Cellulose Nanowhiskers Research Articles

High-toughness PLA/Bamboo cellulose nanowhiskers bionanocomposite strengthened with silylated ultrafine bamboo-char

We prepared poly(lactic acid) (PLA)/bamboo cellulose nanowhiskers (BCNW) bionanocomposite with a high toughness but a low modulus in the previous work. In this paper, a new reinforcement, silane surface-modified ultrafine bamboo-char (UFBC), was employed to strengthen the binary PLA/BCNW bionanocomposite. The ternary bionanocomposite films were fabricated by a solution casting with different contents of surface-treated UFBC in the range of 0.25 wt% to 4.0 wt%. The functionalization of UFBC with (3-mercaptopropyl)trimethoxysilane (A-189) favored its dispersion in the PLA matrix; sea-island and nuclear-shell characteristics were observed by the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). When the UFBC content was 0.25 wt%, the tensile strength and elongation at break increased by 99.26% and 104.93%, respectively, comparing to the neat PLA. Differential scanning calorimetry (DSC) results showed that glass transition temperature, crystallization temperature, crystallization enthalpy and crystallinity increased with the increase of UFBC contents. Thermogravimetric analysis demonstrated that the thermal degradation stability decreased with the UFBC addition. BCNW and UFBC produced a synergistic effect on composites’ toughening and strengthening. These results provided a basic understanding of PLA enhancement mechanism and a simple approach for PLA composite manufacture with sound mechanical properties.

Helical Fibers via Evaporation‐Driven Self‐Assembly of Surface‐Acylated Cellulose Nanowhiskers

AbstractMany natural materials have helical or twisting shapes. Herein, we show the formation of helical fibers with the lengths of micrometers by the evaporation‐driven self‐assembly on silicon wafers of functionalized cellulose nanowhiskers (CNWs) with surface‐attached acyl chains. The self‐assembly process and the final helical structures were affected by parameters including the wettability of substrates, dispersing solvents, the amount of 10‐undecenoyl groups, the crystallinity, the dimension of CNWs, and the length of acyl chains. In particular, surface‐acylated CNWs with a certain amount of 10‐undecenoyl groups (ca. 3.52 mmol g−1), an appropriate crystallinity (ca. 40 %), a length of about 135 nm, and a diameter of around 4 nm, preferentially self‐assembled into explicit left‐handed helical fibers from their THF suspensions on wafers. Thus, we showed novel particular self‐assembly behaviors of surface‐acylated CNWs, and we expanded the materials spectrum for the construction of helical structures.

Helical Fibers via Evaporation-Driven Self-Assembly of Surface-Acylated Cellulose Nanowhiskers.

Many natural materials have helical or twisting shapes. Herein, we show the formation of helical fibers with the lengths of micrometers by the evaporation-driven self-assembly on silicon wafers of functionalized cellulose nanowhiskers (CNWs) with surface-attached acyl chains. The self-assembly process and the final helical structures were affected by parameters including the wettability of substrates, dispersing solvents, the amount of 10-undecenoyl groups, the crystallinity, the dimension of CNWs, and the length of acyl chains. In particular, surface-acylated CNWs with a certain amount of 10-undecenoyl groups (ca. 3.52 mmol g-1 ), an appropriate crystallinity (ca. 40 %), a length of about 135 nm, and a diameter of around 4 nm, preferentially self-assembled into explicit left-handed helical fibers from their THF suspensions on wafers. Thus, we showed novel particular self-assembly behaviors of surface-acylated CNWs, and we expanded the materials spectrum for the construction of helical structures.

Anomalous dichroism of cellulose nanowhisker embedded composite film

While natural nanoparticles are currently being investigated in a wide range of applications due to their compelling strong potential, they have yet to be employed for practical engineering material systems. Here, we demonstrate a dichroic nanocomposite film that shows outstanding optical properties by introducing cellulose nanowhiskers (CNWs) into PVA iodine complex. CNWs were isolated via acid hydrolysis and the nanocomposite film was elongated and dyed with iodine. The significantly reduced extension and treatment time of iodine were applied for the alignment of iodine and PVA molecules in the film. The results revealed that the degree of polarization and transmittance were enhanced as the draw ratio and the content of the CNWs increased. We expect that this material system can offer a new pathway for designing and processing more advanced engineering materials with high performances by using various natural biomaterials.

