Synthetic mbbers chemical resistance

Nitrile mbber finds broad application in industry because of its excellent resistance to oil and chemicals, its good flexibility at low temperatures, high abrasion and heat resistance (up to 120°C), and good mechanical properties. Nitrile mbber consists of butadiene—acrylonitrile copolymers with an acrylonitrile content ranging from 15 to 45% (see Elastomers, SYNTHETIC, NITRILE RUBBER). In addition to the traditional applications of nitrile mbber for hoses, gaskets, seals, and oil well equipment, new applications have emerged with the development of nitrile mbber blends with poly(vinyl chloride) (PVC). These blends combine the chemical resistance and low temperature flexibility characteristics of nitrile mbber with the stability and ozone resistance of PVC. This has greatly expanded the use of nitrile mbber in outdoor applications for hoses, belts, and cable jackets, where ozone resistance is necessary. 

Liquids. Approximately 170,000 railroad tank cars are used in the United States. The interior surfaces of these cars are tailored to carry a wide variety of products and are constmcted of steel which is either unlined or lined with materials to enhance the chemical compatibiUty with a specific product these lining materials include synthetic mbber, phenoHc or modified epoxy resins, or corrosion-resistant materials such as aluminum, nickel-bearing steel, or stainless steel. 

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). 

Uses Disinfectant solvent for wire enamels pharmaceuticals insecticides fungicides herbicides plasticizers mbber chemicals paints additives to lubricants and gasoline mfg. of polyphenylene oxide wetting agents dyestuff synthetic resin comonomer for alkali-resist, phenolic resins froth flotation agent engine cleaner ingred. 

In recent years, synthetic mbber nanocomposites are of great interest for both academic researches and industrial applications because they frequently exhibit unexpected properties synergistically derived from the two or more components. The properties of elastomeric materials as thermal stability and chemical resistance are of relevant importance considering both economic and ecologic impacts in many different areas. 

The unsaturated double bonds in diene-based mbbers allow vulcanisation (237) in the same manner as natural mbber. Inorganic filler materials are often used to enhance the mechanical properties of synthetic mbbers. Some special purpose diene-based mbbers, such as polychloroprene (325) and acrylonitrile-butadiene, are formulated to contain additional chemical elements in the polymer chain (chlorine and nitrogen, respectively) to improve chemical resistance properties. 

Poly(butadiene- (9-acrylonitrile) [9008-18-3] NBR (64), is another commercially significant random copolymer. This mbber is manufactured by free-radical emulsion polymerization. Important producers include Copolymer Rubber and Chemical (Nysyn), B. F. Goodrich (Hycar), Goodyear (Chemigum), and Uninoyal (Paracdl). The total U.S. production of nitrile mbber (NBR) in 1990 was 95.6 t (65). The most important property of NBR mbber is its oil resistance. It is used in oil well parts, fuels, oil, and solvents (64) (see Elastomers, synthetic— nitrile rubber). 

Acrylic Resins. The first synthetic polymer denture material, used throughout much of the 20th century, was based on the discovery of vulcanised mbber in 1839. Other polymers explored for denture and other dental uses have included ceUuloid, phenolformaldehyde resins, and vinyl chloride copolymers. Polystyrene, polycarbonates, polyurethanes, and acryHc resins have also been used for dental polymers. Because of the unique combination of properties, eg, aesthetics and ease of fabrication, acryHc resins based on methyl methacrylate and its polymer and/or copolymers have received the most attention since their introduction in 1937. However, deficiencies include excessive polymerization shrinkage and poor abrasion resistance. Polymers used in dental appHcation should have minimal dimensional changes during and subsequent to polymerization exceUent chemical, physical, and color stabiHty processabiHty and biocompatibiHty and the abiHty to blend with contiguous tissues. 

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