Investigation into lignin modified PBAT/thermoplastic starch composites: Thermal, mechanical, rheological and water absorption properties

This study prepared ternary composites PBAT/thermoplastic starch (TPS)/lignin containing 20, 30 and 40 wt% of TPS/lignin fillers via thermal compounding, and found that lignin imposes compatibilization effect on PBAT and TPS. Thermal analysis shows that the incorporation of lignin results in higher thermal stability, reduced crystallization temperatures, broader crystallization exotherms and increased T_g due to the rigid aromatic structure of lignin. Tensile tests exhibit that strain at break and tensile strength reaches a maximum at loading 10 wt% of lignin. The reinforcement of lignin is reflected as the enhanced elastic modulus, Shore-D hardness, and more prominent yielding behavior of the composites. Rheological and microscope measurements show that the incorporation of lignin leads to higher approximation to theoretical Han curve, and reduced TPS particle size in the composites, indicating that lignin improves the interfacial compatibility between the PBAT and TPS phases. Contact angle and water absorption results demonstrate that lignin improves the hydrophobicity and water repelling ability of the composites, which are favorable for products with prolonged mechanical properties and shelf life.