Effect Of Cellulose Nanocrystals Research Articles

Chitosan/cellulose nanocrystals/graphene oxide scaffolds as a potential pH-responsive wound dressing: Tuning physico-chemical, pro-regenerative and antimicrobial properties

Chronic wounds (CWs) treatment still represents a demanding medical challenge. Several intrinsic physiological signals (i.e., pH) help to stimulate and support wound healing. CWs, in fact, are characterized by a predominantly alkaline pH of the exudate, which acidifies as the wound heals. Therefore, pH-responsive wound dressings hold great potential owing to their capability of tuning their functions according to the wound conditions. Herein, porous chitosan (CS)-based scaffolds loaded with cellulose nanocrystals (CNCs) and graphene oxide (GO) were successfully fabricated using a freeze-drying method. CNCs were extracted from bagasse pulps fibers through acid hydrolysis. GO was synthesised by Hummer's method. The scaffolds were then ionically cross-linked using the amino acid L-Arginine (Arg), as a bioactive agent, and tested as potential pH-responsive wound dressing. Notably, the effect of CNCs and GO singly and simultaneously loaded within the CS-Arg scaffolds was investigated. The modulation of CNCs and GO content within CS-Arg scaffolds facilitated the development of scaffolds with an optimal pH-dependent swelling ratio capability and extended degradation time. Furthermore, CS/CNC/GO-Arg scaffolds exhibited tuned biological features, in terms of antimicrobial activity, cellular proliferation/migration ability, and the expression of extracellular matrix specific markers (i.e., elastin and collagen I) related to wound healing in human dermal fibroblasts.

Effect of cellulose nanocrystals on the mechanical and free vibration behavior of hybrid glass/kenaf fiber reinforced polyurethane core-based sandwich structures

ABSTRACT Engineering applications widely use foam-core-based sandwich structures. The study incorporated cellulose nanocrystals (CNC) into a hybrid glass/kenaf fiber-based polymeric sandwich structure with a 65 kg/m3 polyurethane foam core. Four unique face sheets (S1, S2, S3, and S4) were made using glass, kenaf, and CNC. Three-point bending, Charpy impact testing, and free vibration testing were used to characterize sandwich structures. The inclusion of CNC in the matrix of face sheets improved the hybrid composite’s bending strength and impact resistance. One layer of Kenaf fabric and two layers of glass make up the hybrid composite, which is stronger in both flexural strength and impact resistance, with 14.56 MPa and 8.1 J, respectively. These improvements are 44.84% and 57.49% compared to the pure glass/epoxy composite face plate. Nevertheless, the incorporation of Computer Numerical Control (CNC) failed to result in a substantial enhancement in vibration characteristics. Both matrix modification and natural fiber (kenaf) can effectively substitute glass fabric in sandwich structures.

Effect of cellulose nanocrystals on performance of PVA fiber-reinforced geopolymer composites: Reaction kinetics, bending behavior, and toughening mechanisms

Geopolymer composites are an attractive alternative to those based on ordinary Portland cement, owing to their lower carbon footprint and higher mechanical performance. However, brittleness is one of the major barriers limiting their use in construction applications. In this work, cellulose nanocrystal (CNC), a cost-effective and eco-friendly nanoparticle, was exploited in polyvinyl alcohol (PVA)-reinforced metakaolin-based geopolymer composite to further increase its mechanical performance. To this end, PVA-reinforced geopolymer composites were prepared by varying the CNC concentration from 0 wt% to 0.15 wt%. Three-point bending and fracture testing, combined with digital image correlation (DIC) and scanning electron microscopy (SEM), were performed to evaluate the bending and fracture behavior of samples containing CNC and reveal various toughening mechanisms. Composites with 0.15 wt% CNC recorded an increase of 190% in flexural strength and a 325 time of increase in fracture energy, compared to the control geopolymer (i.e. without PVA fibers and CNC). Isothermal calorimetry, Fourier transform infrared (FTIR) spectroscopy, and x-ray diffraction (XRD) were also utilized to characterize the heat flow, chemical bonds, and crystalline phases of the samples. These analyses revealed that CNC incorporation increased the amount of formed geopolymer gel with no significant changes in the crystalline structure and chemical bonding. In addition, stronger interfacial bonding between the PVA-geopolymer matrix was achieved, resulting in substantial improvements in flexural strength and fracture energy.

