Document wrrykV9p0m5xdzL3xmzjXRag3

': ,. FRICTION 'HATERIALS STANDA.TU>S IJJSTITUTE, INC., E-210 ROUTE /14, PARAMUS, N.J. 07652 BULLETin N 0. 6 8 8 July 29, 1980 NATIONAL TJORKSHOP ON SUBSTITUTES FOR ASBE~TOS On July 14-1~, 19go the Consumer Product Safety Commission (CPSC) and the Environmental Protection Agency (EPA) sponsored a national workshop on substitutes for asbestos. I attended the July 14, 19P.O session at which a formal presentation l~as given on friction materials. This presentation ~7as Biven by '1r. Charles Brunhofer of the Bendix CorPoration, and emphasized the use of semi-metallic type linings on automotive disc brakes. This was a foroal session with a prepared delivery and a slide program. In the afternoon there were sessions on various subjects which l-7ere called "round table discussions.'~ There l-7as a round table discussion concerning friction products in the afternoon which I attended. I did not participate in sessions on gaskets, packings and other such material. But I did sit in on some pror,rams such as the ones on textiles. I don't believe that there was any major ne-t7 information developed at this workshop. Some speakers used their time to espouse substitutes that they .vere promoting. Others took the opportunity to take Slrl.pes at the use of asbestos to further their products. Some ~rere state of the art type reports and I would characterize the Bendix presentation as such. I1r. Brunhofer' s talk loTas llell documented and illustrated and indicated the considerable Hork that Bendix has done on development of semi-metallic materials for disc brakes. He reached back into the history of this development loJhich started prior to the days Nhen asbestos 'li-7as a target of Ht. Sinai and the environmentalists. The material was developed for use in a brake package to perform at higher levels of severity, lo7hich later tied in l~th reduced sizing of brakes from the vehicle manufacturers' down-sizing programs. This came lo7ith a move back tmrards solid rotors from the ventilated rotors which had been used on most United States passenger cars over the past 10-15 years. An abstract of ~r. Brunhofer's presentation follm1s: Friction materials for automotive brakes are co~plex composites containinP, three Reneral types of ingredient materials: reinforcinr, fibers; modifiers that adjust or maintain friction level, wear rate, and noise properties; and organic resin binders. Historically, the foundation or major constituent of automotive friction materials has been asbestos fiber, so chosen because of thermal stability, friction level, reinforcing properties, aJailability, and relatively lm_. cost. ~lumerous substitutes for asbestos in conventional organic materials have been evaluated, including both naturally occurring and synthetic materials. Direct substitution of these alternative materials in conventional formulations has resulted in poor friction levels, friction instability, rouBhness, FMSI 07028 BULLETIN NO. 686 -~- July 29, 1980 structural failure, increased noise, mating surface deterioration and/or front-to-rear vehicle brake imbalance. Complete reformulation, not simple substitution, is necessary to meet the numerous, complex performance requirements of consumers, manufacturers, and government standards, such as YrlVSS 105-75 arid FMVSS 121. In the 1960's, a n~g class of friction materials called semimetallics was developed to meet severe braking requirements, primarily in heavy-duty disc brake and extreme duty truck block applications. Semimetallics operate satisfactorily against the ventilated cast-iron rotors in the smaller brakes of downsized cars, as ~-rell as against the solid rotors found in the lighter brakes of neH front wheel drive vehicles. Semimetallics rely on steel fiber and po~-rder metallurgy techniques for reinforcement, and do not require asbestos. The improved performance of semimetallics compensates for their higher costs due to more expensive ingredients, higher specific gravity, and more costly processing requirements. Overall development took more than ten years from introduction to significant customer acceptance. The characteristics of semimetallics make them extremely difficult and costly to process as a drum lining segment. Consequently, an additional nel-l' class of friction materials is under development, specifically for drum lining applications. Additional development effort is necessary, not only to confirm the performance c..'l1aracteristics of these ne\"7 substitute fiber formulations, but also to develop ne"t-7 processing techniques. These neH-type friction materials ~rill be more costly, hm-1ever, due to the ingredients and new processing techniques. It will be noted that the talks and discussions at this l-7orkshop ~>Till be typed and made a part of the proceedings of the ~-1orkshop. Copies of the proceedings l-7ill be available from EPA sometime after the next several weeks. I uill attempt to get copies of the proceedings for distribution at that time. During questions following 'Hr. Brunhofer 1s presentation as t'lell as at the round table discussion in the afternoon there l-7ere several comments. Statements ~-1ere made to the effect that while semi-metallic type materials have been proven on disc brakes, drum brakes are a completely different problem. Drum br&~e semi-metallics are difficult process because of ueak green strengths and the difficulty in bending the material, as well as the brittleness of the material. Lengthy lead times are involved. Hhere the changes l-7ere "evolutionaryn they took from 3-4 years. This would be developing a new semi-metallic in an existing brake packaP.;e for example. Hr. Brunhofer indicated that where the