Q. What mechanism(s) causes waterborne latex paints to adhere to their substrates and remain adhered over time? I have some hypotheses and like most physical processes, I’m sure each plays a role in adhesion and a balance exists, but I want to know which plays the largest role. I am also curious about how the change from a liquid during application to a solid film plays a role. Please elaborate on the following points and others as you see fit:
- The penetration of the liquid phase into a porous substrate causes a physical/interlocking bond.
- The rheological properties of the polymer binder give the coating adhesive properties (similar to tapes).
- The ability of the paint to wet out the surface it is being applied to.
- The intermolecular properties of the substrate and the paint cause a chemical attraction. N.W.
A. Theories of adhesion are many and varied. Owing to space constraints, it’s difficult to answer your question in this forum. Rather, it would take a chapter to fully explain the mechanisms and answer your questions. However, I can give you simple answers without elaboration. Point one describes the action of an emulsion. In an emulsion, small droplets of immiscible liquid (discontinuous phase) are dispersed in another liquid (continuous phase). On the other hand, a latex is a dispersion of solid or liquid resin in water. In either case, an emulsion or latex, the water would not cause a physical/interlocking bond. Point two having the rheological properties of the polymer binder give adhesive properties, similar to tapes, doesn’t fit the description of the mechanism. A combination of point three and point four would better fit the description of the mechanism.