GLASS AND POLYMER - WETTING AND ADHESION

The use of glass-polymer compounds is on the advance as for the finish ing of glass products and for the development of materials to be used in new applications. The results from wetting and adhesion experiments of thermoplastic polymers on glass surfaces without coupling agents a re discussed. The attempt to use the thermodynamic work of adhesion as a measure of adhesion proved to be unsuccessful, as it is difficult t o characterize glass according to surface energy. Contact angle measur ements of melted polymers on glass surfaces show that the type of sili cate glass applied does not influence the contact angle. The wetting i s controlled by the viscosity of the polymer melt, and the kinetics fo llows a power law. The fact that non-polar polymers show a low level o f adhesion on glass surfaces is based upon results of strength measure ments of compounds between glass and polymers. Apart from polarity, me chanical and thermal properties of polymers play a decisive role. Grea t importance is attributed to the ability to relieve stress, since the observed cohesion failure inside the glass is caused by brittle polym ers. Adhesion, however, is insignificantly dependent on glass composit ion. If the joint is not achieved by polymer melting but by a solution of the polymer, the surface property (acid-base affinity) of the glas s becomes a critical factor, and adhesion may fail completely.