WALL SLIP IN THE CAPILLARY-FLOW OF MOLTEN POLYMERS SUBJECT TO VISCOUSHEATING

The traditional way of determining the slip velocity of molten polymer s is the classic Mooney technique which utilizes experimental data obt ained from a capillary rheometer. However, measurements of the rheolog ical properties of polymer melts in capillary flow at high shear rates are often complicated by viscous heating which is not taken into acco unt by this mettled. A data analysis procedure based on a mathematical model for nonisothermal capillary flow of molten polymers is develope d. Conduction, convection, and viscous heating are included together w ith the effect of wall slip. The technique provides detailed velocity and temperature fields in the die, and can be used to determine the sl ip velocity at high shear rates corrected for the effect of viscous he ating. It is tested for the capillary flow of several polymers, includ ing polystyrene, polypropylene, high-density, and linear low-density p olyethylenes.