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FILE NAME Brakes BRK DATE 1982 Feb DOC BRK187 DOCUMENT DESCRIPTION EPA Report - Life Cycle of Asbestos in Commercial and Industrial Use 79-73 U.S. ENVIRONMENTAL PROTECTION AGENCY Office of Toxic Substances Washington D.C. Submitted in Partial Fulfillment of Contract No. 68-02-3168 Technical Service Area 3 Work Assignment No. 18 EPA Project Officer James Bulman LIFE CYCLE OF ASBESTOS IN COMMERCIAL AND INDUSTRIAL USE INCLUDING ESTIMATES OF RELEASES TO AIR WATER AND LAND Final Inhouse Report February 1982 Prepared by David Cogley Nancy Krusell Robert McInnes Peter Anderson Ronald Bell GCA CORPORATION TECHNOLOGY DIVISION Bedford Massachusetts HEADQUARTERS LIBRARY ENVIRONMENTAL PROTECTION AGENCY WASHINGD.CT. 2O04N60 U.S. EPA Headquarters Library Mail code 8201 1200 Pennsylvania Avenue Washington DC 20450 DISCLAIMER This Final Inhouse Report was prepared for the Environmental Protection Agency by GCA Corporation 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 1380 PRANNEJ SNYTERISHGAUN YMI MOTTO MOTTO ANUMITAN 2520 2520 MCLOYIHZAW MCLOYIHZAW 8 LEB SECTION 5 FRICTION MATERIALS INTRODUCTION Friction materials are used in clutches for transmitting torque in brakes for slowing or stopping motion and in torque limiters Besides their well- known use in autos trucks buses and railroad cars friction materials are also found in other applications where motion must be controlled ranging from bulldozers and 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 developed bonding agent resulted in a product with ex- cellent durability and heat resistance By the first World War woven asbestos brake linings were in common use on passenger cars commercial vehicles and of ground waste bonded military transports In 1921 a vulcanized combination the first molded brake asbestos and a rubber binder was used to manufacture but molded blocks were not widely accepted until after the second World W ba lorck 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 Impregnated leather in automotive clutch facings in 1905 and was in turn cotton replaced clutch facings of wire covered with asbestos syuaprenrsaerdeedwidbyelyasubseesdtoasnd Tcoondtaiynued progress is being made in die cast and molded clutch facings In 1980 an estimated 43,700 metric the United States fiber consumption was materials Five companies dominate the tons of asbestos about 12 percent of used in the manufacture of friction United States friction material market , but foreign competition is becoming more of a factor Figures for production volumes were not available but a breakdown of the estimated value of asbestos friction materials produced in 1979 is in Table 19. These data were derived by projecting 1972 figures provided given by Meylan to 1979 costs As shown brake linings are by far the largest com- ponent 58.9 percent of the asbestos friction mataenrdiaelmisisnidounsstrayssoCcioantseedquweintthly this section emphasizes the production processes brake linings placing lesser emphasis on other products in the friction . materials group 82 TABLE 19 VALUE OF ASBESTOS FRICTION MATERIAL SHIPMENTS OF 1981 DOLLARS IN MILLIONS Final product Brake linings proprd oduct pruodcuctt shipments including interplant transfers 1981 1972 Percentage of total 1981 Woven containing asbestos yarn tape or cloth Molded including all non- woven types $ 27.8 308.4 $ 10.2 113.1 4.9 54.0 Disc brake pads 38.8 14.2 6.8 Clutch facings Woven containing asbestos yarn tape or cloth Molded including all non- woven 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 Projected from Meylan et al 1972 p 61 using September 1981 Engineering and Mining Journal cost index factors 83 PRODUCT DESCRIPTION Composition Many raw materials including some whose exact roles are regarded as proprietary information are used in varying quantities in the manufacture of friction materials The major or foundation constituent of practically all range friction materials is asbestos fiber which can of the final product by weight depending on end use from 15 to 79 percent In 1980 chrysotile grades 3 through 7 accounted for all of the estimated 43,700 metric tons of asbestos used to produce friction materials be mixed or calcined to improve performance Fiber sizes and types may . Asbestos is used because of its thermal stability relatively high friction level and reinforcing properties but asbestos alone does not offer all of the desired properties Therefore other materials known as property mod- ifiers and binders are added Different types and amounts of modifiers are used to noise tion of provide desired levels of effectiveness wear fade recovery and Binders hold the disparate materials together The average composia typical automobile brake lining is shown in Table 20. Individual product mixes vary considerably from these averag~ s Manufacturers refuse to release their exact product compositions due to proprietary considerations but some details are available in patents Several examples are given in Table 21 Table 22 lists binders and property modifiers used in automobile brake linings Phenolic resins are the most commonly used binders because of their high binding efficiency and ability to withstand pyrolytic breakdown Other resin binding systems are based on elastomers drying oils or combinations ; A wide range of materials are used in friction materials as modifiers property In general property modifiers can be divided into two classes nonabrasive modifiers and abrasive modifiers Nonabrasive friction modifiers can be classified further as being either high friction or low friction mate- rial The most common high friction material is friction dust a cured res- inous material derived from cured or polymerized cashew shell liquid a phenolic compound When heated with hardening agents such as hexamethylene tetramine or formaldehyde it polymerizes becoming sufficiently hard to be granulated Other friction dusts are different combinations of cured resins polymers fillers and cashew resins Ground rubber is normally used for noise wear and abrasion control in particle sizes smaller to or slightly coarser than those of the cashew dustsparticle particles Low friction nonabrasive modifiers like carbon black graphite petroleum coke flour or other carbonaceous material may be added to lower the coefficient of friction and reduce noise Normally the materials are added as fine powders or although graphite is occasionally used as coarse particles or pellets 84 TABLE 20. 