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 st yrene-butadiene (SB) latex and kaolin clay at different levels of pigmentat ion was investigated. As found from X-ray photoelectron spectroscopy, sinte red 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 temperatur e. 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 s urface energy. Drying in the presence of water (wet coalescing) was compare d to drying in the absence of water (sintering). Even though sintered coati ngs were more porous and had higher gloss, no significant difference was fo und 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, t he sintering process yielded a higher SB content at the surface and a lower surface energy than the wet-coalescing process. (C) 2001 John Wiley & Sons , Inc.