Stress recovery and stress relaxation behaviors of PVC 4D printed by FDM technology for high-performance actuation applications

This paper aims at 4D printing of Polyvinyl Chloride (PVC) as an stimuli responsive shape memory polymer (SMP) with a high level of stress recovery, making it interesting for actuation applications. Filament extrusion was implemented for converting raw PVC pellets into 3D printing filament. Then, Lab-made PVC filaments were used to 4D print samples via fused decomposition modeling (FDM). First, thermal and microstructural properties of the 4D printed PVC are characterized and then cold, warm, and hot thermo-mechanical programing strategies are determined based on the temperature zone detected via the Dynamic Mechanical Thermal Analysis (DMTA) test results. Experiments are carried out to examine compressive nonlinear stress-strain behavior, constrained stress recovery, and stress relaxation responses. Results are presented to provide a deep insight into the influence of the programming temperature, compression level, and load holding time on the stress recovery and stress relaxation behaviors. It is shown that warm programming with an 80% compression level and instantaneous cooling/unloading results in the greatest stress recovery compared to other scenarios and parameters. This research is likely to advance state-of-the-art PVC 4D printing and unlock potential in the development of PVC actuators with high shape memory and stress recovery performance for high-capacity actuation applications.