Influence of UV irradiation on mechanical performance and shape memory response of 4D printed SMPU/MWCNT nanocomposites

Abstract

Shape memory polymers (SMPs) are advanced materials capable of recovering predetermined shapes in response to external triggers. Incorporating nanoparticles like multiwalled carbon nanotubes (MWCNTs) into SMPs holds the potential for improving their overall performance. This study developed SMP/MWCNT nanocomposites at various concentrations from 0.25 to 1.0 wt.% and specimens were fabricated via 4D printing. Despite this, the impact of ultraviolet (UV) irradiation on these SMP/MWCNT nanocomposites remains understudied. The current research study explores how UV exposure influences the mechanical, thermal, and shape recovery characteristics of SMP nanocomposite. The specimens were subjected to UV-B irradiation for varying time durations of 250, 500, 750, and 1000 hours (h). The mechanical, thermal, structural, and shape recovery characteristics of pre- and post-irradiation specimens were studied using DSC (Differential Scanning Calorimetry), tensile, flexural, FTIR (Fourier transform infrared spectroscopy), and XRD (X-ray diffraction) tests. The results revealed significant improvements in mechanical, thermal, and shape recovery properties at an irradiation duration of 250 hours, with increases of 41% in tensile strength, 33% in flexural strength, and a 10% increase in glass transition temperature (T_g). Notably, these enhancements were accompanied by a 20-30% acceleration in shape recovery. Significantly, the study showed that all analysed characteristics indicated that 250 hours was the optimal irradiation time. These discoveries offer important insights into the potential use of SMP/MWCNT nanocomposites for outdoor and various other applications.