Efficient downstream valorization of lignocellulose after organosolv fractionation: Synergistic enhancement of waterborne coatings by co-assembled lignin@cellulose nanocrystals

Lignin: An Adaptable Biodegradable Polymer Used in Different Formulation Processes

INTRODUCTION

LIG is a biopolymer found in vascular plant cell walls that is created by networks of hydroxylated and methoxylated phenylpropane that are randomly crosslinked. Plant cell walls contain LIG, a biopolymer with significant potential for usage in modern industrial and pharmaceutical applications. It is a renewable raw resource. The plant is mechanically protected by this substance, which may increase its durability. Because it has antibacterial and antioxidant qualities, LIG also shields plants from biological and chemical challenges from the outside world. Researchers have done a great deal of work to create new materials and substances based on LIG. Numerous applications, including those involving antibacterial agents, antioxidant additives, UV protection agents, hydrogel-forming molecules, nanoparticles, and solid dosage forms, have been made with this biopolymer.

METHODS

For this review, a consistent literature screening using the Pubmed database from 2019-2024 has been performed.

RESULTS

The results showed that there is an increase in interest in lignin as an adaptable biomolecule. The most recent studies are focused on the biosynthesis and antimicrobial properties of lignin-derived molecules. Also, the use of lignin in conjunction with nanostructures is actively explored.

CONCLUSIONS

Overall, lignin is a versatile molecule with multiple uses in industry and medical science.

Micronized Shell-Bioaggregates as Mechanical Reinforcement in Organic Coatings

Shells are primarily composed of calcite and aragonite, making the inclusion of micronized shells as bio-based fillers in organic coatings a potential means to enhance the mechanical properties of the layers. A water-based coating was reinforced with 5 wt.% Acanthocardia tuberculata powder, 5 wt.% Mytilus galloprovincialis powder, and 5 wt.% of an LDPE/ceramic/nanoceramic composite. An improvement in abrasion resistance was achieved using micronized seashells, as demonstrated by the Taber test (evaluating both weight loss and thickness reduction). Additionally, Buchholz hardness improved with powders derived from Mytilus galloprovincialis. No significant differences were observed among the samples in terms of color and gloss after 200 h of UV-B exposure. However, the delamination length from the scratch after 168 h of exposure in a salt spray chamber indicated that the addition of particles to the polymeric matrix resulted in premature degradation, likely due to the formation of preferential paths for water penetration from the scratch. This hypothesis was supported by electrochemical impedance spectroscopy measurements, which revealed a decrease in total impedance at 0.01 Hz shortly after immersion in a 3.5% NaCl solution. In conclusion, the particle size and shape of the micronized shells improved abrasion resistance without altering color and gloss but led to a decrease in the coating's isolation properties.

Preparation of uniform lignin/titanium dioxide nanoparticles by confined assembly: A multifunctional nanofiller for a waterborne polyurethane wood coating

We report a facile synthesis for lignin/titanium dioxide (TiO2) nanoparticles (LT NPs) at room temperature by confining assembly of lignin macromolecules. The LT NPs had a uniform nanosize distribution (average diameter ∼ 68 nm) and were directly employed as multifunctional nanofillers to reinforce a waterborne polyurethane wood coating (WBC). X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy revealed the mechanism by which formed TiO2 confined lignin assembly. The LT NPs considerably increased the tensile strength of a WBC film from 16.3 MPa to 28.1 MPa. The WBC-LT NPs exhibited excellent ultraviolet (UV) A and UVB blocking performances of 87 % and 98 %, respectively, while maintaining 94 % transmittance in the visible region. Incorporating LT NPs into the WBC enhanced the coating performance (the hardness, adhesion, and abrasion resistance) on wood substrates. A quantitative color and texture analysis revealed that the LT NPs increased the decorativeness of actual wooden products. After nearly 1800 h of UV irradiation, wood coated with the WBC-LT NPs exhibited good color stability, where the original color remained unchanged or even became brighter. In this study, value-added valorization of lignin is enabled by using organic-inorganic nanofillers and insights are gained into developing multifunctional WBCs.

Efficient extraction of nanocellulose from lignocellulose using aqueous butanediol fractionation to improve the performance of waterborne wood coating

The highly efficient extraction of cellulose from lignocellulose with an excellent yield of 95.2 % and purity of 96.7 % was demonstrated using acid-catalyzed fractionation with aqueous butanediol. This cellulose was subsequently transformed into cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs) with specific dimensions and surface functional groups through various chemomechanical treatments. The average diameters of CNFs and CNCs produced by sulfuric acid hydrolysis-ultrasonication and deep eutectic solvent treatment-ultrasonication (DES-CNCs) were 29.7, 21.9 and 17.3 nm, respectively. The DES-CNCs were obtained in a good yield of 71 ± 1.27 wt% and exhibited a high zeta potential of -33.5 ± 2.51 mV following posthydrolysis and esterification during the DES treatment. These CNFs and CNCs were used as nanofillers in a waterborne wood coating (WWC), which significantly improved its dynamic viscosity and storage modulus. The addition of these materials also enhanced the mechanical strength of the WWC but had little effect on transmittance. Glossiness, hardness, abrasion resistance and adhesion strength were evaluated, and the DES-CNCs provided the greatest improvements at a low concentration. A plausible reinforcement mechanism was presented. This work provided an efficient cellulose extraction method and detailed structure elucidation of the nanocellulose together with suggestions for value-added applications of cellulosic nanofillers for reinforcing WWC.