Significant Performance Improvement of Thermoplastic Polyurethane Composites by Multiple Effects of Monodispersed Graphene: Micro-Crosslinking, Isolation, and Induced Crystallization

Thermoplastic polyurethane composites (TPCs) in kilogram scale reinforced with monodispersed functionalized graphene (FGr) are prepared by melt-blending on industrial extruder and their properties are studied in this work. It shows that the saturation content of monodispersed FGr in TPCs is approximate to 0.5 wt%, beyond which part of it will agglomerate. The multiple effects of monodispersed FGr-micro-crosslinking, isolation, and induced crystallization-have great impact on the properties of TPCs. With the content increase of FGr, the melt rheological properties, crystallization properties, mechanical properties, and shape memory properties of TPCs show regular changes. More importantly, the tensile fracture behaviors of TPCs are dramatically changed by FGr. Some microfibers with high strength are formed and lay astride the cracks to prevent crack propagation during the damage process. Therefore, the tensile strength of TPC with 0.5 wt% FGr is maximumly improved, showing an increase of 139% compared to neat thermoplastic polyurethane. Its shape fixed ratio and shape recovery ratio are respectively raised to 96% and 94%, showing a good shape memory performance.