Addition Of Cellulose Nanofibers Research Articles

Fabrication of Highly Interconnected Poly(ε-caprolactone)/cellulose Nanofiber Composite Foams by Microcellular Foaming and Leaching Processes.

In this study, microcellular polycaprolactone (PCL)/sodium bicarbonate (NaHCO3)/cellulose nanofiber (CNF) composite foams with highly interconnected porous structures were successfully fabricated by microcellular foaming and particle leaching processes. Supercritical CO2 (scCO2) served as a physical foaming agent, NaHCO3 was chosen as a chemical foaming agent and porogen, and CNF acted as a heterogeneous nucleating agent. The effect of scCO2, NaHCO3, and CNF on pore structures and the cofoaming mechanism were investigated. The results indicated that the addition of NaHCO3 and CNF increased the melt strength of the PCL matrix significantly. During the foaming process, the presence of CNF can form a rigid network due to the hydrogen bonding or mechanical entanglement between individual nanofibers, improving the nucleating efficiency but slowing down the cell growth rate. Additionally, due to the interaction of “soft” PCL matrix and “hard” domains in a PCL-based composite during the foaming process, together with the NaHCO3 leaching process, highly interconnected cell structures appeared. The obtained PCL/NaHCO3/CNF composite foams had a cell size of 15.8 μm and cell density of 6.3 × 107 cells/cm3, as well as an open-cell content of 82%. The reported strategy in this paper may provide the guidelines and data supports for the fabrication of a PCL-based porous scaffold.

Machinability Investigation for Cellulose Nanofiber-Reinforced Polymer Composite by Ultraprecision Diamond Turning

Cellulose nanofiber (CeNF)-reinforced polymer composites have wide potential applications in the manufacturing of optical and mechanical parts owing to their light weight, high mechanical strength, and optical transparency. In this study, CeNF-reinforced homogeneous polypropylene (PP-CeNF) was machined under various conditions by ultraprecision diamond turning, and the results were compared with those of pure PP without CeNF addition. The influence of CeNFs on material removal was investigated by examining the surface topography, chip morphology, cutting forces, and cutting temperature. It was found that the surface defects in pure PP cutting were surface tearing, while the surface defects of PP-CeNF were surface tearing and micro-holes induced by the pulling-outs of CeNFs. Surface tearing increased with cutting speed; pulling-outs of CeNFs were slightly affected by cutting speed but strongly dependent on the tool feed rate. Under a small tool feed rate, the surface roughness could be reduced to ∼10 nm Ra for PP-CeNF. The thermal effect was insignificant in the experiments, whereas the effect of strain rate-induced material hardening was dominant for both workpiece materials at a high cutting speed. This study helps to understand the mechanisms for ultraprecision cutting of CeNF-reinforced polymer composites and provides guidelines for improving the machined surface quality.

Biocomposites Based on Agar and Cellulose Nanofibers Prepared from Carrot Slag

In this study, the effect of cellulose nanofibers (CNF) prepared from carrot slag on the properties of agar biocomposite films is investigated. The composite film was characterized by ultraviolet–visible spectroscopy (UV-Vis), tensile test, fourier transforms infrared (FT-IR) spectroscopy and Transmission electron microscopy (TEM). The transmittance, mechanical properties and chemical structure of the composite film containing different CNF content (0.1, 0.3 and 0.5 phr based on agar) were studied. The UV-Vis showed that the transmittance of the film was decreased with increasing content of CNF. The FT-IR spectrum showed that the generation of hydrogen bonds leads to good interface bonding between Agar and CNF. Moreover, the performance of the bionanocomposite was improved by the addition of CNF. The composite containing 0.3 phr CNF results in a maximum tensile strength of 25.97 MPa. However, the tensile strength of the 0.5 phr CNF containing one is reduced to 24.42 MPa due to the agglomeration of CNF. The TEM shows that the diameter of CNF is 2.5 nm and the length is 18.20 nm. The usage of CNF obtained from carrot slag can not only recycle the waste from food industry, but also can be used as a reinforcing agent for preparing biodegradable composite film. It has potential uses in the development of biodegradable food packaging materials and biomedical applications.

