RHEOLOGY OF SOLVENT-CAST POLYMER FILMS.

This paper describes and analyzes the results of an experiment where various thin polymeric films are continuously sheared between smooth glass substrates. The shear force per unit area has been measured as a function of mean uniaxial stress and temperature using representative 'good' and 'poor' casting solvents followed by a range of heat treatments. The results indicate that the casting solvent has a very pronounced influence upon the rheology of the film. The casting solvents may apparently confer either ductile or brittle failure in the film and also influence the nature of the temperature and pressure dependence of the shear stress. The data have been analyzed using Eyring theory. 'Good' solvents generally tend to promote a brittle mode of failure with little temperature dependence. The same type of solvents also produced films which have higher shear strengths and show greater increases in shear strength with pressure.