Investigation of cure kinetic model and gel point for a vinylester-based SMC material

The capability of modeling the process of Sheet Moulding Compound by numerical tools requires detailed characterization of material in different conditions. A crucial aspect of this technology involves determining the required curing time and the onset of material gelation. These aspects are essential for controlling both the molding time and the flowability of the material. The purpose of this study is to analyze the kinetic and rheological properties of a commercial vinylester-based Sheet Moulding Compound material. The Kamal-Sourour model is employed to monitor the evolution of the Degree of Cure. The model parameters are determined by fitting Differential Scanning Calorimetry data using an ordinary least squares method and validated through a secondary analysis conducted under isothermal conditions. The findings demonstrate a robust correlation with the experimental data, with a deviation of less than 4%. The gel point is evaluated by comparing the conventional methodology employed with a rotational rheometer to an innovative approach utilizing a high-resolution camera able to monitor the flow of the material while compressed. The comparison of the outcomes indicates a discrepancy of approximately 3%, demonstrating the validity of this novel approach for determining the gel point.