Cellulose Nanofibrils Research Articles

The influence of residual pectin composition and content on nanocellulose films from ramie fibers: Micro-nano structure and physical properties

In this study, cellulose nanofibril (CNF) films from ramie fibers were prepared with different pectin compositions and contents, and the influence of residual pectin on the overall performances of CNF films was evaluated. There was no significant effect of the residual pectin composition on the properties of obtained CNF films. However, when the content of residual pectin was increased from 0.45 % to 9.16 %, the surface area and water absorption of CNF films were increased from 0.2223 to 0.3300 m2/g, and from 93.51 % to 122.42 %, respectively. Pectin covers the CNF surface and act as a physical barrier between the cellulose fibrils; thus the nanocellulose films with high pectin content will have a loose and porous structure, resulting in a high surface area and a high water absorption. Besides, with the residual pectin content decreasing from 9.16 % to 0.45 %, the UVA light transmittance and tensile strength of CNF films were increased from 30.6 % to 59.9 %, and from 37.67 to 100.26 MPa, respectively. After removal of amorphous pectins in CNFs, the low pectin containing CNFs are able to pack more compactly to form a strong and thin film. This paper provides guidance for the preparation of CNF films with different performance requirements.

Dynamic Assembly of Strong and Conductive Carbon Nanotube/Nanocellulose Composite Filaments and Their Application in Resistive Liquid Sensing.

The continuous flow assembly of colloidal nanoparticles from aqueous suspensions into macroscopic materials in a field-assisted double flow focusing system offers an attractive way to bridge the outstanding nanoscale characteristics of renewable cellulose nanofibrils (CNFs) at scales most common to human technologies. By incorporating single-walled carbon nanotubes (SWNTs) during the fabrication process, high-performance functional filament nanocomposites were produced. CNFs and SWNTs were first dispersed in water without any external surfactants or binding agents, and the resulting nanocolloids were aligned by means of an alternating electric field combined with extensional sheath flows. The nanoscale orientational anisotropy was then locked by a liquid-gel transition during the materials assembly into macroscopic filaments, which greatly improved their mechanical, electrical, and liquid sensing properties. Significantly, these findings pave the way toward the environmentally friendly and scalable manufacturing of a variety of multifunctional fibers for diverse applications.

Temperature-Mediated Phase Separation Enables Strong yet Reversible Mechanical and Adhesive Hydrogels.

Hydrogels with strong yet reversible mechanical and adhesive properties fabricated in a facile and friendly manner are important for engineering and intelligent electronics applications but are challenging to create and control. Existing approaches for preparing hydrogels involve complicated pretreatments and produce hydrogels that suffer from limited skin applicability. Copolymerized hydrogels are expected to present an intriguing target in this field by means of thermoresponsive features, while the perceived intrinsic flaws of brittleness, easy fracture, and weak adhesion enervate the development prospects. Herein, we report a hydrogel with strong yet reversible mechanical and adhesive properties using cellulose nanofibrils to simultaneously address multiple dilemmas inspired by a temperature-mediated phase separation strategy. This strategy applies temperature-driven formation and dissociation of hydrogen bonds between common copolymers and cellulose nanofibrils to trigger the onset and termination of phase separation for dynamically reversible on-demand properties. The resulting hydrogel exhibits up to 96.0% (117.2 J/m2 vs 4.8 J/m2 for interfacial toughness) and 85.7% (0.02 MPa vs 0.14 MPa for mechanical stiffness) adhesive and mechanical tunability when worked on skin, respectively. Our strategy offers a promising, simple, and efficient way to directly achieve robust adhesion performance in one step using common copolymers and biomass resources, with implications that could go beyond strong yet adhesive hydrogels.

