Surface Property Modification of Epoxy Coatings by Polydimethylsiloxanes

Surface properties of epoxy coatings are modified by PDMS additives in cationic UV curing of a cycloaliphatic epoxy resin. The cured films show a very high hydrophobicity that does not depend on PDMS concentration, indicating that a threshold is reached even at 0.3wt% additive. A slight increase of the water contactangle as a function of PDMS molecular weight is observed. The additive selectively modified the air-side of the film, while the glass-side retains the surface properties of the pure resin. This segregation phenomenon permits to obtain highly hydrophobic films with still good adhesion properties on polar substrates, which is an important advantage over common surface-modified resins.