Cellulose Nanocrystal Composites Research Articles

Cellulose Nanocrystals Composites with Excellent Thermal Stability and High Tensile Strength for Preparing Flexible Resistance Strain Sensors

Cellulose Nanocrystals Composites with Excellent Thermal Stability and High Tensile Strength for Preparing Flexible Resistance Strain Sensors

THERMAL AND MECHANICAL PROPERTIES OF POLYMER COMPOSITES REINFORCED BY SULFURIC ACID-HYDROLYZED AND TEMPO-OXIDIZED NANOCELLULOSE: A COMPARATIVE STUDY

The main drawback of cellulose nanocrystals (CNCs) obtained by conventional sulphuric acid hydrolysis is their low thermal stability in consequence of pyrolysis catalyzed by sulfo-groups on the CNC surface. Replacement of surface sulfo-groups by carboxyl groups as a result of oxidation allows the thermal stability of CNCs to be enhanced significantly. Although a great number of studies have reported properties of polymer nanocomposites reinforced by CNCs, thermal properties of the composites compared to the neat polymers are discrepant and still poorly understood. In this work, CNCs were produced from microcrystalline cellulose by sulfuric acid hydrolysis and (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation. The CNC composites with water-soluble polymers – polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone and polyacrylamide – were obtained. The composites were characterized by various methods, i.e. transmission electron and scanning electron microscopies, energy-dispersive X-ray analysis, Fourier-transform infrared spectroscopy, X-ray diffraction and thermogravimetric analyses, differential scanning calorimetry, and tensile testing. A side-by-side comparison between the thermal and mechanical properties of the polymer composites reinforced by sulfuric acid-hydrolyzed and TEMPO-oxidized nanocellulose was conducted. Analysis of the thermal properties of CNC shows that the surface sulfonate groups replacement with carboxyl groups leads to significant increase of initial temperature of thermal degradation and temperature of the maximum decomposition rate of the CNC. However, the thermal behavior of the composites is much more complicated, and such thermal properties are discussed in detailed. The tensile properties analysis of the composites demonstrates that an addition of TEMPO-oxidized nanocellulose does not improve significantly the tensile strength and Young’s modulus as compared with sulfuric acid-hydrolyzed one.

Cellulose nanocrystals from agricultural resources: Extraction and functionalisation

During the early nineteens, enhanced concern towards “biodegradable materials” and “green chemistry,” along with the significant advancements in nanotechnology, coerce scientists and scholars to ferret out an alternative biomaterial. Prolonged rummage to the alternate biomaterial leads to the discovery of nanoparticles from cellulose as cellulose nanocrystal composites. Various cellulosic sources yield nano cellulosic derivatives after various pretreatment and extraction procedures, including acid hydrolysis, micro grinding, cryocrushing, electron spinning, and centrifugal spinning. Agricultural resources like cotton, wheat, garlic, ramie, switchgrass, and curaua for cellulose nanocrystal composites extraction of varying properties; hence are applicable for distinct functions. Extraction from agricultural resources adds more profit and advancement in the agricultural sector. Pure cellulose nanocrystal composite possesses a mechanical strength of 7000 MPa, a young modulus of 100–140 GPa, and 250–500 m 2 /g surface area. The vulnerability of cellulose nanocrystal composites towards moisture due to alcoholic group nullifies by the modification and grafting processes which yield functionalized cellulose nanocrystal composites. Functionalized cellulose nanocrystal composites find applications in various fields, including biomedicine, catalysis, electronics, and laboratories. The review summarises the extraction procedure of cellulose nanocrystal composites from agricultural resources and functionalization methodologies, facilitating cellulose nanocrystal composite's prospective implementation.

Methylcellulose-Cellulose Nanocrystal Composites for Optomechanically Tunable Hydrogels and Fibers.

