Preparation And Properties Of Toughened And Heat-resistant Bismaleimide Resin For Prepreg

Bismaleimide(BMI)resin is a kind of thermosetting resins which possesses excellent comprehensive properties.In addition to the good performance of liquidity and molding,it also has a lot of good qualities such as high temperature resistance,radiation resistance,humidity resistance,high modulus,good dimension stability,low moisture absorption rate,low thermal expansion coefficient,low dielectric properties and so on.BMI is developing rapidly in many applications such as aerospace,electronic appliances and adhesives.However,on account of high crosslinking density,the cured BMI is embrittlement and easy to break which limit its application scope.The disadvantages of unmodified BMI monomers such as high melting point and poor solubility property also limit its application.To enhance the impact damage resistance and without reducing the original excellent comprehensive performance of BMI resin become the urgent problems to be solved.Therefore,the balance of toughness,manufacturability and heat resistance is particularly important in the modified strategy for BMI resin.In this paper,based on the methods of BMI toughening modification domestic and overseas,we put forward that(1)Typical allyl compounds and active diluents with rigid benzene ring are carried out on the bismaleimide.Viscosity and processing performance can be adjusted,without reducing its heat-resistance performance.(2)Bismaleimide are combined with high temperature resistance thermosetting resin to performance of complementary for further synergistic effect toughened of bismaleimide resin.2,2'-Diallylbisphenol A(DABPA)and 3-Ethynylbenzenamine(m-APA)were adopted to modify N,N'-(4,4'-diphenylmethane)maleimide(BDM)resin.Modified BMI resin formula with excellent comprehensive performance which possess high toughness,high temperature resistance performance,prepolymer stability and good solubility were obtained based on the research of the system formulation and selection.Results show that the modified BMI has the best comprehensive performance when the molar ratio of BDM:m-APA:DABPA is 4:2:2(referred to as BAD422).BAD422 system has the highest impact the performance which can reach at 11.9 kJ/m~2 increased by 35.2%when compared with BAD101.Meanwhile,the bending strength of BAD413 BAD423,BAD422 and BAD432 systems are quite high about 134 MPa.The bending modulus of modified BMI resins are around 4.24GPa.The heat resistance and thermal stability of resin system did not reduce.Polymer crosslinking network is generated which glass transition temperature(T_g)are relatively high and distribute in more than 290?.Mass loss of all resin systems are very small before 350?.Only reaching the decomposition temperature,the mass loss rate is dramatically accelerated.It can be seen that the resin system can adapt to the basic requirements of the advanced composite resin matrix.Then benzoxazine resin(BOZ)from bisphenol A was employed for further toughening to BAD resins system.Two kinds of blends(BAD422/BOZ and BAD432/BOZ)were prepared and tested the various performance.Results show that with the increase of mass fraction of BOZ resin within 0~30 wt%,impact toughness continually increased and thermal performance gradually decline.For example,impact toughness of the BAD422/30 wt%BOZ resin attain 18.3 kJ/m~2 which increased by 52.5%relative to the BAD422 resin.Heat resistance and thermal stability gradually decline,when the mass fraction of BOZ resin from 0%to 30%.The BAD422/30 wt%BOZ down to a single glass transition temperature(T_g,240.0?)compared with BAD422 resin's two glass transition temperature(T_g,341.8?and 292.3?)and the initial thermal decomposition temperature(T5%)value range from 403.3?to 346.5?which was reduced by 56.8?.BOZ resin greatly enhances the impact toughness of the BAD resin but reduces its superior thermal performance.Finally,the curing kinetics of BAD422 and BAD422/BOZ blends were analyzed by using isothermal and non-isothermal DSC method.The dynamic equations were calculated by non-isothermal DSC method,and the relationship between reaction temperature,time and curing degree was analyzed.Isothermal DSC determines that the kinetics model of the curing system is in accordance with the Kamal autocatalytic model and the autocatalytic reaction plays a leading role in the curing process.