2 RNA ee 146 otter & Material AVERAGE BRAKE LINING WEIGHT PERCENT COMPOSITION seer Automobile Truck Asbestos Resins and polymers Oxides and pigments Metals Carbon graphite etc. Total 55 28 9 3 5 100 33 48 16 2 1 100 Lunch quoted by Meylan et al TABLE 21. BRAKE LINING COMPOSITIOFRNOSM PATENT LITERATURE WEIGHT PERCENT4 Lining No. 1" Lining No. 3b Asbestos 55 Barite 10 Phenolic resin binder 20 Brass Magnesium carbonate . Limestone Organic calcium powder 10 Asbestos Barite Graphite Brass Phenolic resin Lead oxide Buna N rubber Naphtha Copper sulfide Methyl ethyl ketone Lining No. Asbestos Phenolic resin Nitrile rubber Cashew dusts Calcium fluoride Copper iodide 60 15 12 Lining No. 4d Asbestos 2222 Tarry residue 2222 Barite 2222 Phenolic resin 20 Graphite " Sakata et al 1974 Hitachi Keller 1969 Abex Toyota Central Research and Development Labs Mitchell 1974 DuPont 1971 TABLE 22. PROPERTY M^ DIFIERSIN FRICTION MATERIALS * Binders Property modifiers Use function Phenolic resins Natural rubber Buna N rubber Nitrile rubber Tire scrap Pitch Cork Gilsonite Elastomers Drying oils Graphite Coke Coal Carbon black Gilsonite Friction dusts Rottenstone SiO2 Quartz SiO2 Wollastonite CaSiO3 Brass Chips Zinc and compounds Aluminum Lower friction coefficient and noise Lower friction coefficient and noise Lower friction coefficient and noise Lower friction coefficient and noise Lower friction coefficient and noise Lower friction coefficient and noise Remove decomposition deposits Remove decomposition deposits Remove decomposition deposits Remove decomposition deposits Remove decomposition deposits Remove decomposition deposits Limestone CaCO3 Improve wear resistance Clays Improve wear resistance 86 Silicas Improve wear resistance - Barite BaSO4 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 Na AlF Fluorspar CaF2 Cardolite Nickel Sulfur Not available Not available Not available Not available Not available Not available Not available Not available Not available Not available Not available Not available Molybdenum sulfide MoS2 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 silicas 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 heavy friction materials break up undesirable surface films while a small amount of zinc chips can assist in recovering normal performance following a fade Particle size is limited to 100 mesh or finer because large hard particles groove and wear mating surface100 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 clutches 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 equip- ment 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 ray machines tape recorders typewriters bicycle brakes snow blowers washing machines and parking meters Special Qualities All products containing tion between mating surfaces energy into heat absorb the friction materials rely on the coefficient of fricto transmit or stop motion Brakes convert kinetic heat and gradually dissipate it into the atmo- sphere Disc brakes consist of two parts the rotor which is connected to the wheel and the stator on which the friction 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 200 392 The special qualities required by friction materials include e Possession of the appropriate coefficient of friction for the desired application e Ability to withstand the high temperatures generated at friction interfaces e Dimensional stability - e Strength 87 e Durability Lack of abrasive characteristics which could lead to scoring of mated surfaces Asbestos is used in friction materials becausoef the properties listed in Table 23. The most important properties are thermal stability reinforcing abilities relatively high friction fiber flexibility and relatively low cost TABLE 23. UNIQUE PROPERTIES OF ASBESTOS APPLICABLE TO FRICTION MATERIALS Properties Fibrous form Fine fiber diameter . Comments Flexibility contributes to forming characteristics Fibers interlace and interlock enhancing strength Flexibility reduces wear at friction interfaces Provide strong reinforcing characteristics because of the large number of fibers per unit weight High tensile strength Temperature resistance Cost Provides strength and durability to friction products Chrysotile unaffected by T 200 400 Stable for short period of time at T around 1000 Able to withstand high temperatures generated at friction interfaces up to 400 750 The temperature of maximum ignition loss is 1000 1800 Provides low cost performance or physical property ratio SUBSTITUTES Most large manufacturers of friction materials have active research and testing programs working toward the development of asbestos 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 manufacturers are optimistic regarding their future use Possible alternatives which have been considered include 1. ' Glass Fiber - Overall strength is lower than that of asbestos but strong enough for friction material appli- cations 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 higher.8 88 Mineral Wools - Overall strength is very low and brittle to the extent of limiting mixing processes 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 attractive for aircraft brakes 8,9 Sintered Materials or Cermets - These materials are now being used to manufacture brake linings for railroad cars and air- planes 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 700 1290 High thermal conductivity can excessively performance heat hydraulic brake fluid causing erratic ever this problem may be avoided by proper design How- Semimetallic Materials - Semimetallics are stable to temperatures of 400 750 and exhibit excellent wear resistance Potassium 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 considerations toxicological effects and other market DuPont to withdraw FYBEX from the market caused Aramid Fibers - These are being researched for