Nanocellulose Films Research Articles

The influence of reed nanocellulose on the quality indicators of paper-basis for wallpapers

Improving the production technology of products with improved quality indicators and with less impact on the environment remains an urgent scientific and practical problem of paper industry enterprises. This refers to the technology for the production of paper-bases for wallpaper using environmentally safe chemical additives, in particular nanocellulose (NC), which was obtained by acid hydrolysis from reed cellulose. The production of cellulose was carried out in two stages - extraction from reed stalks with a solution of alkali and an organosolvent method of cooking in a solution of peracetic acid. The obtained organosolvent cellulose contained the remains of lignin and mineral substances, which allows it to be used for the preparation of NC. As a result of the hydrolysis of organosolvent cellulose, a time-stable NC suspension was extracted, the properties of which were investigated by scanning electron microscopy (morphological changes in the structure of reed cellulose-containing materials), atomic force microscopy (determination of topographic characteristics of NC), analysis of electronic absorption spectra (transparency of NC films). It was established that reed NC films had nanoparticles with a cross-sectional size of 5-25 nm, density up to 1.52 g/cm3, transparency up to 81.6 %, tensile strength up to 65 MPa. For the production of castings of paper-bases for wallpaper samples, sulfated pine bleached cellulose and polyester synthetic fiber were used, to the fibrous mass of which were added the following chemical additives: alkyl ketene dimer, reed NC, binder, and optical brightener. It has been shown that the use of nanocellulose at a rate of 0.35 % to 1.0 % of the paper mass leads to a significant improvement in the physical and mechanical quality indicators of the paper base for wallpaper. It was established that the replacement of 50 % of the synthetic chemical auxiliary substance alkyl ketene dimer with nanocellulose or additional application of nanocellulose at a rate of 0.5 g/m2 on the surface of the casting with 0.7 % alkyl ketene dimer allows to obtain paper that meets the requirements of the standard. The obtained results indicate the prospects of using reed nanocellulose for the production of other mass types of paper and cardboard.

Methods for Fabrication of Freestanding Nanocellulose Film as a Sustainable Material for Packaging and Biomedical Applications: A Review

Biopolymers are a sustainable alternative to traditional plastics in the medical and packaging fields. Biopolymers are biodegradable and can be used to reduce plastic pollution. They are derived from renewable resources like cornstarch, sugarcane, or cellulose. Cellulose nanomaterials have the potential to revolutionize various industries. However, the production process of nanocellulose films is time-consuming, and there is a need for quick and adaptable methods to fabricate these films. Techniques such as solvent casting, spin coating, roll-to-roll printing, layer-by-layer assembly, vacuum filtration, and spraying are used to fabricate free-standing nanocellulose films, each with its advantages and limitations. The spraying process shows promise in producing nanocellulose films quickly and efficiently. In addition to that, the need for free-standing nanocellulose films in medical packaging and tissue engineering areas was admirable. However, the rapid process for fabrication of the film should be developed for large-scale production and commercialization of films.

Thermochromic Nanocellulose Films for Temperature-Adaptive Passive Cooling.

Energy efficiency in habitation spaces is a pivotal topic for maintaining energy sufficiency, cutting climate impact, and facilitating economic savings; thus, there is a critical need for solutions aimed at tackling this problem. One viable approach involves complementing active cooling methods with powerless or passive cooling ones. Moreover, considerable scope remains for the development of passive radiative cooling solutions based on sustainable materials. Cellulose, characterized by its abundance, renewability, and biodegradability, emerges as a promising material for this purpose due to its notable radiative cooling potential exploiting the mid-infrared (MIR) atmospheric transmission window (8-13 μm). In this work, we propose the utilization of thermochromic (TC) materials in conjunction with cellulose nanofibrils (CNF) to confer temperature-dependent adaptivity to hybrid CNF films. We employ a concept where high reflection, coupled with MIR emission in the heated state, facilitates cooling, while high visible light absorption in the cold state allows heating, thus enabling adaptive thermal regulation. CNF films were doped with black-to-leuco TC particles, and a thin silver layer was optionally applied to the films. The films exhibited a rapid transition (within 1 s) in their optical properties at ∼22 °C, becoming transparent above the transition temperature. Visible range transmittance of all samples ranged from 60 to 90%, with pronounced absorption in the 8-13 μm range. The cooling potential of the films was measured at 1-4 °C without any Ag layer and ∼10 °C with a Ag layer. In outdoor field testing, a peak cooling value of 12 °C was achieved during bright sunshine, which is comparable to a commercial solar film. A simulation model was also built based on the experimental results. The concept presented in this study extends beyond applications as standalone films but has applicability also in glass coatings. Overall, this work opens the door for a novel application opportunity for green cellulose-based materials.

