Addition Of Cellulose Nanocrystals Research Articles

Engineered cellulose nanocrystals-based cement mortar from office paper waste: Flow, strength, microstructure, and thermal properties

In this study, three types of cellulose nanocrystals (CNCs), termed as C1, C2 or C3, of varied crystallinity (79.91–89.31%), diameters (0.1–1 μm), lengths (0.8–10 μm) and synthesized at solid to acid ratios (1g:20 ml to 1g:25 ml) were incorporated as a green additive (0–1.5% by wt. of cement) in the preparation of mortar. The performance of the developed mortar was examined by evaluating flow, compressive and flexural strengths, the volume of permeable voids, and thermal conductivity. The results were supported by XRD, FTIR, and SEM-EDX analyses. The C1 (synthesized with mild acid hydrolysis conditions) based mortar outperformed C2 (synthesized with harsh acid hydrolysis conditions having moderate crystallinity) and C3 (synthesized with harsh acid hydrolysis conditions having high crystallinity) based mortars. In general, the flow of mortar dropped linearly with the addition of CNCs due to agglomeration, depending on their particle sizes. The maximum compressive and flexural strengths, thermal conductivity, and minimum volume of voids recorded in C1 specimens were 34 MPa, 4.1 MPa, 0.96 W/mK, and 13.4%, respectively. These values were 21.7%, 28.1%, 17.1% higher, and 14.6% lower than that obtained in CNC-free mortar specimens, respectively. The enhanced performance of C1 specimens was attributed to more precipitation of –OH groups, strong Si–O-T chains, increased crystallinity of the products, and the intertwining of major elements in the cementitious composites. It also imparted crack-bridging effects leading to microstructural densification. It is postulated that the engineered C1 mortar has significant potential as an additive in construction applications from ecological, economic, and technical means.

Thermal and mechanical properties of PLA-based multiscale cellulosic biocomposites

In this work polylactic acid (PLA) based multiscale cellulosic biocomposites were prepared with the aim to evaluate the effect of the incorporation of cellulose nanocrystals (CNCs) on the PLA biocomposites reinforced with cellulose microfibers (MFCs). For this, PLA composite materials reinforced with both MFCs and with a combination of MFCs and CNCs were prepared, while keeping the content of cellulosic reinforcements constant. The thermal and mechanical properties of these multiscale PLA biocomposites were characterized by thermogravimetry (TGA), differential scanning calorimetry (DSC), flexural mechanical and, dynamic mechanical (DMA) tests. Likewise, they were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that the replacement of MFCs by CNCs in the 1–5% range appreciably modifies the thermal and mechanical properties of multiscale compounds. For example, they increase the thermal stability of the materials, modify the PLA crystallization process and play the role of adhesion promoters since the mechanical properties in flexure increase in the order of 40% and the storage modulus increases in the order of 35% at room temperature. Also, the addition of CNCs increases the relaxation temperature of the material from 50 to 60 °C, thereby expanding the temperature range for its use.

High-Performance Polyurethane Nanocomposite Membranes Containing Cellulose Nanocrystals for Protein Separation.

With the aim of exploring new materials and properties, we report the synthesis of a thermoplastic chain extended polyurethane membrane, with superior strength and toughness, obtained by incorporating two different concentrations of reactive cellulose nanocrystals (CNC) for potential use in kidney dialysis. Membrane nanocomposites were prepared by the phase inversion method and their structure and properties were determined. These materials were prepared from a polyurethane (PU) yielded from poly(1,4 butylene adipate) as a soft segment diol, isophorone diisocyanate (IPDI) and hexamethylenediamine (HMDA) as isocyanate and chain extender, respectively (hard segment), filled with 1 or 2% w/w CNC. Membrane preparation was made by the phase inversion method using N,N-dimethylformamide as solvent and water as nonsolvent, and subjected to dead-end microfiltration. Membranes were evaluated by their pure water flux, water content, hydraulic resistance and protein rejection. Polymers and nanocomposites were characterized by scanning electronic and optical microscopy, differential scanning calorimetry, infrared spectroscopy, strain stress testing and 13C solid state nuclear magnetic resonance. The most remarkable effects observed by the addition of CNCs are (i) a substantial increment in Young’s modulus to twenty-two times compared with the neat PU and (ii) a marked increase in pure water flux up to sixty times, for sample containing 1% (w/w) of CNC. We found that nanofiller has a strong affinity to soft segment diol, which crystallizes in the presence of CNCs, developing both superior mechanical and pure water flow properties, compared to neat PU. The presence of nanofiller also modifies PU intermolecular interactions and consequently the nature of membrane pores.

