4D printing of shape memory polyethylene terephthalate glycol/thermoplastic polyurethane (PETG/TPU) blends

Research on 3D/4D printing has seen significant growth in recent years due to the immense potential for applying these techniques across various fields. Polyethylene terephthalate glycol (PETG) and thermoplastic polyurethane (TPU) are commercially utilized polymers in 3D printing, holding promise for application in 4D printing as well. PETG demonstrates excellent shape fixity at room temperature but limited recovery capacity, while TPU exhibits good recovery but poor shape fixity. Hence, this study aims to investigate the shape memory effect (SME) of PETG/TPU blends. The blends were prepared through melt blending, extruded into filaments, and then molded using 3D printing. Chemical, rheological, morphological, and mechanical characterizations were conducted, and the shape memory effect was assessed in a water bath under bending mode and using a rheometer under torsion mode. All compositions demonstrated a more balanced SME compared to individual polymers. For instance, the PETG/TPU (50/50) blend showcased a fixity ratio of approximately 97 % and a recovery ratio of around 93 % in bending mode, while under torsion mode, it exhibited a fixity ratio of approximately 100 % and a recovery ratio of about 87 %. To optimize printing parameters for achieving the best SME, an experimental design was employed, which involved assessing nozzle temperature, printing speed, and layer height. The study revealed that, within defined limits, the most favorable SME outcomes were attained at lower levels of nozzle temperature, printing speed, and layer height.