TPU/EVA shape memory composites with improved properties fabricated via synergic incorporation of EVA-g-MAH compatibilizer and functional graphene oxide nanosheets

To fabricate the thermoplastic polyurethane (TPU) composites with excellent mechanical, thermal and shape memory properties, shape memory composites containing (TPU)/ethylene–vinyl acetate copolymer (EVA)/EVA grafting maleic anhydride (EVA-g-MAH)/functional graphene oxide nanosheets (fGONs) were designed, prepared and reported. The effects of VA contents (VA15 and VA40) in EVA on the compatibility of TPU/EVA blends were first evaluated and based on this, TPU/EVA/EVA-g-MAH/fGONs composites were investigated. The contact angle analysis revealed better interface compatibility of TPU/EVA40 compared to others, and fGONs tended to be distributed more in the TPU phase TPU phase. The enhanced compatibility of EVA and TPU can be attributed to the chemical interactions between EVA-g-MAH and TPU, as confirmed by FTIR and FESEM analysis. Increasing the proportion of EVA content in the TPU/EVA blend resulted in increasing elastic modulus. The mechanical characteristics of TPU composites containing GO and fGONs were enhanced compared with TPU/EVA and TPU/EVA/EVA-g-MAH. The shape memory performance examination indicated that EVA improved the shape fixation rate (R_f) of TPU, and the R_f was 147.3% higher than that of TPU. By incorporating 5% EVA-g-MAH, the blend demonstrated an increased R_f value of 79.60%, alongside a reduced shape recovery rate (R_r) of 75.5%. After adding fGONs, both the R_f and R_r were increased. The R_f and R_r of TPU/EVA/EVA-g-MAH/GO-IPDI composite reached 92.29% and 82.23%. DSC and DMA analysis revealed the glass transition temperature, storage modulus, and loss modulus of the composites were increased after adding fGONs.