Epoxysilane Oligomer for Protective Coatings

By Christopher M. Byrne, Arun N. Kumar, Alain Lejeune

The use of silanes as adhesion promoters and crosslinkers is widely practiced in the coatings industry. The advantages of silanes in coatings systems were first introduced almost a half-century ago.1,2 As additives to formulations or as monomers in polymer synthesis, these products impart many desirable performance characteristics to a cured film.

Coatings prepared with silanes can show improved mar and abrasion resistance, water and solvent resistance, acid and alkali resistance, and adhesion to various substrates.3 The use of silanes in coatings, however, is not limited to interaction between the organic polymer and the substrate. Pigments pretreated with silanes show increased dispersibility and bind-ing, resulting in lower viscosities and better hiding power.

Thus, silanes have steadily grown to become an indispensable component in many aspects of the coatings industry. Organofunctional silanes consist, in general, of an organic functionality (Y, Figure 1) linked through an organic spacer (R’) to one or more silicon atoms each with one, two, or three hydrolyzable alkoxy ligands (OR). The organic moiety (Y) provides a “handle” that can react with functionality on a polymer backbone.

The hydrolyzable groups (OR) can react with water, forming reactive silanol groups (SiOH), and then bond to a filler or substrate or self-condense to form siloxane crosslinks (SiOSi) (Figure 2).