In situ preparation of polyurethane-imide/graphene oxide nano-composite foam: intercalation structure and thermal mechanical stability

Abstract

Based on the industrialized graphene oxide (GO) product, a series of polyurethane-imide (PUI)/GO nano-composite foams were fabricated via in situ prepolymer foaming method. It was found that the formation of hydrogen bonding and covalent bonding between two phases of the composite led to a highly efficient grafting of PUI molecules on the GO surface with high layer thickness, and thus partial exfoliation and uniform dispersion of GO in the matrix were achieved. By addition of proper content of GO (0.5~1 wt%), the relatively uniform cell morphology with thick walls can be observed, and the smaller mean cell size and narrower cell size distributions were presented compared with PUI foam, due to the nucleation effect of GO on PUI foam. TGA analysis presented two steps of degradation process for PUI/GO foams, and the thermal degradation temperatures increased remarkably with GO content at the second degradation stage. Meanwhile the degradation activation energy and the frequency factor increased, indicating the remarkable improvement of the thermal oxidative stability of PUI by compositing with GO. With increasing GO content, the storage modulus and T_g increased first, reaching maximum at 1 wt% GO, and then decreased. At ambient temperature, the storage modulus of PUI/1 wt% GO foam reached as high as 623 MPa, increasing by 48% compared with PUI foam, indicating an obvious reinforcing effect of GO on PUI foam. By addition of GO, the oxygen permeability coefficient decreased significantly, and the radical scavenging ratio increased, which was favorable for inhibiting the oxidative degradation of PUI molecules.