Preparation and application of cellulose nano whiskers (CNWs) in engineered cementitious composites

The cellulose nano whiskers (CNWs) due to their fibrous shape and high crystalline nature seemed to be suitable as reinforcement for cementitious materials. In this research acid hydrolysis were used along with mechanical stirring and sonication to prepare cellulose nano whiskers (CNWs). Prepared nano whiskers were characterized for chemical and crystalline structure, particle size and morphology of micro/nano structure. Then, they were used as reinforcement in a fine aggregate concrete (FAC) at 0, 0.5, 1 and 1.5 vol%. Flexural behavior of the samples was evaluated by a three-point bending test. Moreover, some combinations of CNW and polyvinyl alcohol (PVA) fiber were used as reinforcement of concrete. By adding the CNW at high proportion of PVA fibers, the flexural properties of composite decreased, while, at lower contents of PVA fiber, flexural strength enhanced about 20%. Addition of CNW generally improved flexural properties of FAC, but made it more brittle. Utilizing hybrid of CNW with PVA fibers in the samples decreased the first and second cracking loads up to 40% but still retained its flexural hardening behavior such as engineered cementitious concretes.

Effect of the Incorporation of Micro and Nanocellulose Particles on the Anticorrosive Properties of Epoxy Coatings Applied on Carbon Steel

Polymeric coatings may act as a physical barrier between the aggressive ions and the metal substrate. However, prolonged exposure may cause damage to the polymer coating, leading to a continuous reduction of the barrier effect and consequently loss of the corrosion protection. The objective of this study is to determine the effect of aminopropyltriethoxysilane (APS), cellulose and polyaniline emeraldine-salt (PAni ES) in an epoxy coating on the corrosion protection of mild steel. Microcrystalline cellulose (MCC) and cellulose nanowhiskers (CNW) functionalized or not with PAni ES were used and compared. The coating properties were investigated by electrochemical impedance spectroscopy (EIS), salt spray test and scanning electron microscopy (SEM). The surface of the carbon steel, after 1000 h of exposure, did not present evidence of superficial corrosion. Polymer coatings using CNW and PAni ES showed improved corrosion protection properties even after 90 days of immersion in 3.5 wt% NaCl solution. The greatest increase in the corrosion resistance of the coating was found by EIS for the epoxy coating reinforced with CNW functionalized with PAni ES, revealing a synergistic effect of the electroactivity of a conducting polymer and nanosized cellulose particles.

Mechanical, thermal, and morphological properties of PLA biocomposites toughened with silylated bamboo cellulose nanowhiskers

To improve the surface compatibility between hydrophobic poly(lactic acid) (PLA) and hydrophilic bamboo cellulose nanowhiskers (BCNWs), four commercial available silane coupling agents were employed to modify their interfaces with different concentrations (0, 1, 8, and 16 wt%). PLA/BCNW biocomposite films were fabricated by solution casting. The effects of silylated BCNW on the thermal, mechanical, and morphological properties of PLA biocomposites were investigated. The coupled reaction between coupling agents and cellulose via Si‐O‐C bonding and hydrogen bonding was confirmed. Both, tensile strength and tensile modulus, decreased with the four silane treatments. The maximum elongation at break values increased to 213.8, 111.3, 255.3, and 209.8% after 16 wt% A‐151, 8 wt% A‐1100, 8 wt% A‐174, and 8 wt% A‐189 silane treatments, respectively, with respect to 12.4% of the untreated composite. A wire‐drawing phenomenon was observed on the tensile fractural surface. Glass transition temperature and crystallinity decreased after the surface modifications. POLYM. COMPOS., 40:3012–3019, 2019. © 2018 Society of Plastics Engineers

