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The low concentration of prepared cellulose nanofibril (CNF) suspension limits its large-scale application. In this study, bleached hardwood kraft pulp without any pretreatment was prepared into a CNF suspension with a concentration of about 1.0 wt% by a Supermasscolloider. The CNF suspension was dewatered by centrifugation to obtain concentrated CNFs (labeled 1-CNF). The 1-CNF sample was then mixed with water and dispersed by a high-speed homogenizer and dewatered again to obtain re-concentrated CNFs (labeled 2-CNF). The results showed that the suspension stability, water retention value and specific surface area of redispersed CNFs decreased compared to the unconcentrated CNFs. The cavities or pores formed by nanofibrils in the dewatering process were evaluated by the content of freezing bound water (FBW) that was calculated by differential scanning calorimetry with an isothermal step melting procedure. Pores were not observed in the starting unconcentrated CNFs, while the pores with a size of 0–395.8 nm were found in the two concentrated CNF samples (1-CNF and 2-CNF). The FBW content of the CNF samples increased as the solid content of the two concentrated CNFs increased. After re-concentration, the FBW content of 2-CNF decreased compared to that of 1-CNF. In sum, the concentration process of CNF suspension promoted the formation of pores and pores with small size formed first. However, in the re-dispersion and re-concentration process, the formed pores partially collapsed and shrunk. [ABSTRACT FROM AUTHOR]

Dewatering or drying of diluted cellulose nanofibril suspensions is an effective way for reducing the costs of transportation and storage. In this study, poly(vinylpyrrolidone) (PVP) was introduced into a redispersing system of concentrated CNFs, and the obtained redispersed CNFs were used for fabricating CNF/PANI (polyaniline) nanomaterials by in situ polymerization method. The results showed that mechanical grinding with grinding gap of − 20 μm was an effective way to redisperse the concentrated CNFs, especially when the PVP was added in the redispersing process. The conductivity of the redispersed CNF/PANI film reached 1.08 S/cm and the specific capacitance reached 118.3 F/g (at 0.3 A/g), when the concentrated CNFs were redispersed with 5% PVP. During the polymerization process, PVP facilitated the PANI coating on the CNFs uniformly as steric stabilizer. This study provided a basis for the application of redispersed CNFs in conductive nanomaterials area. [ABSTRACT FROM AUTHOR]

• A pre-assembled framework structure hydrogel (Cu2+-CNF hydrogel) was developed. • Explained the formation mechanism of the pre-assembled framework in Cu2+-CNF hydrogel. • Cu2+-CNF hydrogel exhibited excellent adsorption properties and mechanical properties. • Propose a general strategy for the pre-assembly of framework hydrogels. Hydrogels can effectively address various adsorption requirements as a multifunctional adsorbent material with a three-dimensional spatial network. However, conventional hydrogels, typically synthesized using the one-pot method, often exhibit a heterogeneous internal structural arrangement, leading to non-uniform stress distribution when interacting with heavy metal ions. This has resulted in the structural disruption of conventional hydrogels in the adsorption of heavy metal ions, and they exhibit low adsorption performance, low cycling performance, and non-selective adsorption. Herein, a preassembled framework structure hydrogel (Cu2+-CNF hydrogel) was developed by introducing template ions (Cu2+), which have been coordinated with monomers (Acrylic acid and Acrylamide), into a network of cellulose nanofibrils (CNFs) polymers. The obtained Cu2+-CNF hydrogel exhibited excellent adsorption properties(Cu2+-CNF hydrogel, 402 mg/g) compared to those prepared by the one-pot method(CNF hydrogel, 129 mg/g). In addition, the Cu2+-CNF hydrogel has superior selective adsorption property and tensile strain properties (CNF hydrogel: 20 % to Cu2+-CNF hydrogel: 100 %) at higher swelling ratios (CNF hydrogel: 2313 wt% to Cu2+-CNF hydrogel: 8379 wt%). Even after multiple folding or repeated adsorption–desorption cycles, the integrity of the structure and adsorption function can still be maintained. This work provides a general strategy for preparing a new type of nanocellulose hydrogel. [ABSTRACT FROM AUTHOR]

The aim of this work is to study and compare the morphology and rheology of cellulose nanofibrils (CNFs) from bleached softwood kraft pulp by several mechanical treatment methods. Three different kinds of CNFs were prepared in this work: (i) ones produced by PFI milling and microfluidic homogenization (RM-CNFs), (ii) ones produced by grinding and microfluidic homogenization (GM-CNFs), and (iii) ones produced by ball milling and ultrasonication (BU-CNFs). RM-CNFs had a high aspect ratio and the highest viscosity, storage modulus, and loss modulus. GM-CNFs had homogeneous size distributions, but low aspect ratio due to severe shearing of narrower orifice of chamber in microfluidic homogenization process. For BU-CNFs, the size distributions were heterogeneous, but they had a high aspect ratio. The three kinds of CNFs all had a lower crystallinity index than BSKP, and the degree of polymerization decreased with the increase of treatment intensity. Results of rheology measurements showed that those CNFs had a high degree of fibrillation and had a wider linear viscoelastic region in oscillatory strain measurements. Also the CNFs with high aspect ratio had a high viscosity and modulus. Additional treatments did not always increase the viscosity and modulus due to too severe treatments, which could cause the decrease of aspect ratio of CNFs. The RM-CNFs had a high viscosity and modulus, which means they are suitable in applications of rheology control. [ABSTRACT FROM AUTHOR]