Effect and Mechanism of Acid-Induced Soy Protein Isolate Gels as Influenced by Cellulose Nanocrystals and Microcrystalline Cellulose.

The effects of cellulose nanocrystals (CNC) and microcrystalline cellulose (MCC) on the gel properties and microstructure of glucono-δ-lactone-induced soy protein isolate (SPI) gels were investigated. The water-holding capacity, gel strength, and viscoelastic modulus of CNC–SPI gels were positively associated with CNC concentration from 0 to 0.75% (w/v). In contrast, MCC–SPI gels exhibited decreased water-holding capacity, gel strength, and viscoelastic modulus. All composite gels displayed high frequency dependence and the typical type I (strain thinning) network behavior. Changes in viscoelasticity under large strain were correlated with differences in the microstructure of SPI composite gels. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) showed that CNC were more evenly and steadily distributed in the protein matrix and formed a compact network structure. In contrast, MCC–SPI gels exhibited a discontinued and rough gel network with some large aggregates and pores, in which MCC was randomly entrapped. Fourier transform infrared spectroscopy (FTIR) and molecular forces results revealed that no new chemical bonds were formed in the gelation process and that the disulfide bond was of crucial importance in the gel system. With the addition of CNC, electrostatic interactions, hydrophobic interactions, and hydrogen bonds in the SPI gel network were significantly strengthened. However, the incorporation of MCC might obstruct the connection of the protein network. It is concluded that both cellulose type and concentration affect gelling properties.

Reduced graphene oxide/cellulose nanocrystal composite films with high specific capacitance and tensile strength

Due to the environmental degradation and energy depletion, the strategy for fabricating high-performance supercapacitor electrode materials based on graphene and nanocellulose has received great attention. Herein, an environmentally friendly reduced graphene oxide (RGO)/cellulose nanocrystal (CNC) composite conductive film was prepared using L-ascorbic acid (L-AA) as the reductant of graphene oxide (GO). Based on chemical structure analysis, L-AA was proved to be an effective reductant to remove oxygen containing groups of GO. Through microstructure observation, a unique stacking structure of CNC and RGO was observed, which could be largely attributed to the hydrogen bond interaction. Furthermore, the effect of CNC amount on the performance of RGO/CNC composite films was also systematically investigated. Particularly, the addition of CNC was found to exert a positive effect on the tensile strength, which might be mainly due to a mass of hydrogen bonds between the CNCs. Meanwhile, the RGO/CNC composite conductive film featured ideal electrical double-layer capacitive (EDLC) behavior, exhibiting a gravity specific capacitance of 222.5 F/g and tensile strength of 32.17 MPa at 20 wt% CNC content. Therefore, the RGO/CNC composite conductive films may hold great promise for environmentally friendly electrode materials of supercapacitors and flexible electrical devices.

Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Polycaprolactone Polymer Mixtures Reinforced by Cellulose Nanocrystals: Experimental and Simulation Studies.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/polycaprolactone (PHBV/PCL) polymer mixtures reinforced by cellulose nanocrystals (CNCs) have been obtained. To improve the CNC compatibility with the hydrophobic PHBV/PCL matrix, the CNC surface was modified by amphiphilic polymers, i.e., polyvinylpyrrolidone (PVP) and polyacrylamide (PAM). The polymer composites were characterized by FTIR, DSC, TG, XRD, microscopy, BET surface area, and tensile testing. The morphological, sorption, thermal, and mechanical properties of the obtained composites have been studied. It was found out that with an increase in the CNC content in the composites, the porosity of the films increased, which was reflected in an increase in their specific surface areas and water sorption. An analysis of the IR spectra confirms that hydrogen bonds can be formed between the CNC hydroxyl- and the –CO– groups of PCL and PHBV. The thermal decomposition of CNC in the PHBV/PCL/CNC composites starts at a much higher temperature than the decomposition of pure CNC. It was revealed that CNCs can either induce crystallization and the polymer crystallite growth or act as a compatibilizer of a mixture of the polymers causing their amorphization. The CNC addition significantly reduces the elongation and strength of the composites, but changes Young’s modulus insignificantly, i.e., the mechanical properties of the composites are retained under conditions of small linear deformations. A molecular-dynamics simulation of several systems, starting from simplest binary (solvent-polymer) and finishing with multi-component (CNC—polymer mixture—solvent) systems, has been made. It is concluded that the surface modification of CNCs with amphiphilic polymers makes it possible to obtain the CNC composites with hydrophobic polymer matrices.

