Saturated hydrocarbon elastomers

Blends of Saturated Hydrocarbon Elastomers (Uncompatibilized Blends)... 

Krishnamoorti, R. in Miscibility of Blends of Saturated Hydrocarbon Elastomers. Rubber Division, Proceedings of the American Chemical Society, Nashville, TN, Sept. 29-Oct. 2, 1998, Paper No. 33, 1-14. 

Saturated hydrocarbons (waxes), fatty acids, metal soaps, fatty acid amides and esters (primarily Cig-Cis) act as internal lubricants, fluoro elastomers as external lubricants. Many other polymer additives, e.g. antistatic agents, antifogs, antioxidants, UV stabilisers, etc., act as lubricants in the barrel of the extruder once they are in the liquid form. 

Thus, ethylene, obtained from petroleum or natural gas hydrocarbons, is also a mon< Qer for the direct formation of a plastic such as polyethylene, or of an elastomer such as Ethylene-Prop ene-Termonomer (EPT) rubber. Acetic add, produced in several stq> from acetylene or ethylene, is also produced directly by the oxidation of a mixture of saturated hydrocarbons (naphtha). 

Therban. [Bayer Mite] Saturated hydrocarbon ACN copolymer qwcial elastomer for power transmission belting, hoses, membranes, seals, gaskets, b ws, linings, extruded profiles fix automotive, industrial, and oil field q>piics. 

Saturated hydrocarbon polymers are also crosslinked by the action of organic peroxides, though branching reduces the efficiency. Polyethylene is crosslinked by dicumyl peroxide at an efficiency of about 1.0, saturated EPR gives an efficiency of about 0.4, while butyl rubber cannot be cured at all. For polyethylene, the reaction scheme is similar to that of the unsaturated elastomers. 

Peroxyl radical reaction with the polymer. This is a generally much slower process, which is structure dependent. In saturated hydrocarbon polymers, e g. polyethylene (PE) and polypropylene (PP), it is exclusively a hydrogen atom abstraction. In this case. Per is a hydroperoxide group (POOH). The corresponding rate constant is very low = 10 -10 l.mor. s at ambient temperature (see Table 12.7). In polyenic elastomers, e g. polybutadiene (PBD) and polyisoprene (PIP), step 3 can also be an addition to double bonds. In this case. Per is a peroxide bridge (POOP). The corresponding rate constant is also very low typically = 10 -10 l.mor. s at ambient temperature for an intramolecular addition (see Table 12.7). 

VISTALON elastomers are classified generically as either ethylene-propylene copolymers (EPM) or ethylene-propylene terpolymers saturated hydrocarbon chain which makes them highly resistant to attack by chemical agents such as oxygen, ozone, acids, and the like that seek to react at the site of a double bond. 

The process yields a random, completely soluble polymer that shows no evidence of crystallinity of the polyethylene type down to —60°C. The polymer backbone is fully saturated, making it highly resistant to ozone attack even in the absence of antiozonant additives. The fluid resistance and low temperature properties of ethylene—acryUc elastomers are largely a function of the methyl acrylate to ethylene ratio. At higher methyl acrylate levels, the increased polarity augments resistance to hydrocarbon oils. However, the decreased chain mobiUty associated with this change results in less fiexibihty at low temperatures. 

The properties of these elastomers are widely different. All require vulcanization. In general, sulfur is used only for unsaturated polymers, peroxides, quinones, metallic oxides, or cliisocyauates effect vulcanization with saturated types. Many are special-puipose rubbers, some can be used in tires when loaded with carbon black, others have high resistance to attack by heat and hydrocarbon oils and thus are superior to natural rubber for steam hose, gasoline and oil-loading hose. Most are available in latex form. See also Elastomers. 

Proof of the high reactivity of the unsaturated units present in the elastomers we used was obtained by polymerizing vinyl chloride in the presence of different amounts of two hydrocarbons, n-hexane and 2-methyl-2-butene these may be taken as models of the saturated polyhydrocarbon and of the allyl system present in the EPDM terpolymer. AIBN (0.13%) was used as initiator. 

Ethylene-propylene rubber is a synthetic hydrocarbon-based rubber made either from ethylene-propylene diene monomer or ethylene-propylene terpolymer. These monomers are combined in such a manner as to produce an elastomer with a completely saturated backbone and pendant unsaturation for sulfur vulcanization. As a result of this configuration, vulcanizates of EPDM elastomers are extremely resistant to attack by ozone, oxygen, and weather. 

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