Automotive elastomers

Material Trends of Automotive Elastomer Parts (Hoses)... 

Other sources have listed the automotive RIM market at approximately 41 Mi lbs. in 1982 (BOC) growing to nearly 95 Mi lbs. in 1987, while still another study reports 59 mm for automotive elastomers in 1982 -(Plastics Technology). This last figure of 59 Mi lbs. includes application in buses, trucks, and recreational vehicles. Table II gives data for industrial consumer products. The types of applications in these areas have been discussed previously (2) but include such markets as electronic cabinetry, recreational, shoes, agricultural and various appliances. 

The effects of ethanol/gasollne and MTBE/gasollne mixtures on swell and tensile properties of selected automotive elastomers were determined and compared to those of methanol/gasollne mixtures. 

Methanol, ethanol, and methy t-butyl ether (MTBE) are blended Into some commercial gasolines. It was Important to determine the effects of such blends on automotive elastomers especially those used In the fuel system. A summary of the results of our studies [1] and detailed data on the effects of methanol/gasollne mixtures on sixteen elastomers [2] have already been published. This paper presents detailed results of our Investigation of the effects of ethanol and MTBE mixtures with gasoline on mechanical and swell properties of automotive elastomers. Comparisons will be made with the effects of methanol/gasollne mixtures on elastomers. Experimental... 

Heat and Ofl Resistance of Automotive Elastomers (Based on SAE J200 SpcciBcation stem)... 

K. J. Kim, J. VanderKooi, J. Wasko, and M. Hensel, Halogen Atom Containing Elastomer Compound Processing with Processing Additives , Automotive Elastomer Conference 2004 (AES-2004) (paper no. 18) Dearborn, Ml, June (2004)... 

Although p oly (a-olefin) s (PAO) and esters are the prominent synthetic base stocks for automotive appfications, combinations of the two are becoming the choice in offering a balance of properties such as additive solubility, sludge control, and elastomer compatibility (34). 

Principal uses include automotive V-belts, industrial and hydraulic hose, specialty roofing, heels and soles in footwear, wine coveting, and a wide variety of coated fabric uses, eg, rafts. Chloroprene elastomers are also used extensively in adhesives (qv). It is estimated that about 77,000 t of chloroprene are used each year in the United States. The two main suppHers of chloroprene elastomers in the United States are DuPont and Bayer. In addition, Distiguil (France) sells polymers through the A. Schulman Company. 

DuPont—Dow is the primary suppHer of these polymers. There is an estimated 18,000 t of these elastomers used per year. The main uses of CPE are in constmction, automotive, and electrical appHcations. These include power steering hose, electrical cords used in low voltage appHcations (extension cords, ignition wire), pond liners, and as a plastic modifier to improve impact modification. 

Enichem and DuPont ate two suppHers of acryHc elastomers. It is estimated there ate - 9000 t/yr of these elastomers used in the United States. The principal uses of acryHc elastomers ate in automotive appHcations requiring both oil and heat resistance. These include transmission, valve stem, crankshaft, pinion, and odpan gaskets and seals. In addition hose, tubing, toUs, and belts ate made from acryHc polymers. 

Fluoroelastomers. The fluoroelastomers were introduced to the mbber industry in the late 1950s by the DuPont Company. They were made by modification of Teflon polymers and designed to have exceUent heat and chemical resistance, but remain elastomeric in nature. They were very expensive and have found use in limited appHcations. However, with the increasing demand in the automotive and industrial market for improved reHabUity and longer Hfe, the elastomeric fluoroelastomers have made significant inroads into these appHcations (see Elastomers, synthetic-fluorocarbon ELASTOTffiRS). 

Vluorosilicone. By fluorinating the siHcone polymer molecule it is possible to improve the solvent, fuel, and oil resistance of this already heat-resistant class of elastomers. The resulting polymers are especially useful in select automotive seals and gaskets as weU as military and downhole oilfield parts. 

