Advantage of Preserving Bi-orientation Structure of Isotactic Polypropylene through Die Drawing

The isotactic polypropylene (iPP) usually shows a unique parent-daughter lamellae structure in which the parent and daughter lamellae are against each other with a near perpendicular angle (80 degrees or 100 degrees). Inducing a high fraction of oriented cross-hatched structure in iPP during processing is desirable for designing the bi-oriented iPP products. We processed a commercialiPPviatensile-stretching and die-drawing to evaluate the structural evolution of oriented parent-daughter lamellae. It turned out that the die-drawing process had an advantage in attaining a high fraction of oriented cross-hatched structure ofiPP, as compared to the free tensile stretching. Besides, the presence of alpha-nucleating agents affected the formation of oriented parent-daughter lamellae in the die-drawn samples whereas such influence diminished in the free stretched ones. It was found that the confined deformation inside the die led to the well-preserved oriented cross-hatched structure in the die-drawniPP.

Automated summary

The study on isotactic polypropylene (iPP) processing indicates that die-drawing process is more advantageous in achieving a high fraction of oriented cross-hatched structure compared to free tensile stretching. The presence of alpha-nucleating agents affects the formation of oriented parent-daughter lamellae in die-drawn samples, while the influence diminishes in free stretched ones. Confined deformation inside the die contributes to the well-preserved oriented cross-hatched structure in die-drawn iPP.