DBSA to improve the compatibility, solubility, and infusibility of cellulose nanowhiskers modified by polyaniline in reinforcing a natural rubber-based nanocomposite

In this study, the authors evaluate the potential of the reinforcement of cellulose nanowhiskers coated with polyaniline-DBSA (CNW-PANiDB) in a natural rubber latex nanocomposite. For this purpose, cellulose nanowhiskers (CNWs) were obtained by acid hydrolysis and coated with polyaniline by in situ polymerization in an acidic medium using dodecylbenzenesulfonic acid (DBSA). The nanocomposites based on natural rubber (NR) reinforced with CNW-PANiDB were obtained by a casting/evaporation method. Sample characterization was performed by DC electrical conductivity, thermogravimetric analysis, strain–stress test, UV–Vis–NIR and field emission scanning electron microscope. The UV–Vis–NIR spectrum of the NR/CNW-PANiDB nanocomposite revealed three characteristic absorption peaks around 350, 425, and 830 nm, assigned to PANiDB in emeraldine salt form. The mechanical properties of the nanocomposite, such as Young’s modulus and tensile strength, were improved by increasing the amount of CNW-PANiDB. The electrical conductivity of the nanocomposite increased by seven orders of magnitude by adding 10 mass% of CNW-PANiDB. This result indicates that CNWs coated with polyaniline-DBSA are an excellent material for use as mechanical reinforcement and to improve electrical conductivity. Thus, NR/CNW-PANiDB nanocomposite films have potential to be used as anticorrosive, electrostatic discharge, electromagnetic interference shielding materials, transducers, and electroactive materials.

Preparation and characterization of chitosan based hydrogels chemical cross‐linked by oxidized cellulose nanowhiskers

A novel hydrogel with superior mechanical properties were prepared using chitosan chemical cross‐linked with oxidized cellulose nanowhiskers (CNWs). An increased cross‐linking degree (6–40%) between chitosan and oxidized CNWs was found with the increased oxidation level of CNWs. A series of experiments were performed to evaluate the effect of oxidation level of CNWs on hydrogel properties. The morphology results showed that the cross‐linking reaction increased the hydrogels network density and the porous structure showed more compact and regular. Besides, the change in the morphology properties has an influence on hydrogels swelling behavior, exhibiting relatively reduced water content, and swelling ratio. The rheological measurements exhibited 263% and 394% improvements in storage modulus and loss modulus, respectively, and the maximum compressive stress confirmed an increasement by about 509%, were observed from the hydrogels cross‐linked by oxidized CNWs, compared with noncross‐linked hydrogels. Moreover, the resistance toward thermal degradation of the chitosan hydrogels was also increased by chemical cross‐linking. POLYM. COMPOS., 40:2432–2440, 2019. © 2018 Society of Plastics Engineers

Solution blow spinning (SBS)-assisted synthesis of well-defined carboxymethyl cellulose (CMC) nanowhiskers

In this study, synthesis of well-defined carboxymethyl cellulose (CMC) nanowhiskers through a low-pressure solution blow spinning is achieved for the first time. A mixture of methanol, water, and CMC was sprayed through a locally available spray gun at 4 bars, and the collected sample was dried for two hours at 80 °C. Scanning electron microscopy and Fourier transform infrared spectroscopy characterized the samples. The results showed the successful production of many, uniform and well-defined nanowhiskers. The possible series of mechanisms is also discussed. The primary objective of this study is to give insights of a simple and straightforward method that has potential to mass-produce high-quality nanowhiskers in a quick, cheap, and practical manner.

