The influence of an OH-terminated hyperbranched aliphatic polyester on the reaction kinetics and rheology of a trifunctional triglycidyl-p-aminophenol (TGAP) epoxy resin cured with an aromatic amine, i.e., diamino-diethyltoluene (DETDA), was investigated. The hyperbranched polymer was expected to enhance the reactivity of the trifunctional epoxy resin; a limited modification in the rheology of the trifunctional epoxy resin with the addition of the hyperbranched polymer, however, was not excluded. The reaction mechanism between DETDA amine and TGAP resin is very complex; therefore, a phenomenological kinetic model was employed. The autocatalytic model chosen was able to fit the experimental calorimetric data for the trifunctional epoxy resin as well as for its mixtures with the hyperbranched polymer. The effect of the OH-terminated hyperbranched aliphatic polyester (H 30) on the reactivity of the trifunctional epoxy resin was marked, with a decrease of the temperatures at which the crosslinking reactions begin, even though a reduced rate of the curing reactions was observed. However, the completion of the reactions occurred faster and at lower temperatures. The cure mechanism, moreover, remained broadly autocatalytic in nature, regardless of H 30 concentration. Finally, the addition of hyperbranched polymer H 30, even at low percentages, led to a noticeable increase in the viscosity of the resin. This last aspect is believed to restrict to some extent the range of application of such epoxy systems containing the hyperbranched polymer in the traditional processing techniques. (c) 2007 Wiley Periodicals, Inc.