Synthesis And Properties Of A Novel Low Dielectric Epoxy Curing Agent

With the rapid development of modern communication technology,the signal transmission of electronic equipment is showing a trend of high frequency and high speed.Faster transfer speeds and smaller transmission losses have resulted in lower dielectric and dielectric loss tangent values for printed circuit boards.Epoxy resin is the most widely used polymer material in the field of printed circuit boards.However,epoxy resin itself has a high dielectric constant(Dk)and dielectric loss tangent(Df),which cannot meet the dielectric properties of high-frequency and high-speed copper-clad laminates.Applications of epoxy resin in high-frequency and high-speed circuit board are greatly limited.High-frequency high-speed copper clad laminates have to use expensive resin systems such as polytetrafluoroethylene resin,polyphenylene ether resin and hydrocarbon resin.Therefore,the cost of high-frequency printed circuit board substrates has been high.The traditional epoxy resin curing agent mostly depends on active hydrogen attacking the epoxy group and then realizing ring-opening polymerization.The molecular chain of the epoxy resin cross-link generates a plurality of hydroxyl groups,so that good wetting to the interface of the inorganic base material or the metal base material can be achieved with good bonding strength.However,the presence of a hydroxyl group results in a higher dielectric constant and dielectric loss tangent of the cured epoxy resin.Therefore,development of a novel epoxy curing agent capable of not generating a hydroxyl group may increase the dielectric properties of the epoxy cured product.In this paper,a series of new epoxy curing agents with different chemical structures were synthesized.The synthesis method was optimized initially,and the curing kinetics of the curing system between the curing agent and epoxy resin was studied by non-isothermal DSC.The laminated composite material was prepared and its dielectric properties,high temperature resistance and physical and mechanical properties were tested.The main conclusions are as follows:(1)The optimal synthesis process of a novel epoxy curing agent was obtained by orthogonal experiment.New epoxy curing agents with different chemical structures were prepared according to the process conditions.Fourier transform infrared(FT-IR)and nuclear magnetic NMR-C13(NMR)spectra were used to analyze the obtained products,verifying that the final product was the target product.It was proven that the synthetic process of this product was feasible.The synthetic process was optimized by analyzing the proportion of raw materials,the side reaction process and the influencing factors of product purification process.(2)The non-isothermal DSC method was used for the curing kinetics of the new curing agent epoxy system.The characteristic temperature of the resin curing system was determined by T-? extrapolation.The curing reaction kinetic equation of the new curing agent was determined according to the Kissinger formula,Ozawa formula and Crane formu a.(3)The application performance of new epoxy curing agents was studied.It was proven that the new curing agents can significantly reduce the dielectric constant(Dk)and dielectric loss tangent(Df)of the cured epoxy resin compared to the traditional phenolic resin.This series of products has the value of popularization in high frequency,high speed printed circuit board substrates and insulating composite materials.