Structural design of a hyperbranched chitosan-based bioplastic with excellent strength, antibacterial, and UV shielding performance

Renewable biomaterials have received increasing attention as ideal alternatives to non-biodegradable plastics, but the poor water resistance, antibacterial property, and bonding strength usually limit their development. Inspired by the mussel chemistry, a sustainable and facile strategy is reported for preparing a high-performance chitosan (CS)-based film by incorporating a water-soluble hyperbranched polyamide (HB) and inorganic–organic system. Nanofibrillated cellulose (NFC) serves as a biological template for the preparation of uniformly dispersed zinc oxide quantum dots (ZnO QDs). As a dynamic glue linkage, protocatechualdehyde (PA) containing catechol groups provides additional bridging between the ZnO QDs and the organic CS biopolymer, thus guiding the ZnO QDs to disperse more evenly in the CS matrix and promoting the multiple cross-linking interactions in the hybrid film. The toughness and strength of the composites are simultaneously increased by 276.7% and 150.9%, respectively. Owing to the optimization of hyperbranched structure, catechol chemistry, and inorganic–organic system, the resultant film also exhibits substantially improved water resistance, thermal stability, and UV shielding capability. Additionally, the functional ZnO QDs, catechol PA, and cationic CS synergistically endow the film with superior antibacterial properties. This novel and biomimetic strategy opens up new ideas for the design of multifunctional bioplastics, while driving the development of CS biomaterials in the areas of antibacterial adhesives, high-strength hydrogels, and UV resistant coatings.

CO2 responsive self-standing Pickering emulsion gel stabilized with rosin-based surfactant modified cellulose nanofibrils

Emulsion gel was developed to provide desirable texture, palatability and functionality to food products. Tunable stability of emulsions is often desired, as in certain situations, the chemical content release usually relies on emulsion induced destabilization of the droplet. However, the destabilization for emulsion gel is difficult because of the formation of highly entangled networks. To address this issue, a fully biobased Pickering emulsion gel stabilized by cellulose nanofibrils (CNF) modified with a CO2 responsive rosin-based surfactant, maleopimaric acid glycidyl methacrylate ester 3-dimethylaminopropylamine imide (MPAGN) was reported. The emulsification/de-emulsification can be reversibly regulated because this surfactant has sensitive CO2 responsive property. MPAGN can be reversibly between active cationic (MPAGNH+) and inactive nonionic (MPAGN) responsive to CO2 and N2. The microstructure of the emulsion gel was observed and compared before and after the response. The rheological properties of emulsion gel stabilized by different concentrations of MPAGNH+ and different contents of CNF were studied separately. As 0.2 wt% CNF was dispersed in 1 mM MPAGNH+ solution, the obtained emulsion can be self-standing for long duration. The rheology study indicated that these emulsions show typical gel characteristics with shear-thinning behavior. The stabilization mechanism of these gel emulsion is a synergistic effect caused by the combination of CO2 responsive Pickering emulsion and intertwined network caused by the hydrogen-bond interaction among CNF.

Effect of different electronegative oxygen atoms of cellulose nanofibrils on the formation and photocatalytic property of ZnO/cellulose composite

Cellulose is widely employed as a template in supporting and dispersing ZnO. The oxygen atom of the hydroxyl (–OH) groups of cellulose have a significant impact on the morphology and photocatalytic property of ZnO. This work aims to investigate the effect of different electronegative oxygen atoms of cellulose nanofibrils (CNF) on the formation and photocatalytic properties of ZnO/cellulose composites. The interaction between cellulose and ZnO has been achieved by controlling cellulose fiber size and regulating the electronegativity of oxygen atoms on the CNF surface. The results indicate that etherized CNF (ECNF) with the highest degree of etherification substitution (1.7) and the best electronegativity (−34.6 mV) can synthesize the ZnO/cellulose composite with the largest loading content of ZnO (58.9%) and the best photocatalytic activity for MO degradation (91.1%). It can be concluded that the intenser electrostatic interaction between oxygen atoms on the CNF surface and ZnO can facilitate the fixation and growth of more high-quality ZnO nanoflowers, thus improving the photocatalytic property. In a word, this work can provide a novel perspective for the efficient preparation of ZnO/cellulose composites with designable morphology and structure.

