Polyimide–polyester hybrid UV-curable powder coating

A new UV-curable maleimide-terminated polyimide was prepared and characterized using gel-permeation chromatography, infrared, and nuclear magnetic resonance spectroscopy. The polyimide was formulated with a commercially available UV-curable polyester resin via twin-screw extrusion to prepare a hybrid powder coating system. The hybrid powder coatings were cured by exposing the molten formulation to UV light. The films were studied by dynamic mechanical analysis (DMA), thermomechanical analysis, and differential scanning calorimetry. DMA highlighted the viscoelastic behavior of the films and showed that an increase in Tg was obtained with increasing polyimide content, as determined via the α-transition in the tanδ curve. Thermogravimetric analysis showed an improvement in the thermal stability of the polyester with the addition of the polyimide. Deformation resistance of the UV-cured films was investigated by SAOS and LAOS rheological methods to investigate the relative endurance of these coatings when subjected to different strains. The viscoelastic properties of the hybrid system were most improved when 16% weight percent of polyimide was added into the system.