The aging behavior and mechanism of polyphenylene oxide foams in gamma radiation-compression environments

This study examines the changes in properties and aging mechanisms of polyphenylene oxide (PPO) foams under two densities when subjected to combined γ-radiation (0–1 kGy) and 3% compression. The investigation focuses on the effects of absorbed dose and compression on various characteristics, including the mechanical properties, thermal stability, thermal conductivity, surface morphology, and chemical structure of PPO foams. The types and yields of gases released during radiation exposure are revealed using gas-phase infrared spectroscopy. The results showed that the collapse and permanent deformation of the surface pore structure in PPO foams following γ radiation and compression aging significantly contribute to increase in elastic modulus and thermal conductivity. No significant changes were observed in the internal radicals or surface functional group structures of the samples before and after aging. The concentration of residual radicals within the samples was influenced by radiation-induced chemical changes and the absorbed dose. Upon radiation exposure and subsequent aging in an O2/N2 atmosphere, PPO foams emited CO2, CO, and alkanes. In addition, the CO2 yield of PPO foams after radiation-compression aging was slightly reduced due to the permanent deformation caused by compression, compared to γ-radiation aging alone. These findings hold significant value for the evaluation of γ-radiation–compression aging mechanisms and the lifespan of PPO foams.