A fully CO ₂ -derived high-barrier biodegradable film via melt blending of PPC-X with a CO ₂ -based polyurethane plasticizer

This work develops a structurally CO 2 -derived, high-performance biodegradable packaging material by melt-blending poly (propylene carbonate phthalate-ran-cyclohexene carbonate phthalate) (PPC-X) with a CO 2 -based polyurethane (PPC-PU) as an effective plasticizer. The resulting composites exhibit a dramatic plasticizing effect: elongation at break increases from 3.52% (neat PPC-X) to 47.84% at 20 wt% PPC-PU while maintaining a tensile strength of 22.84 MPa and increases to 168.71% at 30 wt%. DMA, DSC, and SEM analyses confirm excellent miscibility and a homogeneous morphology, with the mechanism attributed to synergistic plasticization, hydrogen bonding, and dipole interactions. The optimized composite (20 wt% PPC-PU) also shows superior barrier properties, with permeability coefficients of 0.54 cm 3 ·mm/(m 2 ·day·atm) for CO 2 , 1.41 cm 3 ·mm/(m 2 ·day·atm) for O 2 , and 3.70 × 10 -4 g·mm/(m 2 ·day) for water vapor, outperforming commercial biodegradable (e.g., PLA/PBS/PBAT) and petroleum-based (e.g., PET) films. The material retains its inherent biodegradability and exhibits improved thermal stability (ΔT d1max ≈ +10°C) with minimal Tg change (ΔTg <4°C). This study establishes a sustainable strategy to create tough, high-barrier PPC-X-based packaging films, addressing a critical need for petrochemical-free alternatives.