Estimation of the elongational viscosity: (a) calculation model of drawdown in a parison; (b) elongational viscosity modified to fit the measured drawdown elongation, where the red dotted line indicates measured data at 190 °C and the blue dashed line indicates viscosity curve data at 210 °C; (c) Comparison of calculated drawdown elongation and measured elongation (cross) as functions of distance from the die core at the condition of die diameter 410 mm, stroke 20%, and flow rate 450 kg/h: the calculation results with the elongational viscosity of HR111 (circle), and the one with the fitted elongational viscosity (diamond).