NEW APPLICATIONS IN STUDIES OF WATERBORNE COATINGS BY ATOMIC-FORCE MICROSCOPY

Atomic force microscopy (AFM) is rapidly emerging as an important tool for coatings characterization. We report several new applications of AFM of particular value to the development of improved waterborne coat ings systems. First, an AFM method was developed to quantitatively ass ess the extent of coalescence and film formation for latex films by me asurement of particle number density of protruding (uncoalesced) parti cles in dried coatings. Second, the use of topographic imaging to eval uate environmental (temperature) effects on film formation was investi gated for a waterborne latex system. Finally, specular gloss of waterb orne epoxy coatings was studied by AFM and optical measurements, and t opographic features analyzed using power spectral density calculations were found to correlate with optical gloss measurements. Mechanisms f or gloss reduction over time (particularly in early pot life coatings) were elucidated in the studies. Further applications in coatings stud ies will be driven by the development of new modes of AFM (friction fo rce, force modulation, and phase contrast) that can be used to map mec hanical properties (friction, stiffness, and adhesion) while simultane ously imaging topography. Examples of the use of the phase contrast mo de to identify chemically different domains in early pot life waterbor ne epoxy coatings are presented. (C) 1997 Elsevier Science S.A.