Preparation of sustainable oxidized nanocellulose films with high UV shielding effect, high transparency and high strength

UV protection has become crucial as increasing environmental pollution has led to the destruction of the ozone layer, which has a weakened ability to block UV rays. In this paper, we successfully prepared cellulose-based biomass films with high UV shielding effect, high transparency and high tensile strength by graft-modifying oxidized cellulose nanocellulose (TOCN) with folic acid (FA) and borrowing vacuum-assisted filtration. The films had tunable UV shielding properties depending on the amount of FA added. When the FA addition was 20 % (V/V), the film showed 0 % transmittance in the UV region (200–400 nm) and 90.61 % transmittance in the visible region (600 nm), while the tensile strength was up to 150.04 MPa. This study provides a new integrated process for the value-added utilization of nanocellulose and a new route for the production of functional biomass packaging materials. The film is expected to be applied in the field of food packaging with UV shielding.

Processing factors affecting roughness, optical and mechanical properties of nanocellulose films for optoelectronics

This work aims to understand how nanocellulose (NC) processing can modify the key characteristics of NC films to align with the main requirements for high-performance optoelectronics. The performance of these devices relies heavily on the light transmittance of the substrate, which serves as a mechanical support and optimizes light interactions with the photoactive component. Critical variables that determine the optical and mechanical properties of the films include the morphology of cellulose nanofibrils (CNF), as well as the concentration and turbidity of the respective aqueous suspensions. This study demonstrates that achieving high transparency was possible by reducing the grammage and adjusting the drying temperature through hot pressing. Furthermore, the use of modified CNF, specifically carboxylated CNF, resulted in more transparent films due to a higher nanosized fraction and lower turbidity. The mechanical properties of the films depended on their structure, homogeneity (spatial uniformity of local grammage), and electrokinetic factors, such as the presence of electrostatic charges on CNF. Additionally, we investigated the angle-dependent transmittance of the CNF films, since solar devices usually operate under indirect light. This work demonstrates the importance of a systematic approach to the optimization of cellulose films, providing valuable insight into the optoelectronic field.

Fabrication of coconut dregs residue derived nano-cellulose film for food packaging

To replace conventional plastic as food packaging, several studies related to the preparation of cellulose films from various types of biomass have been reported. However, there have been no reports regarding the use of coconut dregs residue as source of cellulose for the fabrication of cellulose films. This is the first report on the fabrication of cellulose film from coconut dregs under various conditions. The purpose of this work was to investigate the effect of hydrochloric acid, and ultrasonication during the isolation process of cellulose from coconut dregs on the characteristic of cellulose film produced. Hydrochloric acid was used in the hydrolysis process and the concentrations used were 3 M, 5 M, and 7 M. The ultrasonication process was performed after the bleaching process of cellulose isolation. Cellulose films were prepared from ultrasonicated isolated cellulose particles prepared with different hydrochloric acid concentrations and compared with cellulose films obtained from isolated cellulose without the ultrasonication process. Results showed the higher hydrochloric acid concentration the lower particle size of cellulose produced. The cellulose particle size decreased after ultrasonication treatment and cellulose obtained using hydrochloric acid 7 M became nano-size cellulose particles after the ultrasonication process. These results influence the film properties obtained from these cellulose particles, where the lower the particle size the more transparent the film produced. The most transparent film was produced from cellulose particles isolated using hydrochloric acid 7 M in combination with the ultrasonication process. Furthermore, hydrochloric acid concentration and ultrasonication also influenced the tensile strength, crystallinity, and thermal stability of the films.