Orange Juice Processing Waste as a Biopolymer Base for Biodegradable Film Formation Reinforced with Cellulose Nanofiber and Activated with Nettle Essential Oil

Concerns about environmental problems have led to the development of biodegradable packaging. Food wastes as a byproduct could be a good source for biopolymers. This study aimed to describe the physical and antimicrobial features of nano biocomposite films based on orange waste powder (OWP) with different concentrations of nettle essential oil (NEO) (1.5 and 3%) as an antibacterial agent and cellulose nanofiber (CNF) (3 and 6%) as a structural reinforcement. Thus, Field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry analysis (DSC) were performed. Further, tensile strength, elongation at break, water vapor permeability, and antimicrobial properties were investigated. As a result, the addition of CNF improved the tensile strength and water barrier properties of the samples. Compared to the control film, adding NEO (3%) decreased the tensile strength but increased water vapor permeability and melting temperature. Moreover, the OWP-based film samples had an antimicrobial effect against five foodborne pathogens; this effect was increased considerably by enhancing the NEO concentration. In this regard, the maximum and minimum susceptibility was related to the Staphylococcus aureus and Salmonella enterica, respectively. In conclusion, orange waste could be used to produce an active film with improved physicomechanical and antibacterial properties by incorporating CNF and NEO.

Evaluation of the Mechanical and Physical Properties of Insulation Fiberboard with Cellulose Nanofibers

Abstract The objective of this study was to investigate the lab-scale manufacturing process of insulation fiberboard (IFB) with cellulose nanofibers (CNFs) and evaluate the effects of CNFs on the mechanical and physical properties of the IFB. Because the fabricated IFBs with CNFs had a homogeneous appearance, it was assumed that CNFs can be easily dispersed within IFB by adding them during the mixing stage of the wet process of wood-based board production. The results for the IFBs with CNFs revealed that the density and bending properties increased, while the thickness decreased with an increase in the CNF addition ratio. Furthermore, after the water absorption test, the weight change rates of the IFBs decreased, and the thickness swelling rates increased. Although the size of the specimens was different from the size in JIS A 5905 (Japan Standards Association 2014), the modulus of rupture (MOR) values of IFBs with a target density more than or equal to 0.20 g/cm3 were higher than the value of A-class IFB in the standard for all CNF addition ratios. In addition, lower thermal conductivity may be realized under similar MOR values by adding CNFs to IFB. On the other hand, to produce CNF-reinforced IFBs with target density/thickness, it is necessary to develop a method for decreasing the cohesive force derived from CNF aggregation and the compressive force originating from the water surface tension caused by the high water retention of CNFs.

ارزیابی ویژیگی های فیزیکی و مکانیکی نانو کامپوزیت ساخته شده از پلی وینیل الکل - نانو فیبر سلولوز و نانو اکسید سیلیکون

In this study, the effect of cellulose nanofibers and silicon nanoparticles on the properties of nanocomposites made with polyvinyl alcohol was studied and the physical, mechanical and morphological properties of nanocomposites were investigated. Samples were prepared by casting with different ratios of 0, 5 and 10% by weight. The morphology of nanocomposites was examined by scanning electron microscopy. Observations of water vapor permeability and water uptake by adding cellulose and nanoxide oxide nanofibers in pure polyvinyl alcohol control film and nanocomposite films with different compositions were significantly different from each other. Tensile strength of nanocomposites showed that increasing the amount of cellulose nanofibers and silicon nanoparticles increased the tensile strength and the percentage of elongation increased with the addition of cellulose nanofibers and silicon nanoparticles decreased. The results of the present study show that the addition of small amounts of nanocellulose fibers and silicon nanoparticles strengthens the polyvinyl alcohol polymer and improves the physical and mechanical properties and increases the performance of nanocomposites.

