Extracting Cellulose Nanofibers Research Articles

Coconut husk-derived nanocellulose as reinforcing additives in thermal-responsive hydrogels

Nanocellulose has been widely used as a reinforcing agent for hydrogel systems, but its functions on thermal responsive hydrogels are rarely investigated. In this study, we extracted cellulose nanofibers (CNFs) from coconut biomass (coir fibers and piths, respectively) and aimed to study their effects on the material properties on a new class of thermogel (poly(PCL/PEG/PPG urethane). The CNFs extracted from fiber (FF) and piths (FP) showed different morphology and fiber lengths. FF are uniformed individual fibrous networks with a fiber length of 664 ± 416 nm, while FP display a hybrid structure consisting of individual fiber and large bundles with a relative shorter fiber length of 443 ± 184 nm. Integrating both CNFs into thermogels remained the thermal-responsive characteristics with an enhanced rheological property. The results showed that gels with FF resulted in a higher storage modulus and lower Tan δ value compared to those with FP, indicating that the CNFs with a longer length could form a more intertwined network interacting with the thermogel matrix. Furthermore, we demonstrated the improved capabilities of the nanocomposite thermogels for sustained drug delivery in vitro. This study not only value-adds lignocellulose valorization but also elevates the versatility of thermogels.

The influence of particle size on the extraction of cellulose nanofibers using chemical-ultrasonic process

Chemo-mechanical method is the effective method for extracting cellulose nanofibers from agricultural biomass. Objective of this research was to study the impacts of rice straw with different particle size distributions, on the yield and ultimate properties of cellulose nanofibers (CNF). Rice straw with two different particle size distributions (less than 75 μm and between 150 and 250 μm) were investigated. It was observed that after the stepwise chemical treatment processes, rice straw sample less than 75 μm particle size yielded 27.19 ± 0.99 % and rice straw sample between particle size 150 to 250 μm yielded 38.31 ± 0.85 %. From the extracted cellulose fibers, 64 % CNF was extracted from particle size less than 75 μm sample and 55 % of CNF from particle size between 150 and 250 μm sample via ultrasonic process. Structural, thermal and morphological properties of CNF and its intermediates were ascertained. The study revealed that the particle size of raw material rice straw had a significant effect on properties and yield of extracted cellulose nanofibers.

Effect of Cellulose Nanofibers (CNF) as Reinforcement in Polyvinyl Alcohol/CNF Biocomposite

This research was targeted to use the planetary ball milling method to extract cellulose nanofibers (CNFs) from commercial microcrystalline cellulose and also to utilize the obtained extracted cellulose nanofibers (CNFs) as reinforcement in polyvinyl alcohol (PVA) thin film. The effect of cellulose nanofibers (CNFs) on the mechanical and physical properties of polyvinyl alcohol (PVA) thin films was investigated. As a result of the study, we found that the thin film’s tensile strength is good, and the surface morphology of the CNFs suspension enhances the bonding between the PVA and the reinforcement. Tyndall effect was accurate with the visible light scattering through CNF suspension, and the CNF/PVA thin film exhibited transparent thin film. In contrast, the CNF/PVA composite’s mechanical and physical properties are good due to the excellent dispersion and absence of agglomeration of CNFs. The prepared PVA/CNF biocomposite would be a suitable candidate to be implemented as biodegradable food packaging material.

Functionalization of nanocellulose to quaternized nanocellulose tri-iodide and its evaluation as an antimicrobial agent

The reported research involves formation of quaternized nanocellulose triiodide for use as an agent for controlled release of iodine. Nanocellulose was extracted from bagasse and the extracted cellulose nanofibers (CNFs) were quaternized with 3-chloro-2-hydroxypropyltrimethyl ammonium chloride (CHPTAC) in NaOH/urea solution. This was followed by exchange of Cl− with I3− by reaction with KI/I2. Nanofibers having I3− anions were characterized by SEM, TEM, XRD, XRF and FTIR spectroscopy. The iodine content was estimated to be 33.42% and the fibers showed no leaching of molecular I2 in detectable amounts. The fibers showed a maximum activity of 94.73% and 99.86% against E. coli and S. aureus, respectively. These are capable of sustaining 100% antimicrobial activity over a period of six months. These fibers can thus find potential applications as a disinfectant agent in biomedical and water purification processes.