use in high performance clutch facingisn 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 ? Vermiculite - Delaminated vermiculite is used in friction materials which are commercially available throughout 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 conten1t1 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 m11 ore expensive and heavier than composites eventually adopted 89 11 Others - Various other fibers have been used in phenolic binders such as aluminosilicates wollastonite All have drawbacks and none are yet as good as asbestos especially for temperature applications such as disc brake pads Borg Warner Corporation and Abex Corporation among others have developed proprietary substitutes for automobile brake friction materials Some are in the consumer testing stage but no additional information is available at this time Manhattan has tested a wide range of materials in an attempt to find a substitute for asbestos 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 fibers 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 by using a blend of 10 to 15 components 40 percent fiber 20 percent resin binder and 40 percent friction modifiers discussions with company representatives revealed that this was not strictly true The com- pany 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 is not expected in the foreseeable future Cermet or sintered metals a copper or iron matrix of material reinforced with steel fiber and various ceramic metallic property modifiers are used primarily in heavy 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 continues to grow Currently 95 percent of all new commercial aircraft use cermet brakes The remaining 5 percent are carbon 13 composite Semimetallic or resin bonded metallic brakes are presently in heavyduty automotive applications such as police cars and taxis While their performance is supposedly superior to asbestos brake linings semimetallic brake linings tend to perform erraticallayt different temperatures fade and pro- duce more noise than asbestos linings Currently semimetallics are 50 to 60 percent more expensive than asbestos linings but increased production it is estimated that costs would drop to within 25 percenotf asbestos brake linings 3 Approximately 20 percent of passenger cars using disc brakes are equipped with semimetallic disc brakes as original equipment and it is esti- mated that in 5 to 10 years most original equipment disc brakes in passenger cars and light trucks will be semimetallic General Motors has used a hybrid disc brake consisting of one semimetallic and one organic asbestos lining in some mass produced passenger cars The asbestos lining insulates the brake fluid from heat generated by the semimetallic surface during braking but never actually touches the motor surface In effect the asbestos content of the brakes is reduced Compared to asbestoslined disc brakes the hybrid brakes have a higher coefficient of friction 90 higher heat resistance and wear longer but are more noisy and more expensive While some industry sources feel that hybrid disc brakes will capture the market because of superior performance others believe that trends to lower limits speed brakes. and lighter weight cars will reduce the need for high performance The friction material in disc brakes is formed into an intrinsically stronger shape than in drum brakes and consequently needs less fibrous rein- forcement Asbestos is used in many disc brakes to reduce thermal shrinkage and withstand thermal shock but asbestos semimetallic disc brakes have been developed for automotive uses Table 24 A typical composition is given in TABLE 24 COMPOSITION OF AN ASBESTOS- PERCENT PAD a FREE DISC BRAKE IN VOLUME * Carbon 45 Iron powder 25 Steel fiber 10 Phenolic resin 20 Semimetallic 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 semimetallics American have automobile manufacturers disc brakes will be used targeted 1983 as the last model year asbestos 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 underway with specifics 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 nonasbestos lining was not available for drum brakes however Bendix Corporation is apparently very close to marketing this kind of product American automobile manufacturers have targeted 1985 as the last model year asbestos drum brakes will be installed as original equipment 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 lining substitutes a nonasbestos product for more univer- sal use should become available in the future 91 MANUFACTURING Primary Manufacture Plants manufacturing friction products contain a diverse collection of machinery Typically included are grinders mixing vats mills molds ex- truders curing ovens lathes metal stampers presses paper machines con- veyors and drill presses Chemical operations such as preparation of specific resins may also be performed onsite The exact mix of machinery at any given plant depends rials can be molded textiles or formed upon the manufacturing using either a dry mix like papers processes in or a wet mix use Friction process woven mate- like materials wethie Overview of Manufacturing Process-In the first steps of manufacturing friction bags of asbestos 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 ex- truder wet to form strips that are lengths A release compound is added lations which include a small amount cut and bent into various widths and to prevent sticking mixed formuof 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 materials Dry Mix Molding Process-The steps typically employed in manufacturing friction using the dry 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 cur- ing press to allow the resin to flow and set Only partial curing occurs during this step The material is then cut to product segments and rough ground The resin is then softened by a preheating step after which the proper arc is formed by 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 in- specting and branding are required before the brake linings can be packaged Wet Mix Molding Process-- Figure 7 shows the major steps in the manufacture of mix molded brake linings The term 