Tribological and mechanical properties of cellulose/PMMA composite

Cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) extracted from rice stalks were added to poly-methyl methacrylate (PMMA) with weight ratios of 0.1–1.0 wt%. The tribological and mechanical properties of the resulting composite materials were evaluated and compared. The addition of CNCs and CNFs reduced the wear volume by around 72–90% compared to pure PMMA samples in ball-on-disk wear tests performed against a chrome steel ball counter body. The CNC and CNF reinforcements also effectively improved flow stress under static and dynamic deformation conditions. Furthermore, the flow stress enhancement increased with an increasing CNC/CNF addition for both composite materials. For a constant strain and strain rate, the maximum enhancement effect was observed in the samples reinforced with CNFs. Overall, the CNF/PMMA showed a better tribological and mechanical performance than the CNC/PMMA. In addition, the CNFs had a longer length and higher aspect ratio than CNCs, which led to a more effective mechanical entanglement effect with the PMMA matrix. This physical entanglement improved the structural integrity of the composites. The CNC reinforcement (CNC percentage from 0% to 1.0 wt.%) also enhanced an effective improvement of about 35%∼45% in yield stress and ultimate strength under dynamic deformation conditions and static deformation conditions. Furthermore, the CNF reinforcement (CNF percentage from 0% to 1 wt%) also enhanced an effective improvement of about double yield stress and ultimate strength under dynamic deformation conditions and static deformation conditions.

Effect of the incorporation of cellulose nanocrystals into a microwave‐polymerized denture base resin: Cellulose nanocrystals into a denture base resin

The aim is to evaluate the mechanical, physical, and microbiological properties of a denture base resin (Onda‐Cryl, microwave‐polymerized), after the incorporation of cellulose nanocrystals (CNC). Mixtures of CNC and the resin are prepared at 0% (control group), 0.25%, 0.5%, 0.75% and 1% for the flexural strength (FS) and Vickers hardness (VH) tests. Due to the VH results, surface roughness (SR), surface free energy (SFE), and the single‐ and dual‐species biofilm formation of Candida albicans and methicillin‐susceptible Staphylococcus aureus (MSSA) for metabolic activity (XTT assay), antimicrobial activity (CFU mL−1) and confocal laser microscopy tests are performed for the groups 0% and 0.75% CNC. Data are statistically analyzed (α = .05). For FS, CNC at 0.25%, 0.5% and 0.75% are similar to the control. A significant increase of VH is observed at 0.75% and 1%. The 0.75% CNC group is similar to the control for the SFE and SR tests. There is no significant difference between control group and 0.75% CNC group for adhesion and biofilm formation of different microorganisms analyzed for XTT and CFU mL−1. These results are corroborated by confocal microscopy images. The incorporation of CNC at 0.75% into a microwave‐polymerized denture base resin provides promising results regarding VH and does not influence the physical, mechanical, and microbiological properties evaluated. These results suggest that the addition of CNC in the resin does not display surface alterations capable of increasing adhesion or biofilm formation of C. albicans or S. aureus.

Isolation of high crystalline nanocellulose from Mimosa pudica plant fibres with potential in packaging applications

