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1
Huang, Xu, Yiwen Zhang, Zhi Liang, Yingfeng Zhao, Huiwen Yuan, Mingyang Li, Fengping Peng, and Wei Wang. "Few-layered g-C3N4-derived core–shell isotype heterojunction photocatalysts for efficient environmental remediation." Functional Materials Letters 14, no. 06 (July 12, 2021): 2151032. http://dx.doi.org/10.1142/s1793604721510322.
Повний текст джерелаАнотація:
In this paper, a series of isotype heterojunction photocatalysts with urea-derived g-C3N4 (CNU) as the core and cyanamide-derived g-C3N4 (CNC) as the shell are reported. A much thinner CNC shell which can protect the CNU core from thermal etching and determines the light absorption is beneficial to improve the photocarrier transfer and separation efficiency, pore volume, and the overall crystalline degree of the most active CNU/CNC2 core–shell isotype heterojunction photocatalyst for rhodamine B (RhB) degradation. Contrast experiments confirm that the electron-derived oxidant species (⋅O[Formula: see text] play key roles in driving the RhB degradation.
2
Bowmaker, Graham A., Kevin C. Lim, Neil Somers, Brian W. Skelton, and Allan H. White. "Syntheses, Structures and Vibrational Spectroscopy of Some Adducts of Copper(I) Cyanide with Unidentate Organic Nitriles." Zeitschrift für Naturforschung B 59, no. 11-12 (December 1, 2004): 1301–6. http://dx.doi.org/10.1515/znb-2004-11-1248.
Повний текст джерелаАнотація:
Abstract A number of adducts of copper(I) cyanide, CuCN, have been synthesized by crystallization from its solutions in various unidentate organic nitriles, RCN. Low temperature single crystal X-ray structure determinations are recorded for a number of these, of the form CuCN : RCN (m : n) for R = Me, Et (m : n = 1 : 1), and Ph, o-tolyl (3:2). The 1 : 1 adduct with acetonitrile is a two-dimensional polymeric web, (CN)Cu(μ-CN)2Cu(NC) units being linked by the peripheral nitrogen and carbon atoms, with a fourth coordination site about each copper having MeCN pendant. The other three adducts are onedimensional polymers, the propionitrile adduct being of the form . . .Cu(NCEt)CNCu(NCEt)CN. . . with trigonal planar copper, the bridging cyanide groups being replaced in the benzo- and o-toluo nitrile adducts by linear Cu(CN)−2 moieties. The vibrational spectra of bulk samples are largely consistent with the single crystal structural results, but reveal the possible existence of adducts of higher CuCN content in the case of the CuCN/benzonitrile system.
3
Qian, Hui. "Major Factors Influencing the Size Distribution Analysis of Cellulose Nanocrystals Imaged in Transmission Electron Microscopy." Polymers 13, no. 19 (September 28, 2021): 3318. http://dx.doi.org/10.3390/polym13193318.
Повний текст джерелаАнотація:
Size distributions of cellulose nanocrystals (CNCs), extracted from softwood pulp via strong sulfuric acid hydrolysis, exhibit large variability when analyzed from transmission electron microscopy (TEM) images. In this article, the causes of this variability are studied and discussed. In order to obtain results comparable with those reported, a reference material of CNCs (CNCD-1) was used to evaluate size distribution. CNC TEM specimens were prepared as-stained and dried with a rapid-flushing staining method or hydrated and embedded in vitreous ice with the plunge-freezing method. Several sets of bright-field TEM (BF-TEM), annular dark-field scanning TEM (ADF-STEM) and cryogenic-TEM (cryo-TEM) images were acquired for size distribution analysis to study the contributing factors. The rapid-flushing staining method was found to be the most effective for contrast enhancement of CNCs, not only revealing the helical structure of single CNCs but also resolving the laterally jointed CNCs. During TEM specimen preparation, CNCs were fractionated on TEM grids driven by the coffee-ring effect, as observed from contrast variation of CNCs with a stain-depth gradient. From the edge to the center of the TEM grids, the width of CNCs increases, while the aspect ratio (length to width) decreases. This fractionated dispersion of CNCs suggests that images taken near the center of a droplet would give a larger mean width. In addition to particle fractionation driven by the coffee-ring effect, the arrangement and orientation of CNC particles on the substrate significantly affect the size measurement when CNC aggregation cannot be resolved in images. The coexistence of asymmetric cross-section CNC particles introduces a large variation in size measurement, as TEM images of CNCs are mixed projections of the width and height of particles. As a demonstration of how this contributes to inflated size measurement, twisted CNC particles, rectangular cross-section particles and end-to-end jointed CNCs were revealed in reconstructed three-dimensional (3D) micrographs by electron tomography (ET).
4
Chen, Qijie, Meicun Kang, Zhi Rong, and Zhangyang Zong. "Effect of cellulose nanocrystals on the performance of oil-immersed transformer insulating paper." BioResources 14, no. 3 (July 8, 2019): 6837–50. http://dx.doi.org/10.15376/biores.14.3.6837-6850.
Повний текст джерелаАнотація:
The possibility of enhancing both mechanical and breakdown properties of oil-immersed transformer insulating paper were considered by introduction of cellulose nanocrystals (CNCs). Two kinds of CNCs were taken into account: the TEMPO-oxidized CNCs (T-CNC) and the sulfuric acid hydrolyzed CNCs (S-CNC). Insulating paper containing no CNCs was also prepared as a reference. Obtained samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effects of different amounts of CNC on tensile strength, AC breakdown strength, oil absorption rate, and conductivity of insulating paper extract were studied. The CNC improved the mechanical and electrical performances of insulating paper, and the effect of T-CNC was a little better than that of S-CNC. When the T-CNC dosage was 0.9%, the tensile strength, AC breakdown strength in oil, and oil absorption rate of the insulating paper were 70.22 N • m/g, 59.8 kV/mm, and 53.1%, respectively, which was improved by 21.7%, 24.6%, and 39.4%, respectively, compared with the reference insulating paper. The beating degree of pulp also affected the mechanical and electrical properties of insulating paper containing CNC. Based on overall performance, it was concluded that CNCs are promising nano-additives for oil-immersed transformer insulating paper, especially for T-CNC.
