Synthesis of Phosphazene-Containing, Bisphenol A-Based Benzoxazines and Properties of Corresponding Polybenzoxazines

With the aim of obtaining halogen-free polybenzoxazazines with reduced flammability, phosphazene-containing benzoxazines (PhBZ) were synthesized in a two-stage method. In the first stage of the reaction of hexachlorocycotriphosphazene with bisphenol A at molar ratios of 1:12, 1:16, and 1:24, respectively, mixtures of bisphenol and hydroxyaryloxycyclotriphosphazenes were obtained, which mainly contained P3N3[OC6H4C(CH3)(3)C6H4OH](6). In the second stage, when these mixtures interacted with aniline and an excess of paraformaldehyde in toluene at 80-90 degrees C, PhBZ containing 20-50% of the phosphazene component with M(w)1200-5800 were formed. According to(1)H and(13)C NMR spectroscopy, PhBZ contain a small amount of oligomeric compounds with Mannich aminomethylene bridges. With an increase of the content of the phosphazene component, the curing temperature of PhBZ decreases from 242 degrees C to 215 degrees C. Cured PhBZ samples with a phosphorus content of more than 1.5% have increased flammability resistance according to UL-94.