A new approach on the thermal stability of SDS copolymer for HMPSA, Part I: Oxidation kinetics for the whole process

The poor aging property of the styrene-diene-styrene (SDS) triblock elastomer copolymer hot-melt pressure-sensitive adhesives (HMPSAs) has raised the importance of research on the aging and anti-aging proper-ties of SDS triblock copolymers, such as styrene-butadiene-styrene (SBS) and styrene-isoprene-styrene (SIS). A mechanistic scheme based on the standard scheme for radical chain oxidation, but taking into account the decomposition of the oxidation-induced peroxide, was built. The kinetic equation of oxygen uptake was deduced from the proposed mechanism, which is composed of a set of reasonable parameters. The relationships among the parameters to induction time, maximum oxygen uptake and the maximum oxidation rate were examined. Numerical simulation methods were established to obtain parameters from the experiment data, by which most kinetic equations of oxygen uptake of the ingredients for HMPSAs were numerically fitted and the relativity of the model to the data was discussed. The study results should prove useful for future studies on the anti-aging performance of other materials. (C) 2008 Elsevier Ltd. All rights reserved.