Cellulose最新文献

Over the last years, the potential of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) as fillers in polymers for mechanical reinforcement and extending the operation lifespan of materials is highlighted. Here, we investigate the inclusion of CNCs and CNFs with two distinct functional groups (TEMPO-oxidized, or solely having hydroxyl groups) as nanofillers into cellulose acetate films. Solution blow spinning has been utilized as a novel approach to fabricate composite materials from renewable carbon feedstocks, and the resulting structural, morphological and mechanical properties were evaluated. A maximum concentration of 5 wt% was found for CNCs while this was lower for CNFs, 2.5 wt%, to achieve uninterrupted processing of composite materials via SBS. All-cellulose composites showed differences in morphological features depending on the nanofiller type. Interestingly, a low loading of CNCs (1.5 wt%) increases the strength at break by 30%, while the inclusion of CNFs in a same amount deteriorates the mechanical properties. However, further increase to 2.5 wt% CNFs provides enhanced tensile strength and elastic modulus values. The largest improvements in elongation at break and strength at break is achieved with the inclusion of 2.5 wt% TEMPO-oxidized cellulose nanofibrils. Microscopic analysis after fracture reveals coral-like structured films, providing a unique mechanical behavior. Overall, the results point out that TEMPO-oxidized CNFs are efficient reinforcements to fabricate renewable carbon-containing composite materials with improved mechanical performance. The proposed SBS processing offers a unique advantage in the fabrication of highly flexible cellulose-based films, eliminating the need for plasticizers or additional additives.

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With the escalating prevalence of electromagnetic radiation pollution, flexible electromagnetic interference (EMI) shielding materials hold immense potential for widespread application. Carbonized fabric possesses notable advantages such as flexibility, excellent electrical conductivity, and chemical stability. However, its traditional preparation process is characterized by high energy consumption, intricate atmospheric conditions, and prolonged duration. This study introduces a novel approach of incorporating intumescent flame retardant (IFR) into cotton fabric, aiming to facilitate rapid carbonization in an air atmosphere. Remarkably, this innovative approach yields an outstanding total EMI shielding effectiveness (SE_T) of 17.55 dB within a mere 5 min carbonization process at 900 °C under ambient air conditions. Moreover, in order to enhance the shielding effect, we conducted in-situ growth of polypyrrole (PPy) on the prepared carbonized fabric. The deposition time of 120 min resulted in an impressive SE_T value of 28.22 dB, effectively providing a shielding capability of up to 99.9% against electromagnetic waves (EMW). Moreover, the SE_T value of IFR-C-PPy-60 min can be enhanced to 51.84 dB by stacking 4 layers, enabling the attenuation of 99.999% of EMW. The IFR-C-PPy also demonstrated exceptional fire safety and thermal stability. This study presents a novel approach for the rapid and large-scale fabrication of highly efficient conductive carbonized fabric, which demonstrates potential applications in flexible electronic devices.

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A lot of attention has been paid to cellulose nanocrystals (CNCs) due to their wide availability with a great potential to replace synthetic materials. The formation of CNCs from agricultural waste has numerous positive economic and environmental consequences. Cellulose nanocrystals were synthesized from pineapple leaf by acid hydrolysis and characterized by FT-IR, XRD, SEM, TEM, etc. Different concentrations of cellulose nanocrystals (1%, 3%, and 5% w/w) reinforced gelatin-based bio-nano composite was coated on tissue paper. The optimized fibrogenic solution was infused with three different plant leaf extracts (Banana leaf extract, Mantharai leaf extract, and Lotus leaf extract) used as an antimicrobial agent for hygienic tissue paper. Thickness, grammage, and bulk density analysis show the efficiency of the coating formation. The coated tissue paper shows increased mechanical properties and air permeability but significantly reduced water vapour permeability. Antimicrobial efficacy showed improved activity against Gram-positive bacteria Staphylococcus aureus (ATCC-2913), Gram-negative bacteria Escherichia coli (ATCC-27853), and fungi Candida glabrata (NCYC 388). These results reveal the potential of cellulose materials to serve as accessible platforms for anti-infective or self-sterilizing materials against both bacteria and fungi.

