The quantitative differential thermal analysis determination of polyolefin stabilization

Abstract

AbstractQuantitative Differential, Thermal Analysis has been used in the wire and cable industry for determining the degree of oxidative stability of polyolefins for quality control purposes in lieu of a direct antioxidant analysis, However, it has never been shown whether the presence of each additive in a stabilizer package could be detected by this method. The results presented here indicate that the presence of a primary antioxidant and a copper inhibitor in combination can be detected separately by comparing the oxidative induction times in copper and aluminum pans. The addition of a thioester synergist such as distearyl thiodipropionate, DSTDP, is evidenced by an increased induction time in aluminum pans. However, the presence of DSTDP makes it impossible by this method to determine whether an effective level of copper inhibitor is present since the sample shows a reduced stability on copper compared to aluminum. One of two factors can be invoked to explain these results: a) DSTDP interferes with the complexing ability of the copper inhibitor or b) the copper‐inhibitor complex retards the synergistic effect of the DSTDP. In either case, this factor is not important at lower temperatures since oxygen uptake data at 130°C indicate that DSTDP is an effective synergist in the presence of copper.