Cure characterization of epoxy and polyester clear powder coatings using Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Thermal Analysis (DMTA)

The thermal behaviour of an epoxy/polyester hybrid and a polyester clear powder coatings was evaluated by means of Differential Scanning Calorimetry (DSC). The effect of curing temperature on the coating glass transition temperature ( T g) was also studied using a Dynamic Thermo-Mechanical Analyser (DMTA). The DSC method allows the explanation of powder coating systems. The procedures established enable to clearly identify the periods of melting, flow, onset cure and concluding curing, all parameters affecting the visual aspect as well as the durability of a powder coating. Experiments revealed that T g is dependent on the heating rate in DSC and on the rate of application of stress, the frequency of oscillation and the rate of heating in the dynamic tests. Dynamic mechanical thermal analyses revealed that the different curing regimes do not affect considerably on the T g of the given powder coating samples. DMTA also showed that the rigidity of the polymer structure does not increase significantly with increasing curing temperature.