Pilot-scale supercritical CO₂ impregnation for functionalization of biodegradable PLA/PBAT/TPS films

Abstract

Supercritical fluid impregnation (SFI) is well-documented at lab-scale; however, applications at pilot-scale remain scarce. This study aims to address the gap by investigating the pilot-scale impregnation of biodegradable polylactic acid/poly(butylene adipate-co-terephthalate)/thermoplastic starch (PLA/PBAT/TPS) films using olive leaf extract. The extract of Olea europaea L. leaves was obtained using enhanced solvent extraction. It is a source of pigments and polyphenols, with a concentration of 115 ± 2 mg ml−1 and an EC50 of 33 ± 3 μg ml−1. The SFI of PLA/PBAT/TPS films was optimized at lab scale, being 250 bar and 35 °C, the optimal conditions. Under these conditions, SFI was scaled 4-fold, and the effects of extract volume, film surface area, and contact time were evaluated. The quality of the films was assessed based on impregnation homogeneity, extract loading, chemical composition and antioxidant activity against 2,2 ´ -azinobis(3-ethylbenzothiazoline-6-sulfonic) (ABTS). The films impregnated at pilot scale showed optimal results using 30 ml of extract, a 1360 cm2 film, and 1 h of contact time, achieving an extract loading (1.41 ± 0.08 mg cm−2) and antioxidant activity (52 ± 4 %) comparable to those at lab scale. The results confirmed the successful impregnation of polyphenols and suggested interactions between extract compounds and polymer carbonyl groups. Chlorophylls aided the assessment of impregnation homogeneity, a critical factor for product quality, which proved to be consistent throughout the film as the scale was increased. These findings confirm the technical feasibility of SFI at pilot scale and support its potential for sustainable production of bioactive packaging materials.