Effect of Die Temperature on Morphology and Performance of Polyethylene Pipe Prepared via Mandrel Rotation Extrusion

The effect of die temperature on the mechanical performance and morphology of polyethylene (PE) pipe prepared via mandrel rotation extrusion is described. The experimental results showed that during the rotation extrusion of PE pipe, the hoop flow caused by the mandrel rotation was superimposed on the axial flow to deviate the formed shish-kebab from the axial direction which was favorable to improve the hoop strength of the PE pipe. However, high die temperature caused relaxation of most of the oriented molecular chains and the consequent formation of isotropic crystals in the PE pipe, whereas too low a die temperature led to imperfections in the PE pipe. As a result, there was an optimum temperature range for the enhancement of the hoop strength. When the mandrel rotated at 6 r/min, the hoop strength of the PE pipes prepared at the die temperature of 170°C reached the maximum value, 31.8 MPa, 22% and 29% higher than that at 150°C and 210°C, respectively.