1. Effect of micro- and nano-lignin on the thermal, mechanical, and antioxidant properties of biobased PLA–lignin composite filmsSofia P. Makri, Eleftheria Xanthopoulou, Panagiotis A. Klonos, Alexios Grigoropoulos, Apostolos Kyritsis, Konstantinos Tsachouridis, Antonios Anastasiou, Ioanna Deligkiozi, Nikolaos P. Nikolaidis, Dimitrios Bikiaris, 2022, izvirni znanstveni članek Opis: Bio-based poly(lactic acid) (PLA) composite films were produced using unmodified soda
micro- or nano-lignin as a green filler at four different contents, between 0.5 wt% and 5 wt%. The PLA–
lignin composite polymers were synthesized by solvent casting to prepare a masterbatch, followed by
melt mixing. The composites were then converted into films, to evaluate the effect of lignin content
and size on their physicochemical and mechanical properties. Differential scanning calorimetry
(DSC), supported by polarized light microscopy (PLM), infrared spectroscopy (FTIR-ATR), X-ray
diffraction (XRD), and transmission electron microscopy (TEM) were employed to investigate the
PLA crystallization and the interactions with Lignin (L) and Nanolignin (NL). The presence of
both fillers (L and NL) had a negligible effect on the glass transition temperature (chain diffusion).
However, it resulted in suppression of the corresponding change in heat capacity. This was indicative
of a partial immobilization of the PLA chains on the lignin entities, due to interfacial interactions,
which was slightly stronger in the case of NL. Lignin was also found to facilitate crystallization, in
terms of nucleation; whereas, this was not clear in the crystalline fraction. The addition of L and
NL led to systematically larger crystallites compared with neat PLA, which, combined with the
higher melting temperature, provided indications of a denser crystal structure in the composites. The
mechanical, optical, antioxidant, and surface properties of the composite films were also investigated.
The tensile strength and Young’s modulus were improved by the addition of L and especially NL.
The UV-blocking and antioxidant properties of the composite films were also enhanced, especially
at higher filler contents. Importantly, the PLA–NL composite films constantly outperformed their
PLA–L counterparts, due to the finer dispersion of NL in the PLA matrix, as verified by the TEM
micrographs. These results suggest that bio-based and biodegradable PLA films filled with L, and
particularly NL, can be employed as competitive and green alternatives in the food packaging
industry.
Ključne besede: poly(lactic acid), PLA, lignin, nanolignin, composite films, nucleation, mechanical properties, antioxidant activity, food packaging
Objavljeno v DKUM: 26.03.2025; Ogledov: 0; Prenosov: 1
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