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 ex- ! truded 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 FIBER | RECEIVING AND STORAGE| M BLEND OF ASBESTOS AND H OTHER RAW MATERIALS [ DRY MIXER H | y r MOLD | a r - [ STEAM COOLING | WATER PERFORMING PRESS MOLD REMOVED CURING PRESS uy SHEET CUT INTO STRIPS H ROUGH GRINDING STRIPS CUT TO LENGTH STEAM PREHEAT j | | | 1 CONDENSATE CONDENSATE COOLING WATER __| STEAM ai COOLING WATER HEATED BENDING = CLAMPING INTO LUNNETTES ___s Zz BAKING OVEN L FINISHING OPERATIONS RADIUS GRINDING CCOONNDCONDDENE SATE EN CONS NDSA EANT STAE TEE COOLING Jt WATER 1 _| DRILLING COUNTERBORING [ PACKAGING _| H - Indicates hooded operations Figur6e. mixed molded brake lining manufacture.15 93 1 RAW ASBESTOS FIBER RECEIVING AND STORAGE BLENDING OF ASBESTOS AND OTHER RAW MATERIALS SHEAR MIXER | HAMMER MILL _| ROLL MILL | | CHOPPER H | FORMER [ RACKING FORCED AIR DRYING CHAMBER BAKING OVEN SOLVENT SOLVENT [> RECOVERY _- SOLVENT FINISHING OPERATIONHS [ Note H - Indicates hooded operations PACKAGING ! CONSUMER Figure 7. 15 mixed molded brake lining manufacture 94 material the desired brake lining air dried and baked to remove any operations shape The linings are placed remaining solvent before final in racks finishing In an alternative process 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 molds where pressure is applied shaping the contents which are removed and baked after finishing Molded Clutch Facings-- Molded clutch facings are produced in a similar manner , lustrates Asbestos fiber a rubber friction compound and a as Figure 8 solvent are il- com- bined in a mixer and then conveyed through a rolled mill which compresses the mixture into a continuous strip of material A punch press is used to cut the material into doughnut pieces Scraps from this process are mixed and then fed back into the 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 Finish- ing 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 transmissions are punched from rolls of asbestos paper formed on a Fourdrinier or cylinder machine The forming process 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 are then ground inspected and packaged Die Cast Clutch Facings-- Larger clutch facings are frequently die cast Raw materials which include 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 products Figure woven products is facings shows are the frequently press used classified as being asbestos friction in their manufacture More detail on available in Section 12 Textiles Woven clutch facings and brake linings are manufactured from high strength asbestos fabric that may be reinforced with The fabric is predried in an oven or by autoclave before being impregnated with resin in one of several 95 RAW ASBESTOS FIBER y RECEIVING AND STORAGE BLENDING OF ASBESTOS H AND OTHER RAW MATERIALS SHEAR MIXER H | et wae ee | ROLL MILL | RECYCLE H MIXER I 7A _t- PUNCH PRESS v ' RACKING Lo Wy r DRYING OVEN LI y i BAKING OVEN LE v r SANDING H Ed v c EDGE GRINDING H Py Note DRILLING COUNTER BORING H ia DUSTING 4} wv [ INSPECTION | 1. [ BRANDING H | wv | PACKAGING | H - Indicates hooded operations J CONSUMER Figure 8. Molded clutch facing manufacture 96 STEAM COOLING WATER STEAM COOLING WATER REINFORCED CLOTH ROLLS 1 FRICTION COMPOUND BATH SLITTING TO TAPES H v PREFORM WINDING =a >) HOT PRESSES > PRECURING PRESS v STACKING ON METAL PLATES | BAKING OVEN | | FORCED COOLING FINISHING H | | PACKING CONSUMER , Note H - Indicates hooded operations CONDENSATE COOLING . WATER CONDENSATE CONDENSATE COOLING i WATER Figure 9. *5 Woven clutch facing manufacture 97 be immersed in a resin bath exposed to the binder techniques The fabric may with resin before being wound into yarn or in a pressurized autoclave mixed Once solvents are pressed beneath a roll whose surfamceadeis icntooverberdakweitlhinrinegssinor clutch facings evaporated from the fabric it is made in a manner similar to that described earlier Brake linings are fabric is cut into tape woven clutch facings are made differently Treated width strips by a slitting machine before being wound around a mandrel to form a fabric roll The roll is placed in heated press baked in an oven and packaged to cure the resin in the clutch facing then finished inspected in the by now familiar sequence Secondary Manufacture are sold to secondary manufacturers The division between Some brake pads however is not particularly important since primary and secondary manufacturers considered the secondary manufacturers perf^rma subset of the tasks generally preserve of primary manufacturers Secondary manufacturers take brake pads them and package them as the final rivet or bond them to brake shoes inspect product Any defective assembly could discredit their properly built products Manufacturing Plants and Production Volumes The manufacture of friction products is highly labor intensive with many processing and handling steps Because of the labor intensive production pro- limited to the differences between large and small manufacturers are cess stations devoted to each variety of products formed and the number of work of friction material manufacturers but many There are presently a large number of the smaller firms have extremely limited product lines Table 25 lists the U.S. manufacturers of asbestos friction mate- rials including if known their respective friction product sales in 1975 and the products they manufacture Both larger diversified companies such as and smaller single plant companies are included in this R lisat.ybThee sfit rso t s eight companies listed on this table accounted for 75 to 85 of the total estimated sales of asbestos friction products in 1975 percent with the industry's historical trends From 1954 to a pattern consistent accounted for 86 to 91 percent of 1967 the eight largest companies together the industry's value of shipments ASBESTOS RELEASE For friction materials release of asbestos fibers will be discussed for four general areas during manufacture use replacement and disposal concentrations for various Under manufacture emissions is included workplace to airborne asbestos water emissions and solid waste areas human exposure of the automotive aftermarket Replacement emissions discuss release as a part which includes refacing and rebuilding repackaging and general repairs emissions are included within the manufacturing emissions sections Disposal is shown first to help 1.e. solid waste etc. An output figure detail the path of these emissions TABLE 25. U.S. MANUFACTURERS OF ASBESTOS FRICTION MATERIALS9,16 37,5M5ATERIALS9,16 37,55 Products Brakes Clutches Company Plant loestion Automobile Fenvy Fenvy light truck truck Industrial Railcar Industrial Industrial Vehicle Comments Estinated Estinated 1978 sales ( million million Manhattas Inc Rt Friction Materials Co. Bendix Corporation,, Automative GRP Stratford CT Mannheim PA Crawfordsville IN Fullerton CA Drum disk Dick segpont block Troy NY Cleveland IN Southbend IN Drum disk Block ? . " v Irakes machine tools highway equipment . 