Mechanistic Study on Rheological, Thermal, and Shape Memory Properties of Polyester‐Type and Polyether‐Type <scp>PLA</scp> / <scp>TPU</scp> Composites for <scp>4D</scp> Printing

ABSTRACT To address the lack of systematic comparison regarding the effects of thermoplastic polyurethane (TPU) type differences in 4D‐printed smart materials, this study designed composite systems of polyester‐type and polyether‐type TPU blended with polylactic acid (PLA) (TPU content: 10, 30, and 50 wt%). The differential regulation mechanisms of the two TPU types on the composites' microstructural morphology, rheological properties, thermal properties, and shape memory behaviors were systematically investigated. Results indicate that polyester‐type TPU exhibits stronger interfacial bonding and smoother surfaces due to its polarity matching with PLA. In rheological performance, polyester‐type TPU composites showed smaller increases in storage modulus, loss modulus, and complex viscosity compared to polyether‐type TPU systems. Thermally, polyester‐type PLA/TPU composites demonstrated a higher initial degradation temperature but lower residual mass. Mechanically, polyester‐type TPU composites achieved greater tensile strength, while polyether‐type TPU composites exhibited higher tensile strain. For shape memory performance, increasing TPU content slowed shape recovery in polyester‐type composites but accelerated it in polyether‐type composites, with the latter showing more responsive thermal activation. This study provides critical theoretical insights and data support for the selection of matrix materials and process design in 4D printing.