Urethane methacrylate reactive diluents for UV-curable polyester powder coatings

Three urethane methacrylates, one monofunctional derivative and two di-functional derivatives with different chain lengths were used as reactive diluents in UV-curable polyester powder coatings. Each reactive diluent was formulated with a methacrylated polyester oligomer using conventional melt extrusion techniques. The effect of these compounds on zero-shear melt viscosity was investigated. Incorporation of 10 wt% reactive diluent effectively reduced the viscosity by an order of magnitude. After UV-curing, the viscoelastic, thermal, and mechanical properties of the films were characterized using dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, and tensile tests. The type and concentration of reactive diluent that was used directly influenced the glass transition temperature, modulus, % elongation-at-break, and crosslink density. Of the two di-functional reactive diluents that were used, the derivative that contained a shorter methylene spacer group resulted in more heterogeneous crosslinked networks.

Automated summary

Three urethane methacrylates were used as reactive diluents in UV-curable polyester powder coatings, with one monofunctional derivative and two di-functional derivatives of different chain lengths. The addition of 10 wt% reactive diluent significantly reduced viscosity by an order of magnitude. The type and concentration of reactive diluent directly influenced the properties of the films after UV-curing, such as glass transition temperature, modulus, % elongation-at-break, and crosslink density. Of the di-functional reactive diluents used, the derivative with a shorter methylene spacer group resulted in more heterogeneous crosslinked networks.