The effect of coatings in reducing the damage of glass surfaces

Abstract

Previously etched microscope slides have been coated with films of octadecylamine and tin oxide. The films were applied both singly and in combination. Friction measurements were made in which the coated slide was mounted on a trolley, a spherical glass indenter was pressed by a measured force against the coated surface and the force required to draw the trolley carrying the slide at a constant speed under the indenter was measured. After removing the coatings the slides were subjected to the Ernsberger lithium ion exchange process to reveal the surface flaws produced by the sliding indenter. It was found that the oxide films alone do not have a marked effect on the coefficient of friction, but do reduce the surface damage. The octadecylamine films markedly reduce both the coefficient of friction and the surface damage. Large normal loads are required to break down these films. The most resistant films are those in which a film of octadecylamine is applied on top of a tin oxide film. Such a composite film is extremely resistant to breakdown. The results are discussed in terms of what is known about mechanisms of surface damage and are compared with results of similar experiments carried out on glass containers.