Property enhancement of polybenzoxazine modified with dianhydride

A novel bisphenol-A-aniline type polybenzoxazine (PBA-a) modified with dianhydride was successfully prepared by reacting bisphenol-A-aniline based benzoxazine (BA-a) resin with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) in 1-methyl-2-pyrrolidone (NMP) solvent. The miscible monomer mixture was easily transformed into transparent PBA-a/BTDA copolymers by thermal cure. Fourier-transform infrared spectroscopy reveals the formation of ester linkage which is a covalent interaction between hydroxyl group of the PBA-a and the carbonyl group in the dianhydride. The PBA-a/BTDA copolymers show only one glass transition temperature (Tg) with the value as high as 263 °C at BA-a:BTDA = 1.5:1 mol ratio. The value is remarkably higher than that of the unmodified PBA-a, i.e. 160 °C. In addition, the resulting PBA-a/BTDA copolymers display relatively high degradation temperature up to 364 °C and substantial enhancement in char yield with a value of up to 61% by weight. Moreover, flexibility of the PBA-a/BTDA copolymer samples is also significantly enhanced compared to the unmodified PBA-a. The obtained copolymer demonstrates high potential for those applications that require high thermal and mechanical properties with fire resistant characteristics.