Improving the oxygen barrier of microcapsules using cellulose nanofibres

SummaryIn this study, the oxygen barrier and physical properties of two maltodextrin/gum Arabic (MD/GA) (3:1 w/w) microcapsules with dextrose equivalence (DE) 26 and 6 were assessed with or without the incorporation of cellulose nanofibres (CNF). The oxygen diffusion coefficient (Deff) was between 10.6 × 10−15 m2 s−1 and 17.3 × 10−15 m2 s−1 for all microcapsules. The addition of CNF improved the oxygen barrier of MD/GA microcapsules. The incorporation of CNF did not significantly impact Tg due to the low quantity of CNF present in the microcapsules. Wettability was higher in CNF incorporated microcapsules, and dispersibility was lower only for microcapsules with maltodextrin of DE 26. Spray‐dried microcapsules exhibited poor flowability and high cohesiveness due to the moisture content (2.0–2.5%) of the powders. The results suggest that incorporation of CNF can increase the oxygen barrier of MD/GA microcapsules which may lead to better oxidative stability of micronutrients incorporated in the microcapsules.

A New Ozonated Cassava Film with the Addition of Cellulose Nanofibres: Production and Characterization of Mechanical, Barrier and Functional Properties

In this study cassava starch modified by ozone technology and cellulose nanofibres were used to produce films. These nanocomposites were produced by casting technique using non-modified and ozonated cassava starches, glycerol and, water reinforced with cellulose nanofibres (NCF) at 1%, 2%, and 5%. Films were characterized in terms of mechanical, barrier and functional properties, morphology, opacity and the sealing ability. In general, ozonated cassava films result in increased mechanical properties, water vapour permeability, and hydrophilicity. The addition of cellulose nanofibres, in certain conditions, improved these properties due to the NCF dispersion in the polymeric matrix. However, the formation of agglomerates in higher concentrations (2% and 5%) was visible by SEM images. In specific, the addition of 1% of NCF to the 60 min ozonated film increased the Tensile Strength and the Young Modulus in ~ 117% and ~ 137%, respectively, and decreased the water vapour permeability in ~ 47%, in comparison to the non-modified film without NCF. In conclusion, the addition of NCF to ozonated cassava films improved their properties aiming specific application showing to be an interesting alternative for packaging industries in different areas.

Experimental Study of Polyvinyl Alcohol Nanocomposite Film Reinforced by Cellulose Nanofibers from Agave Cantala

This paper presents an experimental study of addition of cellulose nanofibers (CNF) extracted by the chemical-ultrasonication process from agave cantala leaf plants in the matrix of polyvinyl alcohol (PVA). Combining these materials produce the nanocomposite film with a thickness of 30 μm. The nanocomposite characteristic was investigated by the addition of CNF (0, 2, 5, 8, and 10 wt%) in PVA suspension (3 wt.%). PVA/CNF nanocomposite films were prepared by a casting solution method. The fibrillation of fibers to CNF was analyzed using Scanning Electron Microscopy and Transmission Electron Microscopy. The nanocomposite film functional group's molecular chemical bond and structural analysis were tested using Fourier Transform Infrared and X-ray diffraction. The PVA/CNF nanocomposite film has significant advantages on the ultraviolet barrier, thermal stability tested by Differential Scanning Calorimetry and Thermogravimetric Analyzer, and tensile strength. Overall, the optimal addition of CNF is 8 wt.% in matrix, resulting in the highest crystallinity index (37.5%), the tensile strength and elongation at break was an increase of 79% and 138%, respectively. It has good absorbing ultraviolet rays (82.4%) and high thermal stability (365oC).

Potential of pure cellulose nanofibers as a denture base material.

A study was conducted to evaluate the basic mechanical properties of a pure cellulose nanofiber (CNF) material in comparison with a commercial denture base material (polymethylmethacrylate [PMMA] acrylic resin). The working hypothesis was that CNFs have potential for use as denture base materials. Pure CNF specimens fabricated under various conditions were examined. The flexural strength (FS) and flexural modulus (FM) of the specimens were measured using the three-point bending test, and the morphologies of the fractured surfaces were examined using scanning electron microscopy. Addition of tricalcium phosphate to dehydrate the CNFs did not improve their FS or FM. Conversely, substitution with methanol effectively improved the dehydration process and significantly affected the mechanical properties of the CNFs. As the degree of CNF defibration increased, the physical properties of the specimens improved significantly. However, addition of CNFs to PMMA liquid to create CNF-reinforced PMMA did not improve the mechanical properties. Pure CNF specimens fabricated under particular conditions had higher FS and FM values than the control, suggesting that CNFs have potential as a "petroleum-free" alternative to acrylic resin denture base materials. Pure CNF would be potentially useful as a denture base material, and presumably applicable to computer-aided design/manufacture (CAD/CAM).

