Kinetic study of the thermal and oxidative degradations of poly(arylenether)s containing quinoline units

Abstract

The degradations of five aromatic thermoplastics, in whose repeating units various structures are linked to the same -ArCOQCOAr- moiety (where Ar=1,4-substituted phenylene and Q=3,7-substituted quinoline), were performed in dynamic heating conditions in the temperature range 35–950°C, under nitrogen flow and in static air atmosphere. Experiments under nitrogen suggested that degradations started by random chain scissions, to which branching and crosslinking superimposed at higher temperature, with the formation of residues stable up to 950°C; those in oxidative environment indicated that degradations were due to several processes which were simultaneous at low heating rate and that oxidative stages were involved, as supported by the complete weight loss before the overall temperature scanning. The apparent activation energy values associated with the first degradation stage were obtained by the Kissinger method. Results in inert atmosphere suggested that different linkages were involved in the initial chain scission processes of various polymers and that the comprehensive degradation mechanisms were different from those in air. Anomalous double Kissinger straight lines were found for one of the polymers investigated. The results were discussed and compared with those previously obtained for a similar group of aromatic polymers.