Supercritical CO2-assisted impregnation of polylactic acid films with R-carvone: Effect of processing on loading, mass transfer kinetics, and final properties

Abstract

In this work, the scCO2-assisted impregnation of polylactic acid films with R-(-)-carvone was investigated, as a route to develop an active packaging material. The effect of three process variables (CO2 density: 278 and 683 kg m-3, temperature: 40 and 60 °C, and depressurization rate: 0.6 and 6.0 MPa min-1) on loading and release kinetics of the impregnated films was investigated. ANOVA testing suggested that loading was enhanced by temperature, but decreased with CO2 density and depressurization rate, obtaining values between 6.7 and 29.8 wt%. Processing conditions also showed a significant effect on release kinetics to air, obtaining a range of diffusivity values of 10-15-10-14 m2 s-1. Final properties of the films, such as thermal, mechanical, and UV-Vis transmittance properties, were also assessed. Finally, the impregnation kinetics of carvone in scCO2-swollen films was studied at the highest loading conditions, estimating a diffusion coefficient of 1.9 × 10-11 m2 s-1.