Preparation of Cellulose Nanofibers from Bagasse by Phosphoric Acid and Hydrogen Peroxide Enables Fibrillation via a Swelling, Hydrolysis, and Oxidation Cooperative Mechanism.

Due to the natural cellulose encapsulated in both lignin and hemicellulose matrices, as well as in plant cell walls with a compact and complex hierarchy, extracting cellulose nanofibers (CNFs) from lignocellulosic biomass is challenging. In this study, a sustainable high yield strategy with respect to other CNF preparations was developed. The cellulose was liberated from plant cell walls and fibrillated to a 7–22 nm thickness in one bath treatment with H3PO4 and H2O2 under mild conditions. The cellulose underwent swelling, the lignin underwent oxidative degradation, and the hemicellulose and a small amount of cellulose underwent acid hydrolysis. The CNFs’ width was about 12 nm, with high yields (93% and 50% based on cellulose and biomass, respectively), and a 64% crystallinity and good thermal stability were obtained from bagasse. The current work suggests a strategy with simplicity, mild conditions, and cost-effectiveness, which means that this method can contribute to sustainable development for the preparation of CNFs.

Direct Preparation of Cellulose Nanofibers from Bamboo by Nitric Acid and Hydrogen Peroxide Enables Fibrillation via a Cooperative Mechanism.

Separating the fibers, deconstructing both the interlamellar structures and the intermicrofibrils structures in the cell wall, and cleaving the amorphous regions of cellulose (all reached in one bath chemical-assisted treatment), then extracting cellulose nanofibers (CNFs) from biomass, is both challenging and imperative. A simple, cost-effective and green strategy for extracting CNFs from bamboo using nitric acid and hydrogen peroxide (NCHP), to enable fibrillation via a cooperative mechanism, is demonstrated herein. NCHP-CNFs 13.1 ± 2.0 nm wide, with a high aspect ratio, 74% crystallinity, excellent UV resistance and high thermal stability, were successfully extracted by treatment in HNO3 aqueous solution, at a concentration of 3.2 mol/L, and treatment with 60.00 mmol/g H2O2 at 50 °C for 48 h. The yields of NCHP-CNFs reached 73% and 99% based on biomass and cellulose, respectively, due to the high delignification selectivity of OH+ and the mild aqueous conditions during the NCHP treatment. These NCHP-CNFs with excellent UV resistance can potentially be applied in the field of UV-resistant coatings, to replace organic and inorganic materials.

Extraction of Cellulose Nanofibers via Eco-friendly Supercritical Carbon Dioxide Treatment Followed by Mild Acid Hydrolysis and the Fabrication of Cellulose Nanopapers.

The conventional isolation of cellulose nanofibers (CNFs) process involves high energy input which leads to compromising the pulp fiber’s physical and chemical properties, in addition to the issue of elemental chlorine-based bleaching, which is associated with serious environmental issues. This study investigates the characteristic functional properties of CNFs extracted via total chlorine-free (TCF) bleached kenaf fiber followed by an eco-friendly supercritical carbon dioxide (SC-CO2) treatment process. The Fourier transmission infra-red FTIR spectra result gave remarkable effective delignification of the kenaf fiber as the treatment progressed. TEM images showed that the extracted CNFs have a diameter in the range of 10–15 nm and length of up to several micrometers, and thereby proved that the supercritical carbon dioxide pretreatment followed by mild acid hydrolysis is an efficient technique to extract CNFs from the plant biomass. XRD analysis revealed that crystallinity of the fiber was enhanced after each treatment and the obtained crystallinity index of the raw fiber, alkali treated fiber, bleached fiber, and cellulose nanofiber were 33.2%, 54.6%, 88.4%, and 92.8% respectively. SEM images showed that amorphous portions like hemicellulose and lignin were removed completely after the alkali and bleaching treatment, respectively. Moreover, we fabricated a series of cellulose nanopapers using the extracted CNFs suspension via a simple vacuum filtration technique. The fabricated cellulose nanopaper exhibited a good tensile strength of 75.7 MPa at 2.45% strain.