Double skeleton network structure constructed by cellulose nanofibrils and graphene oxide as efficient oil gelling agent

Double skeleton network structure constructed by cellulose nanofibrils and graphene oxide as efficient oil gelling agent

Versatile cellulose nanofibril assisted preparation of ultralight, scalable carbon nanotube aerogel-based electromagnetic wave absorbers with ultrahigh reflection loss

The sustainable cellulose nanofibril (CNF) was efficiently utilized to facilitate the preparation of a type of ultralight, high-porosity carbon nanotube (CNT) hybrid aerogel-based electromagnetic wave (EMW) absorbers. CNF not only serves as a green surfactant to avoid the agglomeration of CNT, but also acts as supporting matrix or binder to promote the construction of porous CNT-based aerogels. Furthermore, the CNF precursor contributes to the generation of CNF-derived nanocarbon (CNFC) for a high-efficiency dielectric modulator, leading to the tuneable electromagnetic parameters and good impedance matching. Combined with the loss capacity of CNFC, the EMW absorption performance of CNT-based aerogels is enhanced. Consequently, the hybrid aerogels show EMW absorption performance involving an effective absorption bandwidth of 3.3 GHz and an ultrahigh reflection loss of −76.46 dB at a filling ratio of 5 wt%, outperforming that of other CNT-based EMW absorbers ever reported. The synergistic effects of multiple EMW absorption mechanisms for the hybrid aerogels were analyzed at length, demonstrating the indispensable roles of the CNF or CNFC in constructing high-efficiency CNT-based EMW absorbers. Combined with the green, sustainable, facile, and scalable preparation approach, the carbon aerogel-based EMW absorbers are highly promising for applications in electromagnetic compatibility or protection and aerospace.

Tunable, thiol-ene, interpenetrating network hydrogels of norbornene-modified carboxymethyl cellulose and cellulose nanofibrils

Carboxymethyl cellulose modified with norbornene groups (NorCMC) and cellulose nanofibrils (CNFs) produced through mechanical refining without chemical pretreatment formed interpenetrating network hydrogels through a UV-light initiated thiol-ene reaction. The molar ratio of thiols in crosslinkers to norbornene groups off the NorCMC (T:N), total polymer weight percent in the hydrogel, and weight percent of CNFs of the total polymer content of the hydrogels were varied to control hydrogel properties. This method enabled orders of magnitude changes to behavior. Swelling in aqueous environments could be significant (>150 %) without CNFs to minimal (<15 %) with the use of 50 % CNFs. NorCMC and CNF networks interacted synergistically to create hydrogels with compression modulus values spanning 1 to 150 kPa - the values of most biological tissues. T:N and total polymer weight percent could be varied to create hydrogels with different CNF content, but the same compression modulus, targeting 10 and 100 kPa hydrogels and providing a system that can independently vary fibrillar content and bulk modulus. Analysis of the effective crosslinks, thiol-ene network mesh size, and burst release of the polymer indicated synergistic interactions of the NorCMC thiol-ene and CNFs networks. These interactions enhanced modulus and degradation control of the network under physiological conditions.

High-performance and multifunctional conductive aerogel films for outstanding electromagnetic interference shielding, Joule heating and energy harvesting

High-performance polymer-based functional materials have attracted tremendous interests in various applications. However, it is a challenge to integrate multiple functions without losing the advantages of being light, porous, green and so on. Herein, we designed a conductive aramid nanofiber (ANF)/cellulose nanofibril (CNF)/silver nanowire (AgNW) (ACA) composite aerogel film by directional freeze-drying and moderate compressing. The ACA aerogel film obtained an ideal electromagnetic interference shielding efficiency of 34.34 dB while maintaining a high electrical conductivity of 10.81 S/m. On the other hand, the surface steady-state temperature of the aerogel film reached 111 °C under a low applied voltage of 1.6 V. More importantly, a single-electrode triboelectric nanogenerator (TENG) was assembled by ACA aerogel film and polytetrafluoroethylene (PTFE) film. The open-circuit voltages, short-circuit currents, and maximum instantaneous power density of the TENG exhibited a spectacular value of 104 V, 1.52 μA, and 694 mW/m2, respectively, which could light up 23 LED lights at the same time. This novel multifunctional ACA aerogel film holds great application potentials for electromagnetic protection, energy harvesting, and thermal management.

