A study on thermal oxidation mechanism of styrene-butadiene-styrene block copolymer (SBS)

The thermal oxidation process of SBS was studied by in situ FTIR and programming heating up DSC. The thermal oxidation mechanism of SBS was analyzed according to the activation energy and pre-exponential factor calculated by Friedman method. The results show that the oxidation of SBS is mainly on butadiene blocks. It is a self-catalyzed reaction containing four steps. The first step is the initiation of chain by free radical. The second is the growth and decomposition of polymer chain. The third is the formation of anhydride coming from dehydrated carbonyl. The fourth is the annihilation of active centers. Antioxidant which provides H atom easily can annihilate active free radical to protect SBS from thermal oxidation at lower temperature.