Thermal Stability of Polysulphone

Polysulphone, prepared from 2.2‐bis(4‐hydroxyphenyl)propane and 4.4′‐dichlorodiphenyl sulphone, degrades when heated at 380°C i. vac. The mol. wt. increases with time of heating until after about 3 hrs gelation occurs. In addition to crosslinking scission processes have been shown to be important. Degradation is also accompanied by the evolution of gas – mainly SO 2 and CH 4 . Other products include a number of substituted diphenyl ethers, phenol, the major non gaseous product, and a variety of other phenols. Solutions of the degraded polymers react with DPPH and suggest the accumulation of hydroxyl groups with time of heating. The range of products indicates that the ether, isopropylidene and sulphone groups linking the phenylene rings are involved in the degradation. The rates of the crosslinking, scission, hydroxyl accumulation and gas evolution processes have been evaluated and the possible reactions underlying these processes discussed.