Interface interactions driven antioxidant properties in olive leaf extract/cellulose nanocrystals/poly(butylene adipate-co-terephthalate) biomaterials

Functional packaging represents a new frontier for research on food packaging materials. In this context, adding antioxidant properties to packaging films is of interest. In this study, poly(butylene adipate-co-terephthalate) (PBAT) and olive leaf extract (OLE) have been melt-compounded to obtain novel biomaterials suitable for applications which would benefit from the antioxidant activity. The effect of cellulose nanocrystals (CNC) on the PBAT/OLE system was investigated, considering the interface interactions between PBAT/OLE and OLE/CNC. The biomaterials' physical and antioxidant properties were characterized. Morphological analysis corroborates the full miscibility between OLE and PBAT and that OLE favours CNC dispersion into the polymer matrix. Tensile tests show a stable plasticizer effect of OLE for a month in line with good interface PBAT/OLE interactions. Simulant food tests indicate a delay of OLE release from the 20 wt% OLE-based materials. Antioxidant activity tests prove the antioxidant effect of OLE depending on the released polyphenols, prolonged in the system at 20 wt% of OLE. Fluorescence spectroscopy demonstrates the nature of the non-covalent PBAT/OLE interphase interactions in π-π stacking bonds. The presence of CNC in the biomaterials leads to strong hydrogen bonding interactions between CNC and OLE, accelerating OLE released from the PBAT matrix.

In‐situ preparation and performance of cellulose nanocrystals grafted with polyamide 6 composites

AbstractNylon nanocomposites were prepared by in‐situ ring‐opening polymerization to overcome the problem of poor properties due to the uneven dispersion of the nanoparticles by the traditional melt blending. This high‐performance polyamide 6 (PA6) nanocomposites with high dispersion and strong interface was prepared by grafting PA6 onto the surface of cellulose nanocrystals (CNC). The micromorphology, mechanical, crystalline and thermal properties of the composites were also investigated. Firstly, the hydroxyl group on the surface of CNC reacted with the para isocyanate of toluene diisocyanate (TDI), and the remaining ortho isocyanate was blocked by caprolactam to prepare CNC grafted with caprolactam (CNC‐g‐CL). Then CNC‐g‐CL was used as an activator to prepare cellulose nanocrystal grafted with polyamide 6 (CNC‐g‐PA6) composites by the ring‐opening polymerization of caprolactam on the CNC. The effects of different reaction temperatures, solvent amounts and molar ratios on the grafting rate of CNC‐g‐CL were investigated. The results showed that the highest grafting rate of CNC‐g‐CL with 66.7% was achieved at a reaction temperature of 45°C, 0.1 g/mL CNC in toluene, and a molar ratio of 6 for TDI/CNC. Further, different CNC‐g‐PA6 composites prepared from different CNC content and activator content were explored. For CNC‐g‐PA6 composites, CNC was uniformly dispersed in the PA6 matrix and had a good compatibility with the matrix. CNC exhibited significant reinforcement in the composites with a tensile strength of up to 108 MPa. In addition, the glass transition temperature of CNC‐g‐PA6 was increased to 92°C, which significantly improved the heat resistance of the new composites.Highlights Effects of reaction condition of CNC and TDI on DSTDI and DSCL were studied. Effects of CNC and activator content on CNC‐g‐PA6 properties were studied. CNC is uniformly dispersed in PA6 with average particle size less than 1 micron. The nylon matrix was significantly strengthened by the addition of CNC. The addition of CNC significantly improved the heat resistance of the composites.

3D vat photopolymerization printing of hydrophilic silicone-based microfluidic devices and the effect of cellulose nanocrystals as additives for improved printing accuracy

The lack of an ideal silicone-based ink material with optimal printability has significantly limited the potential to fabricate silicone-based microfluidic devices via 3D vat photopolymerization (VPP) printing. Oftentimes, photoabsorbers are incorporated into the ink material for better control of the photocuring depth in order to avoid excessive curing of unwanted parts. However, the search for a suitable photoabsorber without staining the ink material remains challenging due to the need to retain the clear interface in the final printed product. Herein, we present the fabrication of highly precise and transparent microfluidic devices using hydrophilic silicone-based ink via 3D VPP printing upon photocuring depth adjustment with cellulose nanocrystals (CNC). With the optimal CNC content, the ink material demonstrates enhanced printing accuracy with highly precise replication of channel patterns consisting of near zero deviation in width dimension down to 100 µm. Moreover, the addition of optimal CNC content exhibits no distinct final color and has no negative impact on the pre-gel viscosity and the gel point of the developed ink material. Moving on, the printed devices exhibit excellent fluid manipulation with various solvents for up to 24 hours, with incubation temperature up to 100ºC for 5 hours, and with a continuous flow rate up to 20 mL/min. The sustainable hydrophilicity, good organic solvent resistance, and excellent biocompatibility properties of the printed material further eliminate the need for additional surface modification to suit its application with either organic solvents or biological cells. To the best of our knowledge, the approach to tuning the photocuring depth of ink material with CNC is not widely reported. Besides, the successful fabrication of a highly detailed, neutral-colored, and highly functional hydrophilic silicone-based microfluidic device via 3D VPP printing upon the incorporation of CNC introduces a new avenue in terms of printing material and fabrication method for the mass production of microfluidic devices.

