The Effects of Some Antioxidants on the Elastomers Derived from Carboxy-terminated Polybutadiene

Abstract

Abstract The capability of several sorts of conventional antioxidants was studied by means of the tensile and the swelling tests of the elastomers derived from the carboxy-terminated polybutadiene prepolymer. When exposed for one year, the elastomers containing no antioxidants deteriorated remarkably; they became brittle and, without exception, no longer looked like the so-called “elastomers.” Many kinds of the antioxidants worked out and were found to be effective; their capabilities were evaluated as almost the same as far as the tensile properties of the exposed material were concerned. The changes in the reciprocal value of the average chain length between cross-links, 1/Mc, in the course of the exposure, however, would be a convenient semi-quantitative measure of the induced cross-linking reaction. With this assumption, the swelling test might prove that, among the additives covered, the amine-type antioxidants were most effective in preventing the deterioration induced by the over-cross-linking reaction of the elastomer. The relationship between the amount of the sol-fraction and the cross-linking density for the exposed specimens was fitted to that of the random cross-linking and the scission of the polymer with a random distribution of chain lengths.