16 94.5 Abex Corporation,, Cleveland OH Drum dick Block ^' 66.6 Friction Products Group Troy MI . Winchester VA General Motors Dayton 08 Brum disk 16.2 Moraine Div Inland Div E. Parter Company's Huntington IN Drum disk ^' 26.5 Thermaid Div . : Chrysler ration,, Iranton MI Drum disk . . Crelsweld Div . Borg Warner Corporation Bellwood IL Drum disk Sutura Company formerly World Bestos Co. Hashville TN Paulding ON Marement Corp. Crizzly Froducts National Friction Products 99 : Corporation,, Logansport Logansport If Block Auto Specialties Manufacturing Company St. Joseph MI Drum dick | Standes Indust Houston TX v . - 21.3 v vw road vehicles cranes abovals travel trailers mobils hones plent nuchinery appliances Pa road vehicles agricultural equipment road equipment winches cranes drilling rigs 12.0 0.66 8.7 Friction Products Company Rayal Industrial Brake Products Inc. Medina OR Danville M Black Drum disk v 4.0 Assembly of parts from Canadian samufacturers 16.0 Reddaway Manufacturing Companya Neward RJ v7 7 3.0 Maldad Industrial Friction CorporationPrattville AL Block Tractors and trailers 3.6 thealing Brake Block Manufacturing Co_2" Wheeling WV Bridgeport ON - Block 4.0 . Force Contral industries Fairfield ON _@ Disk and plate brakes lear and diesel engine - brakes tramways road vehicles Brassbestos Manufacturing Corporation Paterson Manufacturing NJ Drum disk Rebuilt Rebuilt 8.3 Acto Friction Corporation Lawrence HA brun Brun 26.3 Gatre Corporation Warsaw IN Drum #7 ff Custom manufacturing 12.0 Lase Brake Products Company Oakland CA Drum disk Block - MCM Brakes Incorporated,, * Carlisle Corporation Ridgeway P^ . Block Thiokol Chenical Corporation Trenton KJ Drum disk F. T. Brake Lining Company Inc. Laurence HA Drum Block Eaton Corporation Kenosha WI Block d disk 3.8 road vehicles buses railcars mining equip < sent towing vehicles Buses road vehicles 28.2 Rebuilt only 9.7 ~ - Scan Manufacturing Company Kanones Falls WI 2.8 Output Figure 10 shows estimates of process and disposal emissions for the asbestos friction materials industry These figures are based on Levine's 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 are incorporated into the product and 1111.9 m are sent to disposal as vacuum cleaner and baghouse dust An estimated 10.9 metric tons escape through a control device typically a baghouse Levin's atmospheric emissions estimates are based on gross assumptions with a reported uncertainty of at least an order of magnitude Meylan's estimates of emissions are generally 1 to 3 orders of magnitude less Atmospheric emissions from disposal based on GCA estimates are shown mare to total 2.2 m^tric tons per year for the friction materials industry This last estimate which follows Levine's 1974 data also takes into account the Asbestos NESHAPS regulations adopted in 1975 regarding the disposal of containiwn asg te material During Manufacture Workplace Fiber Concentrations-Table 26 shows the 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 friction products segment during that year Data was ob- tained by Weston in a survey using industry questionnaires and is of question- able 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 WEIGHTED AVERAGE FIBER CONCENTRATIONS OF OPTICAL MICROSCOPE VISIBLE FIBERS GREATER THAN 5 ...m IN FRIC39 TION PRODUCTS MANUFACTURING PLANTS Fiber count Process step Range fiber cc Typical fibers Receiving and storage Fiber introduction 0.25 0.4 - 2.5 4.6 1.0 2.5 Mixing 0.2 ~- 8.0 2.3 i 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 0.1 - 15.0 2.0 Packaging . 1.0 - 2.0 1.5 Based on plants representing 50 percent of asbestos friction material production 100 . 43,700 TPY HANUFACTURING OPERATIONS RECEIFING AND STORAGE If BLENDING f > MIXING tC pt CUTTING = FSF MILLING '= F- >} CHOPPING =3} FINISHING : LsNN NN, N . NS : bd j i . ~~ / < 7 == a | fo 42,575 TPY VACUUMED DUST 101 BAGHOUSE EMISSIONS 10.9 TPY DISPOSAL DISPOSAL 1111.9 TPY tome ee nue ce med ; DISPOSAL EMISSIONS 2.2 TPY AIR EMISSIONS 13.1 TPY LEGENDLEGENDLEGENDLEGEND LEGEND OUTPUT MANUFACTURING PROCESSES PROCES ESCONTROL EQUIPMENT ULTIMATE DEPOSITION SOLID mae ee eee eee WATER AIR Figure 10. 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 vari- ations in the range of fiber counts The largely individual manual and worker practices introduce considerable deviations as does the of asbestos in the product which may range from 30 to 70 percent by techniques percentage weight Receiving and 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 re- ported asbestos paper 0.25 to 2.5 fibers TWA and typical value 1.0 fibers TWA are equally valid for friction materials Fiber introduction of the raw material may be manually opened and dumped into hoppers for transport to mixers Fiber levels during this opera- tion are higher than those in papermaking fiber introduction ranging from 0.4 to 4.6 fibers TWA for friction materials as opposed to a 0.3 to 2.8 fibers cc TWA range for papermaking Typical fiber levels exhibit a similar differ- ence with 2.5 fibers typical of fiber introduction for friction products and 1.9 fibers typical for papermaking 39 It is not clear why such a difference should exist since the processing step is similar Perhaps the fact that in some paper applications it is not necessary to dump the fiber