Cellulose最新文献

Natural chitin/CaCO₃ (ChCC) complex derived from crab shell was modified and used to fabricate an organic/inorganic complex filler to enhance the optical and mechanical properties of polylactic acid (PLA) biocomposite. Crab shell was treated with NaOH to remove proteins and pulverized to produce ChCC microparticles having flake-like shape. The presence of CaCO₃ in ChCC enhanced the hydrophobicity of the microparticles after treatment with fatty acids. The ChCC-filled PLA composite films prepared via melt extrusion displayed good optical properties without harsh discoloration (ΔE of 0.9%). In contrast, the film filled only with chitin showed high ΔE of 15% at same filler content, which is not commonly observed in biopolymer-filled biocomposites. Also, the ChCC-filled film exhibited higher mechanical properties, with an 8% increase in tensile strength compared to PLA, while the chitin-filled film showed a decreased tensile strength of 6% than PLA, which was attributed to the improved compatibility between the hydrophobic ChCC and the PLA matrix. The inexpensive preparation of ChCC and its application as a biocomposite filler is an attractive use of crab shell waste.

CNF-PPy/MXene composite films with excellent electromagnetic interference (EMI) shielding and infrared thermal camouflage performance were fabricated by compounding cellulose nanofiber-polypyrrole (CNF-PPy) and MXene. CNF-PPy was prepared by the modified in-situ polymerization of pyrrole on the surfaces of CNFs and exhibited excellent dispersion stability and storage stability in aqueous phase. CNF-PPy films showed enhanced conductivity (~ 3.91 S/cm) and EMI shielding effectiveness (average ~ 28.1 dB in X-band). The composite films loaded with MXene exhibited even better EMI shielding performance (~ 45.8 dB on average in X-band) and good applicability in other bands (~ 44.7 dB in 26.5–40.0 GHz band). The sample CP3M3 presented excellent infrared thermal camouflage properties on the MXene side (45.0 °C at 100 °C) and exhibited different infrared thermal camouflage properties on the other side (84.4 °C at 100 °C on the CNF-PPy side). Given excellent electrical conductivity, dispersion and storage stability of CNF-PPy, enhanced electromagnetic shielding and adjustable infrared emissivity of CNF-PPy/MXene films, the resulting samples can be chosen according to the scenarios, providing a promising method to ensure the smooth operation of military equipment.

The incorporation of graphene oxide (GO) into a nanocellulose matrix has attracted considerable attention due to the unique advantages of both components. This study focuses on investigating the viscoelastic and flow properties of hybrid aqueous suspensions (2.00 w/v%), composed of TEMPO-oxidized cellulose nanofibrils (TOCNF) and GO at different TOCNF/GO weight ratios. To adjust the elastic properties of the hybrid suspensions, calcium ions are introduced, varying the concentration systematically to study their effects on the hybrid network structure. All blends exhibit shear-thinning behaviour and demonstrate elastic, gel-like properties. Notably, in the absence of calcium ions, the enhancement of elastic properties is more pronounced at higher GO fractions. Conversely, with the introduction of calcium ions, the enhancement of elastic properties becomes particularly important at higher TOCNF fractions. For the quantitative evaluation of these enhancements, we employ the logarithmic mixing rule. Significant positive deviations from the predictions of the logarithmic mixing rule are ascribed to the complex, concentration-dependent arrangement of cellulose nanofibrils and GO liquid crystals in the aqueous suspension, coupled with ionic crosslinking induced by calcium ions. The study aims to contribute to the understanding of the rheological behaviour of the TOCNF/GO hydrogel, showing potential advancements in various applications.

