Shape recovery behavior and mechanical performance of 4D printed Polyurethane/MWCNT nanocomposites under γ-irradiation

Shape memory polymers (SMPs) are a class of smart materials that are used in diverse applications and exhibit unique shape-changing abilities in response to external stimuli. Incorporating nanoparticles such as multi-walled carbon nanotubes (MWCNTs) into SMPs can further enhance their performance. However, Gamma (gamma) irradiation effect on these nanocomposites remains relatively unexplored. In the current work, nanocomposite specimens were subjected to varying gamma-irradiation doses of 100, 200, and 300 kGy. A comprehensive analysis was conducted to evaluate the changes in mechanical, thermal, micrographic, and shape memory behavior of the nanocomposites before and after irradiation. The results revealed a significant improvement in mechanical and thermal properties, with a 41 % increase in tensile strength, a 38 % increase in flexural strength, and a 11 % in glass transition temperature (Tg) observed at the 200 kGy gamma-irradiation dose. The influence of gamma-irradiation on MWCNTs and their interaction with SMP was also examined. Furthermore, the shape recovery responses of strip and waveform specimens in extension and compression were investigated. It was observed that all the investigated parameters of the SMP nanocomposites showed a decline beyond an optimum irradiation dosage.