out of a bag contributes in papermaking However this characteristic should to lower typical values not affect the range re- ported since some paper applications require that the asbestos be removed from the bag Mixing combined raw materials may be mixed either dry or wet depend- ing 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 TWA were reported with 2.5 fibers TWA considered to fibers be typical Forming or rolling product of the mixing stage is fed to a com- pression molder or an extruder again depending on the required product Levels of 0.5 to 22.0 fibers TWA were recorded a level of 3.3 fibers TWA was considered typical The higher exposure levels are caused by the ; manual handling of the dry preform mix which is conveyed in open carts , scooped by hand weighed and poured into a block mold where it is mechani- cally pressed into the shape of the finished product mold Curing formulae require a and bind the mixture In the curing fibers TWA A fiber count of 1.5 heating step that step fiber levels fibers TWA was causes resins to flow ranged from 0.5 to 3.5 typica3l9 Finishing taken out of the curing oven undergo a number of steps to produce the final product These assisted manual finishing steps may include grinding sawing drilling blanking tapping and boring Fiber levels in finishing were typically 2.0 fibers TWA although reported values ranged from 0.6 7.4 fibers TWA 39 102 of Adjustment and printing finishing the friction products are dusted adjusted and printed Fiber levels in this operation are consistently close to 1.0 fibers TWA The range of exposures during this process is narrow 0.7 to 1.0 fibers TWA very . t inspection Inspection considered to be an examination of the finished prod- uct inspection encompasses different activities in different plants Some 1 plant inspection stations only examine the finished product if the product is defective or needs more comprehensive finishing it is returned to the area or rejected entirely finishing Other plants have additional equipment in the area so that any defect in the product can be rectified Consequently fiber counts recorded in inspection areas immediately to 15.0 fibers Usually the fiber level will be vary widely from 0.1 toward the low end of the ~ range with 2.0 fibers TWA considered typical Packaging workers involved in packaging the final product are ex- posed to fibers The range of reported fiber levels in packaging was 1.0 to 2.0 fibers TWA with 1.5 fibers TWA considered 39 typical Emissions to Air-- The maximum allowable exposure over a 40 hour week for workers in the asbestos industries has been set at 2 cc Workers are exposed to an fiber count of 1.9 cc with fiber counts as high as 22 cc being repaovretreadge see Table 26 The values reported reflect levels recorded in or before 1975 and are probably higher than present day concentrations With greater worker awareness and increased employer concern along with the regulatory activities of OSHA it is very likely that friction product worker exposure concentrations are well below the 2 fiber limit Documentation in the open literature to substantiate this belief however is not available With a workplace fiber count of 1.9 cc workers can be expected to inhale 119 billion fibers per year Estimates of nonoccupational ex- asbestos posure to asbestos have been made using a binormal continuous plume dispersion model with assumed plant emissions The affected population was assumed to be those people living within a 5 km radius of a friction material manufacturing plant The atmospheric concentration around the plant was estimated to be 23,000 mand the annual amount of asbestos inhaled was estimated to be 125 million fiberst per person This compares to a mean ambient urban exposure of 5,000 fibers with an average annual inhalation of 27.4 million + fibers per perso4n0 Release to Water-- Water is not used directly in the production of friction for those products formed materials except on paper machines from a 2 to 3 percent solids slurry Water usage and consequent water pollution associated with this cess is discussed in Section 4 Asbestos Paper Products pro- Despite the term . Optical microscope fibers 5 ...min length microscope 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 Solvent dust Wastewater collection is generated in some solvent recovery operations and equipment used to control dust throughout the plant in wet Solvent recovery wastes normally have very low suspended solid levels A typical sol- vent recovery operation has been reported to have 0 mg suspended solids in its waste stream Wastes solids concentrations from wet dust collection have significantly higher i Wastewaters from wet dust collectors are slurries of dust from plant opera- tions and are characterized principally 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 scrub- bers range from 283 to 7079 scmm resulting in discharges of 189,250 to 2,838,750 liters per day Units are for the most part equipped for partial recirculation Sludge or settled slurry is discharged to a settling lagoon where it becomes a solid waste problem In typical plant using wet collec- tion about 1488 kg are landfilling waters 1566 kg of asbestos are collected annually About 95 percent or removed as sludge by clarification The sludge is disposed of by while the remaining 78 kg of asbestos are discharged to surface 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 marshlands and lying areas It is now trucked to sanitary landfills for disposal but as fewer and fewer landfills are for disposal the hazards of asbestos have become better known willing to accept containing materials , ; Estimates of from 12.7 percent the percentage of asbestos lost in grinding and to 30 percent but even with the high cost drilling range of raw mate- rials asbestos in these scraps is not recovered for reuse Once the binders and resins have set it is uneconomicatlo break them down to salvage the fibers In most cased baghouses are used to collect grinding and drilling dusts It has been estimated that wastes can amount to as much as 12.2 month for a plant producing 40,000 brake shoes per day Based upon a total