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Cellulosic fiber from rice straw provides a sustainable alternative to the environmental menace of the field burning problem. Response surface methodology and artificial neural network were applied in the organosolv pulping process to evaluate the responses of total pulp yield (TPY, %), holocellulose content (HC, %), and Klason lignin (KL, %). The optimum input parameters for these reactions were solvent ratio (formic acid: acetone 8:2), chemical doses (68%), time (269 min), and temperature (106 °C) with a response value of TPY (49.8%), HC (80.35%) and KL (3.85%). Artificial neural networks showed better-optimized results as compared to the response surface methodology. An exceptional fiber separation was observed using SEM analysis, while FT-IR analysis confirmed the significant removal of lignin as per drastic reduction in the absorption band at around 1505 cm⁻¹. The cellulose maximization and lignin reduction in the optimized pulp were also confirmed using EDX, XRD, and TGA analysis. Further, the effects of the addition of cationic starch, carboxymethyl cellulose, and xanthan gum were studied for making fiber composite hand sheets. The surface properties were optimum at the bio-additive doses of 3% (oven-dried) in both cases. However, the strength properties reached the maximum with the addition of 2% bio-additives. Nevertheless, cationic starch showed more suitable bio-additive for hand sheet packaging papers with better surface and strength properties. This study determined the optimum organosolv process parameters at the lab scale and further confirmed the suitability of the developed material for packaging applications with improved strength, surface, and optical properties.

The aim of the work was to compare the water retention and moisture sorption of viscose (CV) and cotton (Co) fibers carboxymethylated from aqueous media, in presence of NaOH, with sodium monochloroacetate. It was shown previously that under the same treatment conditions, the degree of carboxymethylation was higher in CV and so was the depth within fiber structures to which the carboxymethylation reactions occurred. It was also shown previously, that in terms of their capacity for sorption of a cationic dye (methylene blue), the Co performed better than CV. In this work, the same fibers were tested for their water retention and moisture sorption propensities. The two were sensitive both to the degree of carboxymethylation and the inherent properties of fibers (accessibility, degree of swelling, hornification). But the moisture sorption levels were less sensitive to the degree of carboxymethylation and more to inherent fiber properties whereas the reverse was observed for water retention. In contrast to the prior observations with dye sorption, CV performed better than Co in both moisture sorption and water retention. The poor performance of CV in dye sorption was attributed to the greater depth of carboxymethylation within the fibers that hindered dye permeation, but the same feature was observed to result in better performance (water retention) or not to hinder performance (moisture sorption). These observations highlight the contrasting effects that may arise, of a given set of treatment parameters (fiber type, alkali level in treatment), on efficacy of the product performance.

While cationic cellulose has yet to find a place in the paper industry, manufacturers show certain interest in a more recent material: cellulose nanofibers (CNFs), generally with negative surface charge. This work suggests both to be combined to increase the mechanical properties of recycled paper while preventing the use of synthetic polyelectrolytes as retention agents. On one hand, a bleached pulp was cationized by etherification, both as-is and following mechanical refining (15,000 PFI revolutions) and submitted to high-pressure homogenization, generating two different kinds of cationic CNFs. On the other, the same pulp was submitted to an enzymatic pretreatment and high-pressure homogenization, producing a negatively charged cellulose micro/nanofiber (CMNF). Two different cellulose-based systems consisting of each type of cationic CNF and the enzymatic CMNF were applied in the papermaking of both virgin and recycled paper. This study demonstrates the effective use of the cationic CNFs as retention agents during sheet formation, which together with the enzymatic CMNFs significantly enhanced the mechanical properties of both types of paper. The study found that refining before cationization favored the retention effect, primarily due to increased surface area and charge of the cationic CNFs, where remarkable increases in the breaking length of virgin (125.1%) and recycled paper (46.5%) were reached. The synergy between cationic CNFs and enzymatic CMNFs outperformed the use of commercial polyacrylamide, a non-biodegradable polyelectrolyte. This research highlights the potential of tailored CNFs in producing high-performance papers, while promoting sustainability and offering a plausible strategy to increase paper recycling rates.