Chemical modification of cellulose offers routes for structurally and functionally diverse biopolymer derivatives for numerous industrial applications. Among cellulose derivatives, cellulose ethers have found extensive use, such as emulsifiers, in food industries and biotechnology. Methylcellulose, one of the simplest cellulose derivatives, has been utilized for biomedical, construction materials and cell culture applications. Its improved water solubility, thermoresponsive gelation, and the ability to act as a matrix for various dopants also offer routes for cellulose-based functional materials. There has been a renewed interest in understanding the structural, mechanical, and optical properties of methylcellulose and its composites. This review focuses on the recent development in optically and mechanically tunable hydrogels derived from methylcellulose and methylcellulose–cellulose nanocrystal composites. We further discuss the application of the gels for preparing highly ductile and strong fibers. Finally, the emerging application of methylcellulose-based fibers as optical fibers and their application potentials are discussed.

Nanocelluloses Reinforced Bio-Waterborne Polyurethane.

The aim of this work was to evaluate the influence of two kinds of bio- nano-reinforcements, cellulose nanocrystals (CNCs) and bacterial cellulose (BC), on the properties of castor oil-based waterborne polyurethane (WBPU) films. CNCs were obtained by the acidolysis of microcrystalline cellulose, while BC was produced from Komagataeibacter medellinensis. A WBPU/BC composite was prepared by the impregnation of a wet BC membrane and further drying, while the WBPU/CNC composite was obtained by casting. The nanoreinforcement was adequately dispersed in the polymer using any of the preparation methods, obtaining optically transparent compounds. Thermal gravimetric analysis, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, dynamical mechanical analysis, differential scanning calorimetry, contact angle, and water absorption tests were carried out to analyze the chemical, physical, and thermal properties, as well as the morphology of nanocelluloses and composites. The incorporation of nanoreinforcements into the formulation increased the storage modulus above the glass transition temperature of the polymer. The thermal stability of the BC-reinforced composites was slightly higher than that of the CNC composites. In addition, BC allowed maintaining the structural integrity of the composites films, when they were immersed in water. The results were related to the relatively high thermal stability and the particular three-dimensional interconnected reticular morphology of BC.

Impact and Tensile Properties of Polyester Nanocomposites Reinforced with Conifer Fiber Cellulose Nanocrystal: A Previous Study Extension.

In a recent paper, novel polyester nanocomposites reinforced with up to 3 wt% of cellulose nanocrystals (CNCs) extracted from conifer fiber were characterized for their crystallinity index, water absorption, and flexural and thermal resistance. The use of this novel class of nanocomposites as a possible substitute for conventional glass fiber composites (fiberglass) was then suggested, especially for the 1 and 2 wt% CNC composites due to promising bending, density, and water absorption results. However, for effective engineering applications requiring impact and tensile performance, the corresponding properties need to be evaluated. Therefore, this extension of the previous work presents additional results on Izod and tensile tests of 1 and 2 wt% CNC-reinforced polyester composites, together with a comparative cost analysis with fiberglass. The chemical effect caused by incorporation of CNCs into polyester was also investigated by FTIR. In comparison to the neat polyester, the Izod impact energy increased 50% and 16% for the 1 and 2 wt% composites, respectively. On the other hand, the tensile strength and Young’s modulus remained constant within the ANOVA statistical analysis. FTIR analysis failed to reveal any chemical modification caused by up to 2 wt% CNC incorporation. The present impact and tensile results corroborate the promising substitution of a polyester composite reinforced with very low amount of CNCs for common fiberglass in engineering application.

Biotemplated Hollow Mesoporous Silica Particles as Efficient Carriers for Drug Delivery.

