Enhancing oriented crystals in injection-molded HDPE through introduction of pre-shear

• Oriented lamellae are formed in core region of injection-molded HDPE upon pre-shear.
• Skin–core structure of injection-molded HDPE can be steadily suppressed by pre-shear.
• HDPE part is mechanically enhanced if pre-shear was exerted at lower temperature.

In the present work, pre-shear was elaborately introduced into melting HDPE and then such pre-sheared melt was injection molded. The hierarchical structure and crystalline morphology of injection-molded HDPE part were investigated by using WAXD and SEM. It was found that pre-shear can enhance the formation of oriented crystals in core region of HDPE part. More interestingly, such enhancing effect becomes more remarkable if pre-shear was exerted at low temperature just slightly above the melting point of HDPE. Naturally, mechanical property was promoted due to the oriented crystals induced by pre-shear at low temperature and the narrowed orientation gap between shear region and core region.

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