Bis(2-hydroxyethyl) terephthalate from depolymerized waste polyester modified graphene as a novel functional crosslinker for electrical and thermal conductive polyurethane composites

Abstract

Bis(2-hydroxyethyl) terephthalate (BHET) with active hydroxyl group derived from waste polyester can be applied as a polyurethane chain extender and an organic modifier for graphene oxide (GO). Herein, functionalized reduced GO (BHET-rGO) with single-layer was obtained by modifying GO with BHET, and then reduced by hydrazine hydrate. Waterborne polyurethane (WPU) nanocomposites with excellent mechanical performance, electrical and thermal conductivities were prepared via in-situ polymerization using the novel functional crosslinker BHET-rGO. Compared with the same content of rGO (7.41 wt%), WPU/BHET-rGO composites exhibit better properties containing equivalent BHET content. For example, BHET-rGO endows the WPU composites with higher tensile strength of 39.1 MPa (enhanced by 454.6%), electrical conductivity of 8×10−3 S/m (improved by 15 times), and thermal conductivity of 0.551 W m−1 K−1 (increased by 21.1%). Meanwhile, the sensitivity of WPU/BHET-rGO composite is well recovered during a large-strain stretching/shrinking cycle, and its resistance is stable under complex deformation. Besides, significant thermal stability ensures the durable of polyurethane to resist high-temperature. Hence, BHET-rGO have greater potential for fabricating high-performance elastomer composites, especially for conductive elastomer composites.