Re‐Dispersible 1D and 2D Nanoparticle Solid Powders without any Surfactant

AbstractNanoparticles possess unique size‐dependent physical and chemical properties and hold considerable interest as ideal, defect‐free building blocks for nanostructured materials. However, due to irreversible and intrinsic self‐aggregation, it is challenging to obtain dried nanoparticle powders with good redispersibility. In this work, we propose a general method to increase the dispersibility of typical 1D and 2D nanoparticles, including cellulose nanowhiskers, graphene, Laponite and montmorillonite, by combining sol‐gel transitions and supercritical CO2 drying. In the resulting dried powders, the nanoparticles adopt a non‐full‐contact mode and maintain a loose packing structure formed during the gelation process; thus, they can be perfectly redispersed in water and some organic solvents under mild conditions. Such a promising strategy, without using a surfactant, deliberate surface‐modification and high energy consumption, provides a practical solution to the transportation, storage and large‐scale industrial applications of nanoparticles.

Mechanical, Thermal, and Swelling Properties of Cross-linked Hydrogels Based on Oxidized Cellulose Nanowhiskers and Chitosan/poly(vinyl alcohol) Blends

Cross-linked hydrogels of chitosan/poly(vinyl alcohol) (PVA)/oxidized cellulose nanowhiskers (CNWs) were prepared by using oxidized CNWs as a cross-linker. The effects of the oxidation level of CNWs on the swelling behavior, thermal stability, viscoelastic properties and compressive strength of the hydrogels were studied. Chemical cross-links, hydrogen bonds, as well as nanofiller reinforcement between the three materials played a major role in determining the properties of the hydrogels. Swelling test results showed that the incorporation of oxidized CNWs decreased the water absorbability of the hydrogels due to the increase in cross-linking degree. Viscoelastic properties of the hydrogels with oxidized CNWs was increased by 537 % in storage modulus, from 4.65 kPa to 29.6 kPa. Compressive strength of 181.5 kPa at 50 % strain was observed from the cross-linked hydrogels, compared with 21.2 kPa of the non-cross-linked hydrogels. The thermal experiments showed that the chemical cross-linking slightly increase the resistance toward thermal degradation of the hydrogels.

Study of nanocomposites based on cellulose nanoparticles and natural rubber latex by ATR/FTIR spectroscopy: The impact of reinforcement

In materials research, polymer nanocomposites have attracted great attention worldwide from both academic and industrial points of view. The material properties of polymers can be enhanced dramatically by incorporating nanoelements from renewable resources depending on their biological origin (e.g., cellulose, starch, and chitin). We have used as the reinforcing phase, in this work, cellulose nanowhiskers (CNWs) and nanofibrillated cellulose (NFC) to prepare nanocomposite films by casting/evaporation using natural rubber (NR) latex as the matrix. Our interest is focused, in this work, especially on the investigation of the chemical bonds of the NR matrix and the chemical links of nanowhiskers added to the matrix and therefore the physical and chemical interactions which could happen between the reinforcement and the matrix. Many techniques have been used to explore the interface. Among these techniques, attenuated total reflectance/Fourier transform infrared spectroscopy (ATR/FTIR), which is employed in this work. It is exhibited that some differences are observed in FTIR spectra of nanocomposite films when adding cellulose nanoparticles into NR matrix. Overall IR spectroscopy clearly demonstrated that the interfacial adhesion in the case of NR‐NFC nanocomposite is higher than that of NR‐CNW one which was explained by the presence of residual lignin at the NFC surface that play the role of “compatibilizing” agent that enhance the adhesion between the NFC and the NR. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Cellulose nanowhiskers decorated with silver nanoparticles as an additive to antibacterial polymers membranes fabricated by electrospinning

