engleski

Modeling the effect of cure conversion on dynamic viscosity of epoxy resin cured by an anhydride curing agent

Published curing profiles of epoxy resins mixed with anhydride curing agent and subsequently crosslinked were reanalyzed using a modified sigmoidal model to describe the dynamic viscosity accompanying resin cure. The sigmoidal analysis yielded two kinetic parameters, one relating to the induction time required to observe meaningful viscosity changes and one relating to the rate of viscosity rise in the rapidly polymerizing zone. Both of these kinetic factors were reduced with increased polymerization temperature. The analysis also led to the interpretation of upper limit in viscosity in the model that correlated with higher network density at higher temperature. The initial viscosity was fixed in our model. The sigmoidal analysis led to a closer representation of the dynamic viscosity data than the WLF-based analysis presented with the original datasets, and while from a more semi-empirical basis, might be both easier and more adaptable to incorporate in other flow models. As a final observation, the induction time identified by the log-sigmoidal model correlated closely with the tgel identified using a modified WLF based model by Ivankovic et al, (J Appl Polym Sci., 2003:90:3012-19) suggesting a similar activation energy threshold for cure advancement.

kinetics(polym.); modeling; rheology; thermosets

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