Influence of functional carbon nanotube and multi‐cyclic shape memory performance on thermally triggered polyurethane nanocomposites

Abstract In this study, thermally triggered shape memory thermoplastic polyurethane‐multiwall carbon nanotube (TPU/MWCNTs) nanocomposites with varying nanofiller content (0–5 wt%) were prepared. Melt flow, morphology, and shape memory properties of TPU/MWCNTs nanocomposites were investigated. We attempt to clarify the reinforcement effect of CNTs on the shape memory behavior of TPU/MWCNTs nanocomposites. Moreover, the influence of acid treatment on surface morphology, thermal stability, and dispersion state of MWCNTs has been evaluated. Pristine MWCNTs were treated with highly concentrated nitric acid (68%) and introduced by solution mixing to TPU as an efficient reinforcement phase. The thermogravimetric analysis revealed thermal stability improvement of acid treatment MWCNTs. Field emission‐scanning electron microscopy images confirmed the homogenous distribution of oxidized MWCNTs in the matrix and some aggregated structures at 5 wt% nanofiller. Higher melt flow rate values were observed for composites loaded with 0.5–1 wt% ox‐MWCNTs compared with 2–5 wt% because of their better dispersion in TPU. The experimental results show a higher shape recovery ratio of TPU/ox‐MWCNTs nanocomposites than pure polyurethane (over 20%). A good shape recovery in the 90%–100% range could be obtained during a shape recovery test when ox‐MWCNTs content of 0.5–2 wt% is proposed to synthesize TPU/ox‐MWCNTs nanocomposites.