Elastomer resistances

Viton Fluoro-elastomer Resistant to degradation by fuel, temperature to 500°F (260°C) and compression Fuel line housings metering or needle valves... 

Rynite (Du Pont, USA) PET/Elastomer Resistant to alcohol, gasoline and oils good-to-poor in acid, alkahs... 

Zytel (Du Pont, USA) PA-6,6/ionomer, PA 6,12/ionomer, PA-6/PA-66, PA-6 or PA-6,6 or PA-6,12/elastomer Resistant to alcohol, gasoline, oils excellent-to-poor resistant in alkali, limited in acids... 

Uses Chlorosulfonated PE in jacketing and insulation tor wire/cable, soles and heels, automotive components, coated fabrics, wh. tire sidewalls, sheet rooting liners and covers for reservoirs and waste containment ponds, protective and decorative coatings, hose, linings for chemicals processing equipment, industrial rolls, seals, gaskets, and diaphragms Features n. elastomer resist, to weather, ozone, oil, soivs., chemicals, heat, flame, and abrasion Properties Wh. chips. 

Epichlorohydrin, 6—CihCH—CH2CI, can be obtained by the oxidation of allyl chloride with peracids, by the high-temperature chlorination of propylene with subsequent addition of chlorine/water and elimination of hydrogen chloride, or by a three-stage process starting with acrolein. Elastomers resistant to oil, ozone, and cold can be obtained from the homopolymerization of epichlorohydrin with, for example, Et3Al/H20/acetyl acetone as initiator ... 

Trademarked Kalene, this material is a depolymerized virgin butyl rubber, which is similar to butyl LM rubber. The properties are similar to those of conventional butyl rubber such as the lowest vapor transmission rate of any elastomer, resistance to degradation in high-humidity, high-temperature environments (very Uttle change after 120°C steam for 1(X)0 h), excellent electrical properties (volume resistivity of 5.5 X 10 ohm-cm and a dielectric constant of 3.1), resistance to soil bacteria, excellent weathering, and resistance to chemicals and oxidation. 

Tests for elastomer resistance to air have to be considerably accelerated in the laboratory by exposure to pure oxygen (pressure test, 21 bar, 70°C) or in the ozone test chamber (standard pressure, 50-200 ppm ozone, 25°C, s. Section 2.2.8). While oxygen influence is rated as a percentage loss of properties, comparable to heat aging tests in air, ozone influence is evaluated according to crack formation in the rubber transverse to the tensile or bending direction (evaluation levels 0 to 3) [229]. 

Recent techniques of triple extrusion allow simultaneous extrusion of an internal semi-conductive screen, an insulating layer and an outer semi-conductive screen. In this way, practically all cavities and porosity are eliminated, thus reducing ionisation phenomena to negligible levels. Ethylene-propylene elastomer resistance to the latter is in any case very good. 

Agents, chemical warfare Agent VX [50782-69-9] Age-resistant elastomers AgeRiteDPPD [74-31-7] AgeRite White AgeRite Write [93-46-9] Ageusia Agglomeration... 

Tetrahydrofurfuryl alcohol is used in elastomer production. As a solvent for the polymerization initiator, it finds appHcation in the manufacture of chlorohydrin mbber. Additionally, tetrahydrofurfuryl alcohol is used as a catalyst solvent-activator and reactive diluent in epoxy formulations for a variety of apphcations. Where exceptional moisture resistance is needed, as for outdoor appHcations, furfuryl alcohol is used jointly with tetrahydrofurfuryl alcohol in epoxy adhesive formulations. 

Elastomeric shield materials (ESM) have been developed as low density flexible ablators for low shear appHcations (49). General Electric s RTV 560 is a foamed silicone elastomer loaded with silicon dioxide [7631-86-9] and iron oxide [1317-61 -9] particles, which decomposes to a similar foam of Si02, SiC, and EeSiO. Silicone resins are relatively resistant to thermal decomposition and the silicon dioxide forms a viscous Hquid when molten (50) (see... 

