Supercritical CO2 processing of polylactic acid films: Effect of process variables and the incorporation of R-carvone on crystalline, thermal, and mechanical properties

Abstract

In this contribution, a systematic investigation of the effect of the supercritical processing and the incorporation of R-(–)-carvone on the mechanical, thermal, and crystallinity properties of polylactic acid films at different temperature (40-60 °C), CO2 density (278-683 kg m-3) and depressurization rate (0.6-6.0 MPa min-1) conditions was performed. scCO2-induced crystallization was observed, up to ~32%, and different crystal morphologies were obtained depending on the process variables, affecting the mechanical behavior. Statistical analysis showed that temperature-CO2 density interaction was the main factor affecting the crystalline morphology and the mechanical properties, specially the elastic modulus and the elongation. Final properties also depended strongly on the carvone loading, suggesting the occurrence of phase separation above ~10 wt%. The results obtained here provide useful information for a deeper knowledge of the individual effect of the main process variables and the amount of additive loaded into the polymer matrix on the film final behavior.