Thermal stability of starch bionanocomposites films: Exploring the role of esterified cellulose nanofibers isolated from crop residue

Thermal stability and degradation kinetics were studied for glycerol plasticized starch (GPS) nanocomposites reinforced with cellulose nanofibers (CNFs) extracted from wheat straw, a crop residue. To assess the effect of surface modifications on CNFs in improving thermal degradation behavior, three types of CNFs were used viz pristine (p-CNFs), esterified (m-CNFs) and a mixture of pristine and esterified (x-CNFs) in equal ratio. Three kinetics models Ozawa-Flynn, Freidman and Kissinger’s were used to evaluate activation energy of thermal degradation for pristine and nanocomposite samples. Properties like morphology, crystallinity and water vapor permeability (WVP) were also evaluated. Morphology of m-CNF/GPS bionanocomposites films was superior as compared to other films with better interfacial bonding. Moreover, m-CNFs also exhibited 81 % reduction WVP as compared to pristine GPS films. Activation energy revealed significant enhancement i.e. as high as 52 % in thermal stability with addition of CNFs. Consequent relation between morphology and thermal stability was also established.

Mechanical properties of mechanically-defibrated cellulose nanofiber reinforced epoxy resin matrix composites

Cellulose nanofibers (CNF) have recently attracted attention as one of the reinforcements for composite materials. However, the same as other nanofibers, CNFs can be easily agglomerated and the nano-level defibration is necessary to obtain their outstanding properties in polymer matrices. To overcome this issue, two major defibration methods, chemical and mechanical defibration have been considered. The chemically-defibrated CNF is expensive and so prevents the practical realization of CNF as general-purpose products. Therefore, the mechanical defibration method by a clean low-cost water jet was focused on. Mechanically-defibrated CNF reinforced epoxy resin matrix (Epoxy-CNF) composite was fabricated via mechanical mixing and the variation of their tensile and flexural properties with different CNF volume fractions was evaluated. The tensile and flexural moduli of the epoxy resin were increased by CNF addition, while the fracture elongation was decreased. The calculated ultimate tensile strength (UTS) and ultimate flexural strength (UFS) of the Epoxy-CNF composites, using the aspect ratio of the agglomerated CNF clusters, indicated the validity of the random dispersion model considering the agglomerated CNF as one whole fiber. It seems that epoxy resin is enhanced by the mechanical interaction when the CNF volume fraction is higher than 0.37 vol.%.

Fabrication of all-cellulose nanocomposites from corn stalk.

There is a need to help farmers and industries develop value-added composite and nanocomposite materials from agricultural residuals. Cellulose nanofibers (CNFs) were made using a TEMPO oxidation method and celluloses were prepared by acid-base method and extracting method, which were all from corn stalk, an agricultural residual. The prepared celluloses were dissolved separately in dimethylacetamide/LiCl solvent and CNFs were added at 0.0%, 0.5%, 1.5% and 3.0% to form all-cellulose nanocomposites, and then cast into films. Morphology, structure and properties of the nanocomposite films were characterized using atomic force microscopy, field emission scanning electron microscopy, thermogravimetric analysis, X-ray diffraction and mechanical testing. The all-cellulose nanocomposite films with different cellulose matrices exhibited good optical transparency and layer structure. The all-cellulose nanocomposite films with cellulose prepared by the extracting method (Composite E) exhibited a higher crystallinity, better thermal stability and higher mechanical strength compared to the all-cellulose nanocomposite films with cellulose prepared by the acid-base method (Composite A). The crystal structure of the all-cellulose nanocomposite films indicated the coexistence of cellulose I and cellulose II. However, in contrast to Composite A, the diffraction intensity of cellulose I in Composite E was higher than that of cellulose II. This was another reason that the mechanical properties of Composite E were superior to those of Composite A. In addition, the mechanical properties of the all-cellulose nanocomposite films were significantly different when the addition of CNFs reached 3.0% by weight, as indicated by a multiple-range comparison. © 2020 Society of Chemical Industry.