asbes- tos consumption of friction materials of metric tons in 1980 1,112 tons of asbestos would be lost in product waste Baghouses would collect about three- fourths of this total or about 834 tons while the remainder 278 tons would be collected by vacuum cleaners and as damaged product During Use During vehicle operation friction material whether used as a disc pad drum lining or clutch facing engages with a metal rotor to form asliding friction couple which converts the kinetic energy of rotating members into heat absorbs heat and dissipates it to the surroundings Emissions are gener_ ated 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 asbestos however is heated sufficiently to cause chemical conversion to olivine or forsterite 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 that approximately 33.6 million kilograms of asbestos in friction material wear away annually Based on their experimental 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 performed a similar calculation based on a ysis of friction material wear debris but otherwise retaining and DuCharme's assumptions Their best estimates of the total separate analall of Jacko annual asbestos emission were that 1,329,039 kilograms of asbestos dropped out 172,367 kilo- grams were retained in brake and clutch housings and 49,896 kilograms become airborne Elevated levels of asbestos were found in a study by Bruckman and Rubino in which airborne asbestos concentrations were monitored at three Connecticut toll plazas Asbestos concentrations were found to vary between 41 ng A nearby large industrial asbestos user was suspected the highest measured concentration Although no correlation was 3 ng and of influencing 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 Disposal Friction materials are usually replaced before they are completely worn out Most passenger vehicles reportedly use a set of containing brake . linings every three to four years containing friction products are disposed of in the form of worn brake linings disc pads and clutch facings These materials may be discarded as scrap pieces separated from any metal component which can be reused or scrapped along with the machinery they were a part of such as automobiles ; 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 friction material matrix Ultimately the nonfriable friction material is either incinerated or landfilled 105 TABLE 27 42 SUMMARY OF PUBLISHED DATA - ASBESTOS EMISSIONS FROM BRAKE LINING USE Publication source Lynch 1968 Method used to collect emission or debris samples Laboratory simulations utilizing testing machines or dynamometers Samples collected on 0.8 = pore size membrane filters Method used to determine asbestos content of emission debris samples Asbestos particle size distribution Electron micrographs Not discussed Asbestos content of emission or debris 1 except under stress conditions Hatch 19704 A dust cloud was generated by using compressed air jets to remove dust from brake linings in an auto repair garage Samples were collected by means of a hand pump located in center of dust cloud Not stated 94 of fibers ~ fell in 2-5 pm length category Only % were longer than 5 m 4 Hickish and Knight , 1970 Samples were collected directly from debris remaining as brake dust and from membrane filters exposed during brake cleaning operations utilizing compressed air Filter pore size is not given Not stated Not discussed 1.6 and less 6 a disc brake Neutron activation Not discussed 44 this figure is not 106 Bush et al 1972 Laboratory simulations utilizing accurate see discussion 106 assembly mounted on an inertial dynamometer Samples were collected on suitable filter paper Anderson et al 197347 Laboratory simulations utilizing a assembly mounted on a dynamometer of wear debris collected down wind d^>sc brake Air samples of disc brake Transmission electron microscopy Test results and and procedures precluded a size distribution estimate 0.02 42 Jacko and DuCharme , 1973 contains same data as Jacko et al 1973 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 in lining assemblies and 3 airborne samples collected on membrane ~ filters Optical and electron microscopy 30 of fibers were from 0.25-0.50 m in 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 TABLE 27 continued Publication source Method used to collect emission or debris samples Method used to determine asbestos content of emission debris samples Asbestos particle size distribution Asbestos content of emission or debris - Rohl et al 197649 Ten samples of automobile brake drum dusts were collected from maintenance shops in the New York area ray diffractometry Transmission electron microscopy selected area electron diffraction and electron microprobe analyses 80 of fibers were shorter than 0.4 m Length 2-15 average of 3-6 Consistent with but lower than quantitative determination made by ray diffractometry no percentages are given Alste et al 197650 Samples were taken from fresh and worn brake Electron microscopy Majority were No percent figure given however 107 linings and from the atmosphere near a freeway < um in maximum linear dimension conclusion was that major effect of braking appears to be in separating bunches of fibers and reducing their average length but not in altering their crystal structure . Rohl et al 197751 This is basically a reprint of the Rohl et al 1976 study with the inclusion of brake wear - test samples obtained from Europe and Australia The mean weight percentage ranged from 1.4 in Australia to 2.5 in France Emissions in Automotive Aftermarket The automotive aftermarket in divided into three major sections materials repackaging of friction service which asbestos exposures may occur is refacing or rebuilding of friction materials and general brake repair and 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 parts plants have had local controls for a long time Asbestos exposure reported by NIOSH during levels measured at three of these establishments were 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 sector have been reported to range from 0.2 to 0.6 fibers TWAexposures General Repairs-- . ; From the existing data on asbestos exposure levels during brake repair work it appears that an establishment dual dust from brake lining assemblies limit under the current OSHA standard using compressed air for blowing resi- may exceed the 10.0 fibers ceiling Data reported by Rohl49 on asbestos emissions during brake lining maintenance indicated that a peak exposure of 29.8 fibers had been encountered 0.9 to 1.5 meters from the workplace These data are presented in Table 29 108 TABLE 28 ASBESTOS FIBER"EXPOSURE LEVELS IN REBUILDING BRAKE AND CLUTCH ASSEMBLIES54 Facility Fibers TWA Receiving and cleaning Bonding and Cutting and riveting grinding Inspection and packaging A Mean Range Number of samples . 