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FILE NAME: Z< DATE: & DOC#: Z< DOCUMENT DESCRIPTION WZZ>ZZ Z/h to:;;",.' , l'f; , ..... I ' . '1 " .' " "-: k'\ .'.'i " / , r e'" . 1 ; I , (, (" ." .. I U. S. ENVIRONMENTAL PROTECTION AGENCY Office of Toxic Substances Washington, D.C. 'GCA-TR-79-73-G Submitted in Partial Fulfillment of Contract No. 68-02-3168 Technical Service Area 3. Work Assignment No. 18 EPA Project Officer f' , J mes Bulman .. ,: '" -1'~, \ LIFE CYCLE OF ASBESTOS IN COMMERCIAL , I' AND INDUSTRIAL USE INCLUDING ESTIMATES OF RELEASES TO AIR, WATER AND LAND FinaZ' Inhouse Report February 1982 Prepared by , David Cogley Nancy Krusell Robert 'XcInnes Peter Anderson Ronald Bell U.S. EPA Headquarters Ubral1 , Mall code S2e1 ~T 1200 Pennsylvania Avenue"NW Washington DC 20460 GCA CORPORATION GCA/TECHNOLOGY DIVISION Bedford, Massachusetts I DISCLAIMER This Final Inhouse Report was prepared for the Environmental Protection Agency by GCA Corporation, GCA/Technology Division, Burlington Road, Bedford, Massachusetts 01730. in partial fulfillment of Contract No. 68-02-3168, Technical Service Area 3, Work Assignment Nos. 2 and 18 and Contract No. 68-02-2607, Work Assignment No. 36.. The opinions, findings, and .', conclusions expressed are those of the authors and not necessarily those of the Environmental Protection Agency. .Mention of company or product name is not to be considered as an endorsement by the Environmental Protection Agency. ii I .,.__J. . .,. . mm! ",:,),r'n: R'1 '~n.'1f~w!1tIVMJ !C~': -'it ~e\.~\I!I'" SECTION 5 FRICTION MATERIALS IN TRODUCTION for Friction mater~als slowing or stopping B,re used in motion, and clutches ~,or transmitting torque, in brakes i~ torque limiters. Besides their well- known use in autos, trucks, buses, and railroad cars, friction materials are also from found in other bulldozers and applications where motion must be controlled, ranging tractors to typewriters, tape recorders, and parking meters. Automobile brake ,linings have used asbestos since 1908 when Herbert Frood demonstrated that a combination of pure woven asbestos spun on brass wire com- bined with a specially cellent durability and developed 'bonding heat resistance. agent resulted in a product with exBy the first World War, woven asbestos brake linings were in military transports. common use In 1921, a on passenger tars, commercial vehicles, and vulcanized combination of ground-up waste, bonded abslobceks,tobs,utanmdoladedrubblboe'erk-tsypweerbeinndoet rwwidaselyuseadccetoptemdanuunfaticltuareftethrethfeirssetc'omnodldWedorbldrake War. Disc brake pads were originally developed for aircraft landing wheel brakes in 1944 and have become more universally used in the intervening years. , Clutch facings followed a similar pattern of introduction. cotton replaced leather in automotive clutch acings in 1905 and Impregnated was, in turn, , superseded by asbestos. yarn are widely used and Today, clutch facings continued progress is of wire covered with asbestos being made in die cast and molded clutch facings. 1 ,In 1980, an estimatecdon4s~u,m70p0tiomn,etwriacs tuosnesd oinf athsebemstaonsu. faacbtouuret o12f pfreirccteinotnof the United States materials. 2 Five fiber companies dominate the United States friction S material m, arket, but foreign competitipn is becoming more of a factor. FiRure.s for. production volumes were not,available but a breakdown of the estimated value of given in Table 19,. asbestos-bearing These data were friction materials produced in 1979 is derived by projecting 1972 figures provided by Meylan4 to 1979 costs. As shown, brake linings are by far the largest com- ponent (58.9 this section percent) of the asbestos friction material industry. Consequently, emphasizes the production processes and emissions associated with brake linings, placing lesser emphasis on other products in the friction ' materials group. 82 TABLE 19. VALUE OF ASBESTOS FRICTION MATERIAL SHIPMENTS (IN MILLIONS OF 1981 DOLLARS)a . Final product Total-product shipments, including interplant transfers 1981 1972 Percentage of total (1981) Brake linings Woven, containing asbestos . $ 27.8 $ 10.2 4.9 yarn, tape or cloth Molded. including all nonwoven types 308.4 113.1 54.0 Disc brake pads 38.8 14.2 6.8 Clutch faeings Woven. containing asbestos yarn, tape or cloth Molded. including all nonwoven types 54.2 132.2 19.9 48.5 9.5 23.1 Other 9.8 3.6 1.7 Total asbestos friction _ material $571.2 $209.5 100.0 aprojected from Meylan. et a1. (197'2). p. 61, It using September 1981 Engineering and Mining Journal cost index factors. 83 PRODUCT DESCRIPTION Composition Many raw materials, proprietary information, including some whose exact roles are regarded as are used in.varying quantities in the manufacture of friction f~iction materials. The major materials is asbestos or foundation constituent of practically all fiber, which can rang~ from 15 to 79 percent of the final product by weight depending on end use. In 1980, chrysotile grades 3 asbestos through used to 7 accounted for all of the estimated 43.700 metric tons produce friction materials. 2 Fiber sizes and types may of be mixed or calcined to improve performance. tion Asbestos is used because of ~ts thermal stability, relatively high friclevel, and reinforcing properties, but asbestos alGne does not offer all of the ifiers desired properties. Therefore, other materials known as property modand binders are added. Different types and amounts of modifiers are used to provide desired levels of effectiveness, wear, fade, recovery, and noise. tion of Binders hold the disparate a typical automobile br~ke materials lining is together. The shown in Table average composi20. Individual product release mixes their vary considerably from these averages. Manufacturers refuse exact product compositions due to proprietary considerations to but some details are available in patents'. Several examples are given in Table 21. liningTsa.bleP2h2enloilsitcs-tybpine dreerssinansdaprerotpheertymomstodcoifmimerosnlyuseudsedinbainudtoemrsobbielecaubsraekeof their Other high binding efficiency and ability to withstand pyrolytic breakdown. resin binding systems are based on elastomers. drying oils, or combinations. . A wide range of materials are used in friction materials as property modifiers. In general, property modifiers can be divided into two classes. nonabrasive modifiers and can be c~assified further abrasive as being modifiers. either high Nonabrasive friction or friction modifiers low friction mate- rial. inous rhe most common material derived high from friction cured or mat~rial is polymerized friction dust, a cured cashew shell liquid, a resphenolic compound. When heated with hardening agents such as hexamethyiene tetramine or formaldehyde, it polymerizes becoming sufficiently hard to be Other friction dusts are different combinations of cured resins, granulated. polymers, fillers, and and abrasion cashew resins. Ground rubber is normally used for.noise, wear, control in particle sizes smaller to or slightly coarser than those of the cashew dusts. 4 coke Low friction nonabrasive modifiers like carbon black, flour, or other carbonaceous material may be added to graphite, lower the petroletml, coefficient of or friction and reduce noise. particles although graphite Normally the materials are added as fine is occasionally used as coarse particles powders or p~llets. It 84 TABl,E 20. AVERAGE 'BRAKE tINING COMPOS 1'1'1ON (WEWHT PERCENT) H Material Automobile Truck Asbestos 55 33 Resins and polymers 28 48 Oxides and pigments 9 16 Metals 3 2 Carbon, graphite, etc. 5 1 Total 100 100 aLunch, quoted b1 Meylan.~ et al. TABLE 21.' BRAKE LINING COMPOSITIONS FROM PATENT LITERATURE (WEIGHT PERCENT) 4 Lining No. la Linin& No. 3b Asbestos 55 Barite 10 Phenolic resin binder 20 Brass 5 Magnesium carbonate 8 Limestone 8 Organic calcium powder 10 Asbestos 35 Barite 2.5 Graphite 7 Brass 13 Phenolic resin 7 Lead oxide 11.5 Buna N rubber 8 Naphtha 7 Copper sulfide 12.5 Methyl ethyl ketone 4 Lining No. 2c Asbestos Pheno lie res in Nitrile rubber Cashew dusts Calcium fluoride Copper iodide Lining No. 4d 60 Asbestos 50 15 Tarry residue 12 3 Barite 20 12 . Phenolic resin 20 7 Graphite 2 3 aSakata. et al., 1974 (Hitachi). bKe. 11er, 1969 (Abex). cToyota Central Research and Development dMitchell, 1974 (DuPont) Labs, 1971. 