Cellulose is an attractive biomolecule that exhibits irreversible intermolecular interactions and forms assemblies with high stability and robustness. Nevertheless, its tendency to irregularly aggregate prevents the polysaccharide chains from assembling into a fine structure. Herein, we demonstrate the formation of gels with relatively homogeneous structures via the self-assembly of cello-oligosaccharides modulated by organic solvent additives or elevated temperatures. Cello-oligosaccharides in a dissolved state in an aqueous alkaline solution started to self-assemble upon the addition of an acid for neutralization at room temperature, forming hydrogels with heterogeneity at the sub-micrometer or larger scale. On the other hand, cello-oligosaccharide assembly in the presence of 20% (v/v) water-miscible organic solvents produced approximately ten times stiffer gels with more homogeneous structures. The highest Young's modulus of the gels in this study was ~ 1.5 kPa. Moreover, increasing the assembly temperature from 25 °C to 50 °C also increased the gel stiffness. It was suggested that organic solvent additives and elevated temperatures decreased the solubility of cello-oligosaccharides and thus increased the assembly kinetics for the formation of more homogeneous network structures before non-organized aggregation. These findings promote the development of self-assembled cellulose and cello-oligosaccharide materials with organized structures.

Micro Fibrillated Cellulose (MFC) has emerged as a promising component in film formulations due to its unique barrier prope.rties. In this study, to best of our knowledge, cardanol, a biobased plasticizer derived from cashew processing, was employed for the first time, as a dispersing aid for MFC, during a liquid assisted extrusion technique with a Poly(lactic acid) (PLA)/Poly(butylene succinate adipate) (PBSA) blend. The aim of the work is the production of PLA/PBSA/MFC films for packaging applications. The addition of different MFC amount was investigated (added at 0.5, 0.75 and 1 wt.% concentrations). The results obtained are very interesting, in fact from one hand Cardanol improved the compatibility between PLA and PBSA and avoided the MFC agglomeration. On the other hand, micro fibrillated cellulose ensured a stable film blowing and the achievement of enhanced barrier properties, seal ability and mechanical resistance. In particular, the best result was obtained with an MFC content of 0.75 wt.% for which a good compromise in terms of films ductility, barrier properties and seal ability was achieved.

The hydrophilic property of lignocellulosic fibers is the main obstacle to improve the performance of structural bio-composites. To effectively utilize such fibers in high-performance composites, their hydrophobicity must be significantly increased. This study presents the hydrophobicity enhancement of okra woven fabric (OWF) by the application of hydrophobic nano-fumed silica (NFS) coating. Different concentrations of NFS were investigated, and SEM analysis confirmed that 1% NFS coated OWF presented the greatest quantity of nanoparticle deposition. The 1% NFS treated OWF exhibited the highest water contact angle of 137.2 ± 1° (~ 148% increased than uncoated fabric) and the greatest tensile strength of 21.85 ± 1.64 MPa in the warp direction and 15.66 ± 1.73 MPa in the weft direction (~ 46.35% and ~ 42.75% respectively superior to uncoated one). The TGA analysis demonstrated that the thermal characteristics have also been enhanced by NFS coating. The interaction between NFS and OWF has been investigated using FTIR analysis, while their elemental composition has been assessed using EDX and XPS techniques.

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A promising alternative to extend the limits of chemithermomechanical pulps (CTMPs) has been proposed to produce extremely resistant waterproof paper for use in sustainable packaging products, replacing plastics. The synergies between the incorporation of lignin microparticles (LMPs) in a pulp furnish (mass), with retention agents and hot-pressing technology, have been successfully tested in CTMP paper sheets. The addition of LMPs as a wet-strength agent, combined with the high temperature produced in hot-pressing, allows the softening of the LMPs to enhance mechanical properties. Two retention agents, cationic starch (CS) and chitosan (CH), have been studied to ensure the retention of the LMPs. Results show that both CS and CH remarkably improve the wet tensile index while maintaining or slightly increasing the dry tensile index. Regarding hot-pressing, three seconds of pressing is enough to achieve these properties, and some moisture (20%) in the sheets prior to pressing favors the wet strength. CH is not only the most promising retention agent, but it also significantly increases the wet tensile index (around 50 kNm/kg), maintaining more than 65% of the dry tensile index, creating an extremely resistant waterproof paper. Additionally, LMPs increase the short-span compression test (SCT) index by 180% and reduce air permeability 16 times compared to the untreated CTMP paper.