Effect of carbon nanofibers on the cure kinetics of unsaturated polyester resin: Thermal and chemorheological modelling

We report the study of the effects of carbon nanofibers (CNFs) on the cure kinetics and on the chemorheology of unsaturated polyester resins (UP). Two main experimental techniques were utilized: differential scanning calorimetry and rheometry. Isothermal and dynamic tests were performed on the neat polyester resin and on two nanocomposite systems, with 0.5 and 1.0 wt.% of CNFs. Furthermore, a TGA study of the selected systems at different isothermal temperatures was performed to evaluate the styrene consumption and related loss rate during the curing process. Subsequently, a phenomenological model (autocatalytic approach) was applied to the experimental data, both in isothermal and dynamic conditions. In the case of dynamic curing, the evidence of multiple peaks in the heat flow curves was studied through the deconvolution of the overall reaction thermogram in single reaction steps. An empirical rheological model coupled with the reaction kinetics was successfully applied to simulate the viscosity changes of the UP matrix. Experimental and modelling results demonstrate the presence of a delay effect of the CNFs on the cure of the UP resin matrix.