85 TABLE 22. PROPERTY MODIFIERS IN FRICTION MATERIALS 4 Binders Property modifiers Use function Phenolic-type resins Natural rubber Buna N rubber Nitrile rubber Tire scrap Pitch Cork Gilsonite Elastomers Drying oils Graphite Coke Coal Carbon black Gilsonite . Fric~ion dusts Rott.enstone (Si.Oz) Quartz (Si.02) Wollastonite (CaSi03) Brass Chips Zinc and compounds Aluminum Lower fric~ion'coefficient and Lowe.r friction coefficient and Lower friction coefficient and Lower friction coefficient and Lower friction coefficient and Lower' friction coefficient and Remove decomposition deposits Remove decomposition deposits Remove decomposition deposits Remove decomposition deposits Remove decomposition deposits Remove decomposition deposits noise noise noise noise noise noise Limestone (CaC03) Improve wear resistance (XI Clays Improve wear resistance 0\ Silicas Improve wear resistance Barite (BaS0lt) Improve wear resistance Lead and compounds Lubricant to prevent grabbing Antimony compounds Calcium compounds Copper and compounds Barium hydroxide Potassium dichromate Magnesium carbonate Iron oxide Cryolite (Na6AlF3) Fluorspar (CaF2) Cardolite Nickel Sulfur Not available Not available Not available Not available Not available NQt available Not available Not available Not available Not available Not availab.le Not available Molybdenum sulfide (MoS 2) Lubricant Calcium fluoride Lubricant Abrasive modifiers improve brake lining wear resistance at minimum cost but simultaneously increase noise and decrease mating surface compatibility. In organic materials such as whiting (ground limestone), barite (barium sulfate), clays, silieas, and metals or metal oxides may be added to brake linings in small amounts and fine particle sizes to provide desired characteristics. For example, brass chips in h.eavy-duty friction materials break up undesirable surface films while a small amount of zinc ch~ps can assist in recovering normal performance following a fade. Particle size is limited to 100 mesh or finer because large, hard particles groov.e and wear mating surface. If Clearly, a wide range of .components may be present in any automobile or truck brake lining depending on anticipated application and use patterns. When "material variations are combined with manufacturing variations, it is clear' that brake linings can vary' greatly from company to company, even when intended applications are identical. Thus. emissions during production and use can vary greatly from lining to lining. Uses and Applications Friction materials are used wherever motion must be controlled. Friction materials are used in clutche~ for transmitting torque. in brakes for slowing or stopping motion, and in torque limiters. Although use in automobile.brakes is the most important application commercially, asbestos friction materials are used in buses, trucks, railroad cars, military vehicles, and construction equipment as brakes and clutches. Friction materials are also used in farm tractors, presses, hoists., forklift trucks. machine tools, shuttle cars, mining equipment, chain saws, drilling equipment. spinning and knitting equipment, X-ray machines. tap~ recorders, typewriters, bicycle brakes, snow blowers, washing machines, and parking meters. SEecial Qualities All products containing friction materials rely on the coefficient of friction between mating surfaces to transmit or stop motion. Brakes convert kinetic energy into heat, absorb the heat, and gradually dissipate it into the atmosphere. Disc brakes consist of two parts, the rotor which is connected to the wheel and the stator on which the frict;i.on material is mounted. Clutches transfer kinetic energy from a rotating crankshaft to the transmission and wheels. Both brakes and clutches may operate wet or dry. In dry systems, the heat is conducted to the air and surrounding structure while wet systems operate within oil or another fluid which absorbs the heat to maintain temperatures below 200C (392F). The special qualities required by friction materials include: Possession of the appropriate coefficient of friction for the desired application Ability to withstand the high temperatures generated at friction interfaces Dimensional stability Strength 87 Durab ility Lack of abrasive characteristics which could lead to scoring of mated surfaces Asbestos is used in friction materials because'of the properties listed 1n Table 23. The most important properties are thermal stability. reinforcing ~bilitie~, relatively high friction, fiber flexibility, and relatively low cost. TABLE 23. UNIQUE PROPERTIES OF ASBESTOS APPLICABLE TO FRICTION MATERIALS 3 ,7 Properties Comments Fibrous form Flexibility contributes to forming characteristics. Fibers interlace and interlock, enhancing strength. Flexibility reduces wear at friction interfaces. Fine fiber diameter Provide strong reinforcing characteristics because of the large number of fibera per unit weight. High tensile strength Temperature resistance Provides strength and durability to friction products. Chrysotile unaffected by T <200 oe (400F). Stable for short period of time at T around lOOOoe. Able to withstand high temperatures generated at friction interfaces, up to 400 0 e (750F). The temper- ature of maximum ignition loss is loooDe (1800 0 P). Cost Provides low cost/performance or cost/physical property ratio. ======-~,====================---==-========================================== SUBSTITUfES MO$t large manufacturers of friction materials have active research and testing programs working toward the development of 'asbestos-free brakes. Incentives to change from asbestos to some other material are numerous. Some new nonasbestos products are at the stage of consumer testing and their manufac-' turers are optimistic regarding their future use. Possible alternatives which have be~n considered include: 1. Glass Fiber - Overall strength is lower than that of asbestos, but strong enough for friction material applications. Unfortunately, at the 'temperatures reached by braking operations, glass fiber melts, even in depths below the operating surface. 2. Steel Wool - Compared to asbestos, the overall strength is lower and the cost is much higher. 8, 9 88 3. Mineral Wools - Overall strength is very low and brittle to the extent of limiting mixing processes. 4. Carbon Fiber - The main properties of carbon fibers are good. A major consideration is cost which is a great deal higher than asbestos. It is more efficient than asbestos under high service temperature conditions, but heat flow is uneven and the tensile and impact strengths are relatively low. Carbon fiber has high thermal stability and low density making it especially attr.active for aircraft brakes. 8,9 5. Sintered,Materials or Cermets - These materials are now being used to manufa~ture brake linings for railroad cars and airplanes. Cermets have extremely high thermal stability. The wear resistance is not good enough for automobile use and the cost is too high. Both carbon fibers and cermets are stable to 700C (1290F). High thermal conductivity can excessively, heat hyd~aulic brake fluid causing erratic performance. However, this problem may be avoided by proper design,lO 6. Semimetallic Materials - Semimetallics are stable to temperatures of 400C (750F). and exhibit excelle~t wear resistance. 7. Potassitnn Titanate Fibers - The National Aeronautics and Space Administration (NASA) has investigated new friction materials and their applications outside the space program. As part of this effort an improved friction material for lightweight cars and trucks was developed which utilized potassium titanite fibers with the DuPont trade name FYBEX. However, unfavorable toxicological effects and other market considerations caused DuPont to withdraw FYBEX from the market. 