Effect of physical aging and thermal stress on the behavior of polyester/TGIC powder coatings

Physical aging, thermal stress, dynamic mechanical characteristics and thermal expansion of powder coatings from model terephthalic acid (TPA) and isophthalic acid (IPA)-based polyesters (PEs) cross-linked with triglycidyl isocyanurate (TGIC) were studied. Enthalpy relaxation and maximum compressive thermal stress were the properties used to follow the physical aging. The better mechanical properties of TPA-based PE/TGIC powder coatings seem to be due to a combined effect of several properties, i.e., cross-link density (¿e), thermal expansion coefficient (aFT) and glass transition temperature (Tg). The higher the values of ¿e, (aFT) and Tg, the tighter is the coating network, the greater is the coating ability to expand thermally and the slower the physical aging process, respectively, all factors favoring the TPA polyester-based powder coatings.