Effects of cellulose nanofibrils treatment on antioxidant properties and aroma of fresh-cut apples.

Horticultural products tend to deteriorate during postharvest storage and processing. In this study, cellulose nanofibers (CNFs) were prepared from wood to investigate the effects of CNF treatment on the storage quality, aroma composition, and antioxidant system of fresh-cut apple (Malus domestica) wedges. Compared with control treatment, CNF coating treatment significantly improved the appearance of apple wedges; reduced the decay rate of apple wedges; and delayed the decline in weight loss, firmness, and titratable acid during storage. Gas chromatography-mass spectrometry showed that CNF treatment could maintain the aroma components of apple wedges (stored for 4days). Further investigations showed that CNF treatment increased the antioxidant system level and decreased reactive oxygen species content and membrane lipid peroxidation level of apple wedges. Overall, this study showed that CNF coating could effectively maintain the quality of fresh-cut apples during cold storage.

On the stabilization of emulsions by cellulose nanocrystals and nanofibrils: Interfacial behavior and synergism

Competitive adsorption of cellulose nanofibers at oil-water interface in Pickering emulsion is reported here. Dodecane-in-water emulsions stabilized by either of two types of nanocelluloses, cellulose nanocrystals (CNC) or cellulose nanofibrils (CNF), as well as by their binary mixtures with increasing fractions of CNC, were prepared using particle concentrations of 0.1–0.5 wt% and studied. Despite differences in shape and morphology, both forms of nanofibers produced stable emulsion droplets even at low particle concentrations (0.1 wt%), with CNC producing smaller droplets and emulsions with higher stability. When mixed, an increased fraction of CNC in the mixture reduced the average droplet size, which however applied only for higher contents of oil (30 and 50 wt%) and higher total contents of cellulose particles used under emulsification. The CNC particles controlled the size of emulsion droplets, while the role of CNF contributed to the further surface coverage. When the fraction of CNF in the mixture increased, the capability of CNC particles to readily adsorb at the oil-water interface was reduced by the CNF nanofibrils present in aqueous phase. The stability of emulsions with respect to changes in droplet size and creaming index was influenced more by oil content and total particle concentration than by the fraction of CNC present in the mixture.

Recycling of TEMPO-mediated oxidation medium and its effect on nanocellulose properties

The potential of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy)-mediated oxidation (TMO) to produce cellulose nanofibrils (CNFs) is hindered using costly and environmentally harmful catalysts, limiting its large-scale implementation. To promote sustainability, the TMO medium should be reused but there is a lack of knowledge on this process. The novelty of this research is the identification of the key parameters that affect the recirculation of the TMO medium, and their impact on the quality of the oxidized pulps and CNF products. Contrary to previous hypothesis, results show that the accumulation of salts is not a key parameter; instead, the pulp consistency during oxidation plays a vital role since concentrations higher than 10 g/L led to better CNF quality. Thus, reusing 75 % of the reaction medium, when high pulp consistency is used, does not alter the CNF properties. By reusing the reaction medium up to six times, the catalyst dose is dramatically reduced by >90 % for TEMPO and 80 % for NaBr, compared to the conventional process (0.1 mmol of TEMPO/g and 1 mmol of NaBr/g without medium reuse). Additionally, the high consistency oxidation enables a reduction of >80 % in the reaction time and effluent, and thus a threefold increase in CNF production.