We designed three types of hollow-shaped porous silica materials via a three-step biotemplate-directed method: porous hollow silica nanorods, hollow dendritic fibrous nanostructured silica (DFNS), and ultraporous sponge-like DFNS. The first step was making a biotemplate, for which we used cellulose nanocrystals (CNCs), consisting of rod-shaped nanoparticles synthesized by conventional acid hydrolysis of cellulose fibers. In a second step, core-shell samples were prepared using CNC particles as hard template by two procedures. In the first one, core-shell CNC-silica nanoparticles were synthesized by a polycondensation reaction, which exclusively took place at the surface of the CNCs. In the second procedure, a typical synthesis of DFNS was conducted in a bicontinuous microemulsion with the assistance of additives. DFNS was assembled on the surface of the CNCs, giving rise to core-shell CNC-DFNS structures. Finally, all of the silica-coated CNC composites were calcined, during which the CNC was removed from the core and hollow structures were formed. These materials are very lightweight and highly porous. All three structures were tested as nanocarriers for drug delivery and absorbents for dye removal applications. Dye removal results showed that they can adsorb methylene blue efficiently, with ultraporous sponge-like DFNS showing the highest adsorption capacity, followed by hollow DFNS and hollow silica nanorods. Furthermore, breast cancer cells show a lower cell viability when exposed to doxorubicin-loaded hollow silica nanorods compared with control or doxorubicin cultures, suggesting that the loaded nanorod has a greater anticancer effect than free doxorubicin.

Tetraethylenepentamine modified magnetic cellulose nanocrystal composites for removal of Congo red with high adsorption capacity

A tetraethylenepentamine modified magnetic cellulose nanocrystal composites (Fe3O4@CNC-TEPA) was prepared by the coprecipitation method and Schiff base reaction, which could adsorb Congo red (CR) efficiently. The morphology and structure of the nanoparticles were characterized by atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), zeta potential (ZETA), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET). Subsequently, the Fe3O4@CNC-TEPA adsorbed CR was investigated by comparative experiments, selective adsorption experiments, effect of pH, effect of adsorbent dosage, adsorption isotherms, thermodynamics parameters, adsorption kinetics, leaching experiments, desorption and reusability experiments. Results revealed the fact that the nanoparticles showed excellent adsorption capacity of CR (1049 mg g−1) due to the abundant hydroxyl and amino groups on the surface of the Fe3O4@CNC-TEPA. The adsorption process was best described by the the Langmuir equation and pseudo-second-order kinetic model. Moreover, the Fe3O4@CNC-TEPA loaded with CR can be recycled with NaOH solution easily, which can be used repeatedly for CR adsorption. After six cycles, the adsorption capacity was still about 81.5% of the original particles’. The environmentally friendly nanoparticles have great application prospects as adsorbents for removing CR.

Mechanically tunable elastomer and cellulose nanocrystal composites as scaffolds for in vitro cell studies

Composites based on ε-caprolactone-d,l-lactide-based elastomer with cellulose nanocrystals (CNC) are investigated to understand how matching cells with appropriate mechanical environments can provide important insights into fundamental cell behaviors.

Strong biodegradable cellulose materials with improved crystallinity via hydrogen bonding tailoring strategy for UV blocking and antioxidant activity

It has been a huge challenge to obtain simultaneously excellent mechanical strength and desirable multifunctionality from the cellulose nanocrystals (CNC) based food packing materials. In this work, we demonstrated a hydrogen bonding tailoring strategy that can produce CNC/lignin films with UV blocking and antioxidant activity, while bypassing the loss of mechanical strength. Using a hyperbranched polyester, lignin was first functionalized to increase the amount of hydroxyl groups, thereby increasing the intermolecular interactions. By assembling the polyester modified lignin (H-lignin) into CNC matrix, the hydrogen bonding crosslinks between the H-lignin and CNC chains were successfully promoted, resulting in the CNC composites with the significantly improved mechanical strength, UV blocking and antioxidant activity. The phenolic structure and the hydrogen donation of H-lignin also endowed the resulting CNC composites with excellent UV blocking and antioxidant activity. The experimental results indicated that the H-lignin could bring about 34% and 63% increase in tensile strength and Young's modulus, respectively, higher than the reported ones. The CNC-based composites showed better thermal stability and improved crystallinity property. The H-lignin provides a new insight into the multifunctional exploration of CNC-based composite. This work opens a new avenue for the next generation's biodegradable food packing materials from cellulose-sourced composites.

