Preparation And Characterization Of Polyurethane Modified Epoxy Resin Sizing Agent

Carbon fiber has high strength,large modulus,corrosion resistance,anti-fatigue and other excellent performance,and has been widely used in aerospace,military weapons,sporting goods,automobile manufacturing and other industries.As it is easy to be damaged in the production and application process and its surface is inert,carbon fiber needs the surface sizing in the production process to improve the process performance of carbon fiber and the mechanical properties of the resin matrix composite.The current domestic universal sizing agent for carbon fiber is the waterborne epoxy resin sizing agent.Its main components are the pure epoxy resin and the surfactant.Because the toughness and adhesive properties of polyurethane modified epoxy resin is better than that of the pure epoxy resin,this study aims to develop a polyurethane modified epoxy resin waterborne emulsion sizing agent in order to further improve the domestic carbon fiber processing technology and the mechanical properties of the resin matrix composite.First of all,the polyurethane modified epoxy resin sizing agent emulsion is prepared.The preparation method is divided into three steps:in the first step,the hydrophilic ether bond is grafted to the polyurethane modified epoxy resin through the reaction of the polyether alcohol and the polyurethane modified epoxy resin to get the initial product;in the second step,the diethanolamine reacts with the initial product to get the secondary product;in the third step,the secondary product reacts with the acetic acid to have the neutralization reaction into the salt and then the emulsion is prepared.The self-made polyurethane modified epoxy resin emulsion is compared with the domestic and foreign commercial sizing agent emulsion.The results show that the sizing agent emulsion prepared in this study has high solid content and is neutral.The particle size of the emulsion is small and the distribution is narrow.It can be used for the domestic carbon fiber sizing.Secondly,the sizing agent emulsion prepared in this study,the domestic sizing agent emulsion and the Japanese sizing agent emulsion are sized on the domestic T800 carbon fiber of Jilin Chemical Industrial Co.,Ltd.,then,the surface appearance,wettability,surface chemical elements and functional groups of the carbon fiber after sizing are characterized.The results show that the fiber sized by the sizing agent prepared in this study has less amount of fuzz with good bundling property.The contact angle of the carbon fiber after epoxy resin sizing is small and the wettability is good.The active functional groups on the carbon fiber surface after sizing by the sizing agent prepared in this study are 2.05%less than that by the Japanese sizing agent,and 5.58%more than that by the domestic sizing agent.Finally,the sized carbon fiber is used to prepare the carbon fiber epoxy resin composite and the mechanical properties of the composite are characterized.The results show that the interlaminar shear strength of the composite prepared by the carbon fiber sized by the sizing agent in this study is 1.2 times that of the composite prepared by the carbon fiber sized by the domestic sizing agent and slightly lower than that of the composite prepared by the carbon fiber sized by the Japanese sizing agent.