3, 8. Aramid Fibers - These are being researched for use in high performance clutch facings'in automatic transmissions. They do not possess the flexural or physical strength of asbestos, and the fibers are not easily dispersed as they tend to clump together. a 9. Vermiculite - Delaminated vermiculite is used in friction materials which are commercially available tnroughout Europe. It maintains strength at high temperatures, is compatible with phenolic resins, require little attention in,manufacturing methods, and may be used with asbestos to help reduce asbestos content. 11 10. Silicon Nitride - This material was used for the brake pads in' prototypes of the Concorde. It has a longer service life than asbestos and higher thermal conductivity' (desirable in this application) but is more expensive and heavier than composites eventually adopted. 11 89 11. Others - Various other fibers have been used in phenolic binders. such as aluminosllicates (wollastonite). All have drawbacks and none are yet as good as asbestos. especially for high-temperature applications such as disc brake pads. 11 Borg Warner Corporation and Abex Corporation (among others) haye developed proprietary substitutes for automobile brake friction materials. Some are in the consumer testing stage. but no additional information is available at this time. Raybestos-Manhattan has tested a wide range of materials in an attempt to find a substitute for aspestos. Fibrous glass. ,mineral wool. wollastonite. potassium titanate fibers, heat resistant organic mineral fibers and natural organic fibers such as cotton and sisal have been considered. ,;Except for wollastonite and the natural organics. the fibera are more expensive than ,asbestos. Unfortunately, the less expensive fibers lack the heat resistance and fiber strength needed in brakes. Another problem is that many of the fibers tend to break up in the milling process and would require some process modification. Although Raybestos stated publicly in May 1979 that the company would "halt the manufacture of brake linings and other parts that contain asbestos,,12 by using a blend of 10 to 15 components (40 percent fiber. 20 percent resin binde~, and 40 percent friction modifiers), discussions with company representatives revealed that this WilB not strictly true . lS The company has developed some nonasbestos substitute products for certain applications and has committed itself to a search for nonasbestos substitutes, but the complete removal of asbestos from' all friction materials 1s not expected in the foreseeable future. Cermet or sintered metals, a copper or iron matrix of material reinforced with steel fiber.and various ceramic and,metallic property modifiers. are used primarily in heavy-duty applications where high torque capacities and longer life are desired. In many applications, cermet products outperform asbestos products. One example is the aircraft brake market where cermet's market share continue's to grow. Currently, 95 percent of all new conimercial aircraft use cennet brakes. The remaining 5 percent are carbon composite.la Semimetal1ic or resin bonded metallic brakes are present1y,used in heavyduty automotive applications sU,ch as police cars and taxis. While their performance 1s supposedly superior to asbestos brake linings, semimetallic brake linings tend to perform erratically ,at different temperat'ures. fade. and produce more noise than, asbestos linings. Currently, semimetallics are 50 to ~O percent more expensive than asbestos linings but with ,increased production it ~s estimated that costs would drop to within 25 percent 'of asbestos brake linings. s Approximately 20 percent of passenger cars using disc brakes are equipped with semimetallic disc brakes as original equipment and it is estimated that in 5 to 10 years. mODt original equipment disc brakes in passenger cars and light trucks will be semimetallic. 1ij General Motors has used a hybrid disc brake consisting of one semimeta11ic an4 one organic asbestos lining in some mass produced passenger cars. The asbestos lining insulates the brake fluid from heat generated by the se~imeta1lie surface during braking, but never ~ctually touches the motor surface. In effect, the asbestos content of the brakes is reduced. Compared to asbestoslined disc brakes. t~e hybrid brakes have a higher coefficient of friction, 90 " higher heat resistance. 'and wear longer but are more noisy and more expensive. f While some industry sources feel that hybrid disc brakes will capture the market because of superior performance, others believe that trends to lower speed Ifmits and lighter weight cars will reduce the need for high performance brakes. s The friction material in disc brakes is formed into an intrinsically stronger shape than in drum brakes ~nd consequently needs less fibrous rein- forcement. Asbestos is used in many disc brakes to reduce thermal shrinkage and withstand thermal shock, but asbestos-free semimetallic disc brakes have been developed for automotive uses. A typical composition is given in Table 24. TABLE 24. COMPOSITION OF AN ASBESTOS- FREE D'ISC BRAKE PAD (IN VOLUME PERCENT) It Carbon 45 Iron powder 25 Steel fiber 10 Phenolic resin 20 Semimetal1ic disc brakes, originally designed and produced by Bendix Corporation and now also manufactured by two other companies, are expected to increase their market share relative to asbestos disc brakes. In fact, it is projected that in 5 years nearly all original equipment disc brakes made for passenger cars and light trucks will be made with semimeta11ics. American automobile manufacturers have targeted 1983 as the last model year asbestos disc brakes will be used.l~ As for drum brake linings, a nonasbestos product for passenger, cars is not available commercially at this time. However, intense research in this area is undetway, with speci.fics still proprietary at this time. The first commercially available nonasbestos drUm lining may contain some combination of steel fibers, synthetics, cotton, ceramic, carbon, natural materials, glass, and mineral fibers. For model year 1980, commercial nonasbestc?',~ lining was not available for drum brakes; however, Bendix Corporation 1'6 apparently ,very close to mar*Ung this kind of product. American automobile manufactur~rs have targeted 1985 as the last model year asbestos drum brakes will be installed as original equipment. .,. r' _ ......... , The use of cermet brake linings may increase once the problem of their interaction with hydraulic brake fluid can be solved. With all of the current research into brake H.ning substitutes, a nonasbestos product for more universal use should become available in the future. 91 ,.' . ' MANUFA01'URING Primary Manufacture Plants manufacturing friction products contain a diverse collection of machinery. Typically included are grinders. mixing vats, mills, molds, extruders, curing ovens, lathes, metal stampers, presses, paper machines, conveyors, and drill presses. Chemical operations, such as preparation of specificresins, may also be performed onsite. The exact mix of machinery at any given plant depends upon the manufacturing processes in use. Friction materials can be molded using either a dry mix or a wet mix process, woven like textiles. or formed like papers. Overview of Manufacturing Process-In the first steps of manufacturing friction materials, bags of asbest,os are typically dumped into mixers that blend the formulations in either a wet or dry state depending on product specifications. A fluffing device may also be used. Next, the mix is fed through a compression molder (dry) or 'an extruder (wet). to form strips that are cut and bent into various widths and lengths. A release compound is added to prevent sticking. D~-mixed formulations. which include a small amount of solvent, are transferred to pressing molds where slabs are formed, sometimes after a preheating step. Slabs are then hot pressed, causing resin in the slabs to flow, binding the mixture upon curing. The slabs are sawed into specific parts and sent to a curing oven. Dry Mix Molding Process~The steps typically employed in manufacturing friction materials using the dry-mix molding process are shown in Figure 6. Asbestos fibers, metallic constituents, bonding agents, and other additives are.weighed, mixed, then placed into a metal mold and formed into a 'uniform sheet using a preforming