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For addressing the issue of limited durable antibacterial cotton fabric, this study developed and synthesized quaternary ammonium salt antimicrobial agents. The chemical structure was analyzed by FTIR and ¹H NMR. The cotton fabric was subjected to surface modification techniques, such as pad-dry-cure, following the careful selection of appropriate quaternary ammonium salt. The chemical state and surface morphology were evaluated through XPS and SEM. Furthermore, the cotton fabric underwent comprehensive assessments, which included antibacterial testing, laundering cycle testing, evaluation of mechanical properties, and analysis of comfort performance. The results demonstrated that the treated cotton fabric achieved a high bacteriostatic and fungistatic rate of 99.99%, 87.5%, and 99.99% against S. aureus, E. coli, and C. albicans respectively even after 50 laundering cycles, while maintaining exceptional antibacterial effectiveness and laundering durability due to the formation of covalent bonds with the cotton fabric. The treated cotton fabric met AAA grade standards for antibacterial rate without causing any significant decline in mechanical properties. Furthermore, enhancements in hydrophilicity, softness, and wrinkle resistance were observed.

High dielectric biobased composites of TEMPO-oxidized cellulose nanofibers (TOCNFs) reinforced with cationic modified barium titanate (BTO) nanoparticles were fabricated in this work. In order to greatly eliminate the agglomeration of the nanofiller and improve the dielectric properties of the resulting film, the modification of BTO was achieved via the cationization with an etherifying agent on the basis of cladding polydopamine around BTO. The results showed that the modified BTO nanofiller had a good interfacial compatibility and dispersion in the TOCNF matrix due to the ionic and hydrogen bonds formed between the cationic modified BTO and anionic TOCNFs. Meanwhile, the modified BTO reinforced composites exhibited better dielectric properties. Especially, the composite film with 40 wt% modified BTO exhibited an ultrahigh dielectric constant of 116.2 (at 1 kHz) and a breakdown strength of 57.7 kV/mm, which was 696% and 51.4% respectively higher than that of pure TOCNF film. It was noticed that the hydrophobicity of the composite films was also slightly improved without sacrificing its mechanical strength.

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In the current study, cupric oxide nanoparticles (CuO NPs) are chemically synthesized and blended with polyvinyl alcohol and chitosan (PVA-CS) solution to produce nanofibrous wound dressing material using an electrospinning technique. The fibrous morphology of CuO-blended nanofibers was studied by SEM, showing smooth beads and uniform nanofibers with an average diameter of around 86.4 nm. The nanofibers are further characterized using XRD to confirm the presence of CuO NPs. The incorporation of CuO NPs with polymer is evident from the peaks obtained from infrared spectrum. The addition of CuO NPs retained the hydrophilic nature of scaffold, as evident from the contact angle measurement. Further, the wound healing properties of scaffold are apparent from the studies such as antioxidant activity, MTT assay, wound scratch assay, and antibacterial studies. These results indicate the greater efficacy of CuO NPs incorporated in PVA/CS for wound healing applications.

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Developing high value-added utilization of waste cotton provides a promising approach for the sustainable development. Herein, the carboxylated cellulose aerogels (CCAs) featuring in micro/nanostructure and directional channel are fabricated from cotton fabrics via the ingenious combination of selective oxidation, high-speed cutting, and freeze-drying. The as-prepared 2.0-CCA demonstrates not only excellent adsorption capacity for cationic dyes in water but also recyclability due to the abundant carboxyl groups (3.20 mmol/g) and the robust porous structure. And it shows a static maximum adsorption capacity (q_m) of 751 mg/g and a dynamic breakthrough amount more than 700 mg/g for methylene blue (MB), more efficient than most reported cellulose-based adsorbents. In addition, the 2.0-CCA shows a high equilibrium adsorption capacity (q_e) about 680 mg/g for MB at pH = 6 and keeps q_e above 600 mg/g even in a broad pH range of 3‒10, indicating a high tolerance to the solution pH value. At an ion concentration lower than 0.25 mol/L, the additional cations such as Na⁺ and K⁺ or anions such as Cl^‒, SO₄^2‒, and NO₃^‒ show a little effect on the q_e (higher than 500 mg/g) of 2.0-CCA for MB. The treated dye wastewater can be recycled for fabric dyeing, and there is no significant color difference (∆E) between fabrics dyed with dye liquors prepared with fresh or recycled water. The theoretical study confirms the importance of the electrostatic attraction between carboxyl groups of 2.0-CCA and dye molecules for the efficient adsorption.

