Cellulose最新文献

Cellulose can be an abundant and sustainable raw material for the fabrication of plastic-replacing products. However, many traditional and modern production processes are polluting and expensive. Recently, a new route has been identified to obtain films out of mildly carboxymethylated cellulose pulps that have shown very promising properties. Films are produced by dissolving the modified pulps in alkaline solution and by subsequently regenerating the dope in an acid bath. Here, we investigate the effects of the composition of the acid bath on the key properties of the film, as well as the influence of the degree of substitution of carboxyl groups in the pulp. Films are characterized through optical microscopy and X-ray diffraction. The mechanical properties of the films have been measured as well as their porosity. The results clearly indicate that bath composition and degree of substitution play a role in determining the final properties of the film. In particular, it has been found that the regeneration bath influences the degree of orientation of the biopolymer along a preferential direction, and that it also affects the final porosity of the film as a result of a different drying rate. This evidence provides solid basis for the optimization of the properties and production process of these films, towards the obtainment of more sustainable and affordable materials.

Fire events, being an acute hazard, claim human lives at risk on one side and pose great damage to occupancies and properties on the other side. Textiles and furnishings are highly vulnerable to these hazards. However, such fire incidents can be mitigated by incorporating flame retardancy into textiles. This study proposes a novel flame retardant based on phosphorus and nitrogen-rich oligomeric structures obtained via condensation polymerization. The impact of phosphorus content has been investigated on the degree of flame retardancy. The structural morphology of the as-prepared flame retardants has been probed using scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Thermal responses of the prepared flame retardants and treated fabrics are characterized through thermogravimetric analysis (TGA), thermal protective performance (TPP), cone calorimeter, and differential scanning calorimetry (DSC). The treated fabrics have effectively inhibited flame propagation on fire exposure. The wash durability of the treated fabrics was found remarkable owing to the retention of high retardancy even after 30 washes. The treated fabrics exhibited a higher TPP rating by a factor of 61% due to catalyzed dehydration and the formation of a protective char layer. Furthermore, the cone calorimetry test showed a significant reduction in the HRR value by 40%, and the THR value by 27%. While LOIs of cotton textiles treated with 15% FR range from 18.2% to 37.2%. The presence of antibacterial characteristics, sustained breathability, and retention of mechanical strength of cotton fabrics adds advantages to the as-prepared flame-retardant fabrics. The current synthesis, serving as a formaldehyde-free alternative, is exceptionally well-suited for the advancement of workwear development.

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A novel type of durable flame retardant applied to cotton fabrics, phosphoacetamide phosphate ammonium phosphate (PAPAP), was synthesized. The PAPAP structure characterization was determined via nuclear magnetism resonance, X-ray photoelectron spectroscopy and Fourier transform infrared (FTIR). Scanning electron microscopy and X-ray diffraction revealed that PAPAP diffused into fibers and did not significantly influence their morphology and crystal structure. The FTIR analysis and wash fastness of samples suggested that PAPAP was bound to cellulose through N–(P = O)–O–C and O–(P = O)–O–C covalent bonds. The presence of p-π conjugated effect in the (P = O)–N group of PAPAP strengthen the stability of the N–(P = O)–O–C bond, resulting in highly durable flame resistance in the finished cotton fabrics, which is supported by the fact that the treatment of cotton with 30 wt% PAPAP (30%FRC) exhibited an LOI value of 54.7%. Even after undergoing 50 washing cycles based on the AATCC 61–2013 3A standard, 30%FRC maintained an LOI value of 44.1%. Thermogravimetry (TG), TG–FTIR, cone calorimetry, and char residue analyses indicated that PAPAP modified the thermal decomposition pathway of cellulose, reduced the generation of flammable gases and promoted char formation, effectively resisting fabric fires. The whiteness, breaking strength and comfortability of the treated cotton fabrics were well sustained, and their softness was very well, even softer than that of control cotton. In conclusion, the introduction of N-P(= O) group and phosphate ester groups into a flame-retardant molecule effectively improved the durability and softness of finished cotton fabrics.