We describe an effective method to create nanocomposites of silver nanoparticles that were stabilized by cellulose nanofibrils (CNF-AgNPs) that were then mixed with a starch matrix. The incorporation of CNF-AgNPs nanocomposites significantly enhanced the mechanical and antibacterial properties of hybrid films. The starch-based films with only 5.0 wt% CNF-AgNPs content exhibited superior mechanical properties in which the Young's modulus increased from 80.3 to 381.5 MPa and tensile strength increased from 6.06 to 9.96 MPa at 50% RH. Taking advantage of the denser microstructure and strong interfibrillar networks, the nanocomposite film can resist more external tensile forces and show excellent barrier property and thermostability. Moreover, antibacterial analysis indicated that CNF-AgNPs/starch nanocomposite films exhibited strong bactericidal effects against representative both Escherichia coli and Staphylococcus aureus. The cell viability of 87.71% and clear morphologies of live cells implied good biocompatibility of nanocomposite films. The demonstrated characteristics of CNF-AgNPs/starch nanocomposite film verified its suitability as a sustainable material for food packaging. [ABSTRACT FROM AUTHOR]

Post-fibrillation endoglucanase treatment was employed to reduce the entanglement of cellulose nanofibrils (CNFs) produced with low extent of mechanical milling. The results showed that post-fibrillation endoglucanase treatment can effectively reduce the fibril degree of polymerization (DP) values and therefore entanglement. Cellulose DP was reduced from 520 for CNFs prepared by milling using a SuperMassColloider with 1 pass to 225 after endoglucanase treatment at a low dosage of 1 mg protein/g fibril for 24 h. Endoglucanase treatment can also effectively reduce the fibril mean diameter from 66 nm to 25 nm. Applying post-fibrillation endoglucanase treatment produced more uniform CNFs than the feed CNFs from pure mechanical treatment. All CNFs suspensions prepared by post-fibrillation endoglucanase treatment were non-Newtonian (except at very low concentrations below 0.5 wt%) with shear thinning behavior. Post-fibrillation endoglucanase treatment reduced the viscosity of CNF suspensions due to decreasing fibril DP values and the extent of entanglement. [Display omitted] [ABSTRACT FROM AUTHOR]

• Relationship between CNF morphology and reinforced effect for recycled fibers. • CNFs had good reinforced effect and little damage on dewatering efficiency. • CNFs reinforced recycled fibers with no need of polyelectrolytes. • CNF form deposited on fibers and mechanism of reinforcement were discussed. In current study, CNFs produced by different mechanical methods, were used to improve the mechanical properties of recycled paper. The result showed the morphology of CNFs had great impact on reinforced effect and the length of fibrils determined their contribution in recycled paper strength. For different CNFs with similar diameter, the higher aspect ratio resulted in better reinforced effect. The CNFs produced by microfluidic homogenization and suitable PFI milling conditions (RM-CNF1) got best reinforced effect which improved tensile index and burst index by 35.5 % and 49.4 % at 5.0 wt% addition, respectively, due to their high aspect ratio. Although the CNFs produced by ball milling and ultrasonication (BU-CNF2) still had many bundles that were not fibrillated completely, their reinforced effect just below RM-CNF1 due to their special morphology and high retention rate. This work aims to study the influence of CNFs on recycled fibers reinforcement. [ABSTRACT FROM AUTHOR]

• Dye-labeled CNFs was successfully prepared via an environmentally friendly method. • Dye-labeling was an accurate method to detect the distribution of CNFs in paper. • The Distribution of CNFs was influenced by the types and beating degree of pulps. • CNFs showed a non-uniform distribution in the Z-direction of paper structure. Due to the nanoscale and the same chemical structure to cellulosic fibers, it is difficult to directly observe the distribution of CNFs in paper sheets. Herein, dye-labeled CNFs were introduced to analyze the distribution of CNFs in paper handsheets. The dye was successfully loaded on CNFs through hydrogen bonding with an environmentally friendly method. Dye-labeled CNFs were mixed with four types of pulps with different beating degrees to form paper handsheets. The results showed that with the beating degree increasing, the colorimetric values of wire side and felt side were different among the four types of paper, which indicated that distributions of CNFs in the Z-direction of papers were not uniform. The study demonstrated that the dye-labeled CNFs methods is an effective way to analyze the distribution of CNFs in paper-based materials. [ABSTRACT FROM AUTHOR]