Development and multifunctional characterization of poly(butylene adipate-co-terephthalate) (PBAT) based bio-composites reinforced with natural fillers: a comprehensive review

Poly(butylene adipate-co-terephthalate) (PBAT) is a synthetic biodegradable polyester with high ductility and excellent film-forming ability, but its relatively low stiffness, limited thermal resistance, and higher cost restrict broader applications. Reinforcement with natural, agro-waste-derived fillers offers a promising strategy to enhance PBAT performance while supporting sustainability and circular bioeconomy principles. This review provides a comprehensive and critical overview of recent advances in PBAT bio-composites reinforced with lignocellulosic fibers, biochar, lignin, microcrystalline cellulose, and other agro-residues. Particular emphasis is placed on filler selection, surface treatment, matrix modification, reactive compatibilization, and chain extension. The review critically compares conflicting findings and identifies the roles of filler dispersion, interfacial chemistry, PBAT grade/MFI, matrix rheology, filler morphology, processing route, and processing history in determining composite performance. Common fabrication routes, including melt compounding, injection molding, cast film extrusion, and blown film extrusion, are discussed in terms of processing, scalability, and industrial relevance. Multifunctional characterization covering mechanical, rheological, thermal, morphological, physical, and chemical properties is systematically reviewed, highlighting the coupled effects of filler dispersion, interfacial adhesion, and polymer rheology. Natural fillers are also examined as nucleating agents, rheology modifiers, and functional additives. Findings from the life cycle assessment demonstrate that environmental benefits depend on feedstock origin, filler-processing requirements, PBAT reduction, processing energy, and end-of-life pathways rather than filler content alone. Key challenges, design strategies, and future research directions are identified for developing high-performance, sustainable PBAT bio-composites for large-scale industrial adoption.