Self-stratifying epoxy/silicone coatings
The self-stratification is an eco-efficient process since it reduces solvent emission, time of implementation and labor cost. Moreover it could lead to the development of a large range of new products for extensive application fields. For self-stratification to occur, liquid coatings must contain at least two incompatible resins, giving rise in “one pot” to a two-phases mixture after the formation of the solid film. In this work, an innovative self-stratifying coating, based on an epoxy/silicone blend, has been developed and applied on a plastic substrate (Polycarbonate). The perfect self-stratification of this system was evidenced by microscopic analysis coupled with X-ray mappings. The influence of solvents and a curing agent on the stratification process has been investigated. It is shown that the system diluted in butylacetate:xylene (at a 1:1 ratio) leads to the best stratification pattern, with the silicone phase located on the top of the coating. Three pigments (red iron oxide, calcium carbonate and zinc phosphate) were also incorporated in this epoxy/silicone system. They do not affect stratification, whereas visual appearance and adhesion are strongly dependent on the phase in which pigments are dispersed, as well as on the solvent used.