As a good alternative to natural fibers and petroleum-derived fibers, Lyocell fibers draw increasing interests owing to its advantages of sustainable forest source, low carbon emission, high strength and comfort. However, Lyocell exhibits significant fibrillation behavior under friction, which seriously reduce product quality and limit its further development. Herein, dual crosslinking networks were innovatively constructed in Lyocell cellulose structure to enhance the interaction of cellulose macromolecular chains. Bifunctional reactive dyes were loaded in the inner part of Lyocell fiber to form a primary crosslinking network. Then, the cellulose interaction in Lyocell skin layer was further enhanced after the coating by cationic waterborne polyurethane. The mechanism was determined and results showed that durable dual crosslinking networks were formed in Lyocell cellulose structure. From scanning electron microscope (SEM) observation, fibrillation behavior of Lyocell fibers was effectively prevented by dual crosslinking networks. Meanwhile, the durability was evaluated, showing that the treated fabric maintained good anti-fibrillation performance after washing for 50 times. Furthermore, the interaction of dyes and fibers was also enhanced by the cationic polymer via electrostatic attraction force, realizing high dye utilization efficiency. Therefore, the method exhibits great potential in promoting the application of Lyocell fibers in greener textile.

The toughness and adhesiveness of composite hydrogels play an important role in the field of wearable sensors, where they are used due to their remarkable flexibility and diverse specialized properties. In this work, a composite hydrogel with strong toughness and high adhesion for human motion detection and wireless sensing was obtained. Polydopamine (PDA)-modified cellulose nanofibers (PCNFs) were introduced into a polyvinyl alcohol (PVA) and polyacrylamide (PAM) network, resulting in the fabrication of a PCNF/PVA-PAM composite hydrogel. Lithium chloride served as a crosslinking agent and provided conductive ions, and the PCNFs provided the composite hydrogel with strong toughness and adhesion abilities. The compression strength of the obtained PCNF/PVA-PAM composite hydrogel was 1.1 MPa, and its adhesion strength to glass was 63.8 kPa. Moreover, the composite hydrogel exhibited good anti-freezing properties. The compression sensitivity of the composite hydrogel was 1.29, and it still maintained stability even after 500 testing cycles. The strain-sensing abilities of the composite hydrogel were satisfactory for different human body parts. This composite material holds great promise in the fields of wearable devices and wireless signal transmission.

The development of wound dressing materials with both self-healing and antibacterial properties for promoting wound closure is highly desirable in health care. Herein, a smart double-network hydrogel (GS/DPPDH) with promising traits was developed by combining a dynamic Schiff base reaction between dialdehyde carboxymethyl cellulose (DCMC) and poly(ethylene imine) (PEI) with free radical polymerization. Because of its abundant amino groups, the common antibacterial drug gentamycin sulfate (GS) can be loaded into hydrogels by the formation of Schiff base bonds with DCMC. The slightly acidic wound microenvironment caused hydrolysis of the Schiff base bonds, thus releasing the drug GS on-demand. The prepared hydrogel not only showed good self-healing and injectable properties but also displayed excellent blood compatibility and cytocompatibility. The in vitro antibacterial experimental data proved that the GS/DPPDH had high antibacterial ratios of nearly 90% against both gram-positive (S. aureus) and gram-negative (E. coli) bacteria. In addition, in vivo assessment in a mouse model of S. aureus-infected full-thickness skin wounds revealed a wound closure ratio of 83.22 ± 2.90% after 7 days of healing, which was significantly greater than that in the gauze (59.78 ± 2.60%) and DPPDH (66.08 ± 0.21%) groups. Taken together, the results showed that the prepared antibacterial double-network hydrogel with injectable, self-healing, and pH-responsive properties exhibits great potential as a dressing material for infected wound healing.