AbstractMimosa pudica Linn (sensitive plant) is a medicinal plant of family Fabaceae. Its stem is a good source of cellulose. This research work reports isolation of cellulose nanocrystals (CNCs) from M. pudica stem fibres by combined chemical and mechanical treatments. Polyvinyl alcohol (PVA)/starch composites were prepared with incorporation of isolated CNC (1, 3 and 5 wt.%) by solution casting method. Addition of CNC in polymer composites improved its mechanical strength and barrier properties. Isolation process of CNC includes alkali treatment, bleaching and acid hydrolysis followed by homogenization. Chemical composition, thermal stability, structure, surface morphology, crystallinity and size of the freeze‐dried nanocellulose were studied carefully. Fourier transform infrared analysis of raw fibre and CNC showed elimination of non‐cellulosic fragments from untreated M. pudica stem fibre. Electron microscopy analysis and dynamic light scattering (DLS) confirmed the isolation of nanocellulose. X‐ray diffraction showed improvement in the crystallinity of obtained nanocellulose. Increase in crystallinity indicates high Young's modulus of isolated nanocellulose which makes them proper reinforcement material in composites. Polymer composites with the addition of 3 wt.% of CNC showed the highest tensile strength and lowest water vapour transmission rate (WVTR), moisture absorption and oxygen transmission rate (OTR). As M. pudica is an abundant natural resource, it can be utilized as an efficient source of nanocellulose for different applications especially as fillers in sustainable polymer composites for packaging.

Drug delivery and in vitro biocompatibility studies of gelatin-nanocellulose smart hydrogels cross-linked with gamma radiation

In this study, pH-sensitive gelatin hydrogels reinforced with cellulose nanocrystals (CNCs) from rice husk were fabricated by introducing gamma irradiation to induce green cross-linking method hydrogels. The properties of the hydrogels were studied at varied CNCs and pH. The hydrogels were characterized by fourier-transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), rheology, swelling studies, scanning electron microscopy (SEM), drug loading and release analysis, as well as cytotoxicity tests. The addition of CNC improved both the thermal and dynamic mechanical properties of the hydrogels. The hydrogels were sensitive to changes in pH, and the highest swelling degree was observed at pH 3. The optimum swelling performance was obtained with gelatin/4CNC hydrogels. SEM images revealed that incorporation of CNC content up to 4% improved the porosity of the hydrogels. The drug release analysis using riboflavin as a drug model showed that gelatin/4CNC hydrogels released more than 70% of riboflavin in 12 h. In addition, hydrogels showed non-cytotoxic properties, suggesting their potential application in drug delivery systems.

Glycerol-based polymer adhesives reinforced with cellulose nanocrystals

Biodegradable adhesives are of great scientific and technological interest as an alternative to conventional commercial products, which generally can release toxic substances and take a long time to degrade. Composites using biodegradable polymers synthesized by polycondensation of glycerol and diacids, i.e., poly(glycerol succinate), PGSu, poly(glycerol maleate), PGM, and poly(glycerol maleate-co-succinate), PGMSu, reinforced with cellulose nanocrystals (CNC) were used as adhesives for Angelim ( Vatairea heteroptera Ducke ). CNC were added at 0, 5, 10 and 20 wt% to the glycerol-derived polymers in order to evaluate their effect on mechanical properties. Polymers and composites were analyzed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Adhesive joints were prepared using the synthesized glycerol-based polymers, and poly(vinyl acetate), PVAc, for comparison purposes. Thermal analyses indicated that most of the glycerol-based polymers tested are stable up to 260 °C while adhesion tests indicated that adhesives containing CNC showed superior shear strength as compared to pristine polymers and PVAc. These results suggest that the addition of cellulose nanocrystals (CNC) is a viable approach to tailor the mechanical and adhesive properties. • Biodegradable adhesives are a new generation of adhesives with tailored adhesion and degradation. • Cellulose nanocrystals (CNC) are widely used due to their aspect ratio, crystallinity, mechanical properties and biodegradability. • The combination of glycerol polymers with CNC improves mechanical properties and controls degradation time to produce tailor-made adhesives. • These adhesives can be a viable alternative to using larger amounts of glycerol and adding value to a by-product of the biodiesel production market.

