Cure kinetics of a highly reactive silica–polyurethane nanocomposite

The cure kinetics of a highly reactive polyurethane and silica–polyurethane nanocomposite were studied using differential scanning calorimetry (DSC) as a function of preparation time, amount of material (weight) and silica concentration. The sample weight interfered substantially with the development of heat flow during cure. To avoid this issue, the weight effect was modeled as a superposition of autocatalytic sub-models. The polyurethane cure kinetics were modeled with an autocatalytic reaction. Such model was able to predict the evolution of conversion with good accuracy. For the case of the silica nanocomposite with a concentration range within 0.5–2 wt.%, a decrease in reactivity and a delay of the maximum cure rate was observed. In addition, the kinetics of the reaction was strongly affected by the preparation time. The overall reaction rate decreased linearly as this preparation time increased. A master kinetic model was developed which took into account all the studied variables.