Coupling Nanofibril Lateral Size and Residual Lignin to Tailor the Properties of Lignocellulose Films

Abstract

Lignocellulosic nanofibrils (LCNF) are produced from a single source of unbleached, oxidized wood fibers by serial disintegration, high‐pressure microfluidization, and homogenization. Sequential centrifugation enables fractionation by fibril width (≈5, ≈9, and ≈18 nm). LCNF residual lignin of high molecular mass reports together with the finest fraction (LCNF‐fine), whereas the more strongly cellulose‐bound lignin, of relatively lower molecular mass, associates with the coarsest fraction (LCNF‐coarse). Hot pressing softens the amorphous lignin, which fills the interstices between fibrils and acts as an in‐built interfacial cross‐linker. Thus, going from the LCNF‐fine to the LCNF‐course films, it is possible to obtain a range of values for the structural consolidation (density from 0.9 to 1.2 g cm−3 and porosity from 19% to 40%), surface roughness (RMS from ≈6 to 13 nm), and strength (elastic modulus from 8 to ≈12 GPa). The concentration of free hydroxyl groups controls effectively the direct surface interactions with liquids. The apparent surface energy dispersive component tracks with the total surface free energy and appears to be strongly influenced by the higher porosity as the fibril lateral size increases. The results demonstrate the possibility to tailor nanofibril cross‐linking and associated optical and thermo‐mechanical performance of LCNF films.

Cellulose Nanofibers from a Dutch Elm Disease-Resistant Ulmus minor Clone

“…Regarding the influence of lignin content on the thermal stability of nanofibrillated cellulose, slightly higher T deg , T on and T off were found for CNF-UnBl-Elm compared to CNF-Bl-Elm. This slightly higher thermal stability could be attributed to the presence of aromatic groups, ether and carbon–carbon bonds from residual lignin, which usually decompose at a higher temperature range (250–600 °C) [ 37 ]. Nevertheless, the amount of residual lignin on unbleached samples was only 2.5%, explaining that only a slight increase in thermal stability was observed.…”

Mesoporous Carbon Microfibers for Electroactive Materials Derived from Lignocellulose Nanofibrils

“…On the other hand, lignocellulose fibrils can be further defibrillated into LCNF using variety of mechanical procedures such as grinding and refining. Several works have reported on the production of lignocellulose nanofibrils (LCNF) from lignin-containing cellulose fibrils (Rojo et al 2015;Imani et al 2019). Lee et al also demonstrated that LCNF with 13% lignin content can be directly wet-spun into fibres by using first tert-butanol and then acetone as coagulants (Park et al 2020).…”

Coupling Biocompatible Au Nanoclusters and Cellulose Nanofibrils to Prepare the Antibacterial Nanocomposite Films

“…All AuNCs@CNF films showed the decreased tensile strength and tensile strain of 43.2–54.1 MPa and 4.1–4.7%, respectively. Typically, the tensile properties of the cellulose film are related to single fibrils and interfibrillar bonding, which are linked to the chemical composition, aspect ratio, and the added ingredient ( Wang et al, 2018 ; Imani et al, 2019 ). Moreover, the CNF films consisted of AuNCs at the concentration of 0.05–0.1 mM had the lower Young’s modulus (4.7–2.1 GPa) than that of neat CNF film (5.9 GPa).…”

“…Moreover, the increased amount of AuNCs made the surface of the prepared films rather uneven, which could be attributed to the presence of the surface-active functional groups in the AuNCs particles that can be linked to nanofibrils in the CNF composites ( Bian et al, 2019 ). This can be explained that the AuNCs can cause the flocculation of nanofibrils and disrupt the interfibrillar hydrogen bonding during the dried process for AuNCs@CNF film forming, leading to the uneven surface of the prepared films ( Imani et al, 2019 ). In addition, AuNCs can facilitate to form a relatively compact structure of AuNCs@CNF films, which can be indicated by more compact and flat structures appeared in the AuNCs@CNF films with the increased amount of introduced AuNCs particles.…”