The integrity of a structurally glazed building envelope depends on the strength of adhesion at several interfaces, e.g. glass- glass coating, glass coating-silicone sealant, silicon sealant-substrate coating, substrate coating-primer, primer-substrate.
Frequently, the frame and cladding are aluminium alloys which are either anodised or finished with an organic coating to satisfy aesthetic and/or long-term corrosion resistance requirements.
In this paper, the mechanism of adhesion between organic-coated aluminium and silicone sealants is analysed. The sealants investigated are neutral-, alkaline-, and acid-cured, 1-part RTV silicones as well as 2-part RTV silicones, all commercially available. The organic coatings investigated are powder and wet-coated polyester, PVF2 (polyvinylidene flouride), acrylic and siliconised finishes, also all commercially available products.
It is shown that the strength of adhesion between any silicone sealant and the organic-coated substrate, as well as the extent of adhesive failure, depend on the substrate surface properties as quantified by the non-dispersive component of the substrate surface energy, γn-d. A typical relationship is shown to exist for strength v. γn-d and [%] adhesive failure v. γn-d.
Finally it is shown that the organic-coated substrates used in structural glazing can be assessed for their potential bondability with silicone sealants by determining the non-dispersive component of their surface energy. This technique is described in detail in this paper.