Effect of Supercritical Carbon Dioxide Treatment on Physical Properties of Polypropylene Films

ABSTRACT Supercritical carbon dioxide (ScCO 2 ) is becoming an important “green” solvent, primarily due to its low toxicity, recyclability, and environmental sustainability compared with conventional organic solvents. Recent advancements in large‐scale manufacturing technology have made ScCO 2 increasingly feasible and attractive for a wide range of industrial applications, such as foaming and coffee extraction. In this paper, we investigate the physical properties of commercial polypropylene (PP) mono‐oriented films after treatment with ScCO 2 . We have observed a remarkable increase of over 40% in elongation at break and a 30% increase in tensile strength along the machine direction (MD) concurrently, a rather unusual phenomenon. Additionally, the smoothness of the film surface is significantly enhanced. Various studies have been conducted to uncover the underlying mechanism. The newly formed γ‐crystal structure may contribute to the improved mechanical properties along the MD. Other important contributing factors may include increased free volume and chain relaxation resulting from the ScCO 2 treatment. These findings hold considerable promise for various industrial applications, thanks to the low cost, simplicity, scalability, and environmental benefits associated with the ScCO 2 treatment process.