Adhesion of Silicone Coatings to Plastic Films

Abstract

This work aimed to elucidate the mechanisms of adhesion of a silicone coating to corona discharge treated polypropylene (PP) and poly(ethylene terephthalate) (PET) films. A physico-chemical study of the PP and PET surface utilizing contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) was carried out. Surface energies investigated the role of physisorption, whilst chemisorption was examined by the surface chemistry changes. The presence of mechanical interlocking was studied by observing changes in the morphology of the films, and a combination of these techniques on washed samples made possible the scrutinizing of a weak boundary layer. These results, in addition to practical adhesion measurements, have enabled identification of the dominant mechanisms of adhesion of silicones to PP and PET films. Physisorption and mechanical interlocking are not dominant causes of enhanced adhesion after corona discharge treatment in this system. It is believed that the principal mechanisms of adhesion of silicone to corona treated PP and PET are chemisorption and weak boundary layer formation.