Die-swell behavior of glass bead-filled low-density polyethylene compositemelts at high extrusion rates

The extrudate swell behavior of glass bead-filled low-density polyethylene (LDPE) composite melts was investigated using a constant rate type of capil lary rheometer at high extrusion rates and test temperatures varied from 14 0 to 170 degrees C. The results show that the die swell ratio (B) of the me lts increases nonlinearly with increasing apparent shear rates for the syst em filled with the surface of glass beads pretreated with a silane coupling agent, while the B for the system filled with uncoated particles remains a lmost constant when the true wall shear rate is greater than 2000 s(-1) at a constant temperature. The values of B for both the pure LDPE and the fill ed systems decreases linearly with an increase of the temperature and an in crease of the die diameter at fixed shear rates, and the sensitivity of B o n the die diameter and temperature for the former is higher than that of th e latter. Furthermore, the effect of the filler content on B is insignifica nt, while the values of B decreases, obviously, with an increasing glass be ad diameter (d) when d is smaller than 50 mu m; then B varies slightly with d. (C) 2000 John Wiley & Sons, Inc.