Thermal and dielectric properties of powder coatings based on carboxylated polyester and β-hydroxyalkylamide

Thermal transitions, relaxations and the crosslinking reaction in varnishes and pigmented paints based on carboxylated polyester and β-hydroxyalkylamide (Primid) were studied by differential scanning calorimetry (DSC), temperature modulated DSC (TMDSC), thermogravimetry (TGA) and dielectric analysis (DEA). The effect of the Primid content on the glass transition of the powder coatings before and after crosslinking was analysed. The melting and flow regions were studied by TMDSC and correlated with the loss factor, which was measured by DEA. A comparison of the DSC and TGA scans showed that the crosslinking reaction was masked by the vaporisation of water formed during esterification. The resulting endothermic reaction made it difficult to analyse the crosslinking by DSC. Nevertheless, it was possible to detect the crosslinking reaction by the dielectric measurement of the loss factor and the conductivity.