Polyhexahydrotriazine Crosslinked Polyimide/Graphene Shape Memory Composite

Shape memory polymers (SMPs) are a class of smart materials that have the ability of transform shape in response to external stimuli, such as heat, light, electricity and magnetic. To design suitable macromolecules and crosslinking mode of polyimide to obtain shape memory polymer with high transition temperature, high strength for application of aerospace, high temperature and other harsh environment is very important. Herein, using well-dispersed graphene oxide (GO) as the reinforced phase, polyhexahydrotriazine crosslinked polyimide/graphene shape memory composite (PI-PHT) was prepared by solvent volatilization and high temperature cyclization. The structure of the materials was characterized by nuclear magnetism and infrared spectrum demonstrating the successful preparation of composites. The mechanical properties tested by universal testing machine showed that after introduction of graphene, the strength, toughness, thermo-mechanical properties and shape memory properties of the composite were significantly improved. When the mass fraction ofGO was 5%, the tensile strength and toughness of PI-PHT reached 105.7 MPa and 12.4 MJ/m³, respectively (1.3 times and 2 times higher than that of PI-PHT without adding GO, respectively) duo to the strong interaction between the well-dispersed grapheme and polyimide. The shape memory properties and shape recovery force were detected by dynamic thermo-mechanical analyzer. The results showed that the shape fixation rate, recovery rate and recovery stress of PI-PHT-5% reached 97.2%, 92.6% and 9.46 MPa, respectively.