High-density polyethylene pipe with high resistance to slow crack growth prepared via rotation extrusion |
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Authors: | Min Nie ShiBing Bai Qi Wang |
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Affiliation: | (1) State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, 610065 Chengdu, China; |
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Abstract: | Slow crack growth (SCG) is one failure principal mode in polyethylene (PE) pressure pipe applications. In the conventional
extrusion process, the molecular chains in the plastic pipes are oriented along the axial direction, which are disadvantageous
to their resistance to SCG. In order to change the orientation direction of molecules in the plastic pipe, a new rotation
extrusion processing system was designed to extrude high-density polyethylene (HDPE) pipes, and a thorough research was done
on the effect of the rotation speed on its microstructure and resistance to SCG during the rotation extrusion. The experimental
results showed that when the die rotated during the extrusion process of PE pipes, the hoop stress exerted on the polymer
melt could make the molecular orientation deviate from the axial direction, and therefore the consequent multi-axial orientation
of molecular chains could be obtained. As a result, the PE pipe with better resistance to SCG was prepared. Compared to the
PE pipe produced by the conventional extrusion, the crack initiation time of the PE pipe manufactured by the novel method
increased from 27 to 57 h. |
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