press. The mold is removed and the material is heated sufficiently in a curing press to allow the resin to flow and set. Only partial curing occurs during this step. The material is then cut to product-sized segments and rough ground. The resin is then softened by a preheating.step after which the proper arc is formed by steam-heated bending. In the final curing step, the segments are placed in compression molds (lunnettes) and baked at a pressure of 1,000 to 2,000 psi. This converts the resin to a permanent thermoset bond so that the desired arc will be retained. Finishing steps. including sanding and grind- . ing to the correct thickness, edge grinding, drilling holes for rivets, inspecting and branding are required before the brake linings can be packaged. Wet Mix' Molding Process~Figure 1 shows the major steps in the manufacture of wet-mix molded brake linings. The t~rm "wet mix" Is actually a misnomer since the ingredients: of the molded lining are relatively dry. The term arises from the use of a wet solvent in the process. The raw materials are blended in the proper proportions, mixed and then sent through a hammer mill in order to ensure homogeneity. The mixture is then forced into the nip of two roll formers where it is compressed or extruded into one continuous strip of friction material. A chopper cuts the material to the proper length after which an arc former is used to give the 92 Note: I RAW ASBESTOS rlBER ! .RECE IVING AND STORAGE ..It BLEND OF ASBESTOS AND (H) OTHER RAW MATERIALS ~ DRY MIXER(H) .J, MOLD J, PERFORMING PRESS(H) ~ MOLD REMOVED J, CURING PRESS SHEET CUT INTO STR IP'S (H) STEAM COOLING WATER' STEAM ROUGH '"GRINDING 01- STRIPS CUT TO LENGTH(H) .J, STEAM PREHEAT 1 \ CONDENSATE COOLING WATER CONDENSATE COOL ING. WATER STEAM-HEATED BENDING J, CLAMPING INTO LUNNETTES J, BAKING OVEN ~ FINISHING OPERATIONS \lr RADIUS GRINDING(H) ll-. OR' LLI NG COUNTERBORING(H) COOLING WATER PACK-"AGING J (H) - Indicates hooded operations, Figure -6. Dry-mixed molded brake lining manufacture,lS 93 I RAW ASBESTOS FIBER I RECEIVING AND STORAGE BLENDING OF ASBESTOS AND OTHER RAW MATERIALS HIGH-SHEAR MIXER(H) t HAMMER MILL(H) TWO-ROLL MILL(H) CHOPPER(H) ARC FORMER FORCED AIR DRYING CHAMBER BAKING OVEN FINISHING OPERATIONS(H) PACKAGING Note: (H) - Indicates hooded operations. CONSUMER SOLVENT SOLVENT 1----+ RECOVERY SOLVENT . Figure .7. ~et-mixed molded brake lining manufacture. 15 94 material the desired brake lining shape. The linings are placed in racks, air dried and baked to remove ,any remaining solvent before final finishing operations. In an alternative process, arc-formed linings are placed in metal molds and baked in an oven prior to finishing and inspection. Another variation has automatically measured volumes of the raw material mixture dropped into disc brake maIds where pressure is applied, shaping the contents which are removed and baked after finishing. ' Molded Clutch Facings-Molded clu~ch facings are produced in a similar manner, as Figure 8 il- lustrates. Asbestos fiber, a rubber friction compound and a solvent are combined in a mixer and then conveyed t1:lrough a two-rolled mill which compresses the mixture into a continuous strip of material. A punc,h press is used to cut the material into doughnut-shaped pieces. Scraps from this process are mixed and then fed back into the two-roll mill while punched sheets are racked", placed in drying ovens and then into baking ovens for final curing and solvent extraction. Oven dried sheets are finished', inspected and packaged. Finishing operations include sanding, edge grinding, drilling and dusting. Paper Products-Some friction materials can be classified as paper products based on their method of manufacture. In particular, discs for automatic automotive t'ransmissions are punched from rolls of asbestos paper formed on a FO\,1rdrinier or cylinder machine., The forming process, is discussed in detail in Section 4; Asbestos Paper Products. Since transmission discs are annular, much of the paper produced becomes scrap. About 70 percent of a roll is wasted in cutting and must be recycled. In a later step the paper discs are sprayed with a phenoliC resin, heated. and bonded to steel wafers. The ,product transmission plates, steel cores with friction material on either side, ate then ground, inspected. and packaged. Die Cast Clutch Facings-- Larger clutch facings are frequently die cast. Raw materials which in- clude ,asbestos and perhaps rubber and metallic oxides impregnated with resin are mixed, then brought to the work station. A worker measures out the necessary amount and pours it into a mold where it is pressed to the required density., After drying, the form is gear cut and bonded to a metal backing. The face is then ground with a pattern designed specifically for the eventual product application. Woven Products-Woven clutch faclngs are frequently classified as being asbestos friction products. Figure 9, shows the press used in their manufacture. More detail on woven products is available in Section 12, Textiles. Woven clutch facings and brake linings are manufactured from high strength asbestos fabric that may be reinforced with,wire. The fabric is predried in an oven or by autoclav~ before being impregnated with ~esin in one of several 95 RAW ASBESTOS FIBER RECEIVING AND STORAGE BLENDING OF ASBESTOS (H) AND OTHER RAW MATERIALS HIGH-SHEAR MIXER (H) TWO-ROLL MILL PUNCH PRESS RACKING DRY ING OVEN SANDING (H) EDGE GRINDING (H) DRILLING COUNTER BORING (H) DUSTING INSPECTION BRANDING (H) PACKAGING Note: (H) - Indicates hooded operations. CONSUMER Figure 8. Molded clutch facing manufacture. 15 96 STEAM COOLING WATER WIRE-REINFORCED CLOTH ROLLS FRICTION COMPOUND BATH CONDENSATE COOLING WATER STEAM COOLING WATER HOT PRESSES CONDENSAT COOLING WATER Note: (H) - Indicates hooded operations. CONSUMER Figure 9. Woven clutch facing manufacture. 15 97 ,~ " techniques. The fabric may be immersed in a resin bath, exposed to the binder in a pressurized autoclave, mixed with resin before being wound into yarn or pressed beneath a roll whose surface is covered with resin. Once solvents are evaporated from the fabric, it is made into brake linings or clutch facings. Brake linings are made in a manner similar to that described earlier: woven width clutch strips facings are made different ly. Treated fabric is cut into by a slitting machine before being wound around a mandrel tape to form a fabric roll. The roll to cure the reSin in the is placed in a clutch facing, steam-heated, press, baked in then finished, inspected and an oven packaged in the by now familiar sequence. t Secondary Manufacture primaSroymaendbraskeceopnaddasryamreansuofldacttuoresresc,onhdowareyvemr.aniusfancotturpearsr.ticTuhleardlyiviimsipoonrtbaenttwseiennce secondary manufacturers perform a subset of the tasks generally considered the preserve rivet or of primary manufacturers. bond them to brake shoes, Secondary manufacturers take brake pads, inspect them, and package them as the final product. Any defective' assembly could discredit their properly built products. Manufacturing Plants and Production Volumes The manufacture ogf sftreicptsi.onBpercoaduusectsofisthheiglahblyorlainboternsinivteenpsirvoed,ucwtiiothn mpraony- processing and handlin cess, differences between large and small manufacturers are limited to the variety of products There are presently formed and the a large number number of work stations devoted to of friction material manufacturers each. but many of the smaller firms have extremely limited product lines. Table 25 lists the U.S. manufacturers of asbestos-bearing friction mate- rials including, if known, theit respective friction product' sales in 1975 and the products they manufacture. Both larger diversified Raybestos-Manhattan and smaller, single plant companies companies such as are included in this list. The first eight companies listed on this table accounted for 75 to 85 percent of the total estimated sales of asbestos frict,ion products in 1975, a pattern 1967, the consistent with the industry's historical trends. eight largest companies together accounted for 86 From to 91 1954 to percent of. the industry's value of shipments. ~ ASBESTOS RELEASE For friction materials, release of asbestos fibers will be discussed for four general areas: during Under manufacture emissions manufacture, use, replacement, and disposal. is included workplace concentrations, for various areas, human exposure Replacement emissions to airborne asbestos, water emissions, and solid waste. discuss release as a part of the automotive aftermarket which Dispo inc sal ludes emiss i refa ons cing are i and nclu re de b d uild wit in hi g n , t rep he ackaging manufact and urin general g emissio re ns pairs. sectio n s (i.e., solid waste, etc.). An input/output figure is shown first to help detail the path of these emissions., 98 TABLE 25. U.S. MANUFACTURERS OF ASBESTOS-BEARING FRICTION MATERlALS 9 ,16-37 7 55 eo.p...,. It&,,ben.,,..