5
Teipel, Blake R., Ryan J. Vano, Bryan S. Zahner, Elisa M. Teipel, I.-Cheng Chen, and Mustafa Akbulut. "Nanocomposites of Hydrophobized Cellulose Nanocrystals and Polypropylene." MRS Advances 1, no. 10 (2016): 659–65. http://dx.doi.org/10.1557/adv.2016.88.
Повний текст джерелаАнотація:
ABSTRACTCellulose nanocrystals (CNCs) are high-strength sustainable nanomaterials, the incorporation of which to a host polymer matrix can potentially lead to nanocomposites with superior mechanical properties. However, the mismatch in surface energy of CNCs and common structural polymers is a challenge that needs to be overcome to prevent the aggregation of CNCs and ensure the robust integration of CNCs into a polymer matrix. Herein, we report an approach involving the functionalization of CNCs with maleated-anhydride polypropylene (MAPP) through diethylenetriamine (DETA) linkers to significantly enhance the compatibility between CNCs and polypropylene. Polypropylene/modified CNC nanocomposites displayed 74% and 76% increase in elastic modulus in comparison to neat polypropylene and polypropylene/untreated CNC nanocomposites, respectively. The tensile strength was also higher for nanocomposites with modified CNC than neat polypropylene, as well as nanocomposites with untreated CNCs. The tensile strength at 5.5% strain of polypropylene/modified CNC nanocomposites was 32% and 28% larger that of polypropylene and polypropylene/untreated CNC nanocomposites, respectively. Finally, such CNC-based nanocomposites have a lower density than many competitive systems resulting in opportunities to propagate this environmentally-responsible technology to nanocomposites used in additive manufacturing, automotive applications, construction materials and consumer products.
6
Aguayo, María Graciela, Arturo Fernández-Pérez, Claudia Oviedo, Guillermo Reyes, and Pablo Reyes-Contreras. "Relationship between Structural Characteristics of Cellulose Nanocrystals Obtained from Kraft Pulp." Nanomaterials 10, no. 9 (September 8, 2020): 1775. http://dx.doi.org/10.3390/nano10091775.
Повний текст джерелаАнотація:
Kraft pulp cellulose was hydrolyzed using sulfuric acid, under different thermophysical conditions of temperature, time, pulp concentration, and sonication time. The experimental design revealed the effect of these conditions and their interaction on the hydrolysis yield obtained. In addition, the top five cellulose nanocrystals (CNCs) yields from this experiment design were analyzed. The results obtained indicated that CNCs possess a morphology that can be described as individualized rod particles, with average diameters less than 50 nm and different size distribution. In the analysis of CNCs features, significant Pearson correlations were established between the crystallinity of the CNC, CNC yield, and interplanar crystallites distance (Δd/d). The thermogravimetric (DTG) profiles exhibited two CNCs degradation stages, where the second stage CNCs degradation showed a significative correlation with CNC sulfur content. In our analysis, the crystallographic parameters exhibited a correlation with the mechanical behavior of the CNC, since the potential variation between the distances of the crystalline planes is related to the stress and deformation present in the crystallites of CNCs. This study provides new knowledge regarding CNCs, further enhancing information for CNC-based industries and the processability of CNCs for the development of new materials.
7
Feng, Xinhao, Zhihui Wu, Yanjun Xie, and Siqun Wang. "Reinforcing 3D print methacrylate resin/cellulose nanocrystal composites: Effect of cellulose nanocrystal modification." BioResources 14, no. 2 (March 20, 2019): 3701–16. http://dx.doi.org/10.15376/biores.14.2.3701-3716.
Повний текст джерелаАнотація:
Cellulose nanocrystals (CNCs) were modified with methyl methacrylate (MMA) to improve the properties of the resulting three-dimensional (3D) stereolithography printed CNC/methacrylate (MA) resin composites. The dispersibility of the MMA-modified CNCs (MMA-CNCs) was substantially improved, as evidenced by the limited precipitation in the MA solution. Thermal gravimetry and differential scanning calorimetry measurements showed that the pyrolytic temperature of the MMA-CNC was 110 °C higher than that of the CNCs; the pyrolytic temperature and glass transition temperature of the resulting MMA-CNC/MA composites were higher than those of the CNC/MA. The tensile strength and modulus of the MMA-CNC/MA composites were improved by up to 38.3 MPa and 3.07 GPa, respectively, compared to those of the CNC/MA composites. These results demonstrated that the modification of CNC with MMA is a feasible approach to substantially improve the mechanical properties and thermal stability of the resulting MA-based composites.
8
Abushammala, Hatem, and Jia Mao. "Impact of the Surface Properties of Cellulose Nanocrystals on the Crystallization Kinetics of Poly(Butylene Succinate)." Crystals 10, no. 3 (March 13, 2020): 196. http://dx.doi.org/10.3390/cryst10030196.
Повний текст джерелаАнотація:
The hydrophilicity of cellulose nanocrystals (CNCs) is a major challenge for their processing with hydrophobic polymers and matrices. As a result, many surface modifications have been proposed to hydrophobize CNCs. The authors showed in an earlier study that grafting alcohols of different chain lengths onto the surface of CNCs using toluene diisocyanate (TDI) as a linker can systematically hydrophobize CNCs to a water contact angle of up to 120° depending on the alcohol chain length. Then, the hydrophobized CNCs were used to mechanically reinforce poly(butylene succinate) (PBS), which is a hydrophobic polymer. As a result of hydrophobization, PBS/CNCs interfacial adhesion and the composite mechanical properties significantly improved with the increasing CNC contact angle. Continuing on these results, this paper investigates the impact of CNC surface properties on the crystallization behavior of PBS using differential scanning calorimetry (DSC). The results showed that the crystallization temperature of PBS increased from 74.7 °C to up to 86.6 °C as a result of CNC nucleation activity, and its value was proportionally dependent on the contact angle of the CNCs. In agreement, the nucleation activity factor (φ) estimated using Dobreva and Gutzow’s method decreased with the increasing CNC contact angle. Despite the nucleation action of CNCs, the rate constant of PBS crystallization as estimated using the Avrami model decreased in general as a result of a prevailing impeding effect. This decrease was minimized with increasing the contact angle of the CNCs. The impeding effect also increased the average activation energy of crystallization, which was estimated using the Kissinger method. Moreover, the Avrami exponent (n) decreased because of CNC addition, implying a heterogeneous crystallization, which was also apparent in the crystallization thermograms. Overall, the CNC addition facilitated PBS nucleation but retarded its crystallization, and both processes were significantly affected by the surface properties of the CNCs.
