Grafting of a novel hyperbranched polymer onto carbon fiber for interfacial enhancement of carbon fiber reinforced epoxy composites

Abstract

A novel hyperbranched 2,2-bis-(hydroxymethyl) propionic acid polyester-32-hydroxyl (hyperbranched polymer) was selected to graft onto a carbon fiber (CF) surface to enhance the interfacial properties of carbon fiber/epoxy composites. The homogeneous distribution of hyperbranched polymers on the CF surface could increase the wettability, mechanical interlocking and chemical interaction between the CF and epoxy resin. Compared to untreated carbon fiber, the interfacial shear strength (IFSS), interlaminar shear strength (ILSS), and impact strength of the modified carbon fiber/epoxy composite increased by 78.2%, 40.9% and 39.2%, respectively. Furthermore, the thermal stability of the composites improved. The interfacial strengthening mechanism was also investigated by in-depth analysis of the fracture interface microstructure. Interfacial property enhancement was related to the decrease in stress concentration due to the introduction of the gradient modulus interphase induced by the grafted hyperbranched polymer layer.