DSC study of selected antioxidants and their binary mixtures in styrene-butadiene rubber

The antioxidant effects of iminostilbene, phenothiazine, diphenylamine, three substituted diphenylamines and their mixtures with commercial product N-(1,3-dimethyl-butyl)-N′-phenyl-benzene-1,4-diamine (6PPD) in thermal oxidation of styrene-butadiene rubber (SBR) were examined by non-isothermal DSC measurements. For the treatment of experimental data, isoconversional methods based on two non-Arrhenian temperature functions have been applied. Protection factors were calculated to compare the stabilizing effect of individual compounds and their mixtures. Among the individual compounds, the highest antioxidant performance in the stability of SBR is observed for iminostilbene. In the case of mixtures the best stabilizing properties can be assigned to the mixture of 6PPD with 4-phenylamino phenol. The cooperation between antioxidants in the binary mixtures was characterized by the values of S-factor. The results indicate that only the mixture of 6PPD with 4-phenylamino phenol exhibits a synergistic effect at 130 °C.