9
Huang, Hsuan-Ming, Hung-Chieh Tsai, I.-Chun Liu, and Raymond Chien-Chao Tsiang. "Synthesis of polystyrene-grafted carbon nanocapsules." Journal of Materials Research 22, no. 1 (January 2007): 132–40. http://dx.doi.org/10.1557/jmr.2007.0017.
Повний текст джерелаАнотація:
A novel polymeric composite material, polystyrene (PS)-grafted carbon nanocapsules (CNCs), has been prepared. sec-butyllithium was first used to introduce negative charges on CNCs, and these CNC carbanions acted then as initiators for anionic polymerization of styrene. Based on a weight loss at the decomposition temperature of the butyl groups, the quantity of the butyls attached to the CNC surface was determined as 1.18 wt%, corresponding to 0.25 mol% initiator per mol of carbon atom on the CNC surface. Furthermore, the decomposition temperature of butylated CNCs was lower than that of the pristine CNCs by nearly 200 °C. The polystyrene content in our PS-grafted CNC sample was approximately 20%, and the molecular weight of the grafted PS on the surface of CNCs was calculated as 1200 gmol−1. Compared with the molecular weight of the ungrafted PS, the molecular weight of grafted PS was lower, thus indicating rates of initiation and/or propagation for CNC-bound carbanions lower than those of the free sec-butyllithium. The PS-grafted CNCs had good dispersion in toluene, tetrahydrofuran, cyclohexane, and other common organic solvents in which polystyrene was dissolvable and thus indicated good compatibility when further blended with other styrenic polymers. The PS-grafted CNCs were characterized and examined by Fourier transform infrared, thermogravimetric analysis, atomic force microscopy, differential scanning calorimetry, ultraviolet-visible spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The electron microscopy images indicated that the PS-grafted CNCs were homogeneous composites containing uniform polymer/CNC ratios.
10
Huang, Shancong, Jialin Xing, Guisheng Zhou, and Xinxing Xia. "A simple and rapid method for the diameter detection of cellulose nanocrystals via sedimentation method." BioResources 17, no. 4 (October 25, 2022): 6941–52. http://dx.doi.org/10.15376/biores.17.4.6941-6952.
Повний текст джерелаАнотація:
The diameter of nanocellulose most often is detected using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and other related techniques. These detection methods are not only expensive, time-consuming, and complicated to operate, but also are not conducive to the detection of the diameter during the actual production of nanocellulose. In this study, the settling height of cellulose nanocrystals (CNCs) was related to CNC diameter by sedimentation method to find a convenient technique for the rapid detection of CNC diameter. The results showed that when the CNC concentration was at 0.2 wt%, the sodium chloride (NaCl) dosage at 40 g/L, and at the standing time of 48 h, the CNC sedimentation performance was the best. Furthermore, with the increase of CNC diameter, the settling height of CNCs gradually decreased. The relationship between CNC diameter and settling height was Y (Settling height) = -30.17 ln(X (CNC diameter)) + 123.64; and the coefficient of determination for the fit was 0.9965. This research provides a new method for the diameter detection of CNCs in the actual CNCs production in enterprises.
11
Dunlop, Matthew J., Ronald Sabo, Rabin Bissessur, and Bishnu Acharya. "Polylactic Acid Cellulose Nanocomposite Films Comprised of Wood and Tunicate CNCs Modified with Tannic Acid and Octadecylamine." Polymers 13, no. 21 (October 24, 2021): 3661. http://dx.doi.org/10.3390/polym13213661.
Повний текст джерелаАнотація:
Herein, a one-pot strategy was used to prepare hydrophobic cellulose nanocrystals (CNCs) surface-modified with tannic acid and octadecylamine. By this strategy, CNCs derived from wood (W-CNC) and tunicates (T-CNC) were modified in situ and incorporated into a polylactic acid (PLA) matrix using two methods, without first drying the CNCs. Films of PLA-CNC nanocomposites were prepared both by solution casting and by wet compounding in a thermo-kinetic mixer, followed by melt extrusion. Various properties of these PLA nanocomposites were evaluated herein, along with an assessment of how these properties vary with the type of CNC reinforcement. Cast films with a hybrid mixture of wood and tunicate CNCs displayed improved mechanical properties compared to either wood or tunicate CNCs, but extruded films did not show this hybrid effect. The water vapor permeability of the extruded nanocomposite films with 1% CNCs was reduced by as much as 60% compared to the PLA films. The composite films also showed enhanced biodegradation compared to neat PLA films. These results demonstrate that wet compounded PLA composites produced with wood or tunicate CNCs modified using a one-pot, water-based route have improved barrier and biodegradation properties, indicating a potential for packaging applications without having to dry the CNCs.
12
BECK, STEPHANIE, and JEAN BOUCHARD. "Effect of storage conditions on cellulose nanocrystal stability." May 2014 13, no. 5 (June 1, 2014): 53–61. http://dx.doi.org/10.32964/tj13.5.53.
