Grafting hyperbranched polymer with terminal hydroxyl groups onto carbon fiber surface in two‐step polycondensation for improving the interfacial properties of carbon fiber/epoxy resin composite

Hyperbranched polymer with terminal hydroxyl groups (HBPH) was grafted successfully onto carbon fiber (CFs) surface in two‐step polycondensation to improve the interfacial properties of CFs‐reinforced epoxy resin composites. The microstructure and interfacial properties of CFs before and after modification were investigated systematically. Experimental results indicated that HBPH were grafted uniformly onto CFs using γ‐aminopropyltriethoxysilane as the coupling agent. The polarity, roughness and wettability of the grafted fiber (CF‐HBPH) were enhanced distinctly in comparison with those of untreated CF. The CF‐HBPH composites displayed remarkable enhancement in interfacial shear strength, flexural strength and modulus (52.9, 29.1, and 42.6%) with no deteriorating fiber tensile strength, which was ascribed to the augment in fiber–epoxy interface through improved chemical interactions and mechanical interlocking. This was in accordance with scanning electron microscopy observations from the fracture surface morphologies of the composites. POLYM. COMPOS., 40:E1378–E1387, 2019. © 2018 Society of Plastics Engineers