Improved thermal stability and mechanical properties of benzoxazine-based composites with the enchantment of nitrile

Benzoxazine and phthalonitrile-based resins play an important role in fields of advanced materials because of their excellent properties. In this work, a kind of matrix resin with various ratios of phthalonitrile and benzoxazine were designed and prepared via co-reaction between aniline and 3-aminophenoxy phthalonitrile in the presence of biphenol and formaldehyde. Curing behaviors and dynamic rheology of matrix resins were investigated with DSC and DRA. Results indicated that obvious double curing stages can be assigned to ringopening polymerization of oxazine rings and ring-forming polymerization of nitrile groups. Possible polymerization mechanisms were discussed in this work. Thermal stability of cured resins was evaluated by TGA testing and an integral decomposition temperature (IPDT). Then, fiber-reinforced composite laminates were prepared and their mechanical properties were investigated and confirmed with SEM images of fracture surfaces. Results demonstrated that this work proposed an improved matrix resin system with outstanding thermal stability and mechanical properties that broadened the foundation and ideas for subsequent researches.