The isothermal degradation of some polyetherketones: a comparative kinetic study between long-term and short-term experiments

Abstract

The kinetics of the isothermal degradation of three high thermally stable aromatic polyetherketones was studied by both a long-term (about 3 years) experiment at a temperature (270 °C) largely lower than the temperatures of fusion, and a set of short-term experiments at temperatures near the temperatures of fusion. An induction period was observed at 270 °C, followed by two degradation stages, the first with an exponential increase of the weight loss rate ( V) as a function of heating time ( t) and the final one showing constant weight loss rate. Short-term experiments showed similar behaviour, but no induction period was observed. The equations V= V o×2 αt and V= K at various temperatures were determined for the exponential and linear degradation stages, respectively. The e-folding time α increased with temperature according to Arrhenius-type equations, by which the apparent activation energy values for degradation could be determined. The results are discussed and indicate that the kinetic parameters of degradation change with temperature.