Preparation and properties of nano SiO₂ functionally modified graphene/thermoplastic polyurethane composites

The graphene oxide (GO) synthesized by Hummers' method was mixed into coupled product nano SiO₂-NH₂ obtained by silane coupling agent (APTES) modifying nano SiO₂ to prepare nano SiO₂ functionally modified graphene sheet composites (nano SiO₂-g-GS) through the graphene sheets grafting with nano SiO₂. The nano SiO₂ functionally modified graphene/thermoplastic polyurethane composites (nano SiO₂-g-GS/TPU) were fabricated by melt compounding method using the thermoplastic polyurethane (TPU) as the matrix and nano SiO₂-g-GS as the filler, and then the fillers and composites were systematically characterized. The tensile tests show that the stress at definite elongation (300%, 500%, 1 000%) of nano SiO₂-g-GS/TPU composites increases due to nano SiO₂-g-GS has strengthening effects on the TPU. DSC tests show that the crystallinity temperature of the nano SiO₂-g-GS/TPU composites increases significantly compared with pure TPU, and the crystallinity temperature of TPU with 1wt% mass fraction of nano SiO₂-g-GS increases by 44℃. The shape memory testing results show that the shape recovery ratio (R_r) of nano SiO₂-g-GS/TPU decreases and the shape fixing ratio (R_f) increases with the increase of the mass fraction of nano SiO₂-g-GS. The nano SiO₂-g-GS/TPU composites with 1 wt% nano SiO₂-g-GS exhibit the best performance.