Effect of hydrophilic-hydrophobic ratio in self-emulsifying amphiphilic epoxy sizing agent on interfacial properties of carbon fibre/epoxy composites

More and more attention has been paid to the synthesis and characterization of self-emulsifying sizing agents without organic solvent due to the demand of environment-friendless. Herein, self-emulsifying amphiphilic epoxy sizing agents with different hydrophilic-hydrophobic ratios were synthesized and used to enhance interfacial adhesion between carbon fibre (CF) and epoxy resin (EP). The effects of hydrophilic-hydrophobic ratio on the characteristics of sizing agent emulsion, the wettability and morphology of sized CFs, the monofilament CF tensile strength and the interfacial shear strength (IFSS) of CF/EP were investigated. The results showed that the emulsions were mono-dispersed nanospheres and the particle size was increased with the hydrophobic groups increasing. High thermal stability with negligible weight loss unless well above 300. was obtained for all the emulsions. The sized CFs by the emulsions of high hydrophobic ratio (9:1 and 19:1) exhibited more favorable wettability. The CF surface defects were healed and the roughness was reduced mildly by sizing treatment. The IFSS showed a growing trend with the hydrophobic groups increasing and was significantly enhanced by 96 % as the hydrophilic-hydrophobic ratio was 19:1. The improvement of IFSS benefited mainly from the strong interphase due to the excellent film-forming property, favorable wettability and mechanical interlocking.