Development of novel nano-biocomposite antioxidant films based on poly (lactic acid) and thymol for active packaging

• Thymol and D43B were added to PLA to get antioxidant nano-biocomposite films.
• A full characterization of all formulations was carried out.
• The presence of thymol in the films and its antioxidant activity were demonstrated.
• The addition of D43B improved oxygen barrier and mechanical properties of films.
• The film with thymol and 2.5 wt% of D43B was considered the best enhanced material.

Novel nano-biocomposite films based on poly (lactic acid) (PLA) were prepared by incorporating thymol, as the active additive, and modified montmorillonite (D43B) at two different concentrations. A complete thermal, structural, mechanical and functional characterization of all nano-biocomposites was carried out. Thermal stability was not significantly affected by the addition of thymol, but the incorporation of D43B improved mechanical properties and reduced the oxygen transmission rate by the formation of intercalated structures, as suggested by wide angle X-ray scattering patterns and transmission electron microscopy images. The addition of thymol decreased the PLA glass transition temperature, as the result of the polymer plasticization, and led to modification of the elastic modulus and elongation at break. Finally, the amount of thymol remaining in these formulations was determined by liquid chromatography (HPLC-UV) and the antioxidant activity by the DPPH spectroscopic method, suggesting that the formulated nano-biocomposites could be considered a promising antioxidant active packaging material.