Effects of operation conditions and die angles on the pressure losses in capillary flow of polystyrene melt

The theological properties of polystyrene (PS) melt were measured using a constant rate type of capillary rheometer over temperatures varied from 240 to 260 degreesC and shear rates varied from 10(2) to 10(3) s(-1). Dies with different entry angles were selected in order to identify the influence of the dir: angles on the pressure losses during extrusion of the melt. It was found that the end pressure losses increased nonlinearly with increasing the piston speeds (V), while the extrusion rate sensitivity of it was insignificant at higher temperature. The total pressure drop (DeltaP) in the die extrusion of the melt also increased non-linearly with the increase of V, and decreased with a rise of temperature. In addition, DeltaP decreased with increasing the die angle (2 alpha) and showed a minimum value when 2 alpha was about 75 degrees. (C) 2001 Elsevier Science B.V. All rights reserved.