Investigation of isothermal and dynamic cure kinetics of epoxy resin/nadic methyl anhydride/dicyandiamide by differential scanning calorimetry (DSC)

Abstract

Isothermal and dynamic differential scanning calorimetry (DSC) was exploited to study the curing behavior of diglycidyl ether bisphenol-A epoxy resin with various combining ratios of dicyandiamide (DICY) and nadic methyl anhydride (NMA). Curves of prepared samples indicated that the enthalpy of the reaction decreased with increasing the molar ratios (NMA/DICY) up to 40% after which an exothermic peak peculiar to the effect of anhydride appeared at a higher temperature. The curing behavior examination of the samples containing the aforementioned molar ratio of NMA/DICY (= 40%) was carried out using isothermal condition at different temperatures (130–145 °C) and dynamic condition DSC at various heating rates (2.5–20 °C min−1). Under the isothermal condition, by constructing a master curve, the values of activation energy (Ea) and pre-exponential factor (A) were calculated 89.3 kJ mol−1 and 1.2 × 10+9 s−1, respectively. The activation energy of the curing reactions in a dynamic mode was obtained 85.32 kJ mol−1 and 88.02 kJ mol−1 using Kissinger and Ozawa methods, respectively. Likewise, pre-exponential factors were also calculated 3.35 × 10+8 and 7.4 × 10 +8 s−1, respectively. The overall order of reaction for both conditions was found to be a value around 3.