Print: | ISSN 0256-1115 |
Online: | ISSN 1975-7220 |
Korean Journal of Chemical Engineering,
Vol.11, No.1, 1-7, 1994 THE EFFECT OF ASYMMETRIES OF DIE EXIT GEOMETRY ON EXTRUDATE SWELL AND MELT FRACTURE
Experimental investigations were performed to see how the die exit geometry and the extrusion velocity influence on extrudate swell and melt fracture for several polymer melts[low-density polyethylene, styrene-butadiene rubber(SBR) and SBR/HAF (carbon black)compound]. Four different types of die exit geometry were considered; Oo(symmetric, usual capillary die), and 30o, 45o and 60o (asymmetric dies)were chosen for the die exit angle. Extrudate diameters were measured without draw-down under isothermal condition. Polymer melts were extruded into an oil that has the same density and temperature as those of the extrudate. Extrudate swells from dies with different diameters were correlated with volumetric flow rates. It was observed that the extrudate swell increases with increasing volumetric flow rate and exhibits through a minimum value at about 45o die exit angle. As to the fracture phenomena, it was observed that the critical shear for the onset of melt fracture increases with the increasing die exit angle up to 45o. However, for 60o die exit angle, the onset of melt fracture is again similar to that of 0o exit angle.
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