Study On Preparation And Properties Of Benzoxazine Resin Modified With Hyperbranched Polyether Epoxy Resin And Phenolic Resin

Due to some unique properties,such as high glass transition temperature(Tg),near-zero volume change during curing,very high char yield and low water absorption,benzoxazine resin has attracted a great deal of attentions.In addition to providing the opportunity to be the replacement materials for the existing polymers,these properties also will allow the development of uique applications.However,it also has the shortcomings of low cross-linking density,brittle and poor toughness,which limit the application as a high-performance matrix resin material,especially the application and development of the major area of the aerospace.Therefore,improving the benzoxazine resin toughness and the overall performance is imperative.Researchers have done a lot of works on bnezoxazine resin toughening modification.In this paper,hyperbranched polyether epoxy resin(HBER)with a combination of aliphatic-aromatic moieties and linear phenolic resin(LPF)were incorporated into an aromatic-diamine type benzoxazines(M-Boz)network,to obtain a new benzoxazine resin system with low viscosity,good toughness and excellent comprehensive performance.In this paper,HBER was incorporated at different concentrations into benzoxazines network without cure-induced phase separation.The resulting homogeneous network architecture was studied using FT-IR and DSC.The results show that HBER and M-Boz had a synergistic reaction during curing.The blend crosslinked network structure was studied by dynamic mechanical analysis(DMA)and the resulting showed no phase separation during the curing process.The mechanical properties tests including flexural and impact tests showed that the hyperbranched structure allowed for simultaneous enhancement in both flexural property and impact toughness as HBER content reaches 10 wt%in the blend.The viscosity of the blend which was measured with rheometer maintains a minimum viscosity platform between 60-190?.Linear phenolic resin(LPF)was used as benzoxazine resin curing agent and catalyst of hyperbranched polyether epoxy resin.Hyperbranched polyether epoxy resin and liner phenolic resin were incorporated at different concentrations into benzoxazines network.The homogeneous network architecture which was measured with DSC and FT-IR showing that HBER,LPF and M-Boz had a synergistic reaction and the curing reaction temperature is lowered.Thermal performance of the blends was studied by TGA.It showed that the heat resistance of the blends was significantly improved.The mechanical properties tests showed that HBER-10/LPF-5 had a good flexural property and HBER-10/LPF-7 had an excellent impact toughness.Overall,as HBER content reaches 10 wt%in the blend it had an optimal mechanical properties.The fracture surface morphology of the cured blend shows the characteristic of in-situ toughness enhancement.The improved mechanical behavior for modified benzoxazine system was obtained by coordinating the composition of the blend.