Viscosity of Amorphous Molecular Substances

Abstract

Because the great majority of flow units in a liquid behave instantaneously in a solid-like manner, rheological properties of molecular liquids subjected to high pressures may be measured by using corresponding molecular solids. An existing simple shear device previously reported is improved allowing the measurement of the viscosity of solid paraffin under controlled pressure and temperature. Experimental results show that some viscosity properties in amorphous solids do not coincide with those found in liquids. To explain this difference, the solid paraffin structure was investigated by aid of an AFM apparatus. This revealed that the structure is formed of a mixture of clusters and simple molecules. A possible mechanism of flow in molecular amorphous solid was advanced which explains the observed discrepancies.