Thermal decomposition of cyanate ester resins

Polycyanurate networks were prepared by thermal polymerization of cyanate ester monomers containing two or more cyanate ester (-O-Cequivalent toN) functional groups. The thermal decomposition chemistry of nine different polycyanurates was studied by thermogravimetry, infrared analysis of solid films, and analysis of the gases evolved during pyrolysis using infrared spectroscopy and gas chromatography-mass spectrometry. It was found that the thermal stability of the polycyanurates was essentially independent of monomer chemical structure with the major mass loss occurring at about 450 degreesC for all materials. Analysis of the solid-state and gas phase thermal degradation chemistry indicates a thermal decomposition mechanism for polycyanurates which begins with hydrocarbon chain scission and cross-linking at temperatures between 400 and 450 degreesC with negligible mass loss, followed by decyclization of the triazine ring at 450 degreesC that liberates volatile cyanate-ester decomposition products. The solid residue after pyrolysis increases with the aromatic content of the polymer and incorporates about two thirds of the nitrogen and oxygen present in the original material. Published by Elsevier Science Ltd.