1.1 0.4 - 4.8 15 0.6 0.2 = 1.4 20 1.1 0.8 - 1.6 6 0.7 0.8 - 1.1 4 B . . Mean 4.0 2.7 5.0 Range 1.0 - 7.6 1.1 - 5.8 1.5 ~- 9.3 - Number of | 5 6 6 samples C Mean Range Number of samples 1.3 1.2 - 1.3 2 0.8 _ 1.5 - 9.3 [oo 6 Fibers 5 to 100 ...mwere counted using phase contrast microscopy according to the NIOSH method TABLE 29. FIBER LEVELS"DURING BRAKE LINING MAINTENANC4E9 Distance from ! workplace from 0.9 to 1.5 exposure 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 ...mwere 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 manufacturing by far Atmospheric release of asbestos fibers during primary the largest source of emissions in this category is 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 sludgies 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 in interest 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 successful substitute is found asbestos consumption in friction materials will drop precipitously 110 REFERENCES 1 Bradfield R.E.N. Asbestos Review of Uses Health Effects Measure- ment and Control Atkins Research and Development Epsom Surry England January 1977 Clifton R.A. Asbestos Washington D.C. 1980 Minerals Yearbook U.S. Bureau of Mines . Wright M.D. et al Asbestos Dust and Economic Impact Analysis of the Standard Part I. U.S. Department Draft Technological Feasibility Assessment Proposed Federal Occupational of Labor OSHA September 1978 Meylan W.M. et al Chemical Market Output Analysis of Selected Chemical Substances to Assess Sources of Environmental Contamination Task III - Asbestos EPA 6-78-005 August 1978 Bark Based 1975 L.S. D. Friction Moran and S.J. Percival Chemical Changes in Materials During Performance A Review Wear Asbestos- 131 139 Zussman J. The Mineralogy of Asbestos In Asbestos Volume , Properties Applications and Hazards L. Michaels and S. S. Chissick eds John Wiley and Sons New York N.Y. 1979. PP 45-65 Hodgson A.A. Chemistry and Physics 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 67-114 8 Jacko M.G. and S.K. Rhee Brake Linings and Clutch Facings Encyclo- pedia of Chemical Technology Third Edition Volume 4. John Wiley & Sons New York N.Y. 1979 Pp 202-212 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 . 137-138 1979 12 Einhaus J.R. Age of Asbestos on Vehicle Parts Ending Industries p 27-31 May 1979 Automobile 111 13. Telecon M. G. Jacko Bendix Materials Center with Nancy Roy GCA Corporation November 19 1979 14 Telecon M. G. Jacko tion August 1979 Bendix Materials Center with Nancy Roy GCA Corpora- 15 U.S. Environmental Protection Agency Air Pollutants Publication 117 Control Techniques February 1973 for Asbestos 16 Telecon Raybestos Inc. with David Cook GCA Corporation February 28 1980. Friction products manufactured 17 Telecon Kevin Peppard Bendix Corporation with David Cook GCA Corpora- tion February 28 1980. Friction product manufacturers 18 Telecon H.K. Sleeth Porter Company with Robert Bouchard tion February 29 1980. Friction products manufactured GCA Corpora- 19 Telecon Terry Blaine Warner Corporation Spring Division with Robert Bouchard GCA Corporation March 4 1980 Friction products manufactured 20 21 Telecon Roy Huckabee Nuturn Company with Robert Bouchard tion February 29 1980. Friction products manufactured GCA Corpora- Telecon Earl Fygert National Friction Products Corporation with Robert Bouchard GCA Corporation February 29 1980. Friction products manufactured 22 Telecon Bill Shine Auto Specialists Manufacturing Company with Robert Bouchard GCA Corporation February 29 1980. Friction products manufactured 23. 24 25 Telecon Standco Industrial with Robert Bouchard GCA Corporation February 28 1980. Friction products manufactured Telecon Jack Payton Friction Products Company with Robert Bouchard GCA Corporation February 29 1980. Friction products manufactured Telecon Bouchard Andrews Royal Industries Brake Products Inc. with Robert GCA Corporation February 28 1980 Friction products - manufactured Montgomery 26. Telecon Montgomery Reddaway Manufacturing Company with Robert Bouchard GCA Corporation February 29 1980. Friction products manufactured 27 Telecon Molded 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 manufactured February 29 1980. Friction products 29 Telecon Brassbestos Manufacturing Corp. with Robert Bouchard GCA Corporation 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 Telecon Robert Randolf Gatke Corporation with Robert Bouchard GCA Corporation March 3 1980. Friction products manufactured 32 Telecon Lasco tion March 3 Brake Products Company with Robert Bouchard 1980. Friction products manufactured GCA Corpora- 33 Telecon Appollageno MGM Brakes Inc. with Robert Bouchard GCA Corporation March 3 1980. Friction products manufactured 34. Telecon March 3 Carlisle Corporation with Robert Bouchard 1980. Friction products manufactured GCA Corporation 35. Telecon Thiokal Chemical Corporation with Robert Bouchard GCA Corporation March 3 1980. Friction products manufactured 36. Telecon Joseph Minky P.T. Brake Lining Company Inc. with Robert Bouchard GCA Corporation March 4 1980. Friction products manufactured 37. Telecon Mr. Baltz Baltz 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 DHEW Publication Number NIH 79-1681 U.S. Department of Health Education and Welfare National Cancer Institute Public Health Service Bethesda Maryland May 1978 39. Daly 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 John Hazards L. Michaels and S.S. Chissick eds New York N.Y. 1979. pp 171-205 Wiley & Sons 113