Cellulose最新文献

As one of the polysaccharide nanocrystals, cellulose nanocrystals (CNCs), also known as nanocrystalline cellulose (NCC), have been widely recognized due to their unique structures and versatile properties in both academic and industrial fields. Combining the green attributes of cellulose with nanoparticle characteristics, CNCs exhibit biodegradability, excellent mechanical properties, and large specific surface area. In contrast to CNCs obtained by conventional acid hydrolysis, hairy cellulose nanocrystals (HCNCs) with the length of about 100–200 nm and the width of about 5–13 nm are composed of central rigid nanorods and flexible hair-like cellulose molecular chains protruding from both ends. The preparation of HCNCs mainly involves processes such as periodate oxidation, chlorite oxidation, and hot-water treatment, resulting in the formation of hairs and high-contents of functional groups up to 6.6 mmol/g. These HCNCs have unique morphology and physicochemical properties, and they have shown broad application prospects, such as in the fields of flocculation, adsorption, scale inhibition, drug delivery, and sterilization. In this comprehensive viewpoint, we categorized HCNCs into three groups: cationic HCNCs (c-HCNCs), anionic HCNCs (a-HCNCs), and neutral HCNCs (n-HCNCs), according to their charges carried by various functional groups. Based on these three categorizations, we showed the various applications of HCNCs in a wide range of fields, and illustrated the structure–function-application relationship of HCNCs. The development of hairy cellulose nanocrystals is anticipated to significantly advance the frontiers of sustainable nanotechnology and renewable materials.

This study investigates the capabilities of various measurement techniques for quantifying the cellulose content in reject material from a carton recycling center, which consists of polyethylene, cellulose, and aluminum, along with impurities. Different measurement techniques, including Fourier Transform Infrared Spectroscopy combined with Attenuated Total Reflectance (FTIR-ATR), cellulose dissolution using cupri-ethylenediamine (CED) from plastic followed by gravimetric analysis, acid hydrolysis combined with chromatography, and Thermal Gravimetric Analysis TGA, are employed in this study. Acid hydrolysis combined with chromatography and TGA shows comparable results when compared to different techniques for analyzing pulper reject. Dissolution with CED showed also comparable results but shows higher variation than TGA or chromatography. FTIR absorbance ratio of 1025/2917 correlates with cellulose content, but it shows high variation and lacks sensitivity below 5% cellulose content in polyethylene. This limitation is attributed to factors such as the limited measurement area (1.8 mm) and the large particle size of the cellulose and LDPE mixtures, possibly caused by inadequate grinding of LDPE. In conclusion, TGA and acid hydrolysis combined with chromatography are the most reliable for quantifying cellulose content in recycling reject, providing more consistent and accurate results than FTIR-ATR or CED dissolution methods.

Cellulose is the most abundant and renewable biopolymers on earth. The hydrophilic nature of cellulose endows cellulosic materials with good compatibility with polar matrices, but it also leads to their poor dispersion in non-polar matrices. Regulating the surface hydrophobicity of cellulosic materials via surface esterification can greatly extend their applications. However, the existing surface esterification methods for cellulosic materials are time-consuming and costly, which makes them less attractive for practical application. Here we found that when vinyl esters were used as esterifying agents, various alkalis can be used to catalyze the ultrafast surface esterification of cellulose materials in aqueous media at room temperature within seconds or minutes, which is highly attractive for the surface esterification of nanocellulose in suspension state. Surface acetylated cellulose nanofibers (ACNF) and surface acetylated cellulose nanocrystals (ACNC) with acetyl group content (Ac%) up to 10.7% and 6.5%, respectively, were successfully prepared within 5 min in aqueous diethylamine solution. Additionally, this method can also be used to achieve the rapid acetylation of phenol hydroxy group in aqueous media.

This study provides a comprehensive analysis of the effects of incorporating low levels of cellulose nanofibrils (CNFs) into an acrylonitrile butadiene styrene (ABS) matrix on the properties of ABS composites. Five samples with varying CNF content (0.125%, 0.25%, 0.5%, and 1%) were prepared, alongside a pure ABS sample for comparison. The preparation involved mechanical blending, followed by extrusion and injection molding. Mechanical, thermal, water absorption, surface gloss, and microstructural properties of the composites were characterized. Tensile and three-point bending tests revealed that the addition of CNFs improved both stiffness and strength, with the highest tensile modulus observed in ABS/NC4 (1% CNFs) and the highest flexural strength in ABS/NC1 (0.125% CNFs). Impact resistance, evaluated through Charpy impact testing, showed enhancement up to 0.5% CNF content, beyond which a decline was observed due to increased particle quantity. Thermal properties exhibited negligible changes, with slight variations in glass transition and melting temperatures observed within a narrow range. SEM analysis confirmed a uniform distribution of CNFs, contributing to enhanced crack resistance, although higher CNF content led to increased void formation. Surface gloss measurements indicated smoother material surfaces with higher CNF content. The study concludes that integrating CNFs into ABS composites improves mechanical properties and impact resistance, necessitating careful consideration of CNF content for optimal performance. Further refinement could tailor ABS/CNF composites for specific applications.

