Lignin Reinforcement in Polybutylene Succinate Copolymers

This study investigated the valorization of industrial lignin for producing biodegradable polybutylene succinate (PBS)-lignin copolymers. PBS was blended with varying lignin contents (0-45 wt. %) and crosslinked/grafted using dicumyl peroxide (DCP). The preparation of the copolymers by reactive extrusion was successful, with mechanical, thermal, and morphological properties comprehensively analyzed. Lignin addition decreased tensile strength but improved stiffness (modulus) and thermal stability. Crosslinking with DCP improved the interfacial adhesion between PBS and lignin, resulting in better flexural performance at moderate lignin levels. Differential scanning calorimetry showed that lignin initially improved the crystallization temperature, but hindered it at higher concentrations due to its rigid, aromatic structure. Scanning electron microscopy analysis showed poor interfacial adhesion in PBS-lignin blends, but the surface morphology improved in crosslinked PBS-lignin copolymers, with less phase separation observed. An optimal lignin concentration appeared to depend on the property of interest. While 30% lignin provided the best improvement in flexural strength, 20% lignin offered a more balanced enhancement for most properties without the severe reduction in tensile strength observed at higher lignin contents.