A Novel Foam Coating Approach to Produce Abrasive Structures on Textiles

Abstract Abrasive materials are classified as paper, nonwoven, or plastic-based multilayer structures, which are used for different kinds of surface finishing. Currently, the production of abrasive structures on textiles is carried out by spraying a slurry of binder and abrasive particles, e.g., Al2O3 or SiC, with subsequent drying and curing of the binder. The drawback of this production method is the poor runnability of the spraying process. Even small variations in the process parameters may lead to an uneven coating. Therefore, a novel coating approach was developed to produce abrasive structures with foam coating on textile substrates. The foam coating method, which is commonly used in the textile industry, has the potential to produce an even coating layer. The runnability and reliability of the foam coating process are good even with high solids. From a workplace safety perspective, another advantage of foam coating is that there are no airborne particles during the coating process. A polyamide woven cloth was foam coated with an aqueous slurry containing abrasive grains (SiC), a water-based UV-curable acrylate binder, and cellulose nanocrystals (CNCs) to adjust the slurry rheology. Stable abrasive-binder foams were generated from the slurries even at high solids of 50% using an anionic foaming agent. The cloth was foam coated and dried, and the resin was cured with a LED-UV lamp on a pilot scale. It was observed that without the addition of CNC the foam did not stay on the surface of the cloth after coating. CNC acts as a rheology modifier and co-binder, which prevent the foam from penetrating deeper into the pores of the cloth. CNC also acted as a dispersing agent: the slurry was effectively stabilized by the CNC to prevent sedimentation of the abrasive grains. An organic solvent-free composition was introduced by combining CNC with a water-based UV-resin.

The Role of Structure and Interactions in Thermoplastic Starch-Nanocellulose Composites.

Composite films were fabricated by using cellulose nanocrystals (CNCs) as reinforcement up to 50 wt% in thermoplastic starch (TPS). Structure and interactions were modified by using different types (glycerol and sorbitol) and different amounts (30 and 40%) of plasticizers. The structure of the composites was characterized by visible spectroscopy, Haze index measurements, and scanning electron microscopy. Tensile properties were determined by tensile testing, and the effect of CNC content on vapor permeability was investigated. Although all composite films are transparent and can hardly be distinguished by human eyes, the addition of CNCs somewhat decreases the transmittance of the films. This can be related to the increased light scattering of the films, which is caused by the aggregation of nanocrystals, leading to the formation of micron-sized particles. Nevertheless, strength is enhanced by CNCs, mostly in the composite series prepared with 30% sorbitol. Additionally, the relatively high water vapor permeability of TPS is considerably decreased by the incorporation of at least 20 wt% CNCs. Reinforcement is determined mostly by the competitive interactions among starch, nanocellulose, and plasticizer molecules. The aging of the films is caused by the additional water uptake from the atmosphere and the retrogradation of starch.

Optimization of nanocomposite films based on quinoa protein isolate incorporated with cellulose nanocrystal and starch

This research aimed to prepare quinoa protein isolate (QPI) based nanocomposite films reinforced with starch and cellulose nanocrystals (CNC). The range of QPI, starch, and CNC contents were chosen as 60%–80%, 10%–30%, and 2.5%–7%, respectively, by mixture design approach. The effect of CNC and starch on physicochemical, mechanical, and barrier properties of the films were then investigated. The obtained results showed that the addition of starch and CNC improved the mechanical properties of films. The incorporation of CNC reduced the film water vapor permeability (WVP). In addition, transparency of the films increased with increasing protein and starch content and reducing CNC content. Furthermore, the optimal formulation of the composite was determined as 78.55% protein, 18.28% starch, and 3.17% CNC. Fourier transform infrared (FTIR) spectroscopy of the film prepared according to optimal formulation demonstrated the interaction of the film's constituents, and its scanning electric spectroscopy (SEM) image was in agreement with the physical and mechanical properties the nanocomposite film. Novelty impact statement Protein extracted from quinoa seeds using alkaline method with high purity (83%). The optimal formulation obtained with 78.55% protein, 18.28% starch, and 3.17% CNC. The optimal film is recommended for packaging of aromatic foodstuff.

Rheological properties of cellulose nanocrystals isolated via mechanical methods in thermoplastic polyurethane matrix