Nanocellulose/natural rubber latex composite film with high barrier and preservation properties

Nanocellulose films have excellent oxygen barrier properties, but their water vapor barrier properties and water resistance are poor. Natural rubber latex (NRL) has been used as a composite material to improve the hydrophobic properties of 2,2,6,6-tetramethylpiperidin-1-oxo (TEMPO) oxidized nanocellulose fibers (TOCNFs) because of its natural core-shell structure that allows for homogeneous mixing with hydrophilic polymers in aqueous solutions. The exposure of the internal hydrophobic isoprene molecular chains of NRL during the drying process allows the composite film to have greatly improved water resistance and excellent water vapor and oxygen barrier properties. The water vapor permeability (WVP) and oxygen permeability (OP) of the film were as low as 6.07 × 10−13 g m/m2·s·Pa and 3.11 × 10−15 cm3 cm/cm2·s·Pa, respectively. The good water resistance of the composite film makes the wet tensile strength of the film up to 15.87 MPa, which reaches 71.69% of the dry tensile strength. In addition, the high ductility of NRL makes the composite film good toughness, and its elongation at break can reach about three times that of most nanocellulose-based films. Strawberry preservation experiments have shown that it can effectively slow down the deterioration of strawberries, extending their shelf life from 2 days to 7 days.

Adjustable strength and toughness of dual cross-linked nanocellulose films via spherical cellulose as soft-phase

Nanocellulose films possess numerous merits ascribing to their inherent biocompatibility, non-toxic and biodegradability properties. The potential for practical applications would be improved if their mechanical strength and toughness requirements could be met simultaneously. Herein, dual cross-linked nanocellulose (DC) film was fabricated by the treatments of chemical and physical cross-linking, which was mechanically superior to pure nanocellulose (CNF) films. To further increase the toughness of DC films, spherical cellulose (Sph) was incorporated into DC film (DC-Sph film), and analyzed under different humidity conditions (RH) (from 10 % to 90 %). The changes of functional groups of CNF, DC and DC-Sph films were detected by FTIR and XPS spectrum. The epichlorohydrin and Sph content were optimized, followed by the investigation of RH on the toughness of films. The highest tensile strength (146.6 ± 4.6 MPa) was obtained in DC film at 50 % RH, while the DC-Sph film showed the largest toughness (40.3 ± 3.7 kJ/m2) at 70 % RH. Furthermore, the possible toughening mechanism of DC-Sph film was also discussed.

Photocrosslinkable and hydroplasicable UV-shielding nanocellulose films facilitated by hydroxyl-yne click reaction

Sustainably-sourced functional nanocellulose materials are vitally important for the green and sustainable development. Herein, we reported photocrosslinkable and hydroplasticable TEMPO-oxidized cellulose nanofiber phenyl propylene ketone ethers (TOCNPPK) films with excellent ultraviolet (UV) shielding, highly reversible processability, and extended mechanical properties, which were facilitated by green hydroxyl-yne click reaction. The introduction of conjugated aromatic ring and vinyl bonds (-C=C-) had been demonstrated the key for the improved overall performance of resultant TOCNPPK, which not only endowed the TOCNPPK with nearly 100 % UV shielding, but also enabled it to be formed into diverse 3D shapes (helix, ring and letters “N, F, U”) via the facile hydrosetting method. The photocrosslinkable-enhanced mechanical performance of TOCNPPK films was also attributed to -C=C- which could crosslink via [2π + 2π] cycloaddition reactions under UV-irradiation. The ultimate stress of TOCNPPK films was as high as 210.0 ± 22.8 MPa and the Young's modulus was 11.5 ± 0.7 GPa, much superior to those of 128.6 ± 8.5 MPa and 9.2 ± 0.6 GPa for pristine TOCN films. Furthermore, the TOCNPPK had been demonstrated as efficient nanofillers for both hydrophilic polyvinyl alcohol and lipophilic polycaprolactone to develop advanced biodegradable composite films with the integration of good water-wetting resistance, excellent UV blocking, and photo-enhanced mechanical performance.

