Preparation Of Heat Resistant Epoxy Resin For Prepreg And Research Of Its Properties

At present,there is a huge space for the development of composite material.Prepreg of excellent comprehensive performance has been widely used in composite materials.Hot melt film Prepreg has the stable performance and less volatile.With the development of composite materials,the use of prepreg is increasing in high temperature environment.Much attention has been paid to improve the heat resistance of prepreg.In terms of improving epoxy curing heat resistance has made great achievements,but there are few reports about the heat resistance epoxy system used in hot melt film prepreg.In this paper,different multifunctional epoxy resin(NPPN-638 s and NPCN-704)is used for improving the heat resistance of system,compound with different general epoxy resin(CYD-128 and E-20)to find the optimal heat resistant resin system(that are suitable for hot melt film prepreg)through the state of film at room temperature and the heat resistance of curing.Studied the suitable ratio of latent curing agent dicyandiamide(DICY)and accelerator phenyl dimethyl urea(UR300)in the resin system by Differential Scanning Calorimeter(DSC),Vicat Softening Point Temperature Tester,Dynamic Thermomechanical Analysis(DMA)and gel time-temperature test,the curing cycle by DSC and Fourier Transform Infrared Spectroscopy(FTIR),and its heat resistance by DMA,Vicat Softening Point Temperature Tester and Thermal Gravimetric Analyzer(TGA).The results show that the ratio of CYD-128/NPPN-638s/NPCN-704 is 25/35/40 that is suitable for hot melt film prepreg and has excellent heat resistance;the suitable ratio of DICY and UR300 are 7% and 1.5% of the total mass of resin respectively,the curing cycle is 105?/2h+130?/2h+160?/2h,the glass transition temperature(Tg)is 206?;the heat distortion temperature is 197 ?;the temperature at the thermal weight loss of 5%,10% and 50% are 330?,360 ?and 416 ?respectively,it higher than pure CYD-128 curing for 20 ~ 30 ?,this system has excellent heat resistance.Isothermal DSC was employed to study the curing kinetic behavior of the compounded systems.The model of compounded system is simulated to find the suitable model.The curing kinetics equation of the suitable model is determined by calculating,that is used as guidelines for the actual molding process.The results show that the system has a certain of induction period in the beginning,the curve of the ?-t is “S” shape;with the temperature increasing,the curing rate changes faster,the system needs less time to achieve the same curing degree;the curing progress is main controlled by autocatalytic,the Kamal model is the most suitable model for the system;the order of reaction is 2.43,the curing kinetics equation is as follows:The compound system and T300 is made into prepreg by hot melt film.The composite material is made by compression molding.The aging behavior of the material is studied in hygrothermal environment.The results show that the higher the temperature,the greater the water absorption and water absorption rate,the shorter the time to balance water absorption;Under the 80 ?,the material's bibulous rate has three stages,it changes fast,then slow and close to balance finally,The material's balance bibulous rate is about 2.9%;the bibulous rate of composite material first is higher than that of matrix resin,and then lower than the matrix resin's;composite material's mechanical properties first falling fast,has slightly upward trend in the middle,and then slow down in the aging,there is a after curing phenomenon,the change of tensile properties is less than the bending performance changes;aging 8 weeks later,the retention fate of the tensile strength,bending strength,bending modulus,energy storage modulus and Tg were 92%,88%,92%,89% and 89% respectively;the composite material's fracture appearance has little change before and after aging,there is a small number of debond between fiber and resin.