Imido-phenolic-triazine network polymers derived from maleimide-functional novolac

Polycyanate esters of an imide-modified novolac of different maleimide-content were synthesised and characterised. The resins underwent a two-stage independent thermal curing through trimerisation of the cyanate groups as well as the addition polymerisation of the maleimide moieties. On heating, the cyanate esters were transformed to the imido-phenolic-triazine network polymers. The cured resins exhibited a higher initial decomposition temperature compared to the cured maleimide novolacs. Despite possessing higher crosslink density, the imido phenolic triazines exhibited inferior thermal properties in comparison to a conventional phenolic-triazine resin. The presence of triazine crosslinks were found to disfavour the char forming reaction of the otherwise high-char yielding maleimide-novolac resins. Kinetics of the nonisothermal degradation revealed a lower activation energy for the phenolic-triazine in contrast to the imido phenolic triazine which was kinetically compensated by a diminished frequency factor to give an overall decreased rate of decomposition for the former.