Fecha de publicación: 19/12/2024 Fuente: Polymers Polymers, Vol. 16, Pages 3542: Lignin Particle Size Affects the Properties of PLA Composites Prepared by In Situ Ring-Opening Polymerization
Polymers doi: 10.3390/polym16243542
Authors:
Sofia P. Makri
Eleftheria Xanthopoulou
Panagiotis A. Klonos
Alexios Grigoropoulos
Apostolos Kyritsis
Ioanna Deligkiozi
Alexandros Zoikis-Karathanasis
Nikolaos Nikolaidis
Dimitrios Bikiaris
Zoi Terzopoulou

The present work focuses on the synthesis and characterization of biobased lignin-poly(lactic) acid (PLA) composites. Organosolv lignin, extracted from beechwood, was used as a filler at 0.5, 1.0, and 2.5 wt% loadings, with ultrasonication reducing the lignin particle size to ~700 nm. The PLA–lignin composites were prepared via in situ ring-opening polymerization (ROP) of L-lactide in the presence of lignin. This method ensured uniform lignin dispersion in the PLA matrix due to grafting of PLA chains onto lignin particles, preventing aggregation. Strong polymer–filler interactions were confirmed through spectroscopic analysis (FTIR and XPS) and their effects on static and dynamic glass transitions (DSC). These interactions enhanced mechanical properties, including a two-fold increase in tensile strength and elongation at 1 wt% lignin. Crystallization was suppressed due to shorter PLA chains, and a 15% drop in dynamical fragility was observed via Broadband Dielectric Spectroscopy (BDS). Antioxidant activity improved significantly, with PLA–2.5% ultrasonicated organosolv lignin reducing DPPH• content to 7% after 8 h, while UV-blocking capability increased with lignin content.