Thermoplastic polyurethanes (TPU) are known for their versatility because they have both thermoplastic and elastomeric properties. Improvement of TPU properties can be accomplished by reinforcement with nanoscale fillers. Cellulose nanocrystals (CNC) are the most attractive nano-filler for reinforcement purposes in polymer matrices because of their high crystallinity and biodegradable materials. Mechanical methods to isolate CNC has sparked interest among researchers due to environmental demands (less solvent consumption). Lately, several researchers also have revealed some remarkable improvement of TPU through the addition of CNC. Thus, this study was aimed to produce CNC via mechanical methods for and to study the rheological properties of CNCs in the TPU matrix to gain insight interactions between CNCs and TPU. Isolation of CNCs via two methods: ultra-sonication (CNC-U) and nano-grinding (CNC-N) methods have been carried out. Then, the CNCs (0.5–2 wt%) were added into the TPU network employing the solution mixing method. The CNC was characterized via FESEM and the rheological behaviour was investigated on TPU/CNC solution. The main outcomes are that CNC-N has shown a higher aspect ratio (10–15), higher yield (>40%), and lower time and energy consumption than CNC-U. Rheological properties of TPU/CNC solution offer its structure-properties relationship via the increase in the concentration of CNCs. At 2 wt% concentration, TPU/CNC-N shows higher viscosity (19.5 Pa.s) than TPU/CNC-U (15.9 Pa.s). Thus, it was proven that the nanocomposite tends to act as a solid than liquid due to higher elastic behaviour. Furthermore, we can suggest the utilization of mechanical methods to produce a high yield of CNCs in notify the environmental issues.

Electrospun Polystyrene and Acid-Treated Cellulose Nanocrystals with Intense Pulsed Light Treatment for N95-Equivalent Filters

The coronavirus (SARS-CoV-2) has prompted a global need and shortage of face masks and respirators. Electrospinning of polystyrene and cellulose nanocrystals (CNCs) is used to fabricate filter materials exceeding N95 standards set by the National Institute for Occupational Health and Safety. The desired filtration efficiency and pressure drop are achieved from filters with varying amounts of input material. The water contact angle, fiber morphology, and surface potential are reported to explain the enhancements in filtration performance after the addition of CNCs or application of intense pulsed light (IPL). The improved durability in the form of increased mechanical properties and lower pressure drop after testing are also examined. The samples exhibited filtration efficiencies greater than 99% and an initial pressure drop as low as 231 Pa. The combination of CNCs and IPL shows the potential to use thinner membranes with less material to achieve comparable filtration performance, which may result in lower manufacturing costs. © 2021 American Chemical Society.

Effects of cellulose nanocrystals on the vulcanization of natural rubber/cellulose nanocrystals nanocomposite and corresponding regulating strategies

AbstractVulcanization is a vital process in rubber processing, it endows rubber with valuable physical and mechanical properties, making rubber a widely used engineering material. In addition to vulcanization agent, reinforcing fillers play a non‐ignorable influence on the vulcanization of rubber nanocomposites. Herein, the effects of cellulose nanocrystals (CNCs) on the vulcanization of natural rubber (NR)/CNCs nanocomposite was studied. It was found that even though the addition of CNCs can effectively improve the dispersion of ZnO in NR matrix, the vulcanization of NR was inhibited. This may be attributed to the CNCs' adsorption of vulcanizing agents (DM, ZnO) and the acidic chemical environment on the surface of CNCs. In order to improve the vulcanization properties of NR/CNCs nanocomposite, tetramethyldithiochloram (TMTD) and triethanolamine (TEOA) were used as a combination accelerator and curing activator, respectively, and polyethylene glycol (PEG) was introduced to screen hydroxyl groups on the surface of CNCs to prohibit the CNCs' adsorption of vulcanizing agents. The results indicate that TMTD and TEOA effectively improved the vulcanization rate of NR/CNCs nanocomposite and increased the crosslink density by an order of magnitude. Subsequently, the tensile strength, tear strength, and so forth. of NR/CNCs nanocomposite were significantly improved. However, PEG hardly help to improve the vulcanization properties of NR/CNCs nanocomposite. In addition, the control samples without CNCs were prepared and characterized, the comparation between NR and NR/CNCs nanocomposite shows that the synergistic effect of crosslink density and CNCs' reinforcement more effectively improve mechanical properties of NR. This work not only elucidates the inhibiting mechanisms of CNCs on the vulcanization of NR, but also provides practical strategies for improving the vulcanization and properties of NR/CNCs nanocomposite. It may accelerate the application of CNCs as rubber reinforcing filler.

Cellulose Nanocrystals Reinforced Zein/Catechin/β-Cyclodextrin Inclusion Complex Nanoparticles Nanocomposite Film for Active Food Packaging.

