Changes in Polybutadiene Rubber under Various Conditions of Aging

Abstract

Abstract 1. The systematic relations of the oxidation of SKB under the action of heat, light, and ionizing radiation are considered and it is shown that the formation of a series of oxygen-containing products takes place (hydroperoxides, alcohols, aldehydes, ketones, acids, ethers, and esters). The general tendency for formation of these compounds was clarified for each separate case. 2. The behavior of double bonds of various configurations (1,2 and cis and trans 1,4) reveals differences in reactivity, namely: in the thermal, light, and radiation reactions, a decrease of the number of double bonds in the 1,2 position takes place, in general this is due to crosslinking and formation of volatile acids, but in the radiation reaction it is also due to hydrogenation. The increased rate of the decrease of the number of cis 1,4-bonds is in all cases interpreted as evidence of isomerization to the trans-configuration. It was shown that migration of 1,4 double bonds along the chain towards the tertiary carbon atoms and formation of conjugated double bonds (band at 1595 cm−1) takes place. 3. A decrease of the number of double bonds in the backbone (cis and trans 1,4) takes place that is mainly due to the formation of oxygen-containing compounds. Therefore, the quantitative investigation of this process can give an idea of the level of oxidative degradation. 4. The increase of the total absorption in the region 1400 to 750 cm−1 is connected with crosslinking. This, together with other existing methods (investigation of equilibrium swelling and stress relaxation) can be used for the estimation of the degree of crosslinking.