Thermal Degradation of Poly(p-phenylenebenzobisoxazole)

TGA runs were performed for investigating thermal stability of(Poly(p-)phenylenebenzobisoxazole)(PBO) fiber.Under the air or nitrogen environment,the decomposition temperature was(affected) by the heating rate;a greater heating rate resulted in a higher decomposition temperature.Oxygen served the role of an initiator in thermal degradation of PBO fiber and significantly reduced its activation energy.Using the Ozawa method,the activation energy of thermal degradation in air was about half of that in nitrogen;therefore,PBO fiber was more heat resistant in nitrogen than in air.Almost the same(activation) energy was calculated from different residual weights suggesting the decomposition of PBO fiber in air or nitrogen was a single step process.IR analysis of the degradation reactions in air was employed for determining the effect of thermo-oxidation behavior on PBO fiber structure.