Modelling of the chemo–rheological behavior of thermosetting polymer nanocomposites

Abstract Epoxy/amine/montmorillonite nanocomposite systems are studied in this article. Both a thermo−kinetic analysis (performed using a differential scanning calorimeter) and a chemorheological characterization were carried out. The comparison of DSC thermograms has shown that the addition the nanofiller does not change the mechanism of crosslinking from a qualitative standpoint, but the nanoreinforcement seemed to produce an evident hindrance on the molecular mobility, which in turn influences the cure reactions. As none of the kinetic models available in literature was able to describe the cure behavior of the aforementioned materials, a new phenomenological model is proposed in this work, which considers the activation energy of the networking process a function of the degree of cure (rising exponentially towards infinity when thesystem approaches vitrification). The effects of the presence of the clay on the chemorheology of the composites was resumed as follows: the viscosity of the nanocomposite was higher at any temperature, furthermore the composite viscosity showed an higher heating sensitivity before networking and gelation occurred at lower degrees of cure, thus determining a narrower shape of the chemoviscosity behavior. A modified version of the classical Williams–Landel–Ferry (WLF) equation that took into account the gelation and the effects of crosslinking was uses as chemorheological model. Once the characteristic parameters of both the neat resin and the nanocomposite were found, the chemoviscosity models were integrated using a numerical algorithm, to check their ability to foresee the behavior of the systems during a dynamic cure process. A very good correspondence between the results and the experimental data was obtained. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers