Adhesion and Internal Strain in Polymeric Coatings
Internal strain is present in many types of polymeric surface coating to a greater or lesser extent. It effectively diminishes the adhesion between coating and substrate, or between binder and filler. Internal strain energy stored in a coating increases with the thickness and, at a certain thickness that energy is sufficient to overcome the interfacial work of adhesion and provoke failure. The effect of internal strain on peel and pull-off adhesive strength is analyzed theoretically and demonstrated with data on clear lacquers. Adhesion data on a pigmented lacquer is presented showing the action of internal strain on the interaction between binder and filler. Results are also given for a crosslinked coating where the strain increases with film thickness showing that there is a much greater reduction in adhesive strength compared to a similar system in which the strain is independent of thickness.
KeywordsCoating Thickness Adhesion Strength Internal Strain Epoxy Coating Peel Test
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