Cellulose最新文献

In this study, single-sided nuclear magnetic resonance (NMR) spectroscopy was used to detect the changes of axial and radial tangential moisture self-diffusion coefficient with diffusion time of Mongolian Scots pine (Pinus sylvestris var. mongolica). The result shows that, the self-diffusion coefficient values ranked as axial > radial > tangential. The axial self-diffusion coefficient exhibited free diffusion, averaging 2.0 × 10^–9 m²/s, while radial and tangential directions showed restricted diffusion, decreasing with time. Based on the restricted diffusion theory, the results are as follows, radial and tangential tracheid surface-to-volume ratios (S/V) were approximately 203,000 ± 10,600/m and 265,000 ± 25,000/m, average size of lumen ends and pits 6.4 ± 0.33 μm and 6.2 ± 0.49 μm in radial and tangential direction respectively, tortuosity values τ_R = 3.96 ± 0.02 and τ_T = 6.59 ± 0.45. Combining S/V with the form factor (Fs) and the T₂ relaxation mechanism yields the following results, average pore sizes for radial and tangential tracheids were 19.7 ± 1.44 μm and 15.09 ± 1.3 μm, cell water transverse surface relaxation rates were ρ_2R = 0.103 ± 0.005 μm/ms and ρ_2T = 0.082 ± 0.007 μm/ms. The pore size obtained above is within an acceptable range with the results of SEM. This study provides a systematic method for wood moisture self-diffusion analysis.

A sufficient understanding of the failure mechanisms that govern the mechanical behavior and failure modes of natural fiber composites is essential. In this regard, acoustic emission (AE) is a potential technique to monitor the mechanical behaviour and to provide the required information about the failure mechanism of natural fiber-reinforced polymer composites. The purpose and novelty of this study is to investigate for first time, the fracture behaviour of banana/ramie/epoxy composites under a 3-point bending test. During the test procedure, the AE parameters were recorded to evaluate the crack growth from the initial crack to the final fracture of the specimen and to determine the damage locations. AE parameters, such as amplitude, frequency, cumulative hits, and AE energy distributions, were used to identify the failure mechanisms associated with matrix cracking, delamination, fiber-matrix debonding, and fiber breakage. Based on these findings, the cumulative effect of AE events (counts/hits) represents the stress risers that cause failure in the specimen. Because natural fiber composites are brittle materials, they weaken when subjected to tensile loads. For this reason, the outermost bottom layer experienced more failure than the compressive layers during the bending of the specimen. The failure modes were studied using scanning electron microscopy. It was observed from the AE activity that the stress level at the crack initiation is 10–15% higher than the stress magnitude at the fracture stage.

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The rhizomes of the wild turmeric plant are harvested while the aerial part is discarded as waste. The current study aims to extract fibers (WTPF) from the petiole portion of the wild turmeric plant by manual (mechanical) retting using metal comb. The fiber extraction is carried out at two stages: the first extraction yielded long and strong fibers (WTPF-1) ranging in length between 20 and 40 cm and the second extraction from the residual biomass yielded comparatively shorter fibers (WTPF-2) ranging in length between 1 and 5 cm. The extracted fibers are evaluated for physical, chemical, thermal, structural and morphological properties. The diameter of both the fibers is observed to be 20 µm and the tensile strength is 2.17 Mpa. The fibers exhibited significant difference in their properties, say the hemi-cellulose content, elongation at break, density, young’s modulus while the cellulose, lignin, wax, pectin, ash and moisture content did not vary much. Based on the properties, the WTPF fiber has potential application in technical textiles field as it could be made into non-wovens and composites.

