Development and characterization of Polylactic acid-Polyhydroxybutyrate (PLA-PHB) blend impregnated with mango extracts for use as active film

Abstract

The study examined the impregnation of Polylactic acid-Polyhydroxybutyrate (PLA-PHB) (75:25 w/w) polymer films with mango leaf extracts (MLE) using solvent casting and a supercritical solvent impregnation process. The effects of pressure, temperature, and depressurization rate on the impregnation and release of bioactive compounds were evaluated. The impregnated and non-impregnated samples were analysed by Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM) to determine their impregnation load, antioxidant capacity, and compound release after 10 days. The FTIR analyses showed that the samples impregnated at 20 MPa exhibited a more intense peak compared to those impregnated at 10 and 30 MPa, indicating higher impregnation loads and antioxidant compound concentration. Thermal studies (TGA and DSC) demonstrated that impregnation did not significantly affect the thermal stability of the material. In X-rays patterns, the promotion of PHB crystallization on top of the amorphous PLA halo was observed at high depressurization rates. Furthermore, SEM images revealed changes in the surface morphology after impregnation. The highest impregnation load was obtained at 20 MPa, 35 °C, and 5 MPa/min (3.39 ± 0.03 mg MLE/100 mg PLA-PHB), while the concentration of antioxidant compounds (IAC) was highest at 20 MPa and 55 °C with slow depressurization (2.72 ± 0.02 mg IAC / 100 mg PLA-PHB). Gallic acid and iriflofenone 3-C-β-D-glucoside were the main released compounds.