Enhanced thermal and mechanical properties of epoxy composites by mixing noncovalently functionalized graphene sheets

Abstract

In this study, a novel thermotropic liquid crystal perylene bisimides polyurethane (LCPU) was synthesized using 3,4,9,10-perylenetetracarboxylic acid anhydride (PTCDA), hexamethylene diisocyanate (HDI), diglycolamine (DGA) and polyethylene glycol-200 (PEG-200) as raw materials. Based on the unique domain structure of π–π conjugate in perylenetetracarboxylic derivatives (PBIs), we modified the reduced graphene oxide (RGO) with LCPU. The graphene-based liquid crystal perylene bisimides polyurethane (LCPU/RGO) was prepared via π–π stacking interactions of RGO with LCPU. LCPU and LCPU/RGO were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), polarizing microscope (POM), wide-angle X-ray diffraction (XRD) and thermogravimetric analysis (TGA). LCPU/RGO was used to modify epoxy resins. The mechanical and thermal properties of the composites were systematically investigated. The results showed that the thermal and mechanical properties of the composites were enhanced effectively by the addition of LCPU/RGO. When the LCPU content was 0.7 wt%, the impact strength and bending modulus of composite were increased by 68.8 and 48.5 %, respectively, compared with neat epoxy. Its thermal decomposition temperature was 31 °C higher than that of neat epoxy.