On the thermal degradation of poly(styrene sulfones). VII. Evaluations of poly(styrene sulfone) thermal stability using invariant kinetic parameters

The thermal degradation behavior of poly(styrene sulfone) was investigated by thermogravimetric analysis (TGA) measurement. This study described its thermal stability by applying the invariant kinetic parameter (IKP) method. The thermogravimetric and differential thermogravimetric analyses of different compositions of poly(styrene sulfones) were carried out over the temperature range 100–500°C under nitrogen. The kinetic parameters (preexponential factor and activation energy) of thermal decomposition of poly(styrene sulfone) can be obtained by dynamic measurement of TGA. The IKP method assumes that the kinetic parameters are independent of the experimental conditions. These parameters are computed without any hypothesis on the form of the kinetic degradation function. Invariant activation energies of the degradation of poly(styrene sulfone) show that the thermal stability decreases as the SO 2 content of poly(styrene sulfone) increases due to the thermal instability of the CS bond. The relation equation, Ea inv = 237.0 − 290.5 X SO2 , where X SO2 is the molecular fraction of SO 2 , was obtained to describe the effect of sulfur dioxide on the thermal stability of poly(styrene sulfone).