Investigation of the isothermal cure kinetics of new series of bis(trimellitimide) derived epoxy-imide resins

The isothermal curing kinetics of a newly synthesized series of trimellitimide-derived epoxy-imide resins were studied compared to their previously obtained non-isothermal results. Although the minimum isothermal curing temperature was ca. 30°C above the highest glass transition temperature of the fully cured systems, the curing processes did not complete. The absolute and relative conversions (α, α')-based values of isothermal activation energy (Ea) are extremely consistent with the non-isothermal ones in the early stages of the curing processes, but the transition to the diffusion control regime at α≈0.7 leads to the dramatic increase of the α-based Ea. We also found that utilizing α' results in physically meaningful trends. Moreover, evaluation of the reactions model showed evidence of autocatalytic behavior, although the curing processes behave like an nth-order reaction in the range of 0.1<α<0.7. The difference between non-catalytic and autocatalytic activation energies indicates that more autocatalytic feature appears in the aromatic resin system.