THERMAL-BEHAVIOR OF SOME POLYARYLENE ETHERS - A COMPARATIVE-STUDY OF THE KINETICS OF DEGRADATION

The degradation of four aromatic thermoplastics containing carbonyl, e ther and sulfone linkages was performed in a thermogravimetric analyze r in both nitrogen and air environments, in isothermal and dynamic hea ting conditions. The obtained results suggest that degradations starte d by random chain scission under all the experimental conditions. Unde r N-2 flow branching and crosslinking were superimposed on the initial process, while in air complete oxidative degradation occurred. The ap parent activation energies associated with the first degradation stage were evaluated and correlated with the linkages present in the polyme r chains. The obtained values indicate that the chemical reactions occ urring under nitrogen are different from those in air. In addition, th e ratio of the chain scission rate to the branching and crosslinking r ates in nitrogen is dependent on temperature in isothermal experiments and on heating rate in the dynamic ones. A comparison with poly(ether ether ketone) is also reported.