Glass and polymer : wetting and adhesion

The use of glass-polymer compounds is on the advance as for the finishing 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 are discussed. The attempt to use the thermodynamic work of adhesion as a measure of adhesion proved to be unsuccessful, as it is difficult to characterize glass according to surface energy. Contact angle measurements of melted polymers on glass surfaces show that the type of silicate glass applied does not influence the contact angle. The wetting is controlled by the viscosity of the polymer melt, and the kinetics follows a power law. The fact that non-polar polymers show a low level of adhesion on glass surfaces is based upon results of strength measurements of compounds between glass and polymers. Apart from polarity, mechanical and thermal properties of polymers play a decisive role. Great importance is attributed to the ability to relieve stress, since the observed cohesion failure inside the glass is caused by brittle polymers. Adhesion, however, is insignificantly dependent on glass composition. If the joint is not achieved by polymer melting but by a solution of the polymer, the surface property (acid-base affinity) of the glass becomes a critical factor, and adhesion may fail completely.