Abstract
Curing behavior of an unsaturated polyester (UP) resin containing 1 wt% organically modified clay (OMC) catalyzed with methyl ethyl ketone peroxide (MEKP) initiator and promoted by cobalt naphthenate accelerator was investigated by dynamic differential scanning calorimetry (DSC) at five different heating rates of 5, 10, 15, 20, and 25ยฐC/min. Xโray diffraction and transmission electron microscopy were used to evaluate the morphology of UP/OMC composites. Results showed a mixture of intercalated and exfoliated morphology. The dynamic DSC curing curves showed a bimodal exothermic peak; therefore, two independent reactions, namely, redox and thermal copolymerizations were assumed. Kinetic parameters were calculated by using autocatalytic model and using Down hill simplex method and RungeโKutta algorithm for each reaction. The addition of nanoclay resulted in decrease of the activation energy of the redox reaction compared to that of the neat UP resin. Also, the preโexponential factor of the first reaction for UP/OMC was less than that of the neat UP. Two factors including decreasing the activation energy and decreasing the number ofcollisions of reactionary components finally resulted in increasing the reaction rate of the first reaction out of the whole reaction in the system containing nanoclay compared to the neat UP resin. It is interesting that nanoclay has no effect on the thermal decomposition reaction. POLYM. COMPOS., ยฉ 2011 Society of Plastics Engineers.