The effect of self-synthesized hydroxyl-terminated hyperbranched polymer interface layer on the properties of carbon fiber reinforced epoxy composites

A simple and green method to functionalize carbon fiber (CF) with hydroxyl-terminated hyperbranched polymer (HTHBP) synthesized directly through one-pot condensation polycondensation between isophorone diisocyanate (IPDI) and Iris (hydroxymethyl) aminomethane (TOAM) was reported. The covalent grafting of HTHBP on the CF surface can greatly increase the polar functional groups, roughness and wettability of CF surface, thereby resulting to significant enhancement of interfacial properties of composites. After grafting, the interlaminar shear strength (ILSS), interfacial shear strength (IFSS) and impact strength of CFs/epoxy composites increased from 58.6 to 81.8 MPa, 48.8 to 87.8 MPa and 55.7 to 76.9 kJm(-2), respectively. Furthermore, this surface functionalization process could remedy the single fiber tensile strength. The interfacial reinforcing mechanism was also revealed by analyzing interfacial microstructure. This research provided a thought that constructing a continuous gradient modulus interphase layer with strong physicochemical interaction and good wettability by a simple and green method, which could reinforce the interfacial performance and have a bright prospect application in high-performance composite.