Cellulose Nanofibril (CNF)-Coated PFAS-Free, Grease-Resistant All-Bio-Based Molded Pulp Containers for Food Packaging

Cellulose Nanofibril (CNF)-Coated PFAS-Free, Grease-Resistant All-Bio-Based Molded Pulp Containers for Food Packaging

Effect of the Pretreatment on the Properties of Cellulose Nanofibril Derived from Recycled Pulp

Effect of the Pretreatment on the Properties of Cellulose Nanofibril Derived from Recycled Pulp

Preparation of cellulose nanofibrils and their effects on the rheological properties and compressive strength of oil-well cement paste

In this study, an efficient hybrid preparation method was developed for isolating cellulose nanofibrils (CNFs) from cellulose fibres using ball milling and tetramethylpiperidine-1-oxyl (TEMPO) oxidation. The chemical structure and microstructure of the obtained CNFs were characterised using Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Additionally, the effects of CNFs on the rheological properties, thickening time, and compressive strength of oil-well cement paste were investigated. Ball milling for 30 min at a revolution speed of 500 r/min changed the microstructure of the cellulose fibres to a ‘fibrous-sheet structure’, reduced their diameters to several micrometres, and increased their specific surface area. Furthermore, this change in the cellulose fibre microstructure reduced the TEMPO oxidation reaction time, thereby improving the preparation efficiency of the CNFs. The TEM and XPS results indicate that CNFs can be obtained via TEMPO oxidation for 2 h. The surface of the CNFs contained up to 5.08% C = O groups. Additionally, compared to the pure oil-well cement sample, the yield stress of the oil-well cement paste containing 0.2% CNFs increased from 2.31 Pa to 9.84 Pa, and its consistency increased from 10.6 Bc to 28.0 Bc, which confirmed that the CNFs formed a ‘fabric structure’ to increase the structural force of the oil-well cement. Moreover, the compressive strength of the oil-well cement paste containing 0.2% CNFs cured for 2 d at 60 °C increased by 50.4%, while that of the paste cured for 14 d increased by 53.0% compared to that of the pure oil-well cement paste. These achievements can provide some sight for designing the high-performance oil-well cement paste.

Dimensional stability, durability and performance of hybrid recycled cellulose fibres reinforcing earth-based materials

Brittle fracture initially occurs at the nanometric and/or interatomic scale without prior plastic deformation under elastic loading. Fibres of different dimensional scales in hybrid composites provide dense packaging and act as reinforcements in the corresponding scales and dimensions. This study evaluated the effect of the inclusion of cellulose pulp (CP) (5wt%, 4.5wt%, 4wt% and 3.5wt%) combined with cellulose nanofibrils (CNF) (0.5wt%, 1wt% and 1.5wt%) from recycled cardboard on the water absorption, density, dimensional stability, thermal insulation, flexural strength and durability of earth-based materials. The total cellulose content (CP and CNF) is set at 5wt%. The results show that the partial replacement of CP by CNF contributes to an increase in the moisture content of the composite from 18% to 21%, while there is a reduction in their dry shrinkage from 2.29% to 1.29% and in their thermal conductivity from 0.42 to 0.39 W/m.K. This is attributed to the different dimensional scales of the fibres in hybrid composites, which provide a dense assembly with greater dimensional stability. The 3.5% CP content combined with 1.5% CNF showed the highest flexural strength (2.76 MPa) and modulus of elasticity (1.93 GPa) of the hybrid materials under four-point bending loading, due to the high anchorage between the cellulose fibres and the matrix. CP and CNF as reinforcing agents in an earth-based matrix is a suitable solution for improving the flexural strength, density, dimensional stability and durability of building bricks. However, bricks reinforced only with CP are recommended where flexural strength and toughness are essential requirements.

