Abstract
Adhesion promoters are traditionally used to improve the durability between an adhesive or any other organic phase, such as a sealant or a paint, and a metallic substrate. There are many different types of molecules which will act as adhesion promoters, but one class which has attracted considerable attention is that based on the organosilanes, such as y-aminotriethoxysilane, or y-glycidoxypropyl trimethoxysilane. Applications of such adhesion promoters are to be found in sealants, rubbers, primers in packaging and primers for coatings and adhesives. Organosilanes as adhesion promoters are widely used in industry, and until recently have been included in adhesive formulations in an empirical way, because it has been observed that the adhesive properties and hydrolytic stability can be improved. However recent work is leading to an understanding of how the silane molecules specifically interact with metallic and inorganic substrates. Little is known at the present time regarding the mode of operation of such molecules when applied to polymeric substrates. The purpose of the current work was to probe interaction of these molecules with low energy polymer substrates, for example, poly(methyl methacrylate) (PMMA) and poly(ethylene terephalate) (PET), using surface analysis techniques. Two factors which have been identified as controlling the adsorption of the organosilanes onto low energy substrates are the solution chemistry and the surface energy of the polymer. Both have been investigated extensively within this project. The latter was identified by means of investigating a series of substrates, with increasing polar contribution towards the surface free energy. The highest polar component was displayed by corona treated PET, which also displayed the highest levels of adsorption of organosilanes. Investigation of the adsorbed layer of the organosilane on the corona discharge treated PET has led to an understanding of the mechanism of the interaction of the molecules with all of the low energy substrates, and models for such interactions are proposed on the basis of spectroscopic observations.