Effect of delignification technique on the ease of fibrillation of cellulose II nanofibers from wood

We report on an efficient method for extracting cellulose nanofibers with cellulose II crystal structure that presents a relatively high yield (approximately 82%) after mechanical treatment. Delignification technique plays an important role in the conversion of crystals from cellulose I to cellulose II during the mercerization process and in the subsequent fibrillation of cellulose II nanofibers. Delignified wood pulps (with half of the lignin removed) were treated with 17.5 wt% sodium hydroxide solution to mercerize the cellulose, and then the remaining lignin was further removed to purify the pulps. The resulting pulps were fibrillated by using only one pass through a grinder. X-ray diffraction patterns revealed that the above mercerized pulps were successfully converted into the cellulose II crystal structure. Morphological observation showed that cellulose II nanofibers with a width of approximately 15–90 nm were successfully obtained using the above method. This may have occurred because the remaining half of the lignin in wood pulps partly prevented the interdigitation and aggregation of the cellulose microfibrils during the mercerization process, thus facilitating the subsequent nanofibrillation. However, for the delignified wood pulps (with more than two-thirds of the lignin removed), the microfibrils in the cell wall bound more easily to each other by aggregation during the mercerization process, which may have caused difficulties in the subsequent nanofibrillation.

Eco-friendly Modification for the Cellulose Nanofibers Derived from Pineapple Leaves for High-performance Nanocomposite

This study extracted cellulose nanofibers (NFC) from pineapple leaves, and then employed eco-friendly aqueous system to modify NFC with a layer of polystyrene (PS). The successful modification was confirmed by FTIR analysis, after acid-base treatment can effectively reduce the lignin content and better water transport, and the PS layer could lower NFC’s surface polarity for improving the interfacial compatibility in PS matrix. By introducing NFC into PS matrix, the PS-modified NFC showed better interfacial adhesion and uniform dispersion, and resulted nanocomposite with higher tensile strength, char yield and transparency. Therefore, the eco-friendly modification could help NFC reinforce nanocomposite for enhancing mechanical property, thermal resistance and transparent appearance.

Production of cellulose nanofibers from Alfa grass and application as reinforcement for polyvinyl alcohol

ABSTRACTThe work reported demonstrates an simple method of extracting cellulose nanofibers (CNF) from cellulose microfibers (CMF) obtained from the plant Stipatenacissima. Here, a method for the production of CNF from CMF extracted from Alfa grass by exfoliation in polyvinyl alcohol (PVA) solution, is demonstrated. The CMF were produced in powder form and exfoliated in PVA aqueous solution to produce composites with 2, 4, 5 and 10 wt-% of CNF. Scanning Electron Microscopy demonstrated exfoliation of CMF, dispersion of the CNF and wetting by the polymer. The composites were characterised by thermogravimetry, differential scanning calorimetry, X-ray diffraction and tensile testing. The addition of CNF to PVA reduced the crystallinity degree of PVA. The large increase of the Young’s modulus from 38 to 113% (relative to pure PVA) for composites with 2 to 10 wt-% of CNF incorporation is consistent with the extensive exfoliation of CMF into CNF and its excellent interface with PVA.

A novel approach for extracting cellulose nanofibers from lignocellulosic biomass by ball milling combined with chemical treatment

ABSTRACTCellulose nanofibers (CNFs) were isolated from kenaf fibers and wheat straw by formic acid (FA)/acetic acid (AA), peroxyformic acid (PFA)/peroxyacetic acid (PAA), hydrogen peroxide (H2O2) treatment; and subsequently through ball milling treatment. Characterization of extracted cellulose and cellulose nanofibers was carried out through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). TEM images showed that extracted cellulose nanofibers had diameter in the range of 8–100 nm. FTIR and XRD results implied that hemicellulose and lignin were mostly removed from lignocellulosic biomass with an increase in crystallinity, and isolation of cellulose nanofibers was successful. The TGA results showed that decomposition temperature of cellulose nanofibers increased by about 27°C when compared with that of untreated lignocellulosic biomass. No significant change was observed in the decomposition temperature of bleached celluloses after ball milling. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42990.

