Impact of rubber side groups
The side group has the same effect as the unsaturated carbon chain rubber, but its oxidation resistance is different due to the presence or absence of substituents on the double bond and the polarity of the substituent. The acrylate rubber in the saturated carbon chain rubber is more polar than the ethylene propylene rubber, and the latter is a methyl group, and the oxidation activity of the former is also much lower than that of the latter. The fluororubber is also a saturated carbon chain rubber but has only a small amount of hydrogen atoms attached to the carbon atom, and is mainly a highly polar fluorine atom or a fluoroalkyl group, and thus exhibits excellent oxidation resistance.
Effect of copolymerization components on oxidation resistance of copolymer rubber
Effect of copolymerization component The oxidation resistance of the copolymer rubber is related to the kind and amount of the second component or the third component in the copolymer. Compared with nitrile rubber, styrene-butadiene rubber has better oxidation resistance than the former, and the oxidation resistance is better with the increase of acrylonitrile content. This is related to the fact that the cyano group is a strongly polar group. On the one hand, it reduces the reactivity in the adjacent butadiene structural unit; on the other hand, it makes the nitrile rubber have a relatively low cohesive energy density and is reduced. The ability to diffuse oxygen.
Although the steric hindrance effect of benzene ring in styrene-butadiene rubber can hinder the diffusion of oxygen, its effect on improving oxidation resistance is limited due to its small styrene content and random distribution. Because its unsaturation is lower than that of natural rubber, it is low. The oxidation resistance is only better than natural rubber, which is comparable to that of butadiene rubber. In addition, the oxidation activity of ethylene propylene diene monomer and butyl rubber increases as the content of the unsaturated third component increases.