Nanostructured Fe2O3@nitrogen-doped multiwalled nanotube/cellulose nanocrystal composite material electrodes for high-performance supercapacitor applications

The controlled synthesis of Fe2O3@N-MWCNT and cellulose nanocrystal composites were followed by hydrothermal reduction process. The composite samples were examined by analytical methods. The Fe2O3@N-MWCNT and Fe2O3@N-MWCNT/CNC composite samples were studied by CV, GCD, and EIS. The Fe2O3@N-MWCNT and Fe2O3@N-MWCNT/CNC composite showed a specific capacitance of 162Fg−1 and 562Fg−1 at the current density of 0.5Ag−1 and 5000 cycle's compromises and increases the active sites to facilitate ion transfer for electrochemical capacitor applications.

Adhesive properties of bio-based epoxy resin reinforced by cellulose nanocrystal additives

Abstract The adhesive properties of a self-prepared bio-based epoxy resin with native cellulose nanocrystals (CNCs) are evaluated in this article. The porosity of actual CNCs is high. The most promising finding is the acquisition of high tensile modulus. The addition of CNC composites significantly increased the tensile modulus at lower wt.%, and the maximum crystallinity of CNCs was obtained. Bearing in mind the advantages of CNCs, scanning electron microscopy (SEM) showed a uniform distribution of concentrated CNCs. Clusters were formed at higher CNCs ratios, and the composite matrix content with high CNCs produced good expansion, low crystallinity, and increased elongation. Our analysis showed that the original CNCs were more evenly distributed in the self-prepared bio-based epoxy resin, which enhanced transformation, supported by improved dispersion of native CNCs. The presence of native CNCs greatly improved and enhanced the bonding performance of the bio-based epoxy resin in the interface area. Enhancing the mechanical properties of native CNCs has broad application prospects in environmental areas. This suggests that the widespread use of native CNCs in environmental engineering applications is feasible, especially in terms of adhesives properties.

Fused deposition modelling of PLA reinforced with cellulose nano-crystals

Additive Manufacturing is a pioneering and prevailing technology used for direct layer-by-layer fabrication of parts from a 3D computer model. Fused Deposition Modeling (FDM) is the most common and simplest technique in 3D printing technology which engrossed many researchers, particularly those interested in its biomedical applications in custom-made implants, tissue and cell printing and the dental industry. Polylactic acid (PLA) is one of the bio-degradable polymers which are now being extensively used by the researchers for biomedical applications. Various research was conducted on PLA to improves its properties by incorporating the nanofillers. Cellulose nanocrystal (CNC) is one of the naturally occur nanofiller which is used to reinforce with PLA to improve its mechanical and biodegradability property. PLA/CNC has a hopeful probable for large-scale manufacture of green composites towards various applications, which include packaging and biomedical fields. In this research work, different samples of PLA/CNC composites were prepared with 1, 2, 5 and 10 wt% CNC as nanofillers. The thermal properties for the different samples of PLA/CNC bio-composite was studied. The results of Differential scanning calorimetry disclosed that there is a shift in the glass transition temperature and a variation in the melting temperatures. The results showed that the crystallinity of the polymer matrix got increased by the addition of Cellulose. 1% cellulose shows the highest cold crystallization peak when compared to the neat PLA. The single-screw extruder is used to obtain the PLA/CNC filament of 1.75 mm diameter. The fabricated PLA/CNC filament is fed into fused deposition modeling for fabricating 3D Printed specimens. The mechanical properties of the 3D printed bio-composites were evaluated. The results of the 3D printed samples show that there is an increase in tensile modulus for 1% CNC composites (4550 MPa) when compared with neat PLA (3030 MPa).

