Stability analysis of PA-6/ethylene elastomer blends for outdoor and nuclear applications

Abstract

The comparative behaviour under the oxidative degradation occurred during accelerating conditions of ageing (γ-irradiation and artificial weathering) is analysed for three polyamide-6-based formulations destined to special services like outdoor and nuclear fields. Pristine PA-6 and its blends with two ethylene elastomers (ethylene–propylene copolymer and ethylene–acrylic ester terpolymer) grafted with maleic anhydride were tested under accelerated degradation (radiation processing and weathering) by chemiluminescence and swelling. The elastomers are minor components with three loading degrees (5, 10 and 20%). The influence of elastomer fractions on the promotion of oxidation is revealed by the comparison with neat PA-6, which is a most stable of the three involved polymers. The results demonstrate that the minor components are the sources of radicals that are reactive spots. The competition between degradation and partial cross-linking is analysed. The calculated activation energies of oxidation allow the prediction of stability for long-term operation. The mechanistic aspects connected to the availability of blending components to oxidation are discussed for the explanation of ageing propagation under various factors acting during ageing promotion service.