Simultaneous Enhancement of Toughness and Strength of Stretched iPP Film via Tiny Amount of β-Nucleating Agent under “Shear-free” Melt-extrusion

Herein, isotactic polypropylene films with small β-nucleating agent content were fabricated via a melt-extrusion-stretched technology with intended “shear-free” in barrel and die. Compared with neat films, the tensile strength, elongation at break and strain energy density at break of iPP film with 0.05 wt% β-nucleating agent are significantly improved by 13.8%, 39.6% and 90.6%, respectively, indicating the simultaneously enhanced toughness and strength. Additionally, the β-crystal content gradually increases with increasing β-NA content, while the relative total daughter content of α- and β-crystal exhibits opposite tendency. Moreover, nucleation and crystal growth induced by various β-NA contents are different. This work proves an efficient strategy to enhance mechanical properties of isotactic polypropylene film via controlling elongation flow and addition of appropriate β-NA content.