Antimicrobial films based on distinct polymer matrices, poly (vinyl alcohol) (PVA) or poly (N-isopropylacrylamide) (PNIPAAm), and silver nanoparticles (AgNPs) immobilized onto cellulose nanowhiskers (CWs) were successfully prepared by either casting or electrospinning. CWs were first functionalized with carboxylate groups (labeled as CWSAc) and later they were immersed in a silver nitrate solution (AgNO3). After Ag+ ions anchored in the COO− groups are chemically reduced to produce AgNPs. The CWSAc/AgNPs biological activity was evaluated against Staphylococcus aureus (S. aureus), Bacillus Subtilis (B. subtilis), Escherichia coli (E. coli), and Candida albicans (C. albicans). The materials were more effective against C. albicans that showed a MIC of 15.6 µg/mL. In the process of AgNPs synthesis, the activity of the stabilizing agent (gelatin) and concentration of precursor and reducing agents were evaluated. The synthesized polymeric films displayed good antimicrobial activity against S. aureus, E. coli, and Pseudomonas aeruginosa (P. aeruginosa) bacteria. The PVA films with CWSAc/AgNPs showed diameter of the inhibition halo of up to 11 mm. The results obtained displayed that the films obtained have a potential application to be used in different fields such as packaging, membrane filtration, wound dressing, clothing and in different biomedical applications.

Mechanical and thermal properties of Moringa oleifera cellulose-based epoxy nanocomposites

Cellulose nanowhiskers were prepared by acid hydrolysis of drumstick fruit fibers from Moringa oleifera. It was incorporated into thermosetting epoxy matrix at various weight fractions (0.06, 0.12 or 0.18 wt%) to investigate their effect on the mechanical and thermal properties of resulting epoxy resin composite. Drumstick fruit nanofibers slightly increased the thermal stability of the prepared composites. The tensile modulus (31.4%) and bending modulus (38.2%) of the epoxy composites filled with 0.18 wt% cellulose nanowhiskers significantly increased in comparison with that of the neat cured epoxy resin. However, the tensile strength (48.7%) and bending strength (41.6%) of the composites significantly decreased as the 0.18 wt% nanowhiskers were added into the epoxy matrix. The nanowhiskers (0.18 wt%) can be efficiently used in the epoxy matrix to improve considerably the tensile and bending modulus of the composites as well as a slight increase in the thermal stability.

Biomimetic synthesis of two different types of renewable cellulosic nanomaterials for scaffolding in tissue engineering

Abstract As a rapidly growing area in materials design, the biomimetic approach at the frontier between biology and materials science aims to introduce advanced materials with structural diversities and functional versatilities by mimicking remarkable systems available in nature. Inspired by the fascinating nanostructured assembly existing in the cell walls of different plant species, we designed two fully bio-based green nanomaterials reinforced with renewable polysaccharide nanoparticles in the form of cellulose nanowhiskers (CNWs). In our initial design, the CNWs were incorporated into a cellulose acetate propionate matrix to form a bionanocomposite film, while in the second design the CNWs were entangled within a network of a collagenous medium to introduce a bionanocomposite hydrogel. Tensile and rheological measurements were carried out to study the system’s deformation as subjected to axial force or oscillatory shear. Biocompatibility was tested via incubation of human bone marrow-derived mesenchymal stem cells in vitro. Careful control of the processing conditions resulted in a three-dimensional rigid CNW network percolating within both biopolymer matrices, giving rise to an excellent performance at only a small fraction of CNWs at 3 wt.%. This study reveals that the fully bio-based green nanomaterials with enhanced mechanical percolation could construct a suitable platform for scaffolding in tissue engineering.

Isolation and Characterization of Nanocellulose Obtained from Industrial Crop Waste Resources by Using Mild Acid Hydrolysis

Cellulose, microcrystalline cellulose and nanocellulose were prepared from three agricultural waste resources: pineapple leaf (PALF), banana rachis (BR), and sugarcane bagasse (SCB). Each waste resource was first converted into microcrystalline cellulose which was subsequently converted into cellulose nanoparticles by using mild (30% w/v) and strong (60% w/v) sulfuric acid concentrations for extraction. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were used to characterize each waste resource and extracted cellulosic materials. Furthermore, nanocelluloses were studied by zeta potential, size analysis, and transmission electron microscopy (TEM). Cellulose nanowhiskers were successfully obtained and isolated with a 33% average yield by applying a mild acid treatment. Substrates BR and SCB proved to be more promising agricultural waste resources in terms of their crystalline cellulosic content and properties.