-YADh&t.tae. l'OI:.. ~ ~ T~.1etloa. rr.te:r~ Co. Jethc CO~f.tl~17 kK=.nlve Cl!' Pl_ local_Co) Str.atfor4.. er llanllbebt. PA CTootfordnUle. III fUll.noft. CA Tro)". Br Cl""e.land. TB Southbead. IX. .... Aut"""1 UPt tne' _ bk p.~. ell.1e. Ir_ ..................,...,. truek Dil1I:. 1>1...1< aloek ......uct. a.u_ _ _trial Cl"",,," ,.......0111 , 1......UJa1 " " . ,. . - _ _. . . coolll ff-blp.,. eII~at. '91._faate.! ~lnr' (5 wtllt~al 1&5.0 94.S .Abex Cb~r.d."'t:l17 r:!.et~ft PTOtUCh cro.., Cl~el&ed.. OR ~I dttk 110ek I '1'10,.. HI Vi_ _t A 66.6 , Cene-l".d !"...:-t:u..t7 :)e!.co-~J~.lce 01...... rral.a1Ml D.1_. Zoo L P,.,ner Cc::apaQ71.a n_7tOll. 011 aunuQ&toa. D 'D'ru.. . . . ." _.lbk ~.f;~14: Dior_ \6.2 :&.5 ,; :,!s!6r Q)r:?-r~LOlI17 CT.:!:el4 Di.... ]bra 1:.ana.n eor;.oraU.oaS ' S..:."".'.. Cc:p~u (r......,ly IIorU Jestos Co.) ~. .e=.)t:I)C CoT?_. Cl'l.ul,. P1:a4~. H ".. 't~toa.. 111 Sell-.l. JL _,,,,1110. tII J'ouloUaa. 011 1I-.4l.a. -.lblL - \0 $a:.14a&l Fl'lcC.1oD PrK.ucte ~.1 1.opnsport.IJi -.'''''' \0 k,;t;> S;..ceLdt.les :r_ufac:ta.t'1.o& ~. St.. .Joeeph. 1Cl S~~CD I:st.:..s-:::last 1 Souat:OD. U Fr!c:lOD .~':C~f Co::r;paa.r lll IIorol 1....... dal 8r..... JOro4uct.. IDe." Hed_,O\I DaJl'91U xr IlIock _.lba. J.e:!dava.y >l.aoufecc,1II"1t\& C-......,,2. lIeva1:d. !U ~..,:tK I::t~trl..l Frlc.t:iall CorponeloDa7 Pran:v111e .AI. IlC>Ck I / -I , I , " , I 21.S , _11a_.. _"'110 _ . tNodd....,.. .,,..... wblc,lSeol.dc:raeN1Dweb. " ...1 tr.d.1era. , Off....... ".b!c1llo. ~...1.1II'01 ~. ,, _f_. . . Off_ ..ut_c. n=-. er_. dnlUq n., 12.. 0 0.65 1.7 '.0 "'_17 of PVU f.... _ i... 16.0 I 3.0 'l'nctClln aa.d &:ra11en. 3.6 ~~~!i:, 5r.a>.e S:ock ~.and'.c.ItQrtOl: Co.. U Vbetl1GC. W Jlri.pport, OB llock ~",:,ce G,).ct.r:lll iM.\:St.rl~.u S.a1r.ft..w. OR I / J.:as,beacoa JS'aaufacc:urlAJ; Co~atiOllII Pal.lteraoft. JU - . " * .It;:to f'rLccioa Co~rac:lo.a.J. t.awrellu. HA. - - , r..o~n Cuqo,.-c.l..,eJJ. :....~ :a"~ 'nC~ COIIEpADy'2_ vU"!&1I. 111i Oul.... , CA _ b .. 81oc1t , Y.Q! !ral:.ea. lr.cot;Ol'aetcSl.I" -I Ca.rlble COrpc:!r.tl='" . D..,..41." n lotr.ol ~bcolca.l eol'pot'&tioa.,1S p:~ T I'aka tia.1a8 Coattny lac."~ - , .:~. COlporaticmJ1 - - - ..... Seat-Pac:. MllDufacwnaa ~ 1t14a8Va1, 1'.& 'l'fimt.oa, lU t..-twac:e .. 11&. KeDo6b_, VI _ _ 1'01111.111 - 8111... -I 1J!oc1t 81...a. 4.0 DI." .... ,1-.. 4,...1 trr.... ntlClft' .at k ..... t..-wa,., oEf-r4l14 veb1claa. -aiM hkl.l t.) 26.' 3.' " Cuet_ tluntfae.tarlas. !l.O _ . off_" Off-R.. vehlel......... l'&11car c.sdD& ...~,... . . . . toMi.....'Net ...uclaa "I 21.2 ..lIu1lc oel,.. 9.7 t.a .Input/Output I"lguro 10 shows est tmlltea of prOCCflS and d ISP0f.llll emiflAions for the al:lbc~tol:l friction materials industry. These, Ugures ar~ bal:lod 011 Levine's38 1974 estimates projected to 1980 U.S. Bureau of Mines consumption figures. Potential sources of emissions include blending mixing, cutting, milling. chopping and finishing operations. Of the 43,700 metric tons of raw asbestos fiber processed in 1980, approximately 42,525,m.t. are'incorporated into the product and 1111.9 m.t. are sent to disposal as vacuum cleaner and baghouse dust. An e'stimated 10.9 metric tons escape through' a control device (typically a baghouse). Levin's38 atmospheric emissions estimates are based on gross assumptions with a reported uncertainty of at least an order of magnitude. Meylan's4 estimate's of emissions are generally 1 to 3 orders of magnitude less. Atmospheric emissions from disposal, based on GCA es~imates, are shown to total 2.2 metric tons per year for the friction materials industry. This last estimate, which follows Levine's38 1974 data, also takes into account the Asbestos NESHAPS regulations adopted in 1975 regarding the disposal of asbestos-containing waste material. During Manufacture ' Workplace Fiber Concentrations-Table 26 shows the time-weighted average exposures at different points in the friction material production process. These figures are based on 12 plants which consumed approximately 35,000 m.t. of asbestos in 1975 and made up about 60 percent of the f~iction products se~ent during that year. Data was obtained by Westori 59 in a survey using industry questionnaires and is of questionable validity as industries may tend to report biased figures. In addition, the range of data reported is extremely broad, indicating questionable sampling and counting procedures. TABLE 26. TIME-WEIGHTED AVERAGE, FIBER CONCENTRATIONS OF OPTICAL MICROSCOPE VISIBLE FIBERS GREATER THAN 5 ~m IN FRIC- TION PRODUCTS MANUFAcTURING PLANTS 3 9 ,-, ==-====-~================~===-~====== Fiber count Process step Range (fiber/cc) +ypical (fibers/cc) Receiving and storage 0.25 - 2.5 1.0 Fiber introduction 0.4 4.6 2.5 Mixing 0.2 8.0 2.3 Forming and rolling 0.5 - 22.0 3.3 Curing 0.5 3.5 1.5 Finishing 0.6' - 7.4 2.0 Adjustment and printing 0.7 1.0 1.0 Inspection Packaging 0.1 - 15.0 2.0 1.0 2.0 1.5 *Based on plants representing 50 percent of asbestos friction material production. 100 AAw ASBESTOS FtBERS ~3.700 ll"f ...... o.....' IWIUFAtnlRING OPERATIONS i\,~ai .iNG AND STORAGE BLENDING IIIXING CUTTING L-"' - . - " " '. ....... ~.-- - - I '-" ....... MILLING CHOPPING .. .. --../ / / --;:r-:-/- ' '" . ",' ",., VACIlUI'IEO DUST I BAGIIOUSE SCRAPS : EMISSIONS I 10., TPY AND REJ EeTED PRODUCT 1111.9 TPY DISPOSAL ElfISSIONS 2.2 ll"f 13.1 TPY . 42.575 TPY .!:ill!!!!. ooC) o INPUT/OUTPUT MANUFACTURING PROCESSES CONTROL EQ.U I PMENT UlTIMATE DEPOSITION SOLID _ _., -" WATER AIR Figure 10. Input/output estimates for the asbestos friction materials industry in metric tons. A review of the data collected indicates that in addition to variations in sampling and counting procedures there are many reasons for the wide variations in the range of fiber counts. The largely individual manual techniques and worker practices introduce considerable deviations, as does the percentage of asbestos in the product which may range-from 30 to 70 percent by weight. Receiving and storage--Exposures during receiving and storage in asbestos friction material production are identical to receiving and storage exposures in all other primary asbestos industry segments. Consequently, the range reported for-asbestos paper, 0.25 to 2.5 fibers/cc TWA and the3~ypical value, 1.0 fibers/cc TWA. are equally valid for friction materials. Fiber introduction--Bags of the raw material may be manually opened and dumped into hoppers for transport t~ mixers. Fiber levels during ~his opera- tion are higher than those in papermaking fiber introduction, rang1ng fr~ 0.4 to 4.6 fibers/cc TWA for friction materials as opposed to a 0.3 to 2.8 f1bers/ cc TWA range for papermaking. Typical fiber levels exhibit a similar differ- ence with 2.5 fibers/cc typical of fiber introduction for friction products Rnd 1, .9 fibers/cc . typical for papermaking. 99 It is not clear why such a difference should exist, since the proces~ing st!'P is similar. Perhaps the fact that in some paper applications it is not necessary to dump the fiber out of a bag contributes to lower typical values in papermaking. However, this characteristic should not affect the range reported since some paper applications require that the as'bestos be removed from the bag. Mixing--The combined raw materials may be mixed either dry or wet, depending on product specifications. The state in which mixing occurs greatly influences the workplace fiber levels, since fibers in water are unlikely to become airborne, while dry fibers can easily be dispersed. Fiber levels of 0.2 to 8.0 fibers/cc TWA were reported with 2.5 fibers/cc TWA considered to be typical. 