Preparation and Characterization of PLLA-Based Microporous Membranes with High CO₂/O₂ Selective Permeability for Food Packaging

To maintain CO₂/O₂ permselectivity of poly(lactic acid) (PLLA) microporous films for better preservation of fresh produce, Polytrifluoropropylmethylsiloxane (PTFPMS) was introduced into PLLA to prepare PLLA-PTFPMS-PLLA (PLTL) block copolymer. And PLTL-n% microporous films were prepared using varying ratios of chloroform/acetone blended solvents as the film-casting solution in this study. PTFPMS filled a portion of the micropores of the PLTL-n% film. While the micropores enhanced the O₂ and CO₂ dioxide permeability of the PLLA microporous film, PTFPMS maintained the CO₂/O₂ selective permeability of the film. In comparison to PLLA films, the CO₂ permeability of mixed solvents-treated PLTL-20% film increased from 1.99 × 10^–8 to 10.08 × 10^–8 cm³ m/m² h Pa, O₂ permeability increased from 0.70 × 10^–8 to 2.02 × 10^–8 cm³ m/m² h Pa, and CO₂/O₂ permselectivity increased from 2.9 to 5.0 at 5°C. In addition, PLTL-n% microporous films also have good flexibility and UV shielding properties.