Mechanical Studies of Film Formation in Waterborne Coatings by Atomic Force Microscopy

Abstract

Atomic force microscopy (AFM) was been used to study film formation in coatings prepared from aqueous dispersions of acrylic/polyurethane hybrid polymers. Analysis of solvent and low heat bake effects on film formation of latex blends of softer (low Tg) and harder (higher Tg) polymers were limited by the inability of topographic AFM methods to identify domains in the blend coatings. New AFM modes (friction force, force modulation, and phase contrast) were used to map mechanical properties (friction, stiffness, and adhesion) while simultaneously imaging topography. This approach was effective in identifying hard and soft domains by supplementing topographic data with mechanical property maps that reflected phase identity in the blend coatings. Mechanical AFM modes will have tremendous utility in film formation studies of waterborne coatings, especially for blends.