Influence of various catalysts on the 1,3-diacetidine-2,4-dione (uretdione) reaction with hydroxyl groups

Lowering the curing temperature for powder coatings is desirable with regard to the coating of temperature sensitive substrates. However, commercial available weather-resistant stable powder coatings need curing temperatures >180 °C. The reactivity of various catalysts on the reaction between an uretdione cross-linker and OH groups were carried out on the basis of low molecular model systems. The results were transferred to polymeric systems consisting of the reactive components of a powder coating composition. The investigations were carried out using non-isothermal and isothermal DSC measurements as well as rheological measurements of the complex melt viscosity. However, the curing reaction occurred in a two-step reaction mechanism whereas the first reaction step could by quantitatively separated applying non-isothermal DSC measurements.