Thermal Degradation of Glass Fibre-Reinforced Polyamide 6,6 Composites: Investigation by Accelerated Thermal Ageing

Polyamide-based glass fibre-reinforced composites are extensively used in electrical and automotive applications due to their excellent mechanical, thermal, and electrical properties. However, prolonged exposure to high temperatures can lead to significant degradation, affecting their long-term performance and reliability. This study investigates the thermal ageing behaviour of polyamide 6,6 composites containing halogenated flame retardants used for electrical applications. The objective of this research is to evaluate the extent of degradation through accelerated ageing tests and to develop an Arrhenius-type ageing model to predict the long-term performance of these materials. This study examines the effects of thermal ageing at temperatures between 160 and 210 °C on flexural properties and explores the underlying degradation mechanisms. Results indicate that short-term exposure to high temperatures can enhance flexural strength due to annealing effects, which are eventually outweighed by thermal oxidation and increased crystallinity, leading to an increase in brittleness. The derived Arrhenius model, with an activation energy of 93 kJ/mol, predicts a service life of approximately 25 years at 80 °C, but a significantly shorter one at 130 °C. These findings underscore the importance of considering thermal ageing effects in the design and application of PA66 composites in high-temperature environments.