Monolithic nanocellulose films patterned with flower-shaped and other microstructures: A facile route to modulate topographical, wetting and optical properties

Surface microstructures are found in nature as a mean to control wettability and adhesion. Efforts to reproduce related architectures in designing functional materials, however, require the use of tedious procedures, such as micro- and nanolithography. Herein, we introduce a facile and scalable method to create highly ordered surface microstructures or patterns supported on films made from the same material, cellulose nanofibrils (CNF). The micropatterning is based on fluid flow through solid grids that transfer three-dimensional designs on the surface of the formed films, with precise control on their spatial distribution. The obtained patterned films can be modulated as far as their wettability, optical and haptic features. The viscosity of the CNF aqueous suspension and strength properties of the produced films are shown to define the architecture of the surface patterns. In particular, multi-scale flower-shaped structures generate new properties, going from super-absorbency through capillary action in unmodified films to superhydrophobic materials after mild hydrophobization treatment. Our results pave the way to scalable and cost-efficient designs based on CNF for water harvesting, microfluidics, anti-reflective surfaces and haptic devices, among others

A novel salt-barrier method of preparation flexible temperature resistant full-component nanocellulose membranes

With the simplification and diversification of separation technologies, nanocellulose membranes have become widely used as insulating materials. Recently, study of nanocellulose membrane modification has become a hot topic. However, the application of nanocellulose membrane has been limited due to their inadequate heat resistance and flexibility. Herein, based on the pyrolytic and thermoplastic properties of cellulose, we innovatively introduced a salt barrier scheme to regulate the degree of hydrogen bonding and thermoplastic bonding between fibers. This was achieved by adding a salt barrier agent, NaCl, in the middle of the nanocellulose to prepare and obtain flexible, high-temperature-resistant nanocellulose film materials. The full-component cellulose films thus prepared exhibited high tensile strength (8 MPa), excellent flexibility (105 mN), high electrical breakdown strength (67 KV/mm), and volume resistivity meeting the standard of insulation materials (3.23 × 1013 Ω·m). This scheme adheres to the principles of low cost, green, non-toxic and non-hazardous, providing a brand new approach for the research and development of high temperature resistant cellulose membrane materials, which is of significant commercial value and industrialization prospect.

Nanocellulose Coating on Kraft Paper

Paper is a biodegradable material, but in food packaging, its hygroscopicity and porosity can cause food contamination due to the exchange of gasses and liquids with the environment. Therefore, it is important to use biodegradable materials for paper coatings, such as nanocellulose, which is chemically compatible with paper but less hygroscopic. The objective of this study was to evaluate the effectiveness of nanofibrillated cellulose (NFC) as a paper coating. NFC produced from bleached eucalyptus pulp was used as a coating on kraft paper sheets produced from Pinus pulp. To prepare the coating, two thicknesses of wet nanocellulose (1 mm and 2 mm) were tested, and two nanocellulose films made with the same thicknesses were evaluated. The morphological, physical, mechanical, and thermal properties of the composites were investigated. The presence of NFC improved the surface of the paper by filling the pores; consequently, the density and barrier properties were also improved. All mechanical properties were improved, with the highest increases observed for bursting and tensile strength; however, the films showed low bursting index values and null values for the tearing index. The thermal stability of the paper with NFC coatings met the minimum requirements for food packaging.

