Oxidation of a carbon/glass reinforced cyanate ester composite

The decomposition/oxidation behaviour of a carbon/glass fibre reinforced thermosetting pre-impregnated material based on polymerized aromatic cyanate ester compounds (commercial name GURIT-PN900-C582-43) has been investigated. Experiments were carried out for thermally thick samples exposed in a preheated reaction chamber (temperatures between 650–950 K) and a continuous gas flow (inlet velocity between 0.6 and 4.2 cm/s). Temperature measurements indicate that, in air, the process takes place under a mixed kinetic-diffusive control with three main dynamic stages corresponding to oxidative decomposition, heterogeneous ignition delay and oxidation. The oxidative decomposition stage is always much faster than the total duration of the ignition delay and oxidation stages (factors of 60–85). SEM pictures show dramatic changes in the material structure with amounts of solid residue, at the conclusion of the conversion process, varying from about 62% (resin char, glass and carbon fibres) to 29% (essentially the glass fibres) (against 85–75% for thermal degradation). Also, with the aid of thermogravimetric curves measured in air for the composite material and a charred residue, a three-step oxidation mechanism is proposed consisting of the oxidative decomposition of the resin, the oxidation of the resin char and the oxidation of the carbon fibres with estimated activation energies of 95, 136 and 185 kJ/mol, respectively.