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

Abstract

Published curing profiles of epoxy resins mixed with an anhydride curing agent and subsequently crosslinked were reanalyzed with a modified sigmoidal model to describe the dynamic viscosity accompanying resin curing. 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 decreased with increasing polymerization temperature. The analysis also led to the interpretation of the upper limit in viscosity in the model that correlated with a higher network density at higher temperatures. The initial viscosity was fixed in our model. The sigmoidal analysis led to a closer representation of the dynamic viscosity data than the Williams-Landel-Ferry (WLF)-based analysis presented with the original data sets and, although from a more semiempirical basis, might be both easier and more adaptable for incorporating into other flow models. As a final observation, the induction time identified by the log-sigmoidal model correlated closely with the gelation time identified with a modified-WLF-based model by Ivankovic et al. (J Appl Polym Sci 2003, 90, 3012); this suggested a similar activation energy threshold for curing advancement.

Effect of Curing Agent and Temperature on the Rheological Behavior of Epoxy Resin Systems

“…Despite the extensive literature on the polymerisation/curing of epoxy resins with amines, detailed studies on the effects of curing agent ratio on the curing kinetic and viscosity of a special system are generally not available [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. The present study was carried out in order to determine the relationship between curing agent ratio and rheological behavior of the resin system.…”

MMA bulk polymerization and its influence on in situ resin viscosity comparing several chemorheological models

“…Both the induction period and the rate of slope rise in viscosity could be accommodated by adjusting the time constants. The model does not predict a viscosity reduction due to the initial cure exotherm but it successfully has tracked viscosity changes of several advancing resins including epoxies, 24,27 polyurethanes, 28 and acrylamides. 29 We compared all of these other models re-evaluating prior published results from Sangwai et al, 30 which could be extracted for reanalysis.…”

Effect of Pickering emulsion on the mechanical performances and fracture toughness of epoxy composites

“…In other words, those parameters decrease with the increase of functional monomer content. The introduction of functional monomer can extend the induction time of curing reaction . This extension is beneficial to eliminating the residual stress .…”