Curing Behaviors and Heat Resistance of Epoxy/Benzoxazine Copolymers
The curing behaviors of epoxy/benzoxazine blends and the properties of their copolymers were investigated in this work.The benzoxazine/epoxy resin copolymers(EDBx,x represents the mass fraction of benzoxazine)were prepared by using bisphenol A-epoxy resin(E51)as the matrix,bisphenol A benzoxazine(BA-mt)as the modifier,and 4,4′-diaminodiphenyl sulfone(DDS)as the curing agent.For the epoxy/benzoxazine systems,their rheological properties,curing behaviors,cross-sectional morphologies of the fracture surfaces,and mechanical properties of the carbon fiber composites at high temperature were examined.The results indicate that BA-mt could accelerate the curing of the blended systems,reducing the gel time.When the BA-mt mass fraction is 20％,the char yield of the resin system at 800℃ under N2 atmosphere reaches 24.6％.Additionally,the Tg of the resin system increases from 180℃ to 190 ℃.The tensile strength of EDB40 is 74.4 MPa,which is very close to E51/DDS.Furthermore,EDB20 exhibits higher bending strength and bending modulus at 180℃,which are respectively increased by 50％and 97.8％compared to E51/DDS.This indicates that the BA-mt modified resin composites have good high-temperature mechanical properties.
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