Development of green nanocomposites reinforced by cellulose nanofibers extracted from paper sludge

Cellulose nanofibers have been showing much greater potential to enhance the mechanical and physical properties of polymer-based composite materials. The purpose of this study is to extract the cellulose nanofibers from waste bio-resources; such as waste newspaper and paper sludge. The cellulosic raw materials were treated chemically and physically in order to extract individualized cellulose nanofiber. The combination of acid hydrolysis and following mechanical treatment resulted in the extraction of cellulose nanofibers having diameter of about 40 nm. In order to examine the reinforcing effect of the extracted cellulose nanofibers, fully biodegradable green nanocomposites were fabricated by composing polyvinyl alcohol (PVA) resin with the extracted cellulose nanofibers, and then the tensile tests were conducted. The results showed that the enhancement in mechanical properties was successfully obtained in the cellulose nanofiber/PVA green nanocomposites.

Preparation and characterization of low‐density polyethylene/thermoplastic starch composites reinforced by cellulose nanofibers

In the current study, the effect of extracted cellulose nanofibers (CNFs) on rheological and mechanical properties and biodegradability of polyethylene/starch blend was investigated. The CNFs were extracted from wheat straws using a chemo‐mechanical method. Polyethylene/starch blend was reinforced by different amounts of CNF (6–14 wt%) using an internal mixer followed by a single screw extruder. The flow properties of nanocomposites were investigated by determining Melt Flow Index (MFI) and viscosity. Due to the weak interaction of cellulosic nanofibers and polymers, the flow behavior of nanocomposites was undesirable. Tensile tests were performed to evaluate the mechanical performance of nanocomposites. By increasing the CNF content, the tensile strength and elongation at break declined; whereas, the Young's modulus was improved. The biodegradation of cellulose nanocomposites was investigated by water absorption and degradability tests. Both experiments confirmed the progressive effect of cellulose nanofibers on the degradation of the composites. POLYM. COMPOS., 36:2309–2316, 2015. © 2014 Society of Plastics Engineers

Isolation and characterization of cellulose nanofibers from the aquatic weed water hyacinth—Eichhornia crassipes

The water hyacinth is one of the fast growing perennial aquatic weeds with a height of 1 m and doubles their population in 2 weeks and is rich in fiber content. The cellulose nanofibers from the water blocking aquatic weed – water hyacinth – were successfully prepared. The crude and pure cellulose microfibers were initially obtained from the weed plant using the chemical treatments such as bleaching and alkaline and sodium chlorite reactions. The micron-sized fibers obtained from the stems were cryocrushed with liquid nitrogen to release the bundles of nanofibers and followed the sonication for individualization of fibers. The treated fibers were screened through Fourier transform infrared spectroscopy (FTIR) to confirm the removal of impurities from the fibers. The surface morphology of the aqueous suspension before cryocrushing and after the sonication process was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Thermal stability of the fiber was increased after chemical treatment; this was confirmed by thermogravimetric analysis (TGA). The synthesized nanofibers were in a diameter range of 20–100 nm from the SEM and 25 nm from the TEM analysis. The extracted cellulose nanofibers from the noxious weeds were used for processing of biodegradable nanocomposites in drug delivery, ligament substitute, filtration, and water purification and also used as flexible optical display in electronics.

Extraction of Bamboo Nanofibers Using Acid Hydrolysis for Functional Chemicals of Ecological Dyeing and Finishing

In this work a study on the feasibility of extracting cellulose nanofibers from bamboo fibers, by means of three different procedures was carried out. These processes included the using of three different types of acids (H2SO4, HCl, and a mixture of H2SO4/HCl). The raw bamboo fibers were mercerized with NaOH solutions. They were then submitted to the three different acid hydrolysis processes. The final bamboo nanofibers were morphologically characterized by transmission electron microscopy (TEM) and their surface charges in suspensions were estimated by Zeta-potential. Their degree of polymerization (DP) was characterized by viscometry and the crystallinity was tested by X-ray diffraction (XRD). All bamboo nanofibers presented a rod-like shape, an average diameter (D) of 6-10 nm and length (L) of 100-180 nm, with an aspect ratio (L/D) of around 16-18. The aggregation state increases with the amount of HCl introduced into the extraction, due to the decrease of surface charges. However, this release presented nanofibers with litter better degree of polymerization than those whose acid hydrolysis was carried out using only H2SO4.