39 Forming or rolling--The product of the mixing stage is fed to a compression molder or an extruder, again depending on the required product. Levels of 0.5 to 22.0 fibers/cc TWA were recorded; a level of 3.3 fibers/cc TWA was considered typical. a9 The higher exposure levels are caused by the manuai handling of' the dry pref,orm miX'-- whfch is conveyed in open carts, scooped by hand, weighed, and poured into a block maId where it is mechanically pressed into the shape of the finished ,product. 38 l.:Ul:lng--Somll formulae require a heating step thoilt causes resins to flow and bind the mixture. In the curing step fiber levels ranged frol1l 0.5 to 3.5 flberH/cc TWA. A flber count of 1.5 fibers/cc TWA was typical. S9 Finishing--Parts taken out of the curing oven undergo a number of steps to produce the final product. These machine-assisted manual finishing steps may include grinding, sawing, drilling, blanking, tapping, and boring. Fiber levels in finishing were typically 2.0 fibers/cc TWA, although reported values ranged from 0.6 to.7.4 fibers/cc TWA. 39 102 Adjustment and printing--After finishing, the friction products 'are dusted, adjusted, and printed. Fiber levels in this operation are consistently close to 1. 0 fibers/cc TWA. The r.angfl of C!X))OSlITE'A dill: ing thi8 ptOCl\SS 11:1 very narrow, 0.7 to 1.Q fibers/cc TWA. 39 . Ins2ection--Generally considered to be an examination of the finished product, inspection encompasses different activities in different plants. Some plant inspection stations only examine the finished product; if the product is defective or needs more comprehensive finishing it is returned to the finishing area or rejected entirely. Other plants have additional equipment in' the inspection area so that any defect in the product can be rectified immediately. Consequently, fiber counts recorded in inspection areas vary widely from 0.1 to 15.0 fibers/cc. Usually, the fiber level will be toward the lo~ end of the _ range, with 2.0 fibers/cc TWA considered typical.S9 . .... .-- ... Packa~ing--Even workers involved in packaging the final product are exposed to f1bers. The range of reported fiber levels in packaging was 1.0 to 2.0 fibers/cc TWA w~th 1.5 fibers/cc TWA considered typica~.S9 Emissions to Air-The maximum allowable exposure over a 40 hour week for workers in the asbestos industries has been set at 2 f/cc.* Workers are exposed to an average fiher count of 1.9 f/cc,* with fibar counts as high as 22 f/cc* being reported .(see Table ~6). The values reported reflect levels recorded in or before 1975 and are probably higher than present day concentrations. With greater worker awareness and increased emploY,er concern, along with the regulatory activities of OSHA, it ls very likely that fric.tion product worker exposure concentrations are well below the 2 fiber/cc limit. Documentation in the open literature to substantiate this belief, however, is not available. With a wo~kplace fiber count of 1.9 flee, workers can be expected to inhale 119'1" billion fibers per year. 40 EstiIl)ates of nonoccupational ex",:, posure to asbestos have been made using a binormal continuous.plume dispersion model,w~th assumed plant emissions. The affected population was ass~ed to be thos~ people living wit-hin a 5 km radius or a friction material manufac.t:uring plant. The atmospheric asbestos:concentration around: the plant was estimated to be 23,000 f/m3t and the annual amount of asbestos inhaled was estimated to be 125 million fiberst per ~erson. This compares to a mean ambient urban exposure of 5,000 fibers/m3 wi,th an average annual inhalation 0' 27.4 'million fibers per person. !to . Release to Water-- Water is not used directly in the production of friction materials except o~ those products formed on paper machines from a 2 to 3 percent solids ~lurr~. Water usage and consequent water pollution associated with this process is discussed in Section 4, Asbestos Paper Produc.ts. Despite the term *O.ptical-microscope-visible fibers >5 ~m in length. t Electron-microscope-vi~ible,fibers. 103 "wet mix" used in the description of one of the manufacturing processes it is actually dry because no wastewater is generated. Solvents are used to make the mix of raw materials more pliable; no excess water is used and no floor drains are present. Wastewater is generated in some solvent recovery operations and in wet dust collection equipment used to control dust throughout the plant. Solven't recovery wastes normally have very low suspended solid levels. A typical sol- vent recovery operation has been reported to have 0 mg/l suspended solids in its waste stream. 41 Wastes from wet dust collection have significantly higher solids concentrations. ' Wastewaters from wet dust collectors are slurries of dust from plant operations, and are characterized principal~y in terms of suspended solids. Clearly, the,concentration will be a function of the amount of dust generated and the water flow rate which can vary from 1.9 to 37.9 liters per minute per 28.3 standard cubic meters of air per minute. Plant air systems served by wet scrubbers range from 283 to' 7079 scmm, resulting in discharges of 189,250 to 2,838,750 liters per day.4l Units are for the mo~t part equipped for partial recirculation. Sludge, or settled slurry is discharged to a settling lagoon where it becomes a solid waste problem. In a typical plant using wet collection, about 1566 kg of asbestos are collected annually. About 95 percent or 1488 kg are removed as. sludge by clarification. The sludge is disposed of by landfilling while the remaining 78 kg of asbestos are discharged to surface waters. 4 Release to Land-- Most of the solid waste generated in the' manufacture of friction material is produced in grinding. In the past, grinding dust was collected for use as solid fill in marsh1ands and low-lying areas. It is now trucked to sanitary landfills for disposal but as the hazards of asbestos have become better known, fewer and fewer landfills are willing to acc,ept asbestos-containing materials for disposal. ' Estimates of the percentage of asbestos lost in grinding and drilling range from 12.7 percent to 30 percent,I+1,42 but even with the high cost of raw mate- ......' rials, asbestos in these scraps is not recovered for reuse. Once the binders ":;;~d resins have set I it is uneconomical' t'o break" them "downtos.irvage-t'ii'e- Hbers. In moat cased baghouses are used to collect grinding and drilling dusts. It has been estimated that wastes can amount to as much as 12.2 tons/month for a plant producing 40,000 brake shoes per day.4 Based upon a total asbestos consumption of friction materials of met~ic tons in 1980, 1,112 tons of asbestos would be lost in product waste. Baghouses would collect about threefourths of this total, or about 834 tons, 'while the remainder, 278 tons, would be collected by vacuum cleaners and as damaged product. 4 During UHe During vehicle operation friction material, whether used as a di~c pad, drum lining or clutch facing, engages with a metal rotor to form a. sliding friction couple which'converts the kinetic energy of rotating members into heat, absorbs heat and diSSipates it to the surroundings. Emissions are generated by wear. Asbestos fibers are pulverized into small particles which are 104 'either trapped in the brake or clutch housing, fall to the road or are emitted'" 'to the atmosphere. Most of the 8flbestos, however, is heated suffi.ciently to 'cl.wse chmnical convcr!:lion to oliv i,lle or fonterite. A number of articles have discussed asbestos emissions from brake linings. ,Table 27 summarized the published data. A detailed discussion of. the reported information is provided in reference 4. ,Jacko and DuCharme reported~Z that approximately 33.6 million kilograms of asbestos in friction ma,terial wear away annually. Based on I;hEdr experim'eritar" finding that only about 0.2 'percent of the debris is not converted to some other substance, total annual asbestos emissions were estimated to be 71,759 kilograms. Of this amount, 85.6 percent or 61.426 kilograms were estimated to drop out on to the ground. 