Повний текст джерелаАнотація:
Cellulose nanocrystals (CNCs) have evolved from a laboratory curiosity to an industrial material manufactured at a scale of up to 1 ton/day. Such large quantities of CNCs will inevitably be stored for different lengths of time before shipping and use. The chemical and physical stability of CNCs during long-term storage under various conditions was monitored. As-produced acidic H-CNCs and neutral salt form Na-CNCs were stored at ambient temperature and at 4°C as never-dried suspensions, and as a freeze-dried solid in the case of Na-CNCs. A variety of parameters were measured at intervals during the storage period. The CNC sulfate half-ester content, the cellulose chain length, and the unique optical properties of CNC films were of particular interest. Changes in these parameters were analyzed to determine the kinetics of long-term CNC degradation and establish the shelf-life of CNCs under different storage conditions.
13
Orellana, Jose Luis, Derek Wichhart, and Christopher L. Kitchens. "Mechanical and Optical Properties of Polylactic Acid Films Containing Surfactant-Modified Cellulose Nanocrystals." Journal of Nanomaterials 2018 (October 2, 2018): 1–12. http://dx.doi.org/10.1155/2018/7124260.
Повний текст джерелаАнотація:
The addition of surface-modified cellulose nanocrystals (CNCs) to polymeric matrices can lead to an enhancement of the mechanical and optical properties of host polymers. The use of surfactants can provide an easy and effective way to change the CNC functionality and to evaluate the effects of surface chemistry in the reinforcement mechanisms. In this work, CNCs were solution blended with polylactic acid (PLA) and melt extruded into films. The PLA toughness increased from 1.70 MJ/m3to 2.74 MJ/m3, a 61% increase, with the addition of 1% of decylamine-modified CNCs without a decrease of the tensile strength or modulus. In this work, we investigated the use of two surfactants, decylamine and cetyltrimethylammonium bromide, to enhance CNC compatibility with the hydrophobic PLA matrix. Decylamine at 1.0 wt.% with respect to CNC loading was found to significantly enhance CNC compatibility and property enhancement. The low concentration of surfactant is notable, as other works typically use significantly higher loadings for CNC incorporation and property enhancement. At high CNC concentrations, mechanical properties decreased but the aligned assembly of the CNCs provided intricate colors to the films when observed between crossed polars. The alignment and nanoscale structure of CNCs within the films play an important role in the properties obtained.
14
Chipón, Josefina, Kassandra Ramírez, José Morales, and Paulo Díaz-Calderón. "Rheological and Thermal Study about the Gelatinization of Different Starches (Potato, Wheat and Waxy) in Blend with Cellulose Nanocrystals." Polymers 14, no. 8 (April 11, 2022): 1560. http://dx.doi.org/10.3390/polym14081560.
Повний текст джерелаАнотація:
The goal of this work was to analyze the effect of CNCs on the gelatinization of different starches (potato, wheat and waxy maize) through the characterization of the rheological and thermal properties of starch–CNC blends. CNCs were blended with different starches, adding CNCs at concentrations of 0, 2, 6 and 10% w/w. Starch–CNC blends were processed by rapid visco-analysis (RVA) and cooled to 70 °C. Pasting parameters such as pasting temperature, peak, hold and breakdown viscosity were assessed. After RVA testing, starch–CNC blends were immediately analyzed by rotational and dynamic rheology at 70 °C. Gelatinization temperature and enthalpy were assessed by differential scanning calorimetry. Our results suggest that CNCs modify the starch gelatinization but that this behavior depends on the starch origin. In potato starch, CNCs promoted a less organized structure after gelatinization which would allow a higher interaction amylose–CNC. However, this behavior was not observed in wheat and waxy maize starch. Insights focusing on the role of CNC on gelatinization yielded relevant information for better understanding the structural changes that take place on starch during storage, which are closely related with starch retrogradation. This insight can be used as an input for the tailored design of novel materials oriented towards different technological applications.
15
Zoia, Luca, Annalisa Morelli, Laura Talamini, Martina B. Violatto, Arianna B. Lovati, Silvia Lopa, Camilla Recordati, et al. "Cellulose nanocrystals: a multimodal tool to enhance the targeted drug delivery against bone disorders." Nanomedicine 15, no. 23 (August 2020): 2271–85. http://dx.doi.org/10.2217/nnm-2020-0139.
Повний текст джерелаАнотація:
Aim: We investigated the use of cellulose nanocrystals (CNCs) as drug nanocarriers combining an anti-osteoporotic agent, alendronate (ALN), and an anti-cancer drug, doxorubicin (DOX). Materials & methods: CNC physicochemical characterization, in vivo imaging coupled with histology and in vitro uptake and toxicity assays were carried out. Results: In vivo CNC-ALN did not modify bone tropism and lung penetration, whereas its liver and kidney accumulation was slightly higher compared with CNCs alone. In vitro studies showed that CNC-ALN did not impair ALN's effect on osteoclasts, whereas CNC-DOX confirmed the therapeutic potential against bone metastatic cancer cells. Conclusions: This study provides robust proof of the potential of CNCs as easy, flexible and specific carriers to deliver compounds to the bone.
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Banerjee, Manali, Sisira Saraswatula, Anna Williams, and Blair Brettmann. "Effect of Purification Methods on Commercially Available Cellulose Nanocrystal Properties and TEMPO Oxidation." Processes 8, no. 6 (June 16, 2020): 698. http://dx.doi.org/10.3390/pr8060698.
Повний текст джерелаАнотація:
Cellulose nanocrystals (CNCs) are attractive for use in polymer composites, biomedical applications, and barrier packaging. In all of these applications they are mixed with other components and compatibility is a major design consideration, as CNCs naturally have a high density of surface hydroxyl groups and primarily disperse well in polar media. Numerous surface modification approaches have been used to address these issues, but challenges remain due to the variability in the commercially available CNC materials. CNCs can be produced from biomass using several extraction methods, most notably acid hydrolysis and biomass extraction, also known as the American Value Added Pulping process. The production method of the CNC material has an impact on both physical and surface properties of CNCs, including size, shape, crystal structure, and zeta potential. In addition, post-treatments can be used to purify the CNC material and further alter these properties. This work studies the properties of CNCs from three different commercial suppliers and after conducting three different post-treatments: dialysis, Soxhlet extraction, and acetone washing to understand the effect of the commercial source and purification on CNC surface properties and modification via 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) mediated oxidation. We show that there is significant variation in CNC physical and surface properties between different commercial suppliers before and after purification. Importantly, we show that for CNCs produced through acid hydrolysis, acetone washing or Soxhlet extraction in ethanol decreases the achievable degree of TEMPO modification, but makes it more consistent between the different commercial suppliers. This has important implications for improving reproducibility in CNC research as well as aiding the expanding fields of applications.
