The wet scrub resistance of a dry paint film is used as an indication of the pigment binding capacity of the binder. However, scrub resistance results vary considerably depending on the method employed. The scrub results of the DIN and ISO standard scrub resistance methods and of an abrasion method known as tribology were compared as a function of binder composition and PVC of the paint film. The results obtained from the three different scrub methods are comparable with regard to differences in binder, but show no strong correlation over the PVC range investigated. Significant differences regarding the error of each measurement were observed. To better understand the effect of the various testing conditions on the morphological characteristics of the substrate, all samples were characterized as follows: The pigment distribution of TiO_2 and various fillers in the paint formulation was analyzed by Electron Microscopy (EM) and Raman Microscopy (RM). The surface structure of pristine and partially scrubbed paint films was studied by means of Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The results of all test methods indicated that binders with higher pigment binding capacity form more cohesive films and thereby exhibit higher mechanical strength.
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