Effects of cellulose micro and nanocrystals on the mechanical, thermal, morphological, and structural properties of rigid polyurethanes

Effects of adding microcrystalline cellulose (MCC) and cellulose nanocrystals (CNC) were evaluated relative to the mechanical, thermal, morphological, and structural properties of rigid polyurethanes (rPUs). The composites were prepared with the blending of polyols/isocyanates and the cellulosic fillers at 0.25%, 0.5%, and 1% loadings. Scanning electron microscopic images showed that the samples had micro-scaled porosity, with cell sizes ranging from 250 to 800 nm. The fillers improved the mechanical strengths and modulus of neat rPUs due to the presence of the nano-sized cells in rPUs matrix. The addition of both fillers generally did not provide a positive effect on the thermal properties, and the weight loss generally increased while the loading rate of the fillers was increased from 0.25% to 1%. The samples had two small crystalline peaks at 18° and 19° according to the X-ray diffraction analysis. From the results, it can be said that the presence of both fillers generally improved all properties of the neat rPUs, and the effects of CNC on the properties were higher than MCC due to both lower particle size and the higher crystallinity of CNC.

Effect of cellulose nanocrystals and carboxylated multiwalled carbon nanotubes on performance of polyethersulfone membrane for humic acid removal

Persistent declines in flux due to membrane fouling result in decreased treated water production, higher energy consumption, and a frequent need for chemical cleaning. Carbon nanotubes-based membranes have shown remarkable separation capabilities in water treatment processes while being relatively resistant to biofouling. Cellulose-based membranes, on the other hand, have demonstrated outstanding biocompatibility and versatile surface chemistry. In the current study, a hybrid polyethersulfone (PES) membrane was synthesized by integrating with single cellulose nanocrystals (CNC), single carboxylated multiwalled carbon nanotubes (MWCNT), and a mixture of CNC and MWCNT utilizing the phase inversion method. This combination of nanomaterials was aimed at eliciting synergistic effects to enhance the overall membrane performance. The evaluation of the hybrid membranes encompassed an analysis of membrane structure, morphology, porosity, hydrophilicity, water flux, humic acid (HA) rejection, and the flux recovery ratio (FRR). The experimental outcomes unveiled notable changes in the morphology of the polymeric membrane when CNC and MWCNT were introduced into the PES membrane structure. All hybrid membranes displayed heightened hydrophilicity compared to the original pristine PES membrane. The PES/CNC0.3/CNT0.03 membrane demonstrated exceptional performance, with a remarkable HA rejection rate and FRR of 93.05% and 92.09%, respectively. This outstanding performance can be attributed to the synergistic combination of two separation mechanisms: electrostatic repulsion and size exclusion. The inclusion of MWCNTs into the hybrid membranes significantly reduced humic acid-induced membrane fouling due to improve surface hydrophilicity and decreased membrane roughness.

Effect of Cellulose Nanocrystals and Hot Stretching on Shish–Kebab Structures of High-Density Polyethylene

Effect of Cellulose Nanocrystals and Hot Stretching on Shish–Kebab Structures of High-Density Polyethylene

Effect of cellulose nanocrystals and green synthesized silver nanoparticles on mechanical properties and antimicrobial activity of banana flour/agar composite films

This study characterized the physicochemical and functional properties of nanocomposite films synthesized by incorporating cotton linter cellulose nanocrystals (CN) and green silver nanoparticles (AgNPs) into banana flour/agar. The results showed that CN could not enhance the tensile strength of the B/A nanocomposite films, but it did prolong the antibacterial activity against the Gram-positive bacterium Listeria monocytogenes when combined with AgNPs. However, the binary blend of CN and AgNPs resulted in a flocculated morphology on the film surface, causing an increase in the film brittleness and a decrease in the water solubility, elongation, and final decomposition temperature. Unfortunately, none of the nanocomposite films were found to inhibit the growth of the Gram-negative species Escherichia coli within 12 h. Further research is needed to assess the migration release of CN/AgNPs in nanocomposite films and to determine their potential for use as active food packaging.

