Effect of graphene oxide-carbon nanotube hybrid filler on the mechanical property and thermal response speed of shape memory epoxy composites

Shape memory polymers (SMPs) will come to act an indispensable part in numerous aspects of human activity. However, the low mechanical strengths and thermal conductivities of SMPs have largely restricted their applications. Remarkable improvements in the mechanical properties and thermal conductivities of SMPs via introducing thermal conductivity fillers have been achieved, though the fillers acted as obstructors or promoters for the thermal response speed of SMPs were unclear. In the present study, ternary hybrid polymeric shape memory composites of graphene oxide/carbon nanotube/waterborne epoxy (GO/CNT/WEP) were fabricated, where GO acted as a non-covalent dispersant for CNT in WEP and as a reactive secondary reinforcing agent to improve the mechanical strength and thermal conductivity of WEP. The experimental results showed that GO and CNT were uniformly dispersed and well incorporated into WEP matrix, significantly enhanced the mechanical properties, thermal conductivity and thermal response speed of the GO/CNT/WEP composites. Moreover, the thermal response speed of the shape memory composites was controlled by their thermal conductivity at low filler content, while the storage modulus was the dominant factor for the thermal response speeds of the shape memory composites at filler content higher than 2 wt%.