West European paintmakers use 2.2 M tonnes/y of pigments, fillers & extenders

Abstract

Pigment-binding capacity as determined by the wet scrub test is the most important characteristic that dispersion binders used in highly pigmented indoor paints must have. Aqueous dispersions used as binders in solvent-free paint formulations must guarantee excellent film forming at room temperature as well as demonstrate a high pigment-binding capacity.In this work, the mechanism of three independent methods used to probe the wet scrub resistance of paints are investigated. The scrub results of the DIN and ISO standard test methods and of an abrasion method (tribology) are compared as a function of pigment volume concentration (PVC). To understand the underlying mechanism, all samples were characterized as follows. The pigment distribution of TiO2 and various fillers in the paint formulation was analyzed by electron microscopy (EM) and Raman microscopy (RM). The surface structure of the original and scrubbed paint films were studied by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM).The results obtained by the three different scrub methods are comparable, but show no strong correlation over the whole PVC range. Significant differences regarding the error of each measurement were observed. However, all test methods indicate that binders with high pigment-binding capacity have relatively strong adhesion at the surface of pigments, are less deformable, and exhibit higher mechanical stability.