LIQUID STRETCHING USING A FALLING CYLINDER

A novel free-fall extensional device was developed and its usefulness in measuring the elongational viscosity of both Newtonian and viscoelastic liquids was demonstrated. A small quantity of liquid is inserted between the ends of two cylinders that are vertically oriented one above the other. The upper cylinder is held fixed while the lower cylinder, initially at rest, is allowed to fall and stretch the adhering sample. Time sequence photos of the stretching process are used to deduce the liquid deformation rate and ligament stress. The elongational viscosity is then determined from the stress/deformation rate ratio. While trial results for Newtonian liquids are consistent with the Trouton expression, viscoelastic testing indicates that the elongational viscosity increases with time and is significantly greater than that of a comparable viscous Newtonian liquid. © 1990, All rights reserved.