Effect of sintering on surface chemistry and surface energy of pigmented latex coatings

Drying in the absence of water (sintering) of pigmented coatings made of styrene–butadiene (SB) latex and kaolin clay at different levels of pigmentation was investigated. As found from X-ray photoelectron spectroscopy, sintered coatings showed a higher SB area percent on the surface than did latex with a high glass-transition temperature (T_g) and dried at room temperature. This was a result of latex spreading at the surface. Sintering the high-T_g coatings that were dried at room temperature caused a decrease in the surface energy. Drying in the presence of water (wet coalescing) was compared to drying in the absence of water (sintering). Even though sintered coatings were more porous and had higher gloss, no significant difference was found in the SB/clay ratio at the surface or in the surface energy above the critical pigment volume concentration (CPVC). However, at and below CPVC, the sintering process yielded a higher SB content at the surface and a lower surface energy than the wet-coalescing process. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 968–975, 2001