Cure Kinetics of Polyurethane/Silica System Topcoats in Naval Applications

Abstract

The cure kinetics of polyurethane/silica system resins (used as topcoats in naval applications) are investigated by means of isothermal differential scanning calorimetry. The enthalpy isotherm generated during the sweep increases, while the residual enthalpy decreases. This is due to the increased mobility of the double bonds as the temperature rises, causing a reduction of the remaining and as yet unreacted double bonds, although the sum of ΔHiso + ΔHres remains practically constant. By representing the Arrhenius equation in its logarithmic form, two slopes (Ea) are obtained for the same system which indicates that both mechanisms are involved in the curing reaction. The first mechanism may correspond to the crosslinking reaction of the urethane group, while the second may correspond to a secondary reaction due to the high temperatures at which the study is conducted.