Designing Soft and Transparent Films Based on Multi-Phase Polypropylene Copolymers and Styrene Block Copolymers

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomedical Engineering

Background:

• Plasticized poly (vinyl chloride) (PVC) faces scrutiny due to environmental and health concerns, including plasticizer loss and microplastic formation.
• A need exists for safer, alternative packaging materials in the medical and pharmaceutical sectors.
• Polyolefin-based materials offer potential as substitutes for PVC in sensitive applications.

Purpose of the Study:

• To investigate the potential of blending polypropylene-ethylene copolymers with styrene-ethylene/butylene-styrene block copolymer (SEBS) as an alternative to PVC.
• To evaluate the mechanical properties, flexibility, durability, and transparency of these novel blends for medical packaging.
• To determine the optimal SEBS content for achieving desired characteristics in different copolymer matrices.

Main Methods:

• Blending of polypropylene-ethylene copolymers (RAHECO, RACO, HECO) with varying ethylene content and SEBS.
• Injection molding of samples and casting of films for property evaluation.
• Characterization of mechanical properties (flexural modulus), toughness, and optical properties (transparency).
• Morphological analysis of film structures to understand phase behavior.

Main Results:

• Blends of SEBS with random-heterophasic (RAHECO) copolymers achieved desired flexibility (150-250 MPa flexural modulus) with lower SEBS content (15-25 wt.-%) compared to single-phase random copolymers (RACO) (37 wt.-%).
• RAHECO blends demonstrated superior toughness and excellent transparency.
• Standard impact copolymers (HECO) required higher SEBS content (45 wt.-%) due to their more crystalline matrix.
• Morphological studies revealed phase structure changes and potential phase inversion at high SEBS concentrations without compromising transparency.

Conclusions:

• Polyolefin-based blends, particularly those using RAHECO copolymers with SEBS, present a viable alternative to plasticized PVC for soft medical packaging.
• These materials offer a tunable balance of flexibility, toughness, and transparency essential for applications like infusion pouches and bottles.
• The study highlights the importance of copolymer structure and SEBS content in tailoring material performance for specific medical packaging requirements.