The Influence of Gloss Level in Polyester-Powder Coatings on the Adhesion of Silicone Sealants

It has been frequently observed that the strength of adhesion between silicone sealants and polymer-coated substrates depends on the coating's gloss level.

The study described in this paper reveals that there seems to be a relationship between the gloss and the coating's surface properties as determined by the non-dispersive, γ^n-d, component of the total surface energy. It is shown that gloss increase is associated with an increase in the substrate γ^n-d. The exact pattern of this relationship cannot yet be established due to the narrow range of experimental data. Experiments carried out with several commercially available silicone sealants show that the higher the coating's gloss level, the stronger the adhesive bond between the sealant and the substrate. This finding is shown to be consistent with the earlier proposed mechanism of adhesion, according to which an increase in the value of the non-dispersive component of the substrate total surface energy leads to increased bond strength to the point where adhesive forces become stronger than the cohesive strength of the bulk sealant.