Dissolving-grade pulps serve as the primary material for producing regenerated cellulose fibers, and their utilization is steadily increasing. Despite extensive research efforts, it remains necessary to deepen our understanding of the inherent factors that impact pulp reactivity apart from the well-known degree of polymerization. The Fock reactivity test is commonly used to quantify the reactivity of cellulose pulp by measuring the percentage of cellulose that reacts with carbon disulfide. Dissolving pulps typically require a reactivity of over 90%. Hemicellulose content, intrinsic viscosity, cell wall porosity, crystallinity, and accessible area of four different pulps were characterized and distinct treatments were employed to try to separate the effect of different pulp properties and assess their effect on Fock reactivity. Hemicelluloses removal by xylanase and cold caustic treatments (86% removal) increased the Fock reactivity by 30%, from 55.7% to 71.3%. Assuming the hemicelluloses are fully accessible by the CS₂, cellulose reactivity increased from 35.6% to 69.5%,but at the expense of an intrinsic viscosity decrease from 990 cm³/g to 689 cm³/g. This unexpected intrinsic viscosity decrease can be due to the cellulose de-shielding effect provoked by hemicellulose removal and some cellulose degradation during cold caustic extraction. Vibrational impact ball-milling applied on a pulp with 5% hemicellulose content notably boosted Fock reactivity by 56%, from 54% to 84.5%, but two pulp properties, intrinsic viscosity, and crystallinity, decreased concurrently due to the high-energy treatment. This phenomenon complicates identifying a direct correlation between heightened reactivity and a single parameter. To address this, endoglucanase treatment was used to separate intrinsic viscosity from crystallinity, clarifying their contributions to changes in Fock reactivity. Unfortunately, the effect of a given physical or bio/chemical pulp treatment affects more than one pulp property, always including the cellulose degree of polymerization, which has made it difficult to isolate the pulp properties that affect Fock reactivity. Several processes have been tested to obtain pulp with dissolving potential.

Properties which control the mechanical performance of regenerated or precipitated cellulose films are currently not well-known and a mechanistic understanding of the underlying phenomena should be established. Solution rheology is a crucial property for casting films and spinning fibres in terms of process runnability, and it can have a considerable effect on the mechanical properties of the prepared cellulose products. We hypothesized that the viscosity of cellulose dissolved in 4-methylmorpholine N-oxide (NMMO) and the mechanical properties of precipitated cellulose films could potentially be improved by controlling the molecular weight distribution of cellulose pulp, taking inspiration from traditional plastic industry. We evaluated the effects of pulp blends on the viscoelastic properties of dissolved cellulose-NMMO dopes and used the dopes to prepare cellulose films and determined their mechanical properties. Lastly, we employed the determined dope and film characteristics to build linear regression models for predicting dope rheology and mechanical performance of films. Mixture films with 2:1 and 1:2 ratios of pulps with both medium and high degree of polymerization showed in average 36% and 46% higher toughness than their unimodal versions. The model results demonstrated that film performance could be tailored by changing the pulp composition. These findings play an important role in optimizing the future processability of dissolved cellulose dopes for producing bio-based cellulose materials and could bring us a step closer to traditional plastic polymer disciplines by tailoring their performance based on pulp properties.

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The work describes an ionizing radiation mediated, toxic solvent free interfacial engineering of a novel Phosphorus-Nitrogen functionalized bifunctional cotton cellulose fabric (BCF) endowed with flame retardant (FR) and antibacterial properties. Monomers bis[2-(methacryloyloxy)ethyl] phosphate (B2MEP) and [2-(methacryloyloxy)ethyl]trimethylammonium chloride (MAETC) in different proportions were co-grafted onto cellulose fabric via ⁶⁰Co radiation mediated Simultaneous Irradiation Grafting Process (SIGP) to incorporate Phosphorus and Nitrogen functionalities. Effects of radiation dose, monomer concentration on the grafting yield (GY) were investigated and samples were characterized using TGA, ATR-FTIR, XRD, SEM–EDX, EDXRF, CHN Elemental Analysis and XPS analytical techniques. Limiting oxygen index (IS:13501/ASTM D 2863) and vertical flammability tests (IS11871-1986) were conducted to establish the halogen free, P-N synergistic FR properties of the fabric. All the co-grafted samples were observed to possess LOI values in excess of 30%, while BCF (1:2) (GY =  ~ 44%) demonstrated LOI of 32% with the least char length of 74 mm in the vertical flammability tests. Tear strength studies were carried out as per ASTMD 1424-09. Antibacterial assay revealed that the fabric possessed activity against both gram positive (S. aureus) and gram negative (E. coli) organisms, with BCF (1:4) (GY =  ~ 48%) demonstrating complete killing of ~ 5 log cycles for both microorganisms in 24 h. BCF retained its FR and antibacterial properties even after multiple washing cycles. With its bonafide green credentials, durability and unique properties, multifunctional BCF fabric prepared under optimized conditions of P/N ratio > 1.7 and GY ~ 45% can be a potential candidate for future applications.

