Thermal, Mechanical and Rheological study of PBAT/PLA biocomposites reinforced with Agri-Food Industry Byproducts

This study explores the valorization of agri-food waste for valuable materials by investigating the thermal, mechanical and rheological behavior of the PBAT/PLA based biocomposites. Poly(butylene adipate-co terephthalate)/polylactic acid (PBAT/PLA) based biocomposites were prepared by incorporating 30 wt.% of four agri-food wastes—beer spent grain (BSG), coffee silverskin (CSS), mandarin pomace (MP), and olive pomace (OP). A comprehensive characterization was carried out including rheological (melt flow rate, mixing torque), thermal (TGA, DSC), and mechanical (tensile tests) properties, and surface characteristics (contact angle, roughness). Thermal analysis findings confirmed all fillers compatible with the processing temperature (160°C), with CSS and BSG exhibiting highest thermal stability. Rheological results revealed that OP and MP reduced melt viscosity and torque, enhancing flowability, while CSS and BSG increased melt resistance and viscoelastic moduli. Mechanical tensile testing demonstrated that CSS significantly enhanced stiffness (up to 259.7 Mpa, 2-4 times higher than neat PBAT/PLA), while OP preserved ductility. Although tensile strength and elongation at break were compromised , the values remain appreciable for "Reuse-Design-Applications". These findings demonstrate the potential of agri-food byproducts as effective fillers for bioplastics, supporting circular economy principles by transforming waste into value-added materials, and reducing reliance on fossil-based plastic pollution and promoting sustainable material innovation.