Differential scanning calorimetry for coating curing
Via the DSC technique it can be verified if the coating is sufficiently cured or not. The DSC is a technique verifying how much energy is needed to have no temperature difference between the substance in test phase and the referential material, determined in according to time and temperature, when two specimen are submitted to identical temperature conditions in a controlled warm or cooled environment.
First of all, the thermal history of the material is disturbed by the fast cool down under liquid nitrogen and warming it up immediately to 240°C. During the curing process the Tg increased (glass transition temperature) in function of the curing time. An initial Tg1 is observed. If the coating is undercured, an exothermic reaction is observed. If no exothermic reaction is observed, than it can be considered that DTg = Tg2 – Tg1 = 0. Undercuring appears when DTg > +2°C