Preparation And Application Of Water-solubility Epoxy Resin Sizing With High-temperature Resistance For Carbon Fiber

Carbon fiber（CF）is an excellent reinforcing material for composites,because of its excellent properties,such as high specific strength,high specific modulus,and corrosion resistance,and so on.However,CF is difficult to interact strongly with resin due to the inert surface of CF.In addition,CF is prone to producing fluffs and filament breakages during manufacturing process,which have a significant impact on the mechanical property of the carbon fiber composites（CFRPs）.It is especially important to sizing the CF to improve the quality of CF and the property of the composites surface.Epoxy resin is the most widely used matrix in CFRPs.According to the principle of"similar compatibility",the epoxy resin is mostly chosen as the main sizing agent,but ordinary epoxy sizing agents have poor temperature resistance.With the expansion of the application field of CFRPs,CFRPs are required to be resistant to high temperature.In addition,the traditional solvent-based sizing agent is environmental pollution during the process of preparation and usage.Therefore,the development of water-soluble sizing agent with high-temperature resistant is of great significance to the development of CFRPs.In order to improve the high temperature resistance of the sizing agent and the interfacial properties of the CFRPs,water-soluble epoxy sizing agents with high-temperature resistant and environmentally friendly were prepared by the self-emulsification method.The research contents are as follows:（1）Based on the principle of"similar compatibility",the multifunctional epoxy resin MF-4101H was modified by cation method,resulting in a modified epoxy resin MF-4101H with high-temperature resistance and self-emulsifying property.The initial decomposition temperature of the modified epoxy resin MF-4101H reached around 350℃,which was50℃higher than that of unmodified resin.The optimum conditions for the sizing agent were:the molar ratio of MF-4101H to DIPA is 1:3,the reaction temperature is 80℃and the reaction time is 2h.The average particle size of the prepared sizing agent was 82.4nm,which had good stability.The transverse tensile strength and interfacial shear strength of the sized CFRPs increased by 21.2%and 19.17%,respectively.By analyzing the surface chemical elements of the sized CF,the content of N and O elements on the surface of the sized CF were increased,indicating that the sizing agent introduced polar groups on the surface of CF,which made CF surface more active.（2）In order to further improve the interfacial property of CFRPs,nano Si O₂modified by silane coupling agent KH-550 was added to the epoxy resin MF-4101H sizing agent to prepare high-temperature resistant sizing agents with different nano Si O₂contents.The average particle size of the sizing agent was 115.5 nm with good stability when the nano Si O₂amount was 2%.The nano Si O₂was uniformly distributed on the surface of the CF after sizing.Compared with unsized CF,the tensile strength of CF monofilament had increased by 14.3%,while the transverse tensile strength and interfacial shear strength of CFRPs were increased by56.5%and 47.9%,respectively.The analysis of chemical elements on the surface of CF showed that the modified epoxy resin MF-4101H sizing agent with nano Si O₂significantly increased the content of O and N elements on the surface of CF.The introduction of nano-Si O₂on the surface of CF could improve the surface roughness of CF and thus improved the interfacial property of CFRPs.The sizing agents prepared in this paper have excellent high-temperature resistance and emulsion stability,which can significantly improve the interfacial mechanical property of CFRPs.It has a great significance to develop sizing agents with high-temperature resistant to expand the application of CFRPs in special high temperature environments.