Enhancing the mechanical properties of 3D printed polylactic acid using nanocellulose

AbstractWe report here a systematic investigation of the mechanical properties of polylactic acid (PLA) processed by fused filament fabrication (FFF) 3D printing vs PLA processed by compression molding. Our results show that the tensile strength and modulus of FFF‐PLA is 49% and 41% lower, respectively, than compression molded samples of PLA. We also demonstrate here an approach to augment the mechanical properties of 3D printed PLA using nanocellulose. Incorporation of a small quantity (1 wt%) of cellulose nanofibers (CNF) was found to enhance the tensile strength and modulus of 3D printed PLA by 84% and 63%, respectively. X‐ray microtomography was used to probe the morphology of 3D printed PLA and PLA/CNF composites. 3D printed PLA/CNF composites had significantly lesser voids as compared to neat 3D printed PLA. Differential scanning calorimetry study revealed that CNF can accelerate the nucleation and crystallization of 3D printed PLA leading to enhanced crystallinity. The thermal stability of 3D printed PLA/CNF composites was not compromised by the addition of CNF. The enhanced mechanical properties of 3D printed PLA/CNF composites can be ascribed to higher crystallinity and lesser defects.

Characterization of Water-Based Paint and Coating Film with Cellulose Nanofiber

Transition from solvent-based paints to water-based paints in the painting industry has progressed to reduce the use of volatile organic compounds, which are harmful to humans and the environment. However, water-based paints have a problem with paint workability because of sagging. Cellulose nanofiber (CNF), which has attracted attention as a novel naturally available material, exhibits high mechanical strength, thickening effects, and a low coefficient of thermal expansion. To resolve difficulties related to water-based paints, we examined paint and coating films characteristics after adding CNF. Results demonstrated that adding 0.2 mass% CNF can prevent sagging. Paint separation attributable to pigment sedimentation was prevented for 10 days. By adding 0.5 mass% CNF, the tensile strength of a coating film became more than double that of a non-CNF coating film. Testing using ballotini method indicated that CNF addition decreased the coating film surface dryness. Measurements using AC impedance indicated decreased coating film water resistance.

Effects of nanocellulose formulation on physicomechanical properties of Aquazol–nanocellulose composites

Aquazol [poly(2-ethyl-2-oxazoline)] is a widely used polymeric material for conservation because of its high reversibility and excellent compatibility with various types of material. However, it is hydrophilic and not recommended for use in weight-bearing applications. The objective of this study is to introduce cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) into Aquazol to evaluate the physicomechanical properties of the resultant composites. Several nanocellulose addition formulations involving two types of nanocellulose were designed at various addition levels. Water sorption investigations revealed that the addition of CNCs or CNFs reduced the maximum moisture content of the resultant composites when compared to the unfilled Aquazol. The tensile test results showed that the critical addition level of CNF (2 wt%) is lower than that of CNC (10 wt%) for the nanocellulose to start acting effectively as a mechanically reinforcing agent. Notably, compared with using a single type of nanocellulose for reinforcement, greater reinforcement was observed when both CNCs and CNFs were combinedly added. Field emission scanning electron microscopy indicated that these strong reinforcement outcomes were probably a result of branch-like structures forming among the mixed fillers. The addition of nanocellulose in general resulted in composites having marginally lower thermal stability and optical transparency. In this study, we demonstrated the increased retention of mechanical properties in variously filled composites exposed to anticipated service conditions (55% RH; 23 °C). Crucially, the discoveries in this study indicate that mixed CNC and CNF fillers could be a reasonable option for future applications where lower levels of nanocellulose are desired for optical transparency considerations.

Well-Dispersed Cellulose Nanofiber in Low Density Polyethylene Nanocomposite by Liquid-Assisted Extrusion.

Two different liquid assisted processing methods: internal melt-blending (IMB) and twin-screw extrusion (TWS) were performed to fabricate polyethylene (PE)/cellulose nanofiber (CNF) nanocomposites. The nanocomposites consisted maleic anhydride-grafted PE (PEgMA) as a compatibilizer, with PE/PEgMA/CNF ratio of 97/3/0.5–5 (wt./wt./wt.), respectively. Morphological analysis exhibited that CNF was well-dispersed in nanocomposites prepared by liquid-assisted TWS. Meanwhile, a randomly oriented and agglomerated CNF was observed in the nanocomposites prepared by liquid-assisted IMB. The nanocomposites obtained from liquid-assisted TWS exhibited the best mechanical properties at 3 wt.% CNF addition with an increment in flexural strength by almost 139%, higher than that of liquid-assisted IMB. Results from this study indicated that liquid feeding of CNF assisted the homogenous dispersion of CNF in PE matrix, and the mechanical properties of the nanocomposites were affected by compounding method due to the CNF dispersion and alignment.

