Further progress in the kinetic modelling of the thermal oxidation of epoxy-diamine matrices

Abstract

The kinetic model established for describing the thermal oxidation of linear polymethylenic substrates, in previous studies conducted in the laboratory PIMM, has been successfully generalized to epoxy-diamine (EPO-DA) matrices in the framework of the research project "COMPosites Tièdes et INNovants" financially supported by the Fonds Unique Interministériel (FUI COMPTINN). It is derived from a radical chain reaction initiated by hydroperoxide decomposition which propagates via C-H bonds located in α of heteroatoms (N and O). Moreover, it couples oxygen diffusion and chemical consumption into a balance equation, giving thus access to the profiles of chemical events throughout the sample thickness and their changes versus time. The different parameters of this model have been identified before checking its predictive value. On the one hand, oxygen transport properties have been compiled from the literature or determined by oxygen permeametry in our laboratory. On the other, the rate constants and yields of the elementary chemical events have been determined by using the model as an inverse approach from thermal oxidation experiments made between 0.21 and 20 bars of oxygen and between 120 and 200 â- C on thin films of TACTIX matrix. Finally, the model predicts accurately the values of ageing criteria reported in the literature for EPO-DA matrices or measured in the framework of this research project, such as the maximal oxidation rate, the critical oxygen pressure or the thickness of oxidized layer.