Wet-Spun Composite Filaments from Lignocellulose Nanofibrils/Alginate and Their Physico-Mechanical Properties

Lignocellulose nanofibrils (LCNFs) with different lignin contents were prepared using choline chloride (ChCl)/lactic acid (LA), deep eutectic solvent (DES) pretreatment, and subsequent mechanical defibrillation. The LCNFs had a diameter of 15.3–18.2 nm, which was similar to the diameter of commercial pure cellulose nanofibrils (PCNFs). The LCNFs and PCNFs were wet-spun in CaCl2 solution for filament fabrication. The addition of sodium alginate (AL) significantly improved the wet-spinnability of the LCNFs. As the AL content increased, the average diameter of the composite filaments increased, and the orientation index decreased. The increase in AL content improved the wet-spinnability of CNFs but deteriorated the tensile properties. The increase in the spinning rate resulted in an increase in the orientation index, which improved the tensile strength and elastic modulus.

Assessment of Bleached and Unbleached Nanofibers from Pistachio Shells for Nanopaper Making

Cellulose and lignocellulose nanofibrils were extracted from pistachio shells utilizing environmentally friendly pulping and totally chlorine-free bleaching. The extracted nanofibers were used to elaborate nanopaper, a continuous film made by gravimetric entanglement of the nanofibers and hot-pressed to enhance intramolecular bonding. The elaborated nanopapers were analyzed through their mechanical, optical, and surface properties to evaluate the influence of non-cellulosic macromolecules on the final properties of the nanopaper. Results have shown that the presence of lignin augmented the viscoelastic properties of the nanopapers by ≈25% compared with fully bleached nanopaper; moreover, the hydrophobicity of the lignocellulose nanopaper was achieved, as the surface free energy was diminished from 62.65 to 32.45 mNm−1 with an almost non-polar component and a water contact angle of 93.52°. On the other hand, the presence of lignin had an apparent visual effect on the color of the nanopapers, with a ΔE of 51.33 and a ΔL of −44.91, meaning a substantial darkening of the film. However, in terms of ultraviolet transmittance, the presence of lignin resulted in a practically nonexistent transmission in the UV spectra, with low transmittance in the visible wavelengths. In general, the presence of lignin resulted in the enhancement of selected properties which are desirable for packaging materials, which makes pistachio shell nano-lignocellulose an attractive option for this field.

Study of LCNF and CNF from pine and eucalyptus pulps

Nanocelluloses produced from wood pulp are widely studied for various economic applications. Most studies of cellulose nanofibrils (CNF) use lignin-free fibres obtained from bleached pulps; however, unbleached fibres with residual lignin may also be used to obtain lignocelluloses nanofibrils (LCNF). Research on lignocellulose nanofibrils is a recent subject in the field; thus, the aim of the present study was to determine the ultrastructure of lignocellulose nanofibrils compared to cellulose nanofibrils produced from the same raw material. Understanding of nanoparticle properties is of great relevance for their various applications; therefore, complete characterisation of the chemical, physical, and morphological structures of LCNF and CNF produced from pine and eucalyptus woods was performed. Unbleached cellulosic fibres are a viable alternative for LCNF production, which has properties comparable to that of traditional CNF production that uses lignin-free fibres. LCNF from pine and eucalyptus were obtained with 4.0 % and 1.8 % residual lignin, respectively. The nanofibrils had high thermal stability because LCNF had a higher maximum degradation temperature. Due to the low interaction of lignin with water, LCNF had a lower water retention value than CNF.

Changes in the Dimensions of Lignocellulose Nanofibrils with Different Lignin Contents by Enzymatic Hydrolysis

Changes in the dimensions of lignocellulose nanofibrils (LCNFs) with different lignin contents from betung bamboo (Dendrocalamus asper) by enzymatic hydrolysis using endoglucanase (EG) were investigated. Lignin contents were adjusted from 3% to 27% by NaClO2/acetic acid treatment, and LCNFs were prepared using a wet disk-mill (WDM). The dimensions of the LCNFs significantly decreased with decreasing lignin content and increasing EG addition. With increasing EG content, the average diameter of the LCNFs significantly decreased, even though they contained parts of hemicellulose and lignin. The crystal structure showed the typical cellulose I structure in all samples, but the intensity of the diffraction peak slightly changed depending on the lignin and EG contents. The crystallinity index (CrI) values of the LCNFs increased a maximum of 23.8% (LCNF-L27) under increasing EG addition, regardless of the lignin content. With the EG addition of three times the LCNF amount, LCNF-L3 showed the highest CrI value (59.1%). By controlling the composition and structure of LCNFs, it is expected that the wide range of properties of these materials can extend the property range available for existing materials.