Improved thermal stability of polybenzoxazines by transition metals

The incorporation of various transition metal salts increases the char formation of polybenzoxazines. It is shown that the effect of the transition metal salt is not simply additive and is independent of the amine and phenol structures. While the metal salts have an insignificant effect on the polymerization, their presence in benzoxazine favors the formation of carbonyl functional groups. It is proposed that reduced flammability of polybenzoxazines is achieved through the evolution of CO₂ during thermal degradation.