Deformation-Induced Crystallization Behavior of Isotactic Polypropylene Sheets Containing a β-Nucleating Agent under...

Area of Science:

• Polymer Science
• Materials Science
• Crystallization Science

Background:

• Isotactic polypropylene (iPP) is a widely used polymer with diverse crystalline forms.
• Understanding deformation-induced crystallization is crucial for tailoring polymer properties.
• The role of β-nucleating agents in iPP phase transformations requires further investigation.

Purpose of the Study:

• To investigate the deformation-induced crystallization and phase transformation of β-iPP.
• To analyze the crystal morphology and molecular orientation under various stretching conditions.
• To evaluate the impact of the resulting structures on the mechanical properties of iPP sheets.

Main Methods:

• Solid-state stretching of iPP sheets containing a β-nucleating agent at different temperatures.
• Observation of crystal morphology at room temperature post-stretching.
• Analysis of phase transformation mechanisms of β-modifications.
• Evaluation of tensile and impact properties.

Main Results:

• Solid-state stretching increased crystallinity and promoted amorphous molecular chain orientation.
• Stretching above the crystallization temperature induced a phase transformation to a shish-kebab structure.
• At temperatures near the melting point, β-modifications melted and recrystallized into α-modifications.
• The shish-kebab structure significantly improved tensile (up to 34%) and impact (up to 126%) strengths.

Conclusions:

• The crystal phase transformation mechanism is linked to molecular chain orientation between lamellae.
• The shish-kebab cylindrite structure is key to enhancing the mechanical performance of iPP.
• Deformation-induced crystallization offers a pathway to significantly improve the functional properties of iPP materials.