Reinforced Poly(ε-caprolactone) Bimodal Foams via Phospho-Calcified Cellulose Nanowhisker for Osteogenic Differentiation of Human Mesenchymal Stem Cells.

In this work, phospho-calcified cellulose nanowhiskers (PCCNWs) were prepared from wastepaper powder (WPP) and were dispersed in poly(ε-caprolactone) (PCL). The biocompatible and biodegradable (PCL)/PCCNW bimodal foam nanocomposites with two species cell sizes were prepared by the solvent casting/particulate leaching method in different weight percentage of PCCNWs. The mechanical, thermal, and in vitro biological properties of PCL/PCCNW nanocomposites were investigated. All PCL/PCCNW scaffolds were hydrophilic, biodegradable, and also noncytotoxic. The human mesenchymal stem cells were cultured on the prepared PCL/PCCNW bimodal foam nanocomposites and differentiated to osteoblasts. On the basis of evaluating tests such as MTT assay, acridine orange/ethidium bromide staining, alkaline phosphatase assay, calcium content assay, and alizarin red staining, PCL/PCCNW scaffolds were introduced as an appropriate option for emulating the behavior of extracellular matrix. Increasing PCCNWs improves the mechanical, hydrophilic, and biodegradability properties of the nanocomposites as well as their osteoconductivity.

Improved properties of PLA biocomposites toughened with bamboo cellulose nanowhiskers through silane modification

Poly(lactic acid) (PLA) is a potential green alternative for conventional petroleum-based plastics. However, the brittleness limits its application (e.g., agricultural films, garbage bags, plastic bags, food containers, food packaging). In this study, silane-compatibilized (triethoxyvinylsilane, A-151) bamboo cellulose nanowhiskers (BCNW) were introduced into a PLA matrix to toughen the composites. The A-151 successfully grafted on the surface of cellulose, and the thermal degradation stability of BCNW decreased after A-151 modification. Morphological, tensile and thermal properties of the toughened PLA bionanocomposites were investigated, and the toughen mechanism was clarified. The silane linked BCNW and PLA via Si–O–C bonds and hydrogen bonds. Elongation at break of the composites remarkably increased from 12.3 ± 1.7% (untreated) to 213.8 ± 21.6% (16 wt% A-151 treated). Both tensile strength and modulus decreased with the silane treatment. Typical toughness fracture characteristic (wire-drawing) was observed on the fractural surface. Glass transition temperature and crystallinity decreased from 45.6 °C/30.33% (untreated) to 33.6 °C/13.23% (16 wt% A-151 treated).

Cytotoxicity and biocompatibility of biomaterials based in polyhydroxybutyrate reinforced with cellulose nanowhiskers determined in human peripheral leukocytes

Implants of materials that are typically considered inert have been shown to cause early inflammatory complications. In addition, implant wear products may also cause overproduction of proinflammatory cytokines in the long run. Among the cytokines is tumor necrosis factor alpha (TNFα), which not only participates in the inflammatory response but also in the degradation of the bone. Therefore, a lack of production of TNFα by the cells of the immune system in contact with a candidate material for implant design is an indication of the acceptance of the biomaterial, and predicts the inflammatory response responsible for implant intolerance. There is no standard laboratory test to evaluate an individual response of a patient to a possible implant, although the use of peripheral blood mononuclear cells (PBMCs) has been suggested. Here, we evaluated the biocompatibility and cytotoxicity of films made of polyhydroxybutyrate (PHB) reinforced with different concentrations of cellulose nanowhiskers (CNWs) using PBMCs from healthy donors. Cells from healthy donors were cultured in the presence of films of the biomaterial during 24 h and 7 d and the cell viability and proinflammatory cytokines TNFα and IL6 production were measured. We confirmed that PHB, CNWs and the reinforced blends (PHB/CNWs) are safe and lack cytotoxicity in human cells, which make them good candidates for implant materials.