Abstract: Toughening of epoxy resins has been a research hotspot for polymer scientists and mechanics experts. However, the epoxy resin is cross-linked to formed a three-dimensional network structure. The structure has high crosslink density and high internal stress, which results in increased brittleness of the material, poor impact toughness and easy cracking. Aiming at the above problems, the method of simultaneous curing of vinyl ester resin (854) and epoxy resin (5241) was used to toughen and modify the epoxy resin. The curing process of the mixed system was studied by rotational viscosity and DSC, and the curing system was determined. In addition, the glass transition temperature, thermodynamic properties and mechanical properties of the fiber reinforced material were studied by DMA, TG and mechanical tests. In particular, when phr (5241∶854)=80∶20, the impact strength of the casting matrix is as high as 15.4 kJ/m², which is 41.3% more than that of pure epoxy resin, and the impact strength of the corresponding fiber reinforced material has reached 605 kJ/m². At the same time, the tensile strength is maintained at 1090 MPa and the maximum storage modulus is only 13 GPa. Therefore, the system has the best comprehensive mechanical properties. Furthermore, the cross-section morphology of the casting matrix was observed by SEM photos and the possible fracture mechanism was inferred.

Key words: epoxy resin, toughening and reinforcing, IPN, castings, fiber reinforced composites