3D printed cellulose nanocrystal composites through digital light processing

Cellulose Nanocrystals (CNC) have received significant attention due to their high Young’s modulus, high strength, biocompatibility, and renewability. These properties make them ideal as a reinforcement phase for polymer composites. However, typical composite processing techniques have limitation in efficiently fabricating composites with different shapes. Inspired by the emerging technology of 3D printing, this work utilized the digital light processing (DLP) 3D printing approach to fabricate CNC reinforced poly (ethylene glycol) diacrylate (PEGDA) glycerol composites. To improve CNC compatibility with PEGDA matrix, 1,3-diglycerolate diacrylate (DiGlyDA) that has a similar chemical structure but also has hydroxyl groups was blended with PEGDA. The dispersibility of CNC was characterized by the Halpin–Tsai model and polarized light microscopy. Mechanical testing results indicated that mechanical properties of DLP 3D printed composites were improved by CNC incorporation. Furthermore, curing layer thickness during DLP 3D printing can also be used to tune the composites’ mechanical and water swelling properties. Complex 3D CNC composites structures were also successfully printed by the DLP 3D printing with great fidelity. This versatile approach of controlling composite’s properties and structure using CNC and DLP 3D printing can be exploited to further advance the utilization of cellulosic materials toward biomedical and many other applications.

Synergistic Toughening of Poly(lactic acid)–Cellulose Nanocrystal Composites through Cooperative Effect of Cavitation and Crazing Deformation Mechanisms

In this work, we present poly(lactic acid) (PLLA)–cellulose nanocrystal (CNC) composites with simultaneous improvements in tensile toughness and impact strength using dual CNC-based fillers. The dual CNC-based fillers were designed to toughen PLLA by control of (a) the morphology and (b) the interfacial interactions in the PLLA composites. The first filler, denoted as CNCaq–rD, was comprised of rigid CNC and a rubber layer (rD), which exhibited immiscibility with the PLLA matrix, albeit with weak interactions. The second filler, denoted as CNCaq–rD–PDLA, was comprised of rigid CNC, a middle rubber layer (rD), and an outer layer of PDLA blocks that could form strong interactions with PLLA matrix via stereocomplexation. The dual fillers superbly improved both tensile toughness and impact strength of PLLA through synergistic effects. Incorporating 10% CNCaq–rD and 10% CNCaq–rD–PDLA into the PLLA matrix, the strain at break (a measure of tensile toughness) and impact strength increased by 100-fold and 3-fold,...

One-Step in Situ Ball Milling Synthesis of Polymer-Functionalized Few-Layered Boron Nitride and Its Application in High Thermally Conductive Cellulose Composites

The chemically inert surface and strong ionic bonds make exfoliation and functionalization of hexagonal boron nitride (h-BN) difficult. This inevitably increases the interface thermal resistance and hinders phonon transfer. Herein, polydopamine (PDA)-coated exfoliated h-BN, denoted as exfoliated h-BN@PDA, was prepared by a one-step ball milling route. During the ball milling process, dopamine self-polymerized into PDA on the surface of the exfoliated h-BN@PDA in an alkaline aqueous solution. The coated PDA contents were estimated to be about 3 wt %. Meanwhile, exfoliation of h-BN occurred due to the hydrolysis of h-BN in water and the shear force introduced by ball milling. The results reveal that the exfoliated h-BN generally composed of <20 layers. The resulting exfoliated h-BN@PDA was further added to cellulose nanocrystal (CNC) and improved thermal conductivity up to 40 W m–1 K–1 with 94 wt % h-BN. By controlling the feed ratio, exfoliated h-BN@PDA/CNC composites with different h-BN contents were fabr...

Rapidly Responsive and Flexible Chiral Nematic Cellulose Nanocrystal Composites as Multifunctional Rewritable Photonic Papers with Eco-Friendly Inks.

Rapidly responsive and flexible photonic papers are manufactured by coassembly of cellulose nanocrystals (CNCs) and waterborne polyurethane (WPU) latex for fully taking advantage of the chiral nematic structure of CNCs and the flexibility of WPU elastomer. The resulting CNC/WPU composite papers exhibit not only tunable iridescent colors by adjusting the helical pitch size, but also instant optical responses to water and wet gas, ascribed to the easy chain movement of the elastomeric WPU that does not restrict the fast water absorption-induced swelling of CNCs. By choosing water or NaCl aqueous solutions as inks, the colorful patterns on the CNC/WPU photonic paper can be made temporary, durable, or even disguisable. In addition, the photonic paper is simultaneously rewritable for all these three types of patterns, and the disguisable patterns, which are invisible at normal times and show up under stimuli, exhibit a quick reveal conversion just by exhaling on the paper. The rewritability, rapid responsibility, easy fabrication, and the eco-friendly nature of the inks make the flexible photonic paper/ink combination highly promising in sensors, displays, and photonic circuits.

