Development of PLA-based bio-composites for sustainable packaging applications

The growing environmental concerns surrounding conventional plastics, especially in food packaging, have heightened the need for alternative materials. Polylactic acid (PLA) offers a greener alternative due to its biodegradability; however, its use is limited by its brittleness, lack of flexibility, and relatively high production costs. To address these issues, biobased composites were prepared by mixing PLA with hay and the bioplasticizer named glycerol trilevulinate (GT). The first part of the study was conducted at the University of Bologna and involved optimizing the synthesis of GT starting from levulinic acid and glycerol. Specifically, by increasing the catalyst amount from 1 to 5%, the yield moved from 68 to 80%. Subsequently, different formulations containing 20 wt.% of hay and increasing GT amount (from 5 to 12.5wt.%) were prepared at the University of Parma using extrusion and injection molding techniques to fabricate biocomposite materials. Thermal analysis performed on dumbbell specimens demonstrated that GT effectively acts as a plasticizer by decreasing the glass transition temperature with a reduction of 23°C observed at 5% GT concentration. Negligible effects were observed on the melting temperature and crystallinity when GT was added with respect to hay alone. Tensile tests suggested that hay made the material stiffer and more brittle, while the addition of GT counterbalanced these effects. Specifically, at 12.5 wt.% GT reduced the Young’s modulus by almost one third (from 3166 to 1302 MPa) and increased the elongation at break from 1.7 to 23%. The obtained biocomposite materials demonstrate the potential for tailoring the mechanical properties of PLA-based materials by optimizing the balance between reinforcement (hay) and plasticization (GT) for the obtainment of sustainable materials suitable for packaging applications but also agriculture and consumer goods, supporting the transition from fossil-based to biobased plastics.