11.2 percent or 8.037 kilograms was estimated to be retained within the brake or clutch housing and only 3.2 percent or 2,296 kilograms was believed to become airborne. Rohl. et al. 49 performed a similar ~alculation based on a separate analysis of friction material wear debris. but otherwise retaining all of Jacko and DuCharme's assumptions. Their best estimates of the total annual asbestos emission were that 1,329.039 kilograms of asbestos dropped out. 172,367,kilograms Were retained in brake and clutch housings, and 49,896 kilograms become airborne. Elevat~d levels of asbestos were found in a study by Bruckman and Rubino sZ in which airborne asbestos concentrations were monitored at three Connecticut toll plazas. Asbestos concentrations were found to vary between 3 ng/m3 and 41 n8/m3. A nearby large industrial asbestos user was suspected of influencing the highest measured concentration. Although no correlation was made between vehicular traffic and the asbestos ,concentration it was concluded that the decomposition of brake linings is a significant source of airborne asbestos fibers. During DisEosal Fric~ion materials are usually replaced before they are completely worn out. Most passenger vehicles reportedly use a set of asbestos-containing brake linings every three to four years. 53 A$bestos-containing friction products, are disposed of in the form of worn brake linings, disc pads. and clutch faeings. These materials may be discarded as scrap pieces separated from any metal component which can be reused or scrappe'd along with the machinery they were a part of such as autqmobiles. Because of the means by which they are manufactured. asbestos fibers are bound within the pieces even though they are worn. During disposal, asbestos material should not be released from the worn pieces due to the lack of sufficient energy to dislodge the fibers bound in the frictio~ material matrix. Ultimately, the nonfriab1e friction materiai is either incinerated or landfilled. 105 TABLE 27. SUMMARY OF PUBLISHED DATA. A.SBESTOS EMISSIONS FROM BRAKE LINING USE it2..1f8 Publicacion souree ~ethod used to collect emission or debris samples ~\ethod used to determine asbestos content oi emission debris s2mples .nsbest.os particle size distribution Asbestos content of emissio~ or debris Lynch, 1968"3 Baech, 19iO" Laboratory simulacions utilizing brake-cesting machines or d}~amometers. Samples collected on 0.8 ~ pore size membrane filters. A dusc cloud was generated by using compressed air jees to r~ve dust from brake linings in an auto repair garage. Samples were collected by means of a hand pump located in center of dust cloud. Electron uicrographs Xot discussed <l~, except uncer severe-stress condicions ~c scated 94% of fibers -1:: . fell in 2-5 ",!m length category. Only 61. were longer than 5 I'm Hickish and Knight,'S 1970 as Samples were COllected directly from debris remaining brake dust an4 from membrane filters exposed during brake cleaning Not stated Not discussed 1. 67. and less operations utilizing compressed air. Filter pore size is not given .....o Bush ~ aL. 1972" Laboratory simulations utilizing a discbrake Neutron activation Not discussed -44% (this figure 1s not 0\ assembly mounted On an inercial dynamometer. accurate; see discussion) Samples were ~ollected on suitable filter paper. Ander90n ~ al., 1973~1 Laboratory simuIacions utilizing a disc brake assembly mounted On a dynamometer. Air samples of wear debris collected down wind of disc brake. Transmission electron microscopy Test results and and. procedures precluded a size distribution estimate -0.02% Jacko and DuCharme,~1 1973 (concains same data as Jacko ~ at., 1973) ,8 Samples were generated by operating a standard American car under typical driving conditions in Detroit, Michigan. More abusive conditions, such as fade tests, were also included. Brake and clutch assemblies were enclosed by spe_ cially designed collectors. Samples were collected from (1) dropouts during use, (2) dust: retained ln lining assemblies, and (3) ~irborne samples collected on membrane filters. Optical and electron microscopy 30% of fibers were from 0.25-0.50 \lm 1n length; 60~ were longer than 0.5 um 0.25% overall average (an independent check done by Batelle Labs give a figure of 0.171%) (continued) .... trok' TABLE 27 (continued) Publi.cation source ~!ethod used to collect emission or debris samples Method used to detet'1lli.ne asbestos content of emission debris samples Asbestos .particle size d1.stribution Asbestos content of emission or debris Rob! .!.!!,., 1976~f Ten samples of automobile brake drum dusts were collected from maintenance shops in the New York area. X-ray diffractometry Transmission electron mlcroscopy, selected area electron diffraction, and electron microprobe analyses 80% of fibers were short:er than 0.4 !lIDlengt:h 2w 15%; average of 3-6% Consistent with, but lower than, quant:itative detet'1lli.nation ~de by X-ray diffractometry; no percentages are given --- 0-0 Alste ~ !!.. 1976 50 Samples were taken from fresh and worn brake Electron microscopy Majority were No percent figure given, however. o linings and from the atmosphere near a freeway. <2 Um in maximum conclusion waS that major effece '-I linear dimension of braking appears to be in separating bunches of fibers and reducing their average length, but not in altering their crystal structure Rohl ~ 51., 197751 This is basically a reprint of the Rohl et sI., 1976 study wf.th the inclusion of brak.e wear- test samples obtained from Europe and Australia. The mean weight percentage ranged from 1.4% in Australia to 2.5% in France Emiss:i,ons in .Automotive Af~ermark<::.~_ The automotive aftermarket in which asbestos exposures may occur is divided into three major sections: Tefacing or rebuilding of friction 'materials. repackaging of friction materials. and general brake repair and service. 39 Refacing and Rebuilding-- . '~'." .. -. The major difference between refacing operations and plants in the primary friction materials segments is that no raw asbestos fiber is handled in the smaller rebuilding plants. Therefore, the control problems are not as acute. Most rebuilt asbestos-bearing parts plants have had local controls for a long time. Asbestos exposure levels measured at three of these establishments were reported by NIOSH during the American Industrial Hygiene Conference in New Orleans in May 1977 and are presented by process step in Table 28. Repackaging-- Repackaging operations in the automotive aftermarket consist of manually transferring asbestos friction material products from one container to another at a location other than the facility where the friction material was produced. Asbestos exposures for this sectot have been reported to range from 0.2 to 0.6 fibers/cc TWA.~ , General Repairs-From the existing data on asbestos exposure levels during,brake'repair work, it appears t~at an establishment using compressed air for blowing residual dust from brake lining assemblies may exceed the 10.0 fibers/cc ceiling limit under the current OSHA standard. Data reported by Rohl~9 on asbestos emissions during brake lining maintenance indicated that a peak exposure of 29.8 fibers/cc had been encountered 0.9 to 1.5 meters from the workplace. These data are presented in Table 29. 108 TABLE 28. ASBESTOS FIBERa EXPOSURE LEVELS IN REBUILDING BRAKE AND CLUTCH: ASSEMBL,IES 5 It Facility Fibers/cc TWA Receiving and Bonding and ' Cutting and Inspection and cleaning riveting grinding packaging A Mean Range Number of samples 1.1 0.4 - 4.8 15 0.6 0.2 - 1.4 20 1.1 O.~ - 1.6 6 0.7 0.8 - 1.1 4 B Mean Range Number of samples 4.0 1.0-7.6 5 2.7 1.1 - 5.8 6 50 1.5 - 9.3 6 c Mean Range Number of samples 1.3 1.2 - 1.3 2 0.8 1.5 - 9.3 6 aFibers 5 to 100 ~m were counted using phase contrast microscopy according to the NIOSH method. TABLE 29. ..... -.-....~. -.,... FIBER LEVELS a DURING BRAKE LINING MAINTENANCE49 , , , Distance from workplace (meters) Peak exposure (fibers-/cc) 0.9 to 1.5 6.6 to 29.8 1.5 to 3.05 2.0 to 4.2 3.05 to 6.1 0.4 to 4.8 Background samples 0.1 to 0,8 aFibers 5 to 100 ~m were counted using phase contrast microscopy. 