2 13Lo.s5s 3 19.3 & 31.0 This sample was apparently contaminated with dried paint flakes and other material found in the box Amount of Dust Recovered in Run Sample Sample 3 & Grama Recovered 2.4 3.54 0.214 of airborne dust was recovered from the Gelman It is estimated that 0.31 grams paper after the first run enwoe Infrared 2000 of run 1 airborn dust was obtained using the An infrared spectrumm chart No evidence of chrysotile was observed KBr pellet technique to prepare the sample be indicative of a phenolic A strong band at 3.0 microns may om minattehreiaslpepcrtorbuambly a degradation product of phenolic resin sen Xxx esr were made from ray diffraction patterns The following identifications Identification Sample magnetite and possible trace of iron ULraes fy iron 3 and iron 4 magnetic fraction magnetite $08 ek magnatic fraction rutile T10 Zn5 zincite calcite CaCO3 quartz 5102 Chrysotile was not detected in any of the samples Spectrographic 800F The comop f tho e 6n 00F e ashn of t samps les 1 3 ver vee re found to be similar in aE PL 4 wee titanium and sinc * Sample contains some copper te aa 3 fiber was detected with the electron microscope The amount of chrysotile Chrysatile the airborne sample of run See Report fiber was estimated at 1.4 per cent in _ Int et Reported by ray by Microscopy by Analytical Camistry Section 0.1 Bulley Basic Chemistry Section Spectroscopy by 84 COI A. C. Smith L. Pundsack B. C. Kock B. Spell Attn D. Bailey D. Sinclair C. N. Thompson B. W. Wegrzyn Library 2 saw 6 oo atessererertre orn am ee a w: re cc . ta ceca a tebe . . J. Commistry Beation OE Rese OR etRK