VISCOSITY AND THE FORMATION OF DIE DROOL AT THE POLYMER-METAL INTERFACES - EFFECTS OF SURFACE-COATINGS

The effects of the die-wall material on the apparent viscosity of a blend of Hytrel and Viton and on the formation of a particle-like material, which is commonly referred to as die drool, at the polymer-metal interface were studied. The blend, which consisted of approximately 15% Viton and 85% Hytrel, was prepared by using a twin-co-rotating-screw extruder. During extrusion of this blend, small particles ap pealed on the surface of the extrudates; these particles lr,ere determined by XPS to be a material which consisted largely of Viton. The apparent viscosity of the blend and the amount of die drool were found to decrease as the surface energy of the material used for the construction of the die dea eased. The reduction in the production late of die drool is attributed to reduction of adhesion at the interface.