Bio-Based Impregnated Resin Preparation for Aldehyde-Free Decorative Paper Production

With the growing concern for environmental protection and personal health, utilizing bio-based impregnated resin has become a sustainable approach for producing aldehyde-free decorative paper and in-house decorations. Our current work focuses on the preparation of an aldehyde-free resin (AFR) by formulating quaternized cellulose nanofibrils (QCNFs, Ave. width 10 ± 3 nm, Ave. length of and &gt;500 nm) with aqueous acrylate emulsion. We analyzed the synthesized QCNFs, acrylate emulsion, and AFR by using various methods, including FTIR, XPS, XRD, TGA/DTG, and rheometer, to evaluate their applicability for impregnated paper processing. At a low coating weight of 4.0 g/m2, a 30.8% increase and 4.9-times increase in tensile strength and contact angle were detected, respectively. Meanwhile, the free aldehyde emission from the AFR-coated paper was found to be 0.1 mg/L even at a high coating weight of 18.8 g/m2, which is far below the E0 level requirement in the JAS 234:2003 criteria. Therefore, the surface coating of the decorative base paper was found to be competitive in covering the porous structure of the paper, reinforcing its mechanical strength, and providing high water resistance. Moreover, the lower free aldehyde emission from the AFR-coated paper ensures its safety and potential application in house decoration products.

A mild re-watering strategy for fast and efficient nanoscale redispersion of oven-dried TEMPO-oxidized cellulose nanofibrils in water

Owing to the formation of irreversible aggregation between cellulose nanofibrils during drying, nanoscale redispersion of cellulose nanofibrils therefore remained a challenge. In this study, a re-watering strategy was proposed to achieve nanoscale redispersion of oven-dried TEMPO-oxidized cellulose nanofibrils (TOCN) in water. The results showed that water wetting-up could achieve efficient redispersion of oven-dried TOCN with the highest redispersion rate of 79 %, and the nanoscale redispersion of TOCN was realized as revealed by obvious birefringence and dynamic light scattering (DLS) tests. The observed increase in redispersion rate may be attributed to the ability of water-wetting action to re-open the hydrogen bonding between fibrils. Moreover, the addition of negative sodium lignosulfonate (LS) with high water absorption would further improve the redispersion rate. When the wetting time was 6 h and the LS addition was 10 %, the redispersion rate was as high as 95 %. This was due to the synergistic effect of water adsorption, spatial site resistance as well as electrostatic effects. In addition, there was no significant difference in the mechanical properties of the TOCN films before and after redispersion. Compared to other additives, there was a significant advantage in terms of additional quantity and processing time. Finally, redispersed TOCN can be effectively used as a proppant for fracturing fluids to improve their stability. Hence, a mild and facile solution was suggested here for the preparation of nanoscale redispersion of cellulose nanofibrils with high redispersion efficiency, which was viable for large-scale applications.

Direct ink writing of multifunctional nanocellulose and allyl-modified gelatin biomaterial inks for the fabrication of mechanically and functionally graded constructs

Recreating the intricate mechanical and functional gradients found in natural tissues through additive manufacturing poses significant challenges, including the need for precise control over time and space and the availability of versatile biomaterial inks. In this proof-of-concept study, we developed a new biomaterial ink for direct ink writing, allowing the creation of 3D structures with tailorable functional and mechanical gradients. Our ink formulation combined multifunctional cellulose nanofibrils (CNFs), allyl-functionalized gelatin (0.8–2.0 wt%), and polyethylene glycol dithiol (3.0–7.5 wt%). The CNF served as a rheology modifier, whereas a concentration of 1.8 w/v % in the inks was chosen for optimal printability and shape fidelity. In addition, CNFs were functionalized with azido groups, enabling the spatial distribution of functional moieties within a 3D structure. These functional groups were further modified using a spontaneous click chemistry reaction. Through additive manufacturing and a readily available static mixer, we successfully demonstrated the fabrication of mechanical gradients – ranging from 3 to 6 kPa in indentation strength – and functional gradients. Additionally, we introduced dual gradients by combining gradient printing with an anisotropic photocrosslinking step. The developed biomaterial ink opens up possibilities for printing intricate multigradient structures, resembling the complex hierarchical organization seen in living tissues.