Polyacrylate elastomers find limited use in hydrauhc systems and gasket apphcations because of their superior heat resistance compared to the nitrile mbbers (219,220). Ethylene—acrylate copolymers were introduced in 1975. The apphcations include transmission seals, vibration dampers, dust boots, and steering and suspension seals. Further details and performance comparisons with other elastomers are given in reference 221 (see also Elastomers, SYNTHETIC-ACRYLIC ELASTOTffiRS). 

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. 

Acrylonitrile (AN), C H N, first became an important polymeric building block in the 1940s. Although it had been discovered in 1893 (1), its unique properties were not realized until the development of nitrile mbbers during World War II (see Elastomers, synthetic, nitrile rubber) and the discovery of solvents for the homopolymer with resultant fiber appHcations (see Fibers, acrylic) for textiles and carbon fibers. As a comonomer, acrylonitrile (qv) contributes hardness, rigidity, solvent and light resistance, gas impermeabiUty, and the abiUty to orient. These properties have led to many copolymer apphcation developments since 1950. 

Thermal Oxidative Stability. ABS undergoes autoxidation and the kinetic features of the oxygen consumption reaction are consistent with an autocatalytic free-radical chain mechanism. Comparisons of the rate of oxidation of ABS with that of polybutadiene and styrene—acrylonitrile copolymer indicate that the polybutadiene component is significantly more sensitive to oxidation than the thermoplastic component (31—33). Oxidation of polybutadiene under these conditions results in embrittlement of the mbber because of cross-linking such embrittlement of the elastomer in ABS results in the loss of impact resistance. Studies have also indicated that oxidation causes detachment of the grafted styrene—acrylonitrile copolymer from the elastomer which contributes to impact deterioration (34). 

Elastomeric Modified Adhesives. The major characteristic of the resins discussed above is that after cure, or after polymerization, they are extremely brittie. Thus, the utility of unmodified common resins as stmctural adhesives would be very limited. Eor highly cross-linked resin systems to be usehil stmctural adhesives, they have to be modified to ensure fracture resistance. Modification can be effected by the addition of an elastomer which is soluble within the cross-linked resin. Modification of a cross-linked resin in this fashion generally decreases the glass-transition temperature but increases the resin dexibiUty, and thus increases the fracture resistance of the cured adhesive. Recendy, stmctural adhesives have been modified by elastomers which are soluble within the uncured stmctural adhesive, but then phase separate during the cure to form a two-phase system. The matrix properties are mosdy retained the glass-transition temperature is only moderately affected by the presence of the elastomer, yet the fracture resistance is substantially improved. 

Gaskets in both dry gas and Hquid chlorine systems are made of mbberi2ed compressed asbestos. Eor wet chlorine gas, mbber or synthetic elastomers are acceptable. PTEE is resistant to both wet and dry chlorine gas and to Hquid chlorine up to 200°C. Tantalum, HasteUoy C, PTEE, PVDE, Monel, and nickel are recommended for membranes, mpture disks, and beUows. 

Hardness. The resistance of a fabricated mbber article to indentation, ie, hardness, is influenced by the amount and shape of its fillers. High loadings increase hardness. Fillers in the form of platelets or flakes, such as clays or mica, impart greater hardness to elastomers than other particle shapes at equivalent loadings. 

Tear Resistance. The resistance of an elastomer to tearing is affected by the particle size and shape of the filler it contains. Tear resistance generally increases with decreasing particle size and increasing sphericity of fillers. 

Low Temperature Properties. The property of solvent resistance makes fluorosihcone elastomers usefiil where alternative fluorocarbon elastomers cannot function. The abiHty to retract to 10% of their original extension after a 100% elongation at low temperature is an important test result. Eluorosihcones can typically pass this test down to —59°C. The brittle point is approximately —68°C. 

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