Mechanical and structural properties of cellulose nanofiber/poly(vinyl alcohol) hydrogels cross-linked by a freezing/thawing method and borax

The effect of cellulose nanofibers (CNFs) on the mechanical and structural properties of poly (vinyl alcohol) (PVA) hydrogels cross-linked dually by a freezing/thawing method and a cross-linker (borax) was investigated using tensile tests, FT-IR measurements and synchrotron simultaneous small-angle/wide-angle X-ray scattering (SAXS/WAXS). The cross-linking with borax and addition of CNF greatly improved the tensile performance of the PVA hydrogels prepared in the freezing/thawing method, e.g., the dual cross-linking resulted in remarkable increase in the fracture strain, the Young’s modulus and the tensile strength. The fiber length effect on the mechanical properties of the CNF/PVA/borax hydrogels was examined, so that addition of CNF with longer fiber length increased the tensile modulus, whereas addition of CNF with shorter length caused extensibility higher than 1000% even at high CNF concentrations. SAXS/WAXS and FT-IR measurements have revealed that PVA was crystallized due to the freezing/thawing process, and both of PVA and CNF were cross-linked with borax, and hydrogen bonds between hydroxy groups of PVA (or/and CNF) were formed, indicating that the multiple cross-linking is effective for improvement of the tensile performance. In addition, the CNF/PVA/borax gel with the multi-physical cross-linking was found to possess the ability of the self-healing.

Assessing the Flexural Properties of Epoxy Composites with Extremely Low Addition of Cellulose Nanofiber Content

Epoxy resins are a widely used common polymer due to their excellent mechanical properties. On the other hand, cellulose nanofiber (CNF) is one of the new generation of fibers, and recent test results show that CNF reinforced polymers have high mechanical properties. It has also been reported that an extremely low CNF addition increases the mechanical properties of the matrix resin. In this study, we prepared extremely-low CNF (~1 wt.%) reinforced epoxy resin matrix (epoxy-CNF) composites, and tried to understand the strengthening mechanism of the epoxy-CNF composite through the three-point flexural test, finite element analysis (FEA), and discussion based on organic chemistry. The flexural modulus and strength were significantly increased by the extremely low CNF addition (less than 0.2 wt.%), although the theories for short-fiber-reinforced composites cannot explain the strengthening mechanism of the epoxy-CNF composite. Hence, we propose the possibility that CNF behaves as an auxiliary agent to enhance the structure of the epoxy molecule, and not as a reinforcing fiber in the epoxy resin matrix.

CELLULOSE NANOFIBERS FROM CASSAVA AGRO-INDUSTRIAL WASTE AS REINFORCEMENT IN PVA FILMS

Cellulose nanofibers (CNF) have been applied in composite systems due to the abundance of raw material, excellent mechanical and thermal properties. In this work, CNF was prepared from agroindustrial waste and used in specified amounts in polyvinyl alcohol (PVA) composites. The FTIR spectra of CNF, chemically purified cellulose (CPC) and Cassava Agro-industrial Waste (CAW) indicate the removal of hemicellulose and lignin. The increase of the crystallinity phase in CNF was observed, by XRD analysis and neither is observed the transition from cellulose I to II. Thermogravimetric analysis showed displacement that the initial degradation of the CNF over 43 °C degradation proceeds at single step. The chemical and dimensional homogeneity of CNF can be observed with the calculation of the crystalline phase content obtained by deconvoluted dTG curve and XRD spectra, obtaining 80% crystallinity by both techniques. SEM micrographs showed fibers with diameters of 22.30 ± 1.52 nm. An increase in the mechanical properties of PVA was observed with the addition of CNF. With 2.5% CNF in the PVA, the elastic module increased by approximately three times, with the addition of 10% CNF, a saturated system with poor mechanical properties was observed.