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The results of the study of plastic composites from degradable poly(3-hydroxybutyrate) P(3HB) and cellulose-containing natural materials of various origins are presented. For the first time, P(3HB) composites filled with bacterial nanocellulose (BNC) or wood (Pinus sibirica) flour (WF) were produced by melt pressing at 170 °C and 2000 Pa. The influence of the filler type and amount (30, 40, 50, 70 and 90 wt%) on the physicochemical and mechanical properties of the composites and their degradability in soil laboratory microcosms was revealed. The P(3HB)/WF composites compared with P(3HB)/BNC ones were thermally stable; their thermal degradation temperatures were 266 and 227 °C, respectively. Both composites had lower values of Young's modulus and fracture strength compared to P(3HB). As BNC content was increased, Young's modulus and fracture strength of the composites increased from 1831 to 14 MPa to 3049 and 19 MPa, in contrast to P(3HB)/WF, where the values decreased by a factor of 1.5–2.0. The half-life of composites with BNC and WF in soil was 180 and 220 days, respectively. Changes in the structure of the microbial community were determined as depending on the filler type; primary destructors among bacteria and fungi were isolated and identified. Environmentally friendly and completely degradable composites show promise as cellulose-plastic materials for practical application.

The development of porous, water-resistant cellulose-based materials with shape-recovery performance requires control of the swelling behaviour of these materials. In this context, TEMPO-oxidized cellulose nanofiber (TCNF) cryogels, were prepared by non-directional (ND) and unidirectional (UD) freezing step followed by freeze-drying to obtain lightweight porous materials (22.6 kg m⁻³ and 98% air content), TCNF-ND or TCNF-UD, with different pore morphologies. Indeed, honeycomb-like or lamellar structures were obtained as evidenced by microscopy and X-ray tomography analysis. The determination of the absorption capacities of these cryogels in water (pH 6) or HCl solution (pH 2) showed different swelling behaviours depending on the charge state of carboxyl groups, but depending also on the pore morphology of the TCNF cryogels. Measurements of ¹H T₂ relaxation times using Low-Field (LF) NMR demonstrated the appearance of different populations of water molecules characterized by different mobilities due to the structuration of TCNF gel during the freeze-casting procedure. Finally, uniaxial cyclic compression tests were conducted on H₂O- or HCl-swollen TCNF-ND and TCNF-UD cryogels. A higher compressive resistance of swollen-cryogels after protonation and a recovery shape performance of about 87% were obtained after 50 compression cycles.

Chromatogeny is a hydrophobization technique with fatty acid chloride without solvent that confers an improved barrier to water and water vapour, thanks to a technology that can be implemented on an industrial scale and adapted to any hydroxylated substrate, including cellulosic materials. In this work, a chromatogenically modified polyvinyl alcohol (PVA) coating layer was used as a high oxygen barrier material and as a model for hydroxylated polymers, including microfibrillated cellulose coating. Multiple passes can be applied to the coated layer to improve grafting densities. However, little is known about the molecular mechanisms and distribution of the reagent in the coated layer or whether it also modifies the board. In this work, we have demonstrated that the modification proceeds from the surface to the interior of the PVA layer by developing an imaging technique based on labelling with osmium tetroxide (OsO₄) of the double bond of an oleyl acyl chloride used as an unsaturated hydrophobizing agent. The result is a brilliant marking of the modified PVA layer strictly limited to the top surface, as revealed by SEM images. Calculations based on simple assumptions about volume expansion due to modification were compared with experimental data, i.e. measurements of the thickness of the grafted layers. The results showed that, under our experimental conditions, the reagent penetrates a zone strictly limited to the upper part of the PVA layer and never reaches the board. Moreover, the second pass does not significantly increase the reagent's penetration depth, but does significantly increase the hydrophobicity of the grafted material, as shown by the Cobb measurements. The cardboard remains intact in all the experimental situations explored on a pilot scale. The techniques developed will be transferred to the emergence of a cellulose-based barrier coating with cellulose microfibril films.

This study explored rambutan peel (RP) as a sustainable alternative food bioproduct to extract cellulose for application in packaging. The RP was pre-extracted with Soxhlet apparatus and the residual fiber was treated with synergetic enzyme (xylanase-laccase) to produce cellulose. The synergetic enzymatic treatment before sodium chlorite bleaching reduced chemical input by 28% with a high crystallinity index. The study showed RP contains a high amount of lignin (> 30%) followed by α-cellulose of 28.3 ± 0.6% and hemicellulose (>19%). The thermogravimetric analysis showed good thermal properties with the maximum mass loss of 54%-59% occurring between 332 °C to 338 °C. The Soxhlet-assisted enzyme bleached cellulose fibers were combined with gum tragacanth (in the ratio of 1:1) to prepare a foam as an absorbent for meat packaging. The pore distribution in the foam was visualized in 3D by synchrotron radiation X-ray tomography, and the crystallinity by Wide-angle X-ray scattering. The as-prepared foam exhibited weight loss, drip loss and swelling properties similar to that of commercial absorbent after 4 days of meat storage. The enzymatic biorefinery approach is promising for the valorization of rambutan peel and other lignocellulosic biomass. The cellulose demonstrates great potential for application in the food industry as an absorbent for meat packaging.