109 CONCLUSION Between 1978 and 1980 there has been a 41 percent decline in the amount of asbestos consumed to manufacture friction products. The decline can be attributed to a slowdown in automobile sales and the increasing use of asbestos substitutes. Atmospheric release of asbestos fibers during primary manufacturing, by far the largest source of emissions in this category, ls estimated to have declined to 13.1 tons per' year in 1980 from 21.6 tons per year in 1978. Asbestos containing solid waste is estimated to have declined from 1,876 tons to 1,112 tons between 1978 and 1980. Process wastewater discharged from friction products manufacturing plants is not expected to be laden with asbestos fibers. Wastewater from wet dust collectors employed to control fiber release, however, will contain asbestos material. About 95 percent of the asbestos material suspended in the control device wastewater is removed as sludge by clarification. The.sludge is typically disposed of by landfilling with the remaining five percent discharged to surface waters. The decline in asbestos releases that has been estimated between 1978 and 1980 is expected to continue through 1981. COinciding with the turndown in the economy and an increased interest' in asbestos substitutes. Beyond 1981. the outlook for the use of asbestos in friction materials is. at best, mixed. The majority of the industry's products are used in passenger automobiles and,' as such, are influenced by the vagaries of the buying public. If a lot of new cars are being sold, a lot of new brakes will be required. ."' Conversely, if fewer new cars are sold, more used cars in the marketplace will result in more sales of replacement brakes. Further uncertainty is introduced by the American automobile manufacturers' avowed intentions to eliminate , asbestos from original equipment brakes by the 1985 model year. If a success- ful substitute is found, asbestos consumption in friction materials will drop precipitously. 110 REFERENCES 1. Bradfield, R.E.N. Asbestos: Review of Uses, Health Effects, Measurement and Control. Atkins Research and Development, Epsom Surry, Engl.and. January t977. 2. Clifton, R.A. Asbestos. 1980 Minerals Yearhook. U.8. Bureau of Mines. Washington. D.C. 3. Wright, M.D., et al. Asbestos Dust Technological Feasibility Assessment and Economic Impact Analysis of the Proposed Federal Occupational Standard: Part I. U.S. Department of Labor, OSHA. September 1978. (Draft) 4. Meylan, W.M., et al. Chemical Market Input/Output Analysis of Selected Chemical Substances to Assess Sources of Environmental Contamination: Task IIi - Asbestos. EPA 560/6-78-005. August 1978. 5. Bark. L.S D. Moran, and S.J. Percival~ Chemical Changes in AsbestosBased Friction Materials During Performance. A Review. Wear. 34:131-139. 1975. 6. Zussman, J. The Mineralogy of Asbestos. In: Asbestos, Volume 1, Properties, Applications and Hazards. L. Michaels and S. S. Chissick, eds. John Wiley and Sons. New York, N.Y. 1979. pp. 45-65. 7. Hodgeon, A.A. Chemistry and Physics of Asbestos. In: Asbestos, Volume I, Properties. Applications and Hazards. L. Michaels and S. S. Chissick, eds. John Wiley and Sons, New York, N.Y. 1979. pp. 67-114. 8. Jacko, M.G. and S.R. Rhee. Brake Linings and C19tch Facings. Encyclopedia of Chemical Technology. Third Edition. Volume 4. John Wiley & Sons, New York, N.Y. 1979. pp. 202-212. 9. Telecon.' Reginal D" Kelley, Force Control Industries, with Robert Bouchard. GCA Corporation. March 3, 1980. 10. ' Green. A.K., and A.M. Pye. Asbestos Characteristics, Applications and Alternatives. Fulmer Research Institute, Fulmer Special Report No. 5, ISSN 0427-7457. 1976. 11. Pye, A.M. A Review of Asbestos Substitute Materials in Industrial Applications. Journal of Hazardous Materials (Netherlands). 3:137-138. 1979. 12. Einhaus, J.R. Age of Asbestos on Vehicle Parts Ending, Automobile Industries. p. 27-31. May 1979, 111 13. Telecon. M. G. Jacko, Bendix Materials Center, with Nancy Roy. GCA Corporation. November 19, 1979. 14. Te1econ. M. G; Jacko. Bendix Materials Center, with Nancy Ray, GCA Corporation. August 1979. 15. U.S. Environmental Protection Agency. Control Techniques for Asbestos Air Pollutants. Publication AP-117. February 197~. 16. Te1econ. Raybestos-Manhattan, Inc. with David Cook. GCA Corporation. February 28, 1980. Friction pr~ducts manufactured. 17. Telecon. Kevin Peppard, Bendix Corporation, with David Cook, GCA Corporation. February 28. 1980. Friction product manufacturers. 18. Te1econ. H.K. Sleeth. Porter Company, with Robert Bouchard. GCA Corporation. February 29 . 1980. Friction products manufactured. 19. Telecon. Terry Blaine, Borg-Warner Corporation, Spring Division with Robert Bouchard, GCA Corporation. March 4, 19BO. Friction products manufactured. 20. Te1econ. Roy Huckabee, NutuI'n Company, with Ro1;>ert Bouchard, GCA Corporation. February 29, 1980 . Friction products manufactured. 21. T~lecon. Earl Fygert, National Friction Products Corporation, with Robert Bouchard, GCA Corporation. February 29. 1980. Friction products manufactured. 22. Te1econ. Bill Shine, Auto Specialists Manufacturing Company, with Robert Bouchard, GCA Corporation. February 29, 1980. Friction products manufactured. 23. Te1econ. Standco Industrial with Robert Bouchard, GCA Corporation. February 28, 1980. Friction products manufactured. 24. Telecon. Jack Payton. Friction Products Company, with Robert ~uchard, GCA Corporation. February 29, 1980. Friction products manufactured. 25. Te1econ. Andrews. Royal Industries Brake Products, Inc. with Robert Bouchard. GCA Corporation. February 28, 1980. Friction products manufactured. 26. Teiecon. Montgomery. Reddaway Manufacturing Company with Robert Bouchard. GCA Corporation. February 29. 1980. Friction products manufactured. 27. Telecon. Mo1ded Industrial Friction Corporation with Robert Bouchard, GCA Corporation. March 3. 1980. Friction products manufactured. 112 28. Telecon. Wheeling Brake Block Manufacturing Company with Robert Bouchard, GCA Corporation. February 29, 1980. Fr,iction products manufactured. 29. Te1econ., Brassbestos Manufacturing Corp. with Robert Bouchard, GCA Corpnrl1tlon. March 3, 1980. Friction products manufactured. 30. Telecon. Paul Biondo, Auto Friction Corp., with Robert Bouchard, GCA Corporation. March 3. 1980. Friction products manufactured. 31. Te1econ. Robert Rando1f, Gatke Corp~ration, with Robert Bouchard, GCA Corporation. March 3, 1980. Friction products manufactured. 3Z. Telecon. Lasco Brake Products Company with Robert Bouchard. GCA Corporation. March 3, 1980. Friction products manufactured. 33. Te1econ. Appo11ageno, MGM Brakes. Inc., with Robert Bouchard. GCA Corporation. March 3, 1980. Friction products manufactured. 34. Telecon. Carlisle Corporation with Robert Bouchard, GCA Corporation. March 3, 1980. Friction products manufactured. 35. Telecon. Thiokal Chemical Corporation with Robert Bouchard, GCA Corporation. March 3. 1980. Friction p'roducts manufactured. 36. Te1econ. Joseph Minky. P.T. Brake Lining Company, Inc., with Robert Bouchard, GCA Corporation. March 4. 1980. Friction products manufactured. 37. Te1econ. Mr. Ba1tz, Ba1tz Company, Inc. (distributors for Eaton Corporation). with Robert Bouchard, GCA Corporation. March 4, 1980. Friction products manufactured. 38. Asbestos: An Information Resource, R.J. Levine. ed. DREW Publication Number (NIH) 79-1681, U.S. Department of He~lth, Education'and Welfare, National Cancer Institute, Public Health Service, Bethesda. Maryland. May 1978. 39. Da1y, A.R., A.J. Zupko and J.L. Hebb. Technological Feasibility and Economic Impact of OSHA. Proposed revision to the Asbestos Standard (construction excluded). Roy F. Weston, Environmental Consultants for Asbestos Information Association/ North America, Washington, D.C., March 29, 1976. 40. Suta, B.E. and R.S. Levine. Nonoccupational Asbestos 'Emissions and Exposures. In: Asbestos, Volume 1, Properties. Applications and Hazards. L. Michaels and S.S. Chissick, eds John Wiley & Sons, New York, N.Y. 1979. pp. 17l-Z05. 113