ADSORPTION-SENSITIVE MECHANICAL AND MACHINING BEHAVIOUR OF SODA-LIME GLASS.

A study was made of the influence of water, toluene, the n-alkanes and the n-alcohols on the pendulum hardness, fracture, and drillingmachining behaviour of a soda-lime glass. The energy, theta, required to propagate cracks was determined by a double-cantilever technique. Drilling experiments revealed, however, that despite the lower value of theta for glass in water, this environment is not an effective cutting medium, and that the higher alcohols and alkanes are superior by factors of up to twenty times. Of particular interest is the observation that the effectiveness of the latter environments varies non-linearly with molecular chain length, being a maximum in heptyl alcohol and heptane, respectively. It was also noted that by mixing two alcohols or alkanes of different chain length, it is possible to reproduce the drilling characteristics of alcohols or alkanes of intermediate chain length in the homologous series. The results of this work reveal that the environment-sensitive machining behaviour of glass in essentially non-aqueous environments is not determined by the water content of the environment, or by any influence of the environment on the ease with which cracks may be propagated, or by the dielectric constant, dipole moment, viscosity, or any other obvious environmental parameter. The possibility that such behaviour could arise as a consequence of a stress-plus-chemisorption-induced redistribution of sodium ions is discussed. Author