Enhanced Interfacial Compatibility and Properties of PBAT /Lotus Root Starch Composites With Polyurethane Prepolymers

ABSTRACT This study innovatively used the abundant Lotus root starch (LRS) as a biomass filler and blended it with biodegradable and environmentally friendly Poly (1,4‐butylene adipate) (PBAT) to prepare PBAT/LRS composite materials, while addressing a critical challenge in developing bio‐based polymer composites: the poor interfacial compatibility between hydrophilic natural fillers and hydrophobic biodegradable polyesters. Two types of polyurethane prepolymers (PUP), namely poly(caprolactone)‐based polyurethane prepolymer (PCLPU) and Poly (1,4‐butylene adipate)‐based polyurethane prepolymer (PBAPU), were synthesized and incorporated into the composites at loadings of 0 wt%–15 wt%. The results demonstrate that PBAPU significantly enhances the toughness of the composites, increasing the elongation at break from 14.6% to 245.0% and the impact strength from 4.92 to 12.80 kJ/m 2 , while maintaining tensile strength. SEM analysis and mechanical tests confirm improved interfacial compatibility, attributed to chemical crosslinking and physical entanglement between PUP and the matrix. Furthermore, the hydrophobicity and water resistance of the composites were markedly improved with PUP addition. This work provides an effective strategy for developing high‐performance, fully bio‐based composites with potential applications in sustainable packaging and agricultural materials.