Cure behavior of unsaturated polyester (UP)/montmorillonite (MMT)/methyl ethyl ketone peroxide (MEKP)/cobalt octoate intercalated nanocomposites with various MMT loadings was investigated by dynamic differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). UP/MMT nanocomposites were prepared by' sequential mixing. Non-isothermal DSC curves were obtained by applying heating rates ranging from 5 to 20 degrees C/min. They presented two exothermic peaks, which should correspond to two independent cure reactions. The effective activation energy E-a, was determined by applying both the Kissinger's and Starink's methods. The results showed slightly higher activation energy for nanocomposites, except for UP/10-MMT. It was found that the dependence of E-a on alpha is complex. All the systems in this study fitted Sestak Berggren (SB) model in overall reaction controlled kinetics and the corresponding model parameters, n,m, A were obtained, but it was insufficient in depicting the complex reaction kinetics. Transmission electron microscopy data support the formation of a partially delaminated nanocomposite Material. UP and nanocomposites showed similar behavior on thermal stability. (C) 2015 Elsevier B.V. All rights reserved.