Degeneration and damage mechanism of epoxy-based shape memory polymer under 170 keV vacuum proton irradiation

Shape memory polymers are the promising candidates for the next generation space deployable structures. However, to design highly reliable, long-life space deployable structures, it is essential to study the performance of shape memory polymers in the harsh space environments. In this work, the epoxy-based shape memory polymer was irradiated by 170 keV proton beam in vacuum condition. Multiple characterization techniques including dynamic mechanical analysis, electron paramagnetic resonance spectra, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to study the properties and microstructure changes after irradiation. Experimental results showed that the shape fixity rate remained almost unchanged at approximately 99.6% after proton irradiation while the shape recovery rate decreased sharply from its original 98.6% to 76.3% with increasing fluence up to 10 × 10¹⁵ cm⁻². Moreover, the decrease of glass transition temperature and the accelerated growth of free radical concentration indicated dominant chain scissions. Further research found that the cleavage of aliphatic chemical bonds, especially C–N and C–O groups of aromatic ether and aliphatic ether were responsible for the significant drop of the shape recovery rate, suggesting that epoxy-based shape memory polymers with more aromatic rings are thought to be better choices when designing the materials for applications in space deployable structures.