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Zhang, Maolan, Xiujuan Lu, Guiping Zhang, Xiaoling Liao, Jiale Wang, Na Zhang, Chunyi Yu, and Guoming Zeng. "Novel Cellulose Nanocrystals-Based Polyurethane: Synthesis, Characterization and Antibacterial Activity." Polymers 14, no. 11 (May 28, 2022): 2197. http://dx.doi.org/10.3390/polym14112197.
Повний текст джерелаАнотація:
As a new type of polymer, water-driven polyurethane (PU) has attracted increasing attention of researchers; however, with the popularization of its application, the following infection problems limit their applications, especially in the biomedical field. Herein, a series of novel cellulose nanocrystals (CNCs)-based PUs were first synthesized by chemical cross-linking CNCs with triblock copolymer polylactide–poly (ethylene glycol)–polylactide (CNC-PU). After covalent binding with tannic acid (TA-CNC-PU), the silver nanoparticles (Ag NPs) were further introduced into the material by a reduction reaction (Ag/TA-CNC-PU). Finally, the prepared serial CNCs-based PU nanocomposites were fully characterized, including the microstructure, water contact angle, water uptake, thermal properties as well as antibacterial activity. Compared with CNC-PU, the obtained TA-CNC-PU and Ag/TA-CNC-PU were capable of lower glass transition temperatures and improved thermal stability. In addition, we found that the introduction of tannic acid and Ag NPs clearly increased the material hydrophobicity and antibacterial activity. In particular, the Ag/TA-CNC-PU had a better antibacterial effect on E. coli, while TA-CNC-PU had better inhibitory effect on S. aureus over a 24 h time period. Therefore, these novel CNCs-based PUs may be more beneficial for thermal processing and could potentially be developed into a new class of smart biomaterial material with good antibacterial properties by adjusting the ratio of TA or Ag NPs in their structures.
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WU, GUOMIN, QIAN LI, CAN JIN, ZHENWU KONG, and SIQUN WANG. "Characterization of the redispersibility of cellulose nanocrystals by particle size analysis using dynamic light scattering." TAPPI Journal 18, no. 4 (May 1, 2019): 223–31. http://dx.doi.org/10.32964/tj18.4.223.
Повний текст джерелаАнотація:
Cellulose nanocrystals (CNCs), which are derived from the most abundant and inexhaustible natural polymer, cellulose, have received significant interest owing to their mechanical, optical, chemical, and rheological properties. In order to transport CNC products conveniently and efficiently, they are ideally dried and stored as powders using freeze-drying or spray-drying technologies. The redispersibility of CNC powders is quite important for their end use; hence, a convenient method is required to characterize the redispersibility of CNC powders. In this paper, the possibility of characterizing the redispersibility of CNC powders by particle size analysis using dynamic light scattering (DLS) was investigated by comparing the results from transmission electron microscopy (TEM) and DLS. The particle size obtained with DLS approximately matched that obtained with TEM. Compared with TEM, DLS is a quick and convenient method to measure the particle size distribution of CNCs in water. Two kinds of dispersing methods, sonication and high-speed shearing, and two kinds of CNCs prepared by different methods, sulfuric acid hydrolysis and the TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) oxidization method, were used to study the redispersibility of CNCs. Sonication was more efficient than the high-speed shearing method for nanoscale dispersion of CNC powders in water. CNCs prepared by sulfuric acid hydrolysis could be more easily redispersed in water than those prepared by TEMPO oxidation.
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Anžlovar, Alojz, Matjaž Kunaver, Andraž Krajnc, and Ema Žagar. "Nanocomposites of LLDPE and Surface-Modified Cellulose Nanocrystals Prepared by Melt Processing." Molecules 23, no. 7 (July 19, 2018): 1782. http://dx.doi.org/10.3390/molecules23071782.
Повний текст джерелаАнотація:
Cellulose nanocrystals (CNCs) were surface modified by esterification in tetrahydrofuran (THF) at 25 °C using different catalysts and anhydrides bearing different alkyl side chain lengths. Unmodified and acetic anhydride (AcAnh)-modified CNCs were studied as potential nanofillers for linear low-density poly(ethylene) (LLDPE). Nanocomposites were prepared by melt processing. Determination of the size and size distribution of CNCs in the nanocomposites by SEM revealed an enhanced compatibility of the AcAnh-modified CNCs with the LLDPE matrix, since the average size of the aggregates of the modified CNCs (0.5–5 μm) was smaller compared to that of the unmodified CNCs (2–20 μm). Tensile test experiments revealed an increase in the nanocomposites’ stiffness and strain at break—by 20% and up to 90%, respectively—at the CNC concentration of 5 wt %, which is close to the critical percolation concentration. Since the CNC nanofiller simultaneously reduced LLDPE crystallinity, the reinforcement effect of CNCs was hampered. Therefore, the molding temperature was increased to 120 °C, and, in this way, the greatest increase of the Young’s modulus was achieved (by ~45%). Despite the enhanced compatibility of the AcAnh-modified CNCs with the LLDPE matrix, no additional effect on the mechanical properties of the nanocomposites was observed in comparison to the unmodified CNC.
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Vanderfleet, Oriana M., Daniel A. Osorio, and Emily D. Cranston. "Optimization of cellulose nanocrystal length and surface charge density through phosphoric acid hydrolysis." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 376, no. 2112 (December 25, 2017): 20170041. http://dx.doi.org/10.1098/rsta.2017.0041.
