Study On Toughening Modified Bismaleimide System By Benzoxazine Resin

Bismaleimide(BMI)as a common high-performance resin matrix with high temperature,humidity,radiation resistance,corrosion resistance,processing performance,low prices and so on,has a huge field of application in the aerospace structural materials,electronic appliances.However,bismaleimide resins exhibit brittleness,poor impact toughness,severe curing shrinkage and other problems that limit its application.Diallyl bisphenol A(BA)can improve the toughness of BMI,But reduces its heat resistance,and the problem of serious curing shrinkage still exists.Based on the modification of BMI by BA,bisphenol A benzoxazine(BOZ)was used to modify the BA/BMI resin system in this paper.The research targets and pilot program of this project are determined based upon literature search,and the research works are carried out as follows.First of all,the dynamic reaction kinetics of BOZ/BMI resin system was studied by dynamic DSC method.The semi-empirical phenomenological model was established and the kinetic parameters of curing reaction were fitted.The curing degree of resin was obtained by Kissinger equation combined with the kinetic parameters(?)and time(t).The influence of BOZ on the gel time of modified BMI resin was studied.The reaction mechanism of BOZ resin system was studied by infrared spectroscopy.The curing process parameters of modified resin system were obtained by studying the curing kinetics.Secondly,based on optimized process parameters,the BA/BOZ/BMI ternary blends with different mass fraction of BOZ were prepared.The effects of the addition of BOZ on the mechanical properties,heat resistance,performance,thermomechanical properties and microstructure has been studied.Finally,a multiphase ternary blend of BOZ/BA/BMI(PBOZ10/PTSM)was prepared by the reaction-induced phase separation method with the addition of cationic catalyst methyl p-toluenesulfonate(PTSM)Analysis of the appearance to study its phase separation mechanism,and focus on the mechanical properties and heat resistance.The results show that the addition of BOZ improves the mechanical properties of BMI/BA.When the amount of BOZ is 10wt%,the impact strength and flexural strength of ternary blends BOZ/BA/BMI(referred to as PBOZ10)are 20.6 kJ/m~2 and 146.1Mpa,an increase of 57%and 58%than BA/BMI system,respectively,the flexural strength and the impact strength of PBOZ10/PTSM system increased by 20.9%and 8.7%compared with PBOZ10 system.The heat resistance greatly improved,the initial thermal decomposition temperature and glass transition temperature increased by34?and 38?,respectively,the heat-resistance of PBOZ10/PTSM system equivalent to the PBOZ10 system.SEM analysis showed dimples appeared in the PBOZ10 resin system,showing typical ductile yield characteristics,the morphology of PBOZ10/PTSM system was rough with many dimple structures.It expressed as“island-like structure”that“dispersed phase”distributed in the“continuous phase”.The EDS analysis showed that the“dispersed phase”was BOZ-rich phase,while the“continuous phase”was mainly BA/BMI phase.The above research laid the foundation for expanding the application of BMI and BOZ in high-performance resin-based composites.