In this study, following the green, environmentally friendly and sustainable development strategy, cellulose nanocrystals (CNCs) were prepared through a solvent-free esterification reaction between microcrystalline cellulose and maleic anhydride, combined with subsequent ultrasonic treatment, and maleic-anhydride-modified CNC-reinforced zein/catechin/β-cyclodextrin inclusion complex nanoparticles nanocomposite films were prepared by a facile solution casting. The amount of CNCs in the film matrix was 0–8 wt%, and their effect on structural, physicochemical and functional properties of the resulting films were investigated. SEM images showed that the addition of CNCs made the microstructure of the film more smooth and uniform. The intermolecular hydrogen bonds between CNCs and film matrix were supported by FT-IR. XRD analysis also confirmed the appearance of a crystalline peak due to the existence of CNCs inside the films. The incorporation of CNCs significantly reduced water vapor permeability, water solubility and the swelling degree of the nanocomposite film, and also significantly increased tensile strength and elongation at break from 12.66 to 37.82 MPa and 4.5% to 5.2% (p < 0.05). Moreover, nanocomposite film packaging with CNCs can effectively inhibit the oxidation of soybean oil.

How latex film formation and adhesion at the nanoscale correlate to performance of pressure sensitive adhesives with cellulose nanocrystals.

Emulsion polymerized latex-based pressure-sensitive adhesives (PSAs) are more environmentally benign because they are synthesized in water but often underperform compared to their solution polymerized counterparts. Studies have shown a simultaneous improvement in the tack, and peel and shear strength of various acrylic PSAs upon the addition of cellulose nanocrystals (CNCs). This work uses atomic force microscopy (AFM) to examine the role of CNCs in (i) the coalescence of hydrophobic 2-ethyl hexyl acrylate/n-butyl acrylate/methyl methacrylate (EHA/BA/MMA) latex films and (ii) as adhesion modifiers over multiple length scales. Thin films with varying solids content and CNC loading were prepared by spin coating. AFM revealed that CNCs lowered the solids content threshold for latex particle coalescence during film formation. This improved the cohesive strength of the films, which was directly reflected in the increased shear strength of the EHA/BA/MMA PSAs with increasing CNC loading. Colloidal probe AFM indicated that the nano-adhesion of thicker continuous latex films increased with CNC loading when measured over small contact areas where the effect of surface roughness was negligible. Conversely, the beneficial effects of the CNCs on macroscopic PSA tack and peel strength were outweighed by the effects of increased surface roughness with increasing CNC loading over larger surface areas. This highlights that CNCs can improve both cohesive and adhesive PSA properties; however, the effects are most pronounced when the CNCs interact favourably with the latex polymer and are uniformly dispersed throughout the adhesive film. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 1)'.

Functional Nanocellulose, Alginate and Chitosan Nanocomposites Designed as Active Film Packaging Materials.

The aim of the study was to characterize and compare films made of cellulose nanocrystals (CNC), nano-fibrils (CNF), and bacterial nanocellulose (BNC) in combination with chitosan and alginate in terms of applicability for potential food packaging applications. In total, 25 different formulations were made and evaluated, and seven biopolymer films with the best mechanical performance (tensile strength, strain)—alginate, alginate with 5% CNC, chitosan, chitosan with 3% CNC, BNC with and without glycerol, and CNF with glycerol—were selected and investigated regarding morphology (SEM), density, contact angle, surface energy, water absorption, and oxygen and water barrier properties. Studies revealed that polysaccharide-based films with added CNC are the most suitable for packaging purposes, and better dispersing of nanocellulose in chitosan than in alginate was observed. Results showed an increase in hydrophobicity (increase of contact angle and reduced moisture absorption) of chitosan and alginate films with the addition of CNC, and chitosan with 3% CNC had the highest contact angle, 108 ± 2, and 15% lower moisture absorption compared to pure chitosan. Overall, the ability of nanocellulose additives to preserve the structure and function of chitosan and alginate materials in a humid environment was convincingly demonstrated. Barrier properties were improved by combining the biopolymers, and water vapor transmission rate (WVTR) was reduced by 15–45% and oxygen permeability (OTR) up to 45% by adding nanocellulose compared to single biopolymer formulations. It was concluded that with a good oxygen barrier, a water barrier that is comparable to PLA, and good mechanical properties, biopolymer films would be a good alternative to conventional plastic packaging used for ready-to-eat foods with short storage time.