Interfacially reinforced unsaturated polyester carbon fiber composites with a vinyl ester-carbon nanotubes sizing agent

A amino-functionalized carbon nanotubes (CNTs)-containing sizing agent was prepared for improving the interface bonding and impact toughness of carbon fibers (CFs) reinforced unsaturated polyester (UP) composites. More reactive groups and better interfacial compatibility with UP make vinyl resin M7270 a more suitable polymer for preparing sizing agent for CF/UP composites when compared to epoxy, MR13006 and R806. The surface characteristics of CFs and the interfacial properties of the composites before and after surface modification were investigated. The observed uniformly dispersed CNTs-containing sizing agent on the CF surface obviously increased the surface roughness. The amount of polar functional groups and the wettability of CFs were significantly enhanced after the coating treatment. The interlaminar shear strength (ILSS) and impact toughness were enhanced by 32.3 and 55.2%, respectively. The sizing agent effectively enhanced the interfacial adhesion by improving the surface energy, and increasing chemical bonding and mechanical interlocking.