Повний текст джерелаАнотація:
Cellulose nanocrystals (CNCs) are emerging nanomaterials with a large range of potential applications. CNCs are typically produced through acid hydrolysis with sulfuric acid; however, phosphoric acid has the advantage of generating CNCs with higher thermal stability. This paper presents a design of experiments approach to optimize the hydrolysis of CNCs from cotton with phosphoric acid. Hydrolysis time, temperature and acid concentration were varied across nine experiments and a linear least-squares regression analysis was applied to understand the effects of these parameters on CNC properties. In all but one case, rod-shaped nanoparticles with a high degree of crystallinity and thermal stability were produced. A statistical model was generated to predict CNC length, and trends in phosphate content and zeta potential were elucidated. The CNC length could be tuned over a relatively large range (238–475 nm) and the polydispersity could be narrowed most effectively by increasing the hydrolysis temperature and acid concentration. The CNC phosphate content was most affected by hydrolysis temperature and time; however, the charge density and colloidal stability were considered low compared with sulfuric acid hydrolysed CNCs. This study provides insight into weak acid hydrolysis and proposes ‘design rules’ for CNCs with improved size uniformity and charge density. This article is part of a discussion meeting issue ‘New horizons for cellulose nanotechnology’.
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Liu, Yan. "Application and Study of CNC Network System Based on DNC." Advanced Materials Research 655-657 (January 2013): 1214–17. http://dx.doi.org/10.4028/www.scientific.net/amr.655-657.1214.
Повний текст джерелаАнотація:
Three solutions to network CNC machines are introduced. Advantages and disadvantages are compared. Wireless network solution supports a wider range of CNC communications but easy be disturbed. Single port server solution ensure stable signal but hardware cost is high. TCP/IP solution is stable and reliability while most low-end CNCs do not have Ethernet ports. CNC quantity, port type, distance between CNCs and computers, required speed and cost should be considered to choose right solutions.
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Wang, Yue, Yulong Wang, Yanxin Liu, Qingjian Liu, Jinwon Jang, and Junyuan Han. "Preparation, characterization, and antioxidant activities of cellulose nanocrystals/genistein nanocomposites." BioResources 14, no. 1 (November 20, 2018): 336–48. http://dx.doi.org/10.15376/biores.14.1.336-348.
Повний текст джерелаАнотація:
Genistein (GEN), a typical isoflavone compound, exhibits desirable pharmacological activities, such as antioxidation, anti-inflammatory, , and anti-cancer properties. However, the pharmaceutical application of GEN is limited because of its poor water solubility in aqueous systems. In this study, cellulose nanocrystals (CNCs) and cetyltrimethylammonium bromide (CTAB)-coated CNCs were used as carriers for GEN to improve its dissolution rate and antioxidant activity in aqueous systems. The CNC/GEN and CNC/CTAB/GEN nanocomposites were successfully prepared and characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and X-ray diffraction analysis. The results showed that the nanonized GEN performed better and its crystalline structure decreased because of the formation of the CNC/GEN and CNC/CTAB/GEN nanocomposites. The GEN dissolution rates in the CNC/GEN and CNC/CTAB/GEN nanocomposites increased to 72.1% and 92.5% at 120 min, respectively, compared with that of the original GEN (0.85%). Furthermore, the in vitro antioxidant activity of the GEN, which was evaluated by the hydroxyl radical scavenging efficiency, was remarkably enhanced. Based on the above results, CNCs as nanocarriers are a useful method for improving the dissolution and antioxidant activities of GEN in aqueous system.
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Rosli, Noor Afizah, Wan Hafizi Wan Ishak, Siti Salwani Darwis, Ishak Ahmad, and Mohammad Fauzul Azim Mohd Khairudin. "Bio-nanocomposites based on compatibilized poly(lactic acid) blend-reinforced agave cellulose nanocrystals." BioResources 16, no. 3 (June 16, 2021): 5538–55. http://dx.doi.org/10.15376/biores.16.3.5538-5555.
Повний текст джерелаАнотація:
Enhancing the mechanical, thermal, and degradation properties of a poly(lactic acid) (PLA) blend without deteriorating its other useful features was the goal of this work. The isolation of cellulose nanocrystals (CNCs) from Agave angustifolia fibers was carried out, and the properties of the bio-nanocomposites comprising these CNCs were evaluated, which included PLA, natural rubber (NR), and liquid NR (LNR). Transmission electron microscopy and zeta potential analysis confirmed the successful isolation of CNCs from agave fibers after several chemical treatment steps. The effects of different CNC loadings on the properties of the bio-nanocomposites were investigated using tensile tests, thermal analysis, morphological analysis, and water absorption tests. Bio-nanocomposites containing 5 wt% and 7.5 wt% CNC had the optimal tensile modulus and strength, respectively. Different levels of CNC did not noticeably affect the thermal stability of the bio-nanocomposites, although the thermogram curves increased slightly as CNC content increased. The addition of CNC at different loadings affects the crystallization rate of PLA blend. The water absorption capacity increased as CNC level increased, and 5 wt% CNC gave rise to the highest water absorption. The four-component bio-nanocomposites created in this study provided an alternative for producing new green materials with tunable physical, mechanical, and thermal properties.
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Lizundia, Erlantz, Ander Reizabal, Carlos M. Costa, Alberto Maceiras та Senentxu Lanceros-Méndez. "Electroactive γ-Phase, Enhanced Thermal and Mechanical Properties and High Ionic Conductivity Response of Poly (Vinylidene Fluoride)/Cellulose Nanocrystal Hybrid Nanocomposites". Materials 13, № 3 (6 лютого 2020): 743. http://dx.doi.org/10.3390/ma13030743.
Повний текст джерелаАнотація:
Cellulose nanocrystals (CNCs) were incorporated into poly (vinylidene fluoride) (PVDF) to tailor the mechanical and dielectric properties of this electroactive polymer. PVDF/CNC nanocomposites with concentrations up to 15 wt.% were prepared by solvent-casting followed by quick vacuum drying in order to ensure the formation of the electroactive γ-phase. The changes induced by the presence of CNCs on the morphology of PVDF and its crystalline structure, thermal properties, mechanical performance and dielectric behavior are explored. The results suggest a relevant role of the CNC surface −OH groups, which interact with PVDF fluorine atoms. The real dielectric constant ε’ of nanocomposites at 200 Hz was found to increase by 3.6 times up to 47 for the 15 wt.% CNC nanocomposite due to an enhanced ionic conductivity provided by CNCs. The approach reported here in order to boost the formation of the γ-phase of PVDF upon the incorporation of CNCs serves to further develop cellulose-based multifunctional materials.
