Gel time and polymerization kinetics of unsaturated polyester resin/clay montmorillonite nanocomposites

This article presents the variation of viscosity, gel point, and curing kinetic process of nanocomposites based on unsaturated polyester resin (UPR) and natural nano‐clay CloisiteNa^+® and organomodified Cloisite15A^® montmorillonites (MMT). Different amounts (1–10 wt%) of nanoclays were added homogeneously before the cross‐linking reaction of the thermoset polymer. The complex viscosity before curing was especially dependent on the CloisiteNa^+® content more than Cloisite15A^®. The G' and G'' slope also as the complex viscosity criterion were used to determine the nanocomposites gel time variation. Isothermal differential scanning calorimetry measurements were performed to calculate the reaction order and the rate constant using different empirical equations. These results demonstrated a catalytic effect of the clays on the UPR cure, with diffusion controlled phenomena predominating at high conversions. The X‐ray diffraction patterns were useful for identifying the nanocomposites formation, and gave information about the clays dispersion, which served to support the rheological and polymerization kinetic results. Finally, natural MMT CloisiteNa^+®decreased gel time and was more compatible with UPR than the organomodified Cloisite15A^®. POLYM. COMPOS., 36:1931–1940, 2015. © 2014 Society of Plastics Engineers