Study On The Synthesis And Properties Of Epoxy Resin With Good Flexibility

Epoxy resin has good electrical insulation,chemical stability,Corrosion resistance and other good characteristics,it is being used in various fields widely.However,the flexibility of epoxy resin is poor,it can break easily because of its brittleness,the application of epoxy resin in certain areas is limited as the shortcoming.If we can enhance the flexibility of epoxy resin,its application areas will have a large degree of widening.In this paper,we introduced HDI with flexible segment in the synthesis process of epoxy resin by using molecular structure design.The problem of poor flexibility of epoxy resin was solved from the root.Firstly,the synthesis technology of epoxy resin was studied.Epoxy value was used as indexes to study the effect of dosage of ECH,amount of sodium hydroxide,concentration of sodium hydroxide,amount of catalyst,etherification temperature,etherification time,closed-loop temperature,closed-loop time by Single factor experiment.In order to continue to optimize the synthesis technology,two orthogonal experiments of four factors and three levels were designed based on the epoxy value.The results showed that the optimal synthesis procedure of epoxy resin was as follows: the amount of ECH was 1:24(molar ratio of bisphenol S and ECH),the amount of catalyst is 2%(molar ratio of hydroxy in bisphenol S),temperature of etherification reaction is 90℃,time of etherification reaction is 4 h;Amount of sodium hydroxide was 1: 1.2(molar ratio of hydroxy in bisphenol S and sodium hydroxide),the mass concentration of sodium hydroxide was 30%,the closed-loop temperature is 60 ℃,the closed-loop time is 4 h.The synthesized epoxy resin was characterized by IR and NMR.The results showed that the HDI was completely reacted and the epoxy group was formed in the product.The curing conditions of the synthesized epoxy resin and E-51 were explored The results showed that the optimal curing conditions were as follows: the equivalent amount of DDM was introduced in the curing system of epoxy resin/DDM,the dosage of ECH was1:24(molar ratio of bisphenol S and ECH),the curing process is GY-D: room temperature,90℃/1h,115℃/1h,150℃/3h,200℃/1h,Room temperature;the dosage of DDM is 28 phr in the curing system of E-51/DDM,the curing process is GY: room temperature,50℃/1h,80℃/1h,100℃/3h,150℃/1h,room temperature.Finally,the properties of the cured epoxy resin and the cured E-51 were compared with.The results showed that the impact strength of the cured epoxy resin was 23.72 KJ/m~2,the impact strength of E-51 was 11.28 KJ/m~2,the impact strength of the cured epoxy resin was higher than that of the cured E-51 about 110.28%.The compressive strength of the cured epoxy resin was 145.50 MPa,which is higher than that of the cured E-51 about 29.07%,and the flexural strength was slightly lower than that of the cured E-51.The water absorption rates were 1.24% and 1.10%.respectively,The mass loss of E-51 was about 90% at high temperature(600℃),which indicated that the synthesized epoxy resin was more resistant than E-51 at high temperature.