Thermal Stability of Poly((RHO)-phenylenebenzobisoxazole) Fibres

The thermal degradation behaviour and service lifetime of poly (p-phenylenbenzo. bisoxazole) (PBO) fibres, prepared by our group, were investigated. The thermal degradation processes of the PBO fibres were studied using TG-DTG at heating rates of 5.0, 10.0 , 15.0, 20.0 K.min 1 under atmospheric air and at heating rate of 10.0 Krnirr under nitrogen atmosphere, respectively. The thermal decomposition process of PBO fibre occurs in a single step in the air, being especially prominent between 900 K and 960 K. The thermal degradation kinetics of the PBO polymer under the non-isothermal condition , gave values for activation energy E and the pre-exponential factor A as 142.51±10 k.Lmol and 2.43 x107±105 rnirr t , respectively. Under nitrogen condition, the thermal degradation has started above 907 K. The thermal stability of PBO in the nitrogen atmosphere was 80 K higher than that in the air atmosphere. Moreover, the oxygen played an important role in the degradation, which initiated the degradation of PBO. The decomposition gases of the PBO were analyzed by TG- FTIR. It was found that CO, CO2 and H20 were the main compounds during the PBO degradation in the air. PBO fibre is transformed into charred material which is stable enough and has no aromatic species. The PBO fibre can be used for long time as the temperature is less than 300°C in air. The serv ice lifetime of the PBO fibres was estimated by the kinetics of thermal degradation, and the lifetime equation at weight-loss of 5% was deduced from the equation In t =-19.954 + 17141 IT.