Nitrocellulose (NC) finds widespread use in propellants and launchers. Nanoscale modification can effectively enhance its combustion performance by shortening the mass and heat transfer distance. However, it also presents greater safety challenges for storage and application. To further investigate the thermal safety characteristics of nanoscale NC, this study explores the impact of additives on nanoscale NC. Nanoscale NC was prepared via electrospinning, and the samples were characterized using focused ion beam scanning electron microscopy to examine the influence of precursor concentration and stabilizer on sample morphology, leading to the formulation determination. Samples incorporating triphenylamine and lithium carbonate (Li₂CO₃) were fabricated using both electrospinning and traditional mechanical mixing techniques. Following preparation, fourier transform infrared spectroscopy, the methyl violet test, and thermogravimetry–differential scanning calorimetry were performed on six samples, each prepared using different methods and additives. These analyses aimed to investigate the thermal decomposition characteristics of the samples under varying heating rates. The study also compared the impact of nanoscale modification on the thermal performance of composite nitrocellulose. Various model-free methods were employed to calculate the relationship between activation energy and conversion rate and to analyze alterations in activation energy. Considering the thermal decomposition characteristic parameters, the study delved into the stabilizing effect of typical stabilizers in nanocomposite fibers. This research is instrumental in guiding preparation process optimization, promoting the application of NC-stabilizer mixtures, and providing valuable references for the preparation and thermal stability investigations of similar nanomaterials.

This study compares the efficacy of reactive extrusion and traditional reactor methods in altering cellulose structure to produce cellulose esters (CEs) with targeted properties. Ionic liquids (ILs) afford high cellulose solubility and recyclability, while chemical reactors enable complete cellulose dissolution and homogeneous transesterification. However, prolonged reaction times and potential oxidation issues necessitate further optimization. Conversely, reactive extrusion allows shorter reaction times, reduced solvent usage, and scalability. The current study aims to investigate how the type of cellulose (microcrystalline and fibrous) and its degree of polymerization (DP) affect the transesterification process and properties of CEs produced by reactive extrusion, as opposed to traditional methods. It was obtained that it is possible to produce cellulose laurates (CLs) with a degree of substitution (DS) of up to 2.5 via reactive extrusion. Examination of CLs obtained from the reactor (R-CLs) and reactive extrusion (REX-CLs) reveals structural properties diverging, with REX-CLs maintaining residual crystallinity despite esterification. Additionally, reactive extrusion produces CLs with lower molar mass due to a reduced DS, and in the case of fibrous celluloses, shear-induced degradation may occur. Cellulose DP emerges as pivotal for attaining desired thermal stability, with higher DP compounds displaying enhanced resistance to thermal degradation. Furthermore, reactive extrusion enhances the thermal stability of CLs more than traditional methods. However, comparative rheological analysis reveals that REX-CLs exhibit higher complex viscosity and G-moduli values than R-CLs. This phenomenon suggests that the structural arrangement of REX-CLs promotes intermolecular interactions, contributing to increased viscosity and stiffness. Reactive extrusion in an IL environment shows promise for scaled-up production of CEs with tailored properties. This indicates its potential as a sustainable and efficient manufacturing method for cellulose-based materials.

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Durable superhydrophobic fabrics with electromagnetic wave absorption were highly valuable in practical applications. In this work, durable superhydrophobic cotton fabrics with electromagnetic wave absorption were successfully prepared by modifying the cotton fabrics with polydopamine (PDA) and then depositing MoS₂/RGO (MR) composites and polydimethylsiloxane (PDMS). The surface morphology, crystal structure, and thermal degradation properties of the obtained products were evaluated. The PDA modification enhanced the affinity and adsorption saturation between the fabrics and the MR composites. Here, the MR composites provided the fabrics with wave-absorbing components and rough micro/nanostructure, and the PDMS offered lower surface energy for the treated fabrics. Ultimately, the water contact angle (WCA) of the obtained cotton fabrics could reach 157.2 ± 0.4 ° and the minimum reflection loss (RL_min) was −45.3 dB at 11.1 GHz, which showed excellent superhydrophobicity and microwave absorption properties. In addition, the obtained cotton fabrics displayed excellent robustness against rubbing, bending, and laundrying and satisfactory chemical stability. This research showed promising prospects for the development of wearable materials with durable electromagnetic wave absorption.