High energy proton irradiation stability and damage mechanism of shape-memory epoxy resin

Abstract

The effects of 1 MeV proton beam irradiation at 70 °C on shape-memory epoxy resin (SMEP) were investigated from the perspective of shape memory properties, dynamic thermomechanical properties and chemical structures in this paper. Results illustrated that the degradation of SMEP’s shape recovery rate was staged in contrast to the negligible degradation of shape fixity rate. The shape recovery rate reduced relatively slowly from 98.59% to 91.16% in the initial stage before the fluence reached 5 × 1014 cm−2 and then came down sharply to 38.82% after the fluence reached 1 × 1015 cm−2 and eventually reduced slowly to 36.29%. Moreover, the degradation of SMEP’s dynamic mechanical properties was also staged with the increasing of irradiation fluence. When the fluence was 2 × 1014 cm−2, there was still one peak in the tan δ spectrum shifting to higher temperature, indicating that the network of SMEP was still homogeneous and crosslinking instead of chain scissions took place mainly and homogeneously. When the fluence reached 5 × 1014 cm−2, the network of SMEP turned to be heterogeneous since there were 3 peaks split from one peak, implying that crosslinking and chain scissions coexisted simultaneously and to a similar extent. After the irradiation fluence reached 1 × 1015 cm−2, the two peaks in higher temperature merged into one peak and the intensity of this peak decreased quickly, revealing that chain scissions turned to be prominent. Structural analysis demonstrated that the chain scissions induced by 1 MeV proton irradiation mainly took place at the sites of aliphatic ether C–O groups on the surface layer, which was responsible for the significantly reduced shape recovery rate after the irradiation fluence reached 1 × 1015 cm−2.