Recently, there has been a significant global focus on the development of fully biobased, strong, and tough filaments. This paper presents a deep investigation into the reinforcing effect of chitin nanofibers (ChNFs) on the fabrication of robust cellulose nanofiber (CNF)-ChNF composite filaments. Three types of ChNFs were produced using distinct. Methods aqueous counter-collision (ChACC), acid hydrolysis (ChAH), and TEMPO-oxidization (ChTEMPO). Subsequently, these ChNFs were blended with CNFs derived from hardwood bleached-kraft pulp to create the nanocomposites. The CNFs underwent TEMPO-oxidization and aqueous counter-collision (ACC) treatment. The composite filaments were fabricated via wet spinning, followed by coagulation in a CaCl₂ solution bath. A comparative analysis was conducted among all composites comprising various ChNFs and CNFs, examining their morphological, thermal, optical, and mechanical properties. Among them, the CNF-ChACC filament displayed the highest UV protection, while the CNF-ChAH filament demonstrated the highest tensile strength (614 MPa) and elongation-at-break, surpassing pure CNF filaments by 31.5% and 47%, respectively. It is anticipated that this study will contribute to a deeper understanding of the production of strong biobased filaments for advanced applications.

Water contamination over the years due to hazardous organic and inorganic pollutants poses an immediate threat to both the environment and human health. Extensive research has been conducted on the application of the adsorption technique to treat these effluents. With a focus on adhering to the principles of Green Chemistry and the circular economy, researchers are directing their efforts toward discovering economical, biodegradable, and readily available adsorbents. In this context, the present review article offers insights into recent studies regarding the utilization of the natural biosorbent Luffa cylindrica. This porous, environmentally friendly, and non-toxic material shows promise in the realm of wastewater treatment. Emphasis was also given to several fiber modifications aimed at enhancing the adsorption capacity of this biosorbent. Additionally, comprehensive physicochemical characterizations were conducted, including SEM, TEM, FTIR, XRD, N₂ adsorption and desorption and contact angle analyses. The impact of adsorption parameters was discussed in detail. The review delves into kinetic, equilibrium, and thermodynamic data, which have been presented and analyzed. Mechanistic insights into the adsorption interactions between the adsorbent and adsorbate are depicted through illustrative diagrams. Ultimately, the findings underscore the potential of both Luffa and Luffa-based materials as promising candidates for effective wastewater treatment applications.

Electronic skin, as an intelligent material capable of simulating human skin functions, plays a crucial role in long-term stable health monitoring, human–computer interaction, and medical devices. However, to achieve the application of highly functional electronic skin, there remains a challenge in fabricating pressure sensors that simultaneously possess flexibility, vapor permeability, and exhibit excellent sensing capabilities. Herein, we prepared a dispersion of 2,2,6,6-tetramethylpiperidinyl-1-oxy oxidized cellulose nanofiber (TOCN) and hollow polypyrrole (hPPy) microspheres prepared through the template method. The hydrogel films were obtained by a simple blending approach and Ca²⁺ crosslinking followed by drying. The resulting TOCN/hPPy hydrogel films exhibited good mechanical properties, exceptional flexibility, and reliable vapor permeability. Notably, the developed piezoresistive pressure sensor demonstrated a sensitivity of 2.08 kPa⁻¹, along with a fast response time (90 ms) and recovery time (150 ms). Furthermore, the sensor exhibited a low detection limit of 7.8 Pa, excellent stability at high pressures, and long-term cycling stability of up to 12,500 cycles.

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Superbase Ionic Liquids (SBILs) are efficient direct-dissolution solvents for cellulose and have found applications such as manufacturing of man-made textile fibers. In this study cellulose beads were prepared from microcrystalline cellulose dissolved in a mixture of SBIL 1,5-diazabicyclo[4.3.0]non-5-enium acetate with dimethyl sulfoxide, [DBNH][OAc]/DMSO, by drop-wise regeneration using water as an antisolvent. This resulted in cellulose regeneration by spinodal decomposition phase separation. The cross-sections of freeze-dried beads were thoroughly investigated using SEM, revealing a complex internal bead structure. Special attention was paid to structures resulting from the inwards moving regeneration front, where the solvent and antisolvent interdiffuse in opposite directions. The phase boundary at the regeneration front showed evidence of Saffman–Taylor instability, i.e., viscous fingering. Altering the diffusion environment surrounding the bead during regeneration resulted in nested layers of cores and shells. The number and placement of the core–shell separations was regulated by the number of transfers between two antisolvent baths and the duration of alternating periods of fast and slow interdiffusion of water and [DBNH][OAc]/DMSO through the bead perimeter.

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