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Sunasee, Rajesh, Usha D. Hemraz, Karina Ckless, James S. Burdick, and Yaman Boluk. "Cationic Cellulose Nanocrystals: Synthesis, Characterization and Cytotoxicity Studies." MRS Proceedings 1718 (2015): 91–96. http://dx.doi.org/10.1557/opl.2015.479.
Повний текст джерелаАнотація:
ABSTRACTCellulose nanocrystals (CNCs) have emerged as a new class of renewable material for various applications due to their remarkable properties and commercialization prospect. The relative low density, expected low cost, non-toxic character, uniform nanosize distribution, high aspect ratios, high surface area, thermal properties and high modulus of elasticity make CNCs attractive nanomaterials that recently prompted the industrial production of CNCs in North America. Surface functionalization of CNCs continues to be an exciting area of research for the design of novel CNC-based materials. In this work, we report the synthesis, characterization and cytotoxicity studies of novel cationic surface modified CNC derivatives. The negative surface of CNC was rendered positive after grafting with cationic polymers via surface-initiated living radical polymerization method. The modified CNCs were characterized by both spectroscopic and microscopic techniques. Their cytotoxicity effects were evaluated using MTT assay in two cell lines such as mouse macrophages (J774.A1) and human breast cancer (MCF7). Preliminary studies indicated that only one of the modified CNCs caused significant decrease in J774.A1 cell viability (50%), at the highest concentration tested (100 µg/mL). However this concentration is well above of what would be applicable for biomedical purposes. MCF7 cells were not affected by any of the cationic CNCs at any concentration. A detailed cytotoxicity study is currently underway to fully understand the interaction of these cationic CNCs with the biological systems for possible bio-inspired applications.
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Shaikh, Hamid M., Arfat Anis, Anesh Manjaly Poulose, Niyaz Ahamad Madhar, and Saeed M. Al-Zahrani. "Date-Palm-Derived Cellulose Nanocrystals as Reinforcing Agents for Poly(vinyl alcohol)/Guar-Gum-Based Phase-Separated Composite Films." Nanomaterials 12, no. 7 (March 27, 2022): 1104. http://dx.doi.org/10.3390/nano12071104.
Повний текст джерелаАнотація:
The current study delineates the use of date-palm-derived cellulose nanocrystals (dp-CNCs) as reinforcing agents. dp-CNCs were incorporated in varying amounts to poly(vinyl alcohol)/guar-gum-based phase-separated composite films. The films were prepared by using the solution casting method, which employed glutaraldehyde as the crosslinking agent. Subsequently, the films were characterized by bright field and polarizing microscopy, UV-Vis spectroscopy, FTIR spectroscopy, and mechanical study. The microscopic techniques suggested that phase-separated films were formed, whose microstructure could be tailored by incorporating dp-CNCs. At higher levels of dp-CNC content, microcracks could be observed in the films. The transparency of the phase-separated films was not significantly altered when the dp-CNC content was on the lower side. FTIR spectroscopy suggested the presence of hydrogen bonding within the phase-separated films. dp-CNCs showed reinforcing effects at the lowest amount, whereas the mechanical properties of the films were compromised at higher dp-CNC content. Moxifloxacin was included in the films to determine the capability of the films as a drug delivery vehicle. It was found that the release of the drug could be tailored by altering the dp-CNC content within the phase-separated films. In gist, the developed dp-CNC-loaded poly(vinyl alcohol)/guar-gum-based phase-separated composite films could be explored as a drug delivery vehicle.
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Redondo, Alexandre, Daseul Jang, LaShanda T. J. Korley, Ilja Gunkel, and Ullrich Steiner. "Electrospinning of Cellulose Nanocrystal-Reinforced Polyurethane Fibrous Mats." Polymers 12, no. 5 (May 1, 2020): 1021. http://dx.doi.org/10.3390/polym12051021.
Повний текст джерелаАнотація:
We report the electrospinning of mechanically-tunable, cellulose nanocrystal (CNC)-reinforced polyurethanes (PUs). Using high-aspect ratio CNCs from tunicates, the stiffness and strength of electrospun PU/CNC mats are shown to generally increase. Furthermore, by tuning the electrospinning conditions, fibrous PU/CNC mats were created with either aligned or non-aligned fibers, as confirmed by scanning electron microscopy. PU/CNC mats having fibers aligned in the strain direction were stiffer and stronger compared to mats containing non-aligned fibers. Interestingly, fiber alignment was accompanied by an anisotropic orientation of the CNCs, as confirmed by wide-angle X-ray scattering, implying their alignment additionally benefits both stiffness and strength of fibrous PU/CNC nanocomposite mats. These findings suggest that CNC alignment could serve as an additional reinforcement mechanism in the design of stronger fibrous nanocomposite mats.
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Gan, Ivy, and Wen Shyang Chow. "Synthesis of phosphoric acid-treated sugarcane bagasse cellulose nanocrystal and its thermal properties enhancement for poly(lactic acid) nanocomposites." Journal of Thermoplastic Composite Materials 32, no. 5 (May 1, 2018): 619–34. http://dx.doi.org/10.1177/0892705718772866.
Повний текст джерелаАнотація:
Poly(lactic acid) (PLA) nanocomposites film reinforced with cellulose nanocrystals (CNCs) extracted from sugarcane bagasse fibre (SBF) was prepared by solvent casting method. The CNCs were obtained through alkaline treatment followed by sulphuric acid hydrolysis or phosphoric acid hydrolysis. The aim of this work was to evaluate the feasibility of utilizing phosphoric acid (mild acid) to extract CNC from the SBF. The properties of the CNC were investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The thermal properties of the PLA/CNC nanocomposites were characterized using thermogravimetric analyser (TGA). TEM results demonstrated that the CNC having diameter of 5.5–6.2 nm and length of 235–300 nm. Results from XPS characterization have confirmed the existence of both sulphate group and phosphate group in the H2SO4-treated CNC (S-CNC) and H3PO4-treated CNC (P-CNC). FTIR results indicated that the presence of hydrogen bonding and chemical interaction between PLA and CNC. The thermal stability of PLA/P-CNC-10 is higher than that of PLA/S-CNC-10 nanocomposites attributed to the char formation of P-CNC in the PLA matrix.
