Direct utilization of cassava flour in biodegradable films: The compatibilizing effect of cassava protein on poly (butylene adipate-co-terephthalate) and cassava starch.

Cassava starch, as a high-yield biological macromolecule, is widely used with poly (butylene adipate-co-terephthalate) (PBAT) to fabricate biodegradable composite films. The performance of composite films critically depends on the compatibility between starch and PBAT. While cassava starch is traditionally obtained by purifying cassava flour to remove crude protein and other impurities, this study reveals that the crude protein in unprocessed cassava flour enhances the compatibility between cassava starch and PBAT. This finding demonstrates that cassava flour can be directly used to prepare composite films without requiring purification into starch. Through detailed characterization, it was found that the protein acts as a plasticizer, strengthening interfacial interactions between cassava starch and PBAT. More hydrogen bonding sites and a stronger network structure were formed when the cassava flour was directly utilized, promoting a more homogeneous composite structure. Thereby the composite films prepared with raw cassava flour exhibit superior tensile strength (21.61 MPa) and water vapor permeability (1.59 × 10 g·cm/cm·s·pa) compared to those made with purified cassava starch. This study establishes a theoretical foundation for the strategy of utilizing cassava flour directly as a raw material for starch-based composites offering an efficient, cost-effective, and sustainable approach for the preparation of biomass-based biodegradable composite films.