Preparation and characterization of encapsulated C.I. pigment yellow 12 via ball-milling and mini-emulsion polymerization

The purpose of this paper is to encapsulate aqueous dispersion of nanoscale C.I. Pigment Yellow 12 (PY12) with styrene-butyl acrylate resin via mini-emulsion polymerization, the PY12 dispersion was prepared through ball milling in the presence of dispersing agent. Comprehensive analyses were performed to characterize the encapsulated pigments, including TEM, FTIR, UV-vis absorption, CIE L*a*b* color scales, encapsulation efficiency, and UV weathering. TEM images revealed that composite particles exhibit a clear core-shell structure, the particle size uniformity and encapsulation integrity of encapsulated particles prepared by ultrasonic dispersion are superior to those prepared by high-speed shear dispersion. Besides, FTIR analysis showed that the organic pigment was actually incorporated into the resin shell but not simply doped or physically absorbed outside. When the PY12 content of the encapsulated particles was 0.6 g, the lightness value (L*) and yellow value (b*) of the sample reached the maximum, and the color performance was the best. Encapsulation efficiency characterization disclosed that the dispersion and encapsulation efficiency of ultrasonication are more superior than those of the high-shear homogenizer, the UV-resistance ability and color stability of encapsulated PY12 were better than those of the original pigment.