Influence of thermoplastic polyurethane and elastomer polymers on self-folding behaviour of 4D-printed polymer-textile composites

Four-dimensional (4D) printing has led to the development of novel pre-configurable shape-memory textiles that transform with time. By 4D printing onto textile substrates, polymer-textile composites (PTCs) with unique mechanical properties have been developed for various applications. However, previous related research has only experimented with single driven/non-reversible polymers due to the difficulties of adhering smart polymers onto textiles which require further scientific inquiry. This study highlights the printing of thermoplastic polyurethane/elastomers (TPU/TPE) with 70 A/82 A/40D Shore hardness to enhance the interfacial bond between thermo-responsive shape-memory polymers (SMPs) and a nylon substrate. The aim is to investigate the influence of TPU/TPE on the peel resistance, mechanical properties, and shape recovery of 4DP PTCs. The results revealed that a 70 A Shore TPU can provide significantly higher peel strength (up to 1600%) compared to 82 A/40D. In addition, Shore hardness also affected 4DP PTC's mechanical behaviours with 82 A 4DP PTCs recording a tensile strength of 652.30 N (warp) and 665.70 N (weft) with a modulus of 0.14Gpa (warp) and 0.18Gpa (weft). Its mechanical properties played a role in making it a more resistant material to give to deformation resulting in better shape recovery (94.72%, SD = 4.78) but lower shape fixity (88.90%, SD = 4.99) in comparison with other 70 A/40D specimens which are prone to better shape fixity but poorer shape recovery. The findings demonstrate the capacity of TPU/TPEs to achieve a consistent shape recovery and use as an alternative material to fabricate 4D printed textiles.