Copolymers based on telechelic benzoxazine with a reactive main-chain and anhydride: monomer and polymer synthesis, and thermal and mechanical properties of carbon fiber composites

Abstract

Enhanced thermomechanical properties of polybenzoxazine based on allylamine-terminated oligomeric benzoxazine (Allyl-oligomer) are obtained by copolymerizing the oligomer with maleic anhydride (MA) in the presence of a free radical initiator. MA is introduced to react with the oxazine ring and allyl groups via different mechanisms. From 10% to 30% of MA are added into benzoxazine systems to explore the optimum copolymerization ratio. The polymerization behavior, glass transition temperature (T_g) and thermal stability of the corresponding polymers are investigated by differential scanning calorimetry (DSC), in situ Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). Addition of 10% MA is found to give the highest thermal stability, while maintaining the highest T_g of the polymer matrix. Using the resulting high performance polymer, carbon fiber composites are prepared and studied. The mechanical properties are evaluated by ASTM tensile and flexural tests. The tensile strength, tensile modulus, and flexural modulus of the composites exceed those of benchmark products with epoxy matrices.