Radiochemical Ageing of Aromatic Polymers PEEK, PSU and Kapton®

This article deals with degradation mechanism of three aromatic polymers submitted to γ‐rays in air at 60° C. Tg measurements and GPC results indicated that thin samples (thickness lower than 200 μm) undergo mostly chain scission whereas sol gel analysis and rheometric measurements showed that thicker ones undergo mainly crosslinking. Both results are explained by oxygen diffusion control of oxidation resulting in the formation of a superficial oxidized layer experimentally observed by μATR InfraRed in which oxidative processes orientate rather to chain scission than crosslinking. Experimental results also allowed discussing relative oxidative stability, sensitivity of Tg to chain scission concentration, and crosslinking mechanism (Y or H).