chan~e ~-1as "revolutionary, this \rould take 5-1/2-8-1/2 years in development, This could be uhere the vehicles Here being down-sized "rith a completely new bral~e caliper and solid rotor for example. In discussions participants indicated that there uill be full semi-metallics on disc brakes by 1985. There also is develoPment under way cc>ncerning organic drum brake linings using substitute materials for asbestos. The earliest that such non-asbestos drum brruce materials may be in production ~-1as indicated as 1982-1983. Questions were raised about the replacement market, where a nel-7 vehicle takes a semi-metallic type lining. Hhat lo70uld be used for replacement? Hould the aftermarket install organics uhere a full semi-metallic was released as original equipment or Hould they install a like material? It was suggested that in practice the aftermarket may very well use conventional asbestos type materials to replace semi-metallics FMSI 07029 BULLET!lq NO. 688 -~- July 29, 1960 but that it Has recommended that replacement be on a like for like basis. That is, ~7here semi-metallic is used as original equipment it was recommended that the replacement also be a semi-metallic type. A participant from Dupont recommended the use of Tevlar as a substitute for asbestos. He suBgested that it not be used as a one for one substitute because it is quite expensive. He suggested that perhaps one mir~t use 5% Tevlar, plus other lower cost inorganic fibers materials to replace the balance of the asbestos. One example of an inorganic material he indicated was wollastonite. It was indicated that ~terials of this type are used on clutCh facings on Mercedes, Audi and Porsche. During the round table discussion !ir. Lee Burgess of lfueeling Brake Block indicated that where substituting for asbestos may be possible for mass production disc brakes. there is an entirely different field ~Yhere substitution is not going to be simple. He indicated the use of asbestos type materials on heavy equipment such as ~~anito~10c and other large off-hightiay equipment. lle particularly mentioned submarines and/or defense equipment. Mr. Burgess indicated that these materials were almost custom made to the requirements of the customer. Hhere substitute materials are going to be higher in price, the costs to the end consumer ~till be staggeringly high. I~. Burgess made several points as regards the fact that straight substitution for asbestos is not as simple as the re~ulators may assume. I am not sure whether the items discussed at the round table discussiop ~-1ill be in the proceedings, but if they are they vYill also be distributed when received. It ~-ras not our intention to distribute copies of the sessions other than those for friction materials. A brief write-up by EPA on asbestos and substitute materials for friction materials is attached. At the round table discussion, personnel from EPA (v7hich included llr. A1 Colli of the Office of Toxic Substances Control) asked generally the same questions that had been asked the Institute earlier concerning non-asbestos disc brake linings. Those answers had been given to the EPA people. A good deal of the session, and particularly that in the afternoon work session, ~-Tas repetitive, as EPA Has again asking questions asked earlier. EHD/lmc Enc. Distribution~ Active Members - List C Delegates &Alternates Regional Members '(u.s. Dues) E. r.y. Drislane Executive Director FMSI 07030 SECTlON 5 FRICTION MATERIALS Asbestos is well suited for usc in friction materials because of its th~rmat stability, reinforcing abilities, and relatively high ability to withstand friction. k~bcstos-containing friction materials are used for brakes for light- and heavy-duty vehicles, aircraft, railcars, various types of heavy equlpment and clutch facings. Severa] manufacturers of friction materials have active research and testing programs to develop asbestos-free materials. Although industry's research and development activities are highly secretive, we know that among the materials proposed in the past as substitutes are: glass fiber, steel wool, mineral wool, carbon fiber, cermets (sintered metals), semimetallic materials, potassium titanate fibers, aramid fibers, vermiculite, and silicon nitrides. Some firms may have ceased research on one or more of these materials but others may still be under consideration. Several manufacturers of friction materials have active research and teatlng programt; to develop asbestos-free materials. Some of the materials propost.d as substitutes are: glass fiber,- steel wool, mineral wool, carbon f1b~r, ccrmets (sintered metals), semimetallic materials, potassium titanate ftberH, arnrnld fibers, vermiculite, and silicpn nitrides. As friction applications vary, so do the materials most appropriate for each usc. Semimetallic and cermet materials may all be used in direct asbestos substitute applications, semimetallic in disc brakes (it is projected that in 5 years nearly all original equipment disc brakes in passenger cars and light trucks will use semimetallics) and cermets for aircraft brakes (95 percent of all new commercial aircraft use cermets). 23,24 Nonasbestos drum brake linings for passenger cars are currently unavailable commercially. 23 A cost comparison for various materials proposed as substitutes for asbeBtos In friction products is given in Table 7. TABLE 7. COSTS OF MATERIALS PROPOSED AS SUBSTITUTES FOR ASBESTOS IN FRICTION MATERIALS 25 Material Price per pound ($} Asbestos Fibrous glass Mineral wool Potassium titanate fibers Graphite and carbon fibers Wollastonite Cotton linters Aramid fibers 0.05-0.15 0.05-0.75 0.15 1.00-1.25 10.00-12.00 0.15 0.15 6.00-8.00 9 FMSI 07031