Bacterial nanocellulose production using cost-effective, environmentally friendly, acid whey based approach

This study investigates the production of bacterial nanocellulose (BNC) film using a symbiotic culture of bacteria and yeasts (SCOBY) in acid whey medium. The yields were 59.58 g/L for wet and 2.75 g/L for freeze-dried BNC films in four days. The film contained cellulose nanofibrils with diameters ranging from 20 nm to 100 nm with a 34.3 % crystallinity index as confirmed by X-ray diffraction. Incorporating glycerol as a plasticizer modified the mechanical and thermal properties of the BNC film, reduced brittleness, and enhanced strain from 0.75 % to above 16 %. Fourier Transform Infrared Spectroscopy analysis identified intermolecular hydrogen bonding between the BNC film and glycerol. The glass transition temperature increased from roughly 158 °C to above 166 °C. The study validates the potential of acid whey as a viable alternative substrate for the production of BNC. The production method providing environmental benefits, cost-efficiency, and scalability, it also delivers an effective circular economy solution.

Ultra-thin parylene-aluminium hybrid coatings on nanocellulose films to resist water sensitivity

Non-sustainable single-use plastics used for food packaging needs to be phased out. Films made from cellulose nanofibrils (CNFs) are suitable candidates for biodegradable and recyclable packaging materials as they exhibit good mechanical properties, excellent oxygen barrier properties and high transparency. Yet, their poor water vapour barrier properties have been a major hindrance in their commercialisation. Here, we describe the preparation of 25 μm thick CNF films with significantly improved water vapour barrier properties after deposition of ultrathin polymeric and metallic coatings, parylene C and aluminium, respectively. When first adding a 40 nm aluminium layer followed by an 80 nm parylene layer, i.e. with a combined thickness of less than one percent of the CNF film, a water vapour transmission rate of 2.8 g m−2 d−1 was achieved at 38 °C and 90 % RH, surpassing a 25 μm polypropylene film (4–12 g m−2 d−1). This is an improvement of more than 700 times compared to uncoated CNF films, under some of the harshest possible conditions a packaging material will need to endure in commercial use. The layers showed a good and even coverage, as assessed by atomic force microscopy, and the parylene-coated surfaces were hydrophobic with a contact angle of 110°, providing good water repellency.

Flexoelectric and piezoelectric effects in micro- and nanocellulose films

In this work, we evaluated the flexoelectric and piezoelectric contributions to the overall macroscopic polarization in cellulose films. To this end, the flexoelectric μ31 and transverse effective piezoelectric e31,f coefficients of cellulose films were determined using cantilever beam bending. The experiments were based on theoretical developments allowing to separate the flexoelectric from the piezoelectric contribution, represented by an effective flexoelectric coefficient, μeff, depending on both e31,f and μ31. Five free-standing and stainless steel/cellulose bilayer films were prepared from cellulose showing different morphologies and surface charge degrees: two almost neutral cellulose microfibers (CMF) and three (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)-oxidized cellulose micro- (TCMF) and nanofibers (TCNF) bearing negative charged groups on the surface.The dielectric properties of the films indicated a low dielectric constant for unmodified CMF, and a huge increase for TEMPO-oxidized samples, which were up to 9 times higher than poly(vinylidene fluoride)-based polymers. TEMPO-oxidized cellulose films exhibited the largest flexoelectric coefficients (almost 7 times higher than those of synthetic polymer dielectrics), which evidenced that the presence of polar groups and surface charge boosted both flexoelectricity and piezoelectricity in unpoled cellulose films. These findings pave the way towards sustainable cellulose-based curvature sensors with large effective flexoelectric coefficients, without the need of preliminary energy consuming poling step.

