Improving pigment dispersing in powder coatings with block copolymer dispersants

The effect of three block copolymer dispersants with a poly(2-vinylpyridine) anchor block and a poly(e-caprolactone) buoy block on the dispersing of TiO2 pigments in a polyester powder coating has been studied with digital image analysis on scanning electron micrographs. The mixing in a lab-scale extruder resulted in a virtually complete break-up of the pigment agglomerates. The average TiO2 particle size was only slightly reduced after further treatment of the TiO2 pigments with any dispersant. However, a significant change in the colloidal stability of the dispersions was observed. Without dispersants, the pigments reagglomerated when heated to 200°C and 235°C. This reagglomeration was completely suppressed by the use of dispersants, as a result of a steric layer around the TiO2 particles