Preparation and Properties of TPU/EVA/EVA-g-MAH Shape Memory Blends

The thermoplastic polyurethane (TPU) / ethylene-vinyl acetate copolymer (EVA) blends with different VA contents were prepared by the melting method, and the ethylene-vinyl acetate copolymer grafted with maleic anhydride (EVA-g-MAH) was used to improve the compatibility of the both. Infrared spectroscopy (FTIR), scanning electron microscope (SEM), contact angle tester and mechanical properties test were used to characterize the microstructure and properties of the obtained composite materials. The research results show that the interfacial tension of EVA40 and TPU is lower. The elastic modulus of TPU / EVA blend increases with the increase of EVA content, which can reach up to 8.5 times of TPU. When the mass fraction of TPU and VA is 15%, the mechanical properties of blends prepared by EVA are better. EVA significantly improves the shape fixation rate (R_f) of TPU, while the shape recovery rate (R_r) decreases slightly. As for the mechanical and shape memory properties of the blend, the optimal ratio of TPU and EVA is 70:30 when VA mass fraction is 15%; EVA-g-MAH improves the compatibility of TPU and EVA; after adding EVA-g-MAH, the mechanical properties and R_f of the blend are significantly improved, but R_r is significantly reduced.