APPLICATION OF INTRINSIC-VISCOSITY AND INTERACTION CONSTANT AS A FORMULATION TOOL FOR FILM COATING .3. MECHANICAL STUDIES ON FREE ETHYL CELLULOSE FILMS, CAST FROM ORGANIC-SOLVENTS

The mechanical properties of ethyl cellulose films, cast from different solvent systems. have been determined and the structures of the films have been visualized in order to assess the solvent systems for use in a coating process. General relationships could not be found between intrinsic viscosity or interaction constant data and the mechanical properties. However, by using the two parameters in combination, favourable solvent systems could be selected, e.g. methylene chloride and ethanol in the ratio of 60:40 (% w/w) or toluene and ethanol in the ratio of 80:20 (% w/w). Water should be avoided in solvent systems for ethyl cellulose since it accumulates in the evaporating solution and impairs the film properties by forming a spongy and porous film.