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

The rheological properties of polystyrene (PS) melt were measured using a constant rate type of capillary rheometer over temperatures varied from 240 to 260°C and shear rates varied from 102 to 103 s−1. Dies with different entry angles were selected in order to identify the influence of the die angles on the pressure losses during extrusion of the melt. It was found that the end pressure losses increased non-linearly with increasing the piston speeds (V), while the extrusion rate sensitivity of it was insignificant at higher temperature. The total pressure drop (ΔP) 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, ΔP decreased with increasing the die angle (2α) and showed a minimum value when 2α was about 75°.