Oil–pressboard insulation in converter transformer is subjected to the combined effects of AC and DC electric fields, high temperature, and mechanical vibration in actual operation, with a serious impact on its deterioration. In this study, comparative tests are performed of coupled electrical–thermal–mechanical aging, and several characteristic parameters that characterize the degree of aging of oil–pressboard are measured. Relationships between aging parameters are established, with the degree of polymerization (DP) of the pressboard being adopted as the criterion to characterize the degree of aging. Scanning electron microscopy and X-ray diffraction are used to investigate the surface morphology and crystal structure of the pressboard at different aging stages. Then, the influences of temperature, electric field and mechanical field on the cracking mechanism of the oil–pressboard insulation in terms of the aging characteristic parameters and the changes in cellulose crystallinity were analyzed. It is finally found that thermal stress is the most important factor involved in insulation pressboard cracking. The addition of electric and mechanical fields will reduce the crystallite size of the cellulose pressboard material, increase the acid value and furfural content of the oil, and increase the rate of decrease in the degree of polymerization of the pressboard. All of which accelerate the aging of the oil–pressboard insulation.

Highly porous and lightweight aerogels of cellulose nanofibers (CNFs) have emerged as a promising class of material. This study delves into the impact of the composition (lignocellulose nanofibers–LCNFs and CNFs) and the drying methods (supercritical drying and freeze-drying) on the morphology and the properties of nanocellulose-based aerogels. The investigation evaluates the concentrations of nanofibers and the influence of lignin, a constituent of LCNFs recognized for enhancing the rigidity of plant cell walls, on the aerogel’s properties. The shrinkage rates, density, pore structure, and mechanical properties of the obtained aerogels are comprehensively compared. Supercritical drying proves advantageous for aerogel formation, resulting in materials with lower density and higher surface area than their freeze-dried counterparts at each concentration level. The use of acetone for supercritical drying contributes to reduce the shrinkage rates compared to ethanol. This decrease is attributed to the formation of a more rigid hydrogel during solvent exchange. Freeze-drying exhibits the lowest shrinkage rates and relatively higher porosity. The presence of lignin in the nanofibers influences the microstructure, yielding smoother and thicker pore walls. This study contributes to the comprehensive understanding of the intricate factors shaping nanocellulose aerogel properties, paving the way for the development of innovative and environmentally-friendly materials.

This study focuses on the development of eco-friendly biobased adsorbents through a sustainable hydrothermal and freeze-drying synthesis process, utilizing cost-effective bio-sourced materials to minimize energy consumption and waste. The biobased adsorbents were elaborated using hydroxyethyl cellulose-ionic liquids and bentonite clay. The elaborated biocomposites were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy/attenuated total reflection (FTIR/ATR), thermogravimetric analysis (TGA), and electron microscopy-energy dispersive X-ray (SEM–EDX), Brunauer–Emmett–Teller (BET) and zeta potential (ZP). Structural analysis confirms the intercalation and incorporation of HEC-ILs polymeric chains into Be-Na matrix and the formation of biocomposites. The [HEC-ILs/Be-Na] composite was subsequently employed for solid-phase extraction of Co(II) by investigating the effect of pH, initial Co(II) concentrations, time, temperature, and the presence of co-existing ions (Na(I), Li(I), Mn(II), Ni(II), and Al(III)). The adsorption kinetics of Co(II) metal ions were suitably characterized using the pseudo-second-order model (with R² > 0.99). Furthermore, the adsorption isotherms conformed to the Langmuir model (with R² > 0.97), suggesting a chemisorption process with an adsorption capacity of 69.8 mg/g. The thermodynamic study reveals that the adsorption process exhibits characteristics of spontaneity and endothermicity (ΔH° = 74.197 kJ mol⁻¹, ΔG° < 0 kJ mol⁻¹). The proposed mechanism for Co(II) adsorption on the developed biocomposite involves electrostatic interactions, ion exchange, and anion-π interactions. The biobased composite exhibited remarkable selectivity for Co(II) and demonstrated great potential as an adsorbent for industrial applications.

Graphical abstract

Cellulose acetate (CA) has been extensively studied with minimal regard to end-of-life analysis. Cigarette filters predominantly comprise CA fibers and chemical additives for filtration and manufacturing, altering their physicochemical and thermal properties and influencing their interactions with the environment upon disposal. This research established and employed multifaceted analyses to determine the physicochemical and thermal properties of cellulose acetate sourced from unsmoked cigarette filters and pristine CA powder, including Fourier transform infrared spectroscopy (FTIR), optical and electron microscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). FTIR analysis ascertained the structure of CA by resolving spectral peaks while pointing out the effects of additives, processing conditions, and the degree of substitution. An increase in the latter indicates reduced biodegradability and potentially longer persistence after disposal. The morphology was examined using electron and optical microscopies, revealing insights into FTIR results. TGA elucidated the decomposition response, evidencing moisture and volatile retention in the CA fibers extracted from unsmoked cigarette filters, suggesting unique decomposition behavior due to the reactivity of the additives with the surrounding environment. The thermal decomposition of unsmoked cigarette filters is insensitive to inter- and intra-filter variability. DSC analysis identified the thermal transitions of the CA fibers and powder, accentuating the effects of morphology, entanglements, and plasticizers on the structural stability of cellulose acetate. Our research establishes a baseline characterization of cigarette filters, laying the scientific foundations for further investigations into this pervasive pollutant.