These thermoplastic natural mbber elastomers have a place in the modem world, where recycling has become so important, and when excessive heat is not found in service. Thus, footwear, gla2ing seals, sports goods, hose, domestic products, and a whole range of automotive products have already been identified for such use. It must be noted, however, that tines are not a potential market for these materials, because of the high temperatures which result from emergency braking. 

The largest segment of the CASE family of polyurethanes are elastomers. Cast polyurethane elastomers reached a new dimension when high pressure impingement mixing led to reaction injection molding (RIM). This technology is used widely in the automotive industry, and reinforced versions (RRIM) and stmctural molded parts (SRIM) have been added in more recent years. 

The total elastomer consumption in the United States in 1994 accounted for 145,000 t automotive RIM appHcations account for 63% of the total. Coatings consumption in the United States in 1994 was 95,000 t, and powder coatings accounted for about 20% of the total. Adhesives and sealants consumption amounted to another 95,000 t. 

Antioxidants resistant to extraction by lubricants and gasoline are preferred for the stabili2ation of elastomers used in automotive appfications such as gaskets and tubing. Aromatic amine antioxidants, such as A/-phenyl-Ar-(p-toluenesulfonyl)-A-phenylenediamine [100-93-6] (37), with low solubifity in hydrocarbons, are extracted slowly from elastomers and are used for these appfications. 

Highly saturated nitrile elastomers (HSN) have become available. These mbbers are prepared by (nearly complete) hydrogenation of the nitrile mbber copolymer. The resulting product has better heat and oxidation resistance than conventional nitrile mbber but still retains some double bonds for vulcanization. Trade names for HSN are Zetpol (Nippon Zeon), Therbar (Bayer), and Tormac (Polysar). HSN has been used, and is being developed, for oil field chemical, automotive, power station, aerospace, military, and industrial appHcations (66). 

Acrylic rubbers, as is the case for most specialty elastomers, are characterized by higher price and smaller consumption compared to general-purpose mbbers. The total mbber consumption ia 1991 was forecast (55) at 15.7 million t worldwide with a 66% share for synthetic elastomers (10.4 x 10 t). Acryhc elastomers consumption, as a minor amount of the total synthetic mbbers consumption, can hardly be estimated. As a first approximation, the ACM consumption is estimated to be 7000 t distributed among the United States, Western Europe, and Japan/Far East, where automotive production is significantly present. 

The favorable balance of properties of ethylene—acryflc elastomers has gained commercial acceptance for these elastomers in a number of demanding applications, especially in the automotive industry and in wire and cable jacketing. 

Considerable amounts of EPM and EPDM are also used in blends with thermoplastics, eg, as impact modifier in quantities up to ca 25% wt/wt for polyamides, polystyrenes, and particularly polypropylene. The latter products are used in many exterior automotive appHcations such as bumpers and body panels. In blends with polypropylene, wherein the EPDM component may be increased to become the larger portion, a thermoplastic elastomer is obtained, provided the EPDM phase is vulcanked during the mixing with polypropylene (dynamic vulcani2ation) to suppress the flow of the EPDM phase and give the end product sufficient set. 

Chemical Resistance. Fluorocarbon elastomer compounds show excellent resistance to automotive fuels and oils, hydrocarbon solvents, aircraft fuels and oils, hydrauHc fluids, and certain chlorinated solvents, and may be used without reservation. 

Commercially available fluorocarbon elastomers meet automotive specifications in the HK section of ASTM D2000 and SAE J-200. ASTM D1418 specifies designations of composition, eg, fluorocarbon elastomers are designated CEM, EKM, or EEKM. Commercially available fluorocarbon elastomers offer a balance of those properties needed to meet the major O-ring specifications, such as AMS 7276, AMS 7280A, AMS 7259, MIL 83248 Amendment 1 Type II, Class I and II. 

The usage pattern in Europe and Japan is more dependent upon the automotive industry. However, with the recent concern about acid rain, the European and U.S. markets should show increased interest in fluorocarbon elastomers for pollution control appHcations. On the other hand, the Japanese market has a sizable outlet in electrical and general machinery manufacturing (eg, copiers). Petroleum appHcations are of Htfle interest outside the United States. 

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