Effects of phenyl-s-triazine moieties on thermal stability and degradation behavior of aromatic polyether sulfones

The effect of the incorporation of phenyl-s-triazine units into the main chain of phthalazinone-based polyether sulfones on initial decomposition temperature, activation energy, thermal-mechanical property and possible degradation mechanism has been investigated. To this purpose, decomposition of poly(phthalazinone ether sulfone phenyl-s-triazine) copolymers (PPESPs) of different monomer compositions have been studied by utilizing thermogravimetry and differential scanning calorimetry. Non-isothermal experiments under nitrogen were performed, and the apparent activation energy (E _a) was calculated by isoconversional and conversional methods including the methods of Flynn-Wall-Ozawa, Friedman and Kissinger. In the conversion range (5–30%) studied, solid-state decomposition process of PPESPs is found to be a mechanism involving phase boundary controlled reaction (E _a: 189–201 kJ mol⁻¹) except that phenyl-s-triazine-rich copolymers exhibit a mechanism involving three-dimensional diffusion (E _a: 196–225 kJ mol⁻¹) in terms of Coats–Redfern method. The phenyl-s-triazine-rich copolymers display much higher E _a and slighter mechanical property-change compared to sulfone-rich copolymers and generic aromatic polyether sulfone, suggesting strong stabilizing effect of the phenyl-s-triazine moieties.