What’s the difference between leafing and non leafing pigments?
Aluminum pigments are classified as either leafing or non-leafing. The type of lubricant utilized in the ball mill determines this property as the pigments surface tension is affected. Stearic acid, will produce a pigment with high interfacial tension and make it more difficult for the binder/solvent to wet its surface. Thus, with leafing pigments, when the metal flake rises to the surface (as a result of convection currents due to solvent evaporation), it is allowed to stay afloat (lack of wetting) forming an overlapping, scale like, dense layer which appears bright and silvery. Akin to a wax coated needle on the surface of water. Non-leafing pigments are created by the use of oleic acid during the milling operation or by the addition of strongly polar substances or wetting agents to leafing pigments. Non-leafing pigments are completely wetted by the binder and are, thus, dispersed evenly throughout the film. Due to the fact that the pigment orients below the surface of the film, the
