Synthesis Of High Heat Resistant Novolac Epoxy Resin And Study On Properties Of Its Composite Materials

With the rapid development of aviation,aerospace and other industries,the heat resistance requirements of the composite materials are getting higher and higher,while the traditional epoxy resins are unable to meet the technical requirements.Therefore,the development of epoxy composites with high heat resistance is of great significance.Firstly,bisphenol A novolac resin(Bis-ANR)was obtained by condensation reaction using bisphenol A and formaldehyde solution in this paper.The synthesized resin was confirmed by IR,1HNMR and GPC.Then,bisphenol A novolac epoxy resin(Bis-ANER)was synthesized by using synthetic phenolic resin and epichlorohydrin(ECH).The structure of the synthesized resin was confirmed by IR,1HNMR and GPC.The optimum synthesis process of Bis-ANRE resin was determined by the exploration of the synthetic conditions of Bis-ANR and Bis-ANER resin,including the phenolic ratio,the type of catalyst,etherification reaction temperature,etherification reaction time,closed-loop reaction temperature,closed-loop reaction time,and ECH ratio.The epoxy value of the obtained resin was 0.51 and the average viscosity was 117Pa·s.Secondly,boron-containing bisphenol A novolac resin(Bis-ABNR)was synthesized by using bisphenol A,formaldehyde solution and boric acid as raw materials in this paper.The structure of the synthesized resin was confirmed by IR,1HNMR,13 CNMR and GPC.Bis-ANER was cured with Bis-ABNR as curing agent,and the curing kinetics of the system was studied by non-isothermal DSC method.The curing process was determined by using the characteristic temperature.The activation energy Ea of the curing reaction was determined by Kissinger method and Ozawa method,and the reaction order number n,the pre-exponential factor A and the rate equation were calculated.The thermal properties of the cured product were measured by differential thermal analysis and thermogravimetric analysis in accordance with the established curing process.The results show that the cured product has high glass transition temperature(Tg)of 165 ? and the initial thermal decomposition temperature(Td)of 309.85 ?,which shows good thermal stability and high char yield.Thirdly,kaolin(KL)was modified by dimethyl sulfoxide(DMSO),and characterized by IR and XRD,indicating that DMSO had successfully entered KL in this paper.The Bis-ANER / Bis-ABNR / KL-DMSO composites were prepared by Bis-ANER as the matrix resin and Bis-ABNR as the curing agent.The thermal properties of the composites were determined by differential thermal analysis and thermogravimetric analysis.The results show that when the amount of kaolin is 5%,the Tg is 168.7 ? and the Td can reach 339.8 ?.It is shown that adding a certain amount of KL can improve the heat resistance of the composites.