Water-in-water Pickering emulsion stabilized by cellulose nanocrystals as space-confined encapsulating systems: From establishment to stability

The development of new water-in-water (W/W) emulsion systems and the improvement of the long-term stability of emulsions could create opportunities for studying interfacial bionic systems and microencapsulation applications. In this study, the new W/W emulsion systems were constructed from hydroxypropyl methylcellulose (HPMC) and maltodextrin (MD). The effects of cellulose nanocrystals (CNC) and environmental factors (ionic strength and pH) on the stability of W/W Pickering emulsions were investigated. The stabilizing effect was observed at contents of CNC as low as 0.025 wt%. The W/W Pickering emulsion showed no phase separation within 30 days when the CNC concentration was above 0.025 wt%, indicating that the emulsions were stable during the observation period. The stability of W/W Pickering emulsions was driven by the electrostatic repulsion provided by the CNC adsorbed at the droplet interface, which decreased with increasing NaCl concentration. This was attributed to the charge-shielding effect of NaCl weakening the electrostatic repulsion of the CNCs at the emulsion droplet interface. Lactobacillus helveticus cells were encapsulated in the W/W Pickering emulsion. These results revealed that the developed W/W Pickering emulsions have potential applications in protecting the activity of probiotic bacteria and investigating the behavior of cells in restricted spaces.

Role of silica-based porous cellulose nanocrystals in improving water absorption and mechanical properties

Epoxy resins are important thermosetting polymers. They are widely used in many applications i.e., adhesives, plastics, coatings and sealers. Epoxy molding compounds have attained dominance among common materials due to their excellent mechanical properties. The sol-gel simple method was applied to distinguish the impact on the colloidal time. The properties were obtained with silica-based fillers to enable their mechanical and thermal improvement. The work which we have done here on epoxy-based nanocomposites was successfully modified. The purpose of this research was to look into the effects of cellulose nanocrystals (CNCs) on various properties and applications. CNCs have recently attracted a lot of interest in a variety of industries due to their high aspect ratio, and low density which makes them perfect candidates. Adding different amounts of silica-based nanocomposites to the epoxy system. Analyzed with different techniques such as Fourier-transformed infrared spectroscope (FTIR), thermogravimetric analysis (TGA) and scanning electronic microscopic (SEM) to investigate the morphological properties of modified composites. The various %-age of silica composite was prepared in the epoxy system. The 20% of silica was shown greater enhancement and improvement. They show a better result than D-400 epoxy. Increasing the silica, the transparency of the films decreased, because clustering appears. This shows that the broad use of CNCs in environmental engineering applications is possible, particularly for surface modification, which was evaluated for qualities such as absorption and chemical resistant behavior.

The Effect of Cellulose Nanocrystals and Acetylated Nanocellulose on the Crystallization Kinetics and Thermal Stability of Polylactic Acid

The Effect of Cellulose Nanocrystals and Acetylated Nanocellulose on the Crystallization Kinetics and Thermal Stability of Polylactic Acid

Effect of cellulose nanocrystals on rheology, liquid crystal, and delivery behavior of metronidazole poloxamer-based in-situ dental medication

Effect of cellulose nanocrystals on rheology, liquid crystal, and delivery behavior of metronidazole poloxamer-based in-situ dental medication

Improved Properties of Composite Edible Films Based on Chitosan by Using Cellulose Nanocrystals and Beta-Cyclodextrin

The aim of this study was to produce innovative edible films and coatings with various combinations of materials, in order to achieve the best possible resulting properties. More specifically, the effect of cellulose nanocrystals (CNC) or beta-cyclodextrin (CD) addition to chitosan (CH) films and the development of composite CH–CNC–CD films were investigated. According to the results, most properties of both CH–CNC and CH–CD edible films were improved. The viscosity of the solutions was decreased up to 50% while the surface tension was minimally changed even at high levels of CNC or CD addition. Furthermore, oxygen and water vapor permeability of the CH–CNC and the CH–CD edible films was decreased, whereas transparency and heterogeneity were increased. On the other hand, the study of the composite CH–CNC–CD films, showed that CNC improved viscosity, supporting thus the coating procedure. Moreover, CNC led to more stable structures with enhanced mechanical properties. Finally, CD mostly contributed to the improvement of the optical properties (lighter color and increased transparency).

