Tuning ester derivatives of organosolv vs. technical lignin for improved thermoplastic materials

In this study, lignin from two different sources - organosolv pine and hydrolysis birch - were chemically modified through esterification of hydroxyl groups using octanoyl (C8), lauroyl (C12), and palmitoyl (C16) chlorides, as well as through chloromethylation followed by esterification with tetradecanoic acid (C14) and benzoic acid. Modification of lignin was confirmed by FTIR and NMR spectroscopy. The esterified lignin samples were loaded into polylactic acid (PLA) at loadings of 10%, 20%, and 30% using a solvent casting method. Thermal and mechanical properties of PLA/lignin composites revealed that esterification significantly affected the polymer matrix properties. PLA could sustain as much as 30% lignin ester loading without affecting the film integrity. Among the variations, hydrolysis lignin ester (HLE) and benzoic acid ester (BAEP) enhanced the heat stability of PLA, while esterification with palmitoyl chloride (OHLE_C16) increased its elasticity through plasticization.