Physico-chemical and mechanical degradation of polyamide 11 induced by hydrolysis and thermal ageing

Abstract : This paper deals with the effect of both temperature and water activity on polyamide 11 physico-chemical and mechanical properties. The purpose of this work is to describe the ductile-brittle transition of polyamides during ageing in a wet environment using a mechanical behavior model. For that it is necessary to make physico-chemical analyzes (DSC, FTIR, GPC, viscosity) and mechanical tests (uniaxial tensile test and DMTA). These characterizations were carried out on safe and samples aged until 60 days under hydrothermal conditions in acid water, and under purely thermal conditions in a neutral environment. Changes in mechanical properties with ageing were observed in the polymer and were correlated to morphological changes deduced from the physicochemical characterizations. An increase of the second yield stress related to the recrystallization and a decrease of the strain at break due to the decrease of the molecular weight were observed during ageing.