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
C/min. They presented two exothermic peaks, which should correspond to two independent cure reactions. The effective activation energy Ea, 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 Ea on a is complex. All the systems in this study fitted Sesták–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.