Poly(vinyl alcohol)/nanocellulose film integrated with phenolic waste-based carbon dots for ultraviolet-blocking and flame retardant applications

Recycling of thermosetting plastic waste and development of functional biopolymer-based films have become captivating issues in the worldwide recently. The current work highlights the facile approach to transform the thermosetting phenolic foam (PF) waste to dual-functional carbon dots (CDs) via simple hydrothermal treatment. The obtained CDs have displayed good graphite structure with rich carbon (C), nitrogen (N), sulfur (S), and phosphorus (P) elements. The absorption peak and quantum yield (QY) values of N, S, P-doped CDs (N,S,P-CDPF) were affected by the hydrothermal precursors and reaction. The fluorescent N,S,P-CDPF derived from PF have further been assembled with the poly(vinyl alcohol) (PVA) and oxidized nanofibrillated cellulose (ONFC) to develop ultraviolet (UV) blocking and flame retardant (FR) films via the solution casting approach. The morphology, transparency, UV–visible behavior, and flame retardancy of the composite films were studied. The light-blocking efficiency and flame retardancy of the films were verified by adjusting the loading ratio of N,S,P-CDPF in the films. The film with 0.05 wt% N,S,P-CDPF can absorb most of UV and some blue light (∼39.6 % at 450 nm), and retain 76.5 % transparency at 800 nm. In addition, the PF-derived N,S,P-CDPF have proved to be good flame retardant owing to the increased limiting oxygen index (LOI) >31.7 %, and reduced heat-release rate (HRR) from 287.4 W/g to 127.2 W/g for the PVA-ONFC@CDPF5 film compared to the pristine PVA film. Finally, the current studies provide a promising strategy for recycling of PF waste as a flame retardant UV absorber and create awareness regarding the flame retardant and flexible UV-blocking packaging materials.

Planar and uniplanar orientation in nanocellulose films: interpretation of 2D diffraction patterns step-by-step

Planar and uniplanar orientation in nanocellulose films: interpretation of 2D diffraction patterns step-by-step

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.

Antimicrobial activity of different nanocellulose films embedded with thyme, cinnamon, and oregano essential oils for active packaging application on raspberries

The study focuses on the antimicrobial activity of nanocellulose films (NFC) embedded with thyme, cinnamon, and oregano essential oils for active packaging application. The activity against model pathogenic bacteria was first tested to obtain each oil's minimum inhibitory concentration (MIC). The tests showed that the surface area of the films and the quantity of essential oil strongly influenced the antimicrobial effect. Then, the different active packaging systems were tested directly on packed raspberries to study their actual commercial packaging conditions. Through 12 days of storage at 1°C, it was observed that thyme and oregano essential oils were more effective in maintaining the firmness and reducing the weight loss of the fruits compared to cinnamon essential oil or the control; no significant effect was observed on the other quality parameters that were considered. The essential oils independently proved effective in preventing fungal growth. However, the combined impact of thyme+oregano (NAP_TO) demonstrated the best performance.

Nanocellulose/Nanodiamond Hybrids: A Review

Nanocellulose can be obtained from low-cost sources and has been extensively studied in the last decades due to its biodegradability, biocompatibility, low weight, large specific surface area, and good mechanical and optical properties. The nanocellulose properties palette can be greatly expanded by incorporating different metals, metal oxides or carbon nanomaterials, with the formation of multifunctional hybrids. Nanocellulose–nanocarbon hybrids are emerging nanomaterials that can respond to many current challenges in areas such as water purification, energy storage and conversion, or biomedicine for drug delivery, tissue engineering, antitumor and antimicrobial therapies, and many others. Although nanocellulose–nanodiamonds hybrids are still in their infancy, these nanomaterials are extremely promising for applications requiring good thermal conductivity and mechanical strength along with optical transparency. A strong increase in the thermal conductivity of a nanocellulose film of about 150 times was obtained after the addition of 90 wt% single-crystal nanodiamonds and a 70% increase in the Young’s modulus of nanocellulose films was produced by the addition of 5 wt% nanodiamonds. Therefore, in this review, data related to the manufacturing routes, main properties, and applications of nanocellulose–nanodiamonds hybrids are presented and discussed. This review paves the way for new methods and procedures to obtain nanocellulose–nanodiamonds hybrids better adapted to practical needs.