3D printing of commercial thermosetting epoxy resin is of great significance for the rapid and low-cost construction of high-strength objects with complex structures. Meanwhile, recycling these commercial epoxy resins is essential for environmental protection and sustainable development. This paper reports direct ink writing 3D printing of a multifunctional composite material based on commercial bisphenol A epoxy resin and a 3D printing compatible technique to recycle the printed composite material. Graphene nanoplatelet is designed as an efficient functional thixotropic additive that turns the liquid epoxy resin prepolymer shear-thinning and suitable for direct ink printing. Composite materials with high resolution and high mechanical strength are printed with epoxy resin/graphene nanoplatelet inks, and they also show high thermal and electrical conductivity and fast thermo-induced shape memory response. The printed objects can be recycled by comminuting them into micropowders, which are then used as a thixotropic agent to prepare recycled DIW ink. The physical properties of the materials printed with recycled inks maintain unchanged for successive four recycling cycles. The graphene nanoplatelets at the surface of recycled comminuted powder are found to modulate the surface energy of the powder, thus making the powder able to serve as a thixotropic agent for the recycled inks. The method here provides a new solution to process commercial epoxy resin and opens a new direction to the more sustainable use of thermosetting plastics.
Keywords: comminution; direct ink writing; electrical conductivity; shape memory; thermal conductivity.