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Abstract

The mechanism of film formation was studied with respect to the flocculation phenomenon. It was observed that almost all latices would air-dry to a point at which coagulation of the latex particles had just occurred and beyond which the wet film was no longer redispersible in water. This flocculation point was sharp and could be detected visually or by immersing the film in water. Two methods have been devised to measure the solids at which incipient flocculation occurred: cross-section method, and cone method. The floc point was found to be about 50–60% for a model acrylic latex depending on the soap present in the dispersion. After flocculation had occurred, further drying would lead to different film properties depending on the hardness of the particles, the rate of drying, the substrate, and the degree of crosslinking.