Quantitative analysis of the distribution and mixing of cellulose nanocrystals in thermoplastic composites using Raman chemical imaging.

Cellulose nanofibers hold much promise for enhancing the mechanical properties of composites owing to their uniquely high stiffness and strength. One major issue limiting this performance however is the dispersion and mixing of cellulose nanofibers within thermoplastic resins. A combination of Raman imaging and chemical analysis has been used to quantify the distribution and mixing of cellulose nanocrystals (CNCs) in a polyethylene-matrix composite. Large area spectral imaging provides information about the effect of a compatibilizer – namely poly(ethylene oxide) (PEO) and maleated polyethylene (MAPE) – on the distribution of CNCs in the thermoplastic matrix. High-resolution images enable quantification of the degree of mixing between the CNCs and HDPE. Lower resolution images, but with greater spatial spread, allow quantification of the distribution of the CNCs. It is shown that the CNCs tend to agglomerate, with little increase in distribution even with the use of the compatibilizer. A shift in the position of characteristic Raman bands indicates the formation of hydrogen bonding between the PEO compatibilizer and the CNCs, which in turn is thought to affect the distribution of aggregates of the reinforcing phase.

Polyurethane/esterified cellulose nanocrystal composites as a transparent moisture barrier coating for encapsulation of dye sensitized solar cells

ABSTRACTThis research work aims to investigate the effects of types and concentration of cellulose nanocrystals (CNCs) prepared from bacterial cellulose (BC) and nanofibrillated cellulose (NFC) on structure properties of polyurethane (PU) composites. Feasibility of applying the polymer composite for encapsulation of dye sensitized solar cells was of interest. Both CNCs were pretreated via esterification before mixing with the polyurethane by a solution process. Tensile strength and thermal stability of the PU/esterified CNCs were found to be superior to those of the systems reinforced with untreated CNCs. With the introduction of both untreated and esterified CNCs, water vapor transmission rates through the PU composite films were lowered while their visible light transmittance values were maintained to be above 80%. Also, better efficiency and stability of the solar cell were obtained when the PU was reinforced with CNCs, indicating its longer lifetime usage. The most suitable cell, described in terms of durability, was obtained when the PU was mixed with 2 wt % of esterified CNCs obtained from BC. Overall, this study shows that the surface modification of the CNCs is an important factor, affecting the reinforcing efficacy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45010.

Bioderived Rubber-Cellulose Nanocrystal Composites with Tunable Water-Responsive Adaptive Mechanical Behavior.

Adaptive mechanical behaviors in nature have inspired the development of synthetic adaptive composites, with those responsive to water particularly relevant for biomedical applications. Polymer nanocomposites containing cellulose nanocrystals (CNCs) are prime examples of water-responsive mechanically adaptive materials. Although CNCs are biobased, the matrixes of these composites are exclusively petroleum-based synthetic elastomers, in sharp contrast to their biological counterparts. In this work, we attempted to probe the possibility of using bioderived rubber(s) as the matrix to fabricate CNC-nanocomposite with water-responsive adaptive mechanical behaviors. Specifically, natural rubber (NR) and epoxidized natural rubber (ENR) were used as the composite matrixes. Our results show that the water-responsive sensitivity and reversibility of ENR composites is much more drastic than that of NR composites. This is attributed to the strong CNC-polymer interaction (hydrogen bonding) for ENR, which leads to better filler dispersion and the formation of an extra CNC-polymer network in addition to the CNC-CNC filler network present in the NR composite. The synergistic effect of the dual networks plays a key role in tuning the mechanical properties and water-responsive sensitivity for various potential biomedical applications. Our study further provides guidance to make use of renewable resources to produce high value added water-responsive nanocomposites.