Study on characteristics of the electric‐field‐sensitive hydrogel inspired by jelly in the ampullae of Lorenzini of elasmobranchs

AbstractThe elasmobranchs can sense the weak electric field signals of marine environment and other lives to adjust follow‐up activities by the jelly in their ampullae of Lorenzini, which provides a new research route for the development of ocean exploration, locating of underwater object, underwater navigation and communication. Inspired by such a characteristic of jelly, this paper presents a novel electric‐field‐sensitive hydrogel in response to weak electric field stimuli in surroundings. The hydrogel is made from I‐carrageenan (IC) and cellulose nanocrystals (CNCs) by the way of blending. The effects of CNCs on the performances of hydrogels have been investigated via the characterization of both IC/CNC blending hydrogel and pure IC hydrogel. Swelling experiments show that the equilibrium swelling ratio of hydrogel is positively related to the mass ratio of IC to CNCs. Electric field sensitivity experiments indicates that the IC/CNC blending hydrogel has a higher sensitivity than the pure IC hydrogel by comparing the bending angles of hydrogels under different electric fields, and the maximum bending angle, 0.5°, of blending hydrogel remains under the 1 mV/cm electric field. The blending hydrogel sensitive to weak electric field stimuli in this paper may provide an alternative strategy to develop intelligent response‐type materials for applications of efficient underwater sensors and actuators.

The impact of cellulose nanocrystals on the rheology of sodium carboxymethyl cellulose and sodium alginate

AbstractAt present, the physical properties of hydrocolloids limit their wide application in food industry. To improve the viscoelasticity of sodium carboxymethyl cellulose (CMC) and sodium alginate (SA), cellulose nanocrystals (CNCs) were added into CMC and SA solutions to regulate the non‐Newtonian flow behaviors of composite systems under different conditions. The rheological properties of CMC/CNCs or SA/CNCs composite systems were studied using steady rheological measurements, dynamic rheological measurements, and creep compliance experiments. It was found that the viscosities and elastic modulus of CMC were positively related to CNCs concentrations in acid, neutral or alkaline environments. When the CNCs content was higher than 5% at pH 9.45, the gelation of CMC was accelerated, and the gelation strength was increased. The damping factor of SA decreased with increasing calcium ions contents. When calcium ions content was higher than 0.07%, the damping factor of SA was less than 1, indicating that SA system achieved gel transformation. The effect of CNCs on the apparent viscosity, shear stress, and storage modulus of CMC was more obvious in comparison to that of SA. Overall, as a rheology modifier, CNCs can minimize the contents of food colloids in any functional fluid while maintaining the thickening rheology.

Effect of cellulose nanocrystals on xylan/chitosan/nanoβ-TCP composite matrix for bone tissue engineering

Effect of cellulose nanocrystals on xylan/chitosan/nanoβ-TCP composite matrix for bone tissue engineering

Effect of cellulose nanocrystals on the properties of the photoactive aloe emodin poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) packaging film

AbstractIn recent years, there has been increasing interest in photoactive packaging materials, which inactivate bacteria via the photoactivation of light‐sensitive compounds. One of the existing challenges is the reduced stability and efficacy of these materials due to light exposure. In this study, the effect of cellulose nanocrystal (CNC) loading on the antimicrobial, barrier, and mechanical properties of the photoactive poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) packaging film has been investigated. The film (CNC‐AE‐PHBV) is composed of aloe emodin (AE) and PHBV at the ratio of 540.48 µg g−1, and CNC. The weight percentage of CNC loading relative to PHBV is varied from 0.5% to 2.0% (w/w). The results show that CNC mitigates the photodegradation of AE in the polymeric matrix and the highest protection is obtained at 0.5% of CNC loading. CNC also augments the hydrophilicity of CNC‐AE‐PHBV films, indicated by the decrease of water contact angle (78°–71.0°). These effects could have led to the increased retention of photodynamic efficacy against Escherichia coli (~4.5 log cycles) of the CNC‐AE‐PHBV films after repeated light irradiation. Nevertheless, no improvement in the barrier as well as mechanical properties of the films has been observed. The findings evidence the important enhancement effect of CNC on the efficacy of photoactive polymer, which can be further explored for developing future antimicrobial packages.

Structure, stability, and rheological properties of zirconia suspensions in the presence of nanocrystals: Effects of ionic strength

Cellulose nanocrystals (CNCs) are used as a stabilizing agent in water-based zirconia suspensions at high concentration. The effects of CNC and NaCl concentrations were studied on the stability, adsorption, zeta potential, size, and rheology of slurries. We characterized samples and visualized CNCs at the surface of solid particles by scanning electron microscopy. The results confirm that the adsorption capacity of CNC on the surface of zirconia particles increases as salt concentration increases and causes an increase in the viscoelastic properties and a denser structure on the surface of adsorbent. The presence of counter-ions from the added electrolyte shortens the range of electrostatic repulsion between CNC particles through screening its electrical double layer resulting in more adsorption of adsorbate on the zirconia surface and, thus, provides stabilization.