Effect of pulsation elongational stress on the structure and properties of preparing self-reinforced sheets

Abstract

A vane-type melt pulsation pumping device induces molecular chain orientation in HDPE melts via pulsating stretch-compression, enabling self-reinforced sheet extrusion. Experiments assess the impact of varying device temperature and rotational speed on the mechanical properties and microstructure of extruded sheets. The results show that the orientation of the samples can be preliminarily verified by heating test. SEM analysis reveals closely aligned HDPE crystal regions along the extrusion direction following pulsating elongational stress. 2D-WAXD analysis demonstrates a shift in diffraction intensity where it diminishes in the meridional direction and intensifies in the equatorial plane, resulting in a maximum orientation index of 0.683, an increase of 16.6% compared to direct extrusion. When the temperature of the melt pulsation pumping device is set to 180°C and the shaft speed is set to 30 rpm, the tensile strength of the sheets in the extrusion direction reached a maximum value of 66.37 MPa, surpassing that of directly extruded samples by 42.7% and that of compression-molded samples by 90%. In summary, this research realizes the self-reinforced and efficient continuous extrusion of single-component HDPE sheets through a simple device and process, which is of great significance for convenient recycling and environmental protection.