Studies on the Cure Kinetics and Networks Properties of Neat and Polydimethylsioxane Modified Tetrafunctional Epoxy Resins

The cure kinetics of tetrafunctional epoxy resins with three different backbone structures and their modification by polydimethylsioxane (PDMS) were studied by means of differential scanning calorimetry with dynamic approach. The development of epoxy networks was characterized by dynamic viscoelastic measurements. Results showed that all the epoxy resins obeyed the autocatalytic reaction mechanism with a reaction order of about 3. Epoxy resin with softer aliphatic backbone demonstrated a higher cure reactivity and stronger tendency towards autocatalysis, as well as lower crosslinking density. The PDMS-modified epoxy resins showed higher early cure reactivity and a lower crosslinking density due to the plasticization and restriction effect of the dispersed PDMS phase, respectively. Based on cure kinetics and dynamic viscoelastic results, the alpha(m) was found to be an effective precursor for describing the developing of epoxy networks during the course of cure. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 581-587, 2010