The effect of layer height and post-curing temperature on the shape memory properties of smart polymers in vat photopolymerization

Abstract

Purpose The purpose of this paper is to evaluate the influence of layer thickness and post-curing temperature on shape memory properties in components manufactured by stereolithography. Design/methodology/approach Layer thicknesses of 20 and 100 µm and 22 and 45°C for post-curing temperature were selected following the design of experiments approach. Tensile and bending tests were applied for quantitative evaluation of the shape memory effect (SME). Qualitative analysis was performed using complex geometries and computed tomography as a measurement tool. Additionally, the degree of photopolymerization and glass transition temperature (Tg) were evaluated. Findings The tensile test resulted in fixity and recovery ratio values close to 100%. In bending, they varied between 97%–111% for fixity and 88%–95% for recovery. The layer thickness was found to have a higher influence on the SME. In complex structures, SME was dependent on geometry and less sensitive to variation in process parameters. The post-curing temperature had a higher influence on the photopolymerization and Tg. Average Tg of 77.5°C was achieved at 45°C, compared to 73.1°C at 22°C. Originality/value In the current state of the art in the processing of shape memory polymers with vat photopolymerization typically, the chemical composition or the thermal and deformation patterns are studied. The effect of the processing parameters is, however, not explored. This paper aims to close the research gap and facilitate the process optimization towards high fixing and recovery characteristics.