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Miao, Chuanwei, Mani Tayebi, and Wadood Y. Hamad. "Investigation of the formation mechanisms in high internal phase Pickering emulsions stabilized by cellulose nanocrystals." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 376, no. 2112 (December 25, 2017): 20170039. http://dx.doi.org/10.1098/rsta.2017.0039.
Повний текст джерелаАнотація:
Medium and high internal phase Pickering emulsions stabilized by cellulose nanocrystals (CNCs) have been prepared and the effects of CNC concentration and type of oil phase on the properties of emulsions were studied. The maximum oil phase volume that can be stabilized by CNCs is 87% when the CNC concentration is 0.6 wt.%; this slightly decreases to 83% when the CNC concentration is increased to 1.2 wt.% or higher. In addition, the oil droplets stabilized with 0.6 wt.% CNC suspensions have a larger size than those stabilized with higher concentration CNC suspensions. As evidenced by the change in oil droplet morphology and size, two different emulsion formation mechanisms are proposed. For a CNC concentration of 0.6 wt.%, the extra oil added into the emulsion is accommodated by the expansion of oil droplet size, whereas for CNC concentrations of 1.2 wt.% and higher, the oil is stabilized mainly by the formation of new oil droplets.
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Kim, Jaehwan, Tippabattini Jayaramudu, Lindong Zhai, Hyun Chan Kim, and Dickens Owino Agumba. "Preparation of Cellulose Nanocrystal-Reinforced Physical Hydrogels for Actuator Application." Crystals 10, no. 11 (October 26, 2020): 969. http://dx.doi.org/10.3390/cryst10110969.
Повний текст джерелаАнотація:
In the present investigation, we prepared cellulose nanocrystal (CNC)-reinforced polyvinyl alcohol-cellulose (PVA-Cell) physical hydrogels using a simple blending method for actuator application. The prepared hydrogels were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and the surface and cross-section were studied by scanning electron microscopy. CNCs were well dispersed in the PVA-Cell hydrogel. In the preparation process, surface hydroxyl groups of the CNC and PVA-Cell matrix hydroxyl groups were interacted to produce uniform dispersion of CNCs in the hydrogels. Swelling behavior and compression studies revealed that the increase of the CNCs reinforced the crosslinking. The actuation test of the prepared hydrogels showed that the displacement linearly increased with the voltage, and the immense output displacement was observed at low CNC concentration. The prepared hydrogels are applicable for soft robot actuators and active lens.
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Niinivaara, Elina, Alexandra Ouzas, Carole Fraschini, Richard M. Berry, Marc A. Dubé, and Emily D. Cranston. "How latex film formation and adhesion at the nanoscale correlate to performance of pressure sensitive adhesives with cellulose nanocrystals." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 379, no. 2206 (August 2, 2021): 20200330. http://dx.doi.org/10.1098/rsta.2020.0330.
Повний текст джерелаАнотація:
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)’.
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Voronova, Marina I., Darya L. Gurina, and Oleg V. Surov. "Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Polycaprolactone Polymer Mixtures Reinforced by Cellulose Nanocrystals: Experimental and Simulation Studies." Polymers 14, no. 2 (January 16, 2022): 340. http://dx.doi.org/10.3390/polym14020340.
Повний текст джерелаАнотація:
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.
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Zakuwan, Siti Zarina, and Ishak Ahmad. "Effects of Hybridized Organically Modified Montmorillonite and Cellulose Nanocrystals on Rheological Properties and Thermal Stability of K-Carrageenan Bio-Nanocomposite." Nanomaterials 9, no. 11 (October 31, 2019): 1547. http://dx.doi.org/10.3390/nano9111547.
Повний текст джерелаАнотація:
Herein, hybrid k-carrageenan bio-nanocomposite films were fabricated by using two types of nanofillers, organically modified montmorillonite (OMMT), and cellulose nanocrystals (CNCs). Hybrid bio-nanocomposite films were made by casting techniques employing 4 wt% of CNCs, OMMT, and hybridized CNCs/OMMT in a 1:1 ratio. The rheological and morphological properties and thermal stability of all composites were investigated using rotational rheometry, thermogravimetry analysis, differential scanning calorimetry, field emission scanning electron microscopy, and transmission electron microscopy (TEM). The results showed that the hybrid CNC/OMMT bio-nanocomposite exhibited significantly improved properties as compared to those for the bio-nanocomposites with single fillers due to the nanosize and homogenous nanofiller dispersion in the matrix. Rheological analysis of the hybrid bio-nanocomposite showed higher dynamic shear storage modulus and complex viscosity values when compared to those for the bio-nanocomposite with individual fillers. The TEM analysis of the hybridized CNC/OMMT bio-nanocomposite revealed that more particles were packed together in the CNC network, which restricted the matrix mobility. The heat resistance and thermal stability bio-nanocomposite k-carrageenan film enhanced rapidly with the addition of hybridized CNCs/OMMT to 275 °C. The hybridized CNCs/OMMT exhibited synergistic effects due to the good affinity through interfacial interactions, resulting in the improvement of the material properties.
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Jeng, Yeau-Ren, Ping-Chi Tsai, Ching-Min Chang, and Kuo-Feng Hsu. "Tribological Properties of Oil-in-Water Emulsion with Carbon Nanocapsule Additives." Materials 13, no. 24 (December 17, 2020): 5762. http://dx.doi.org/10.3390/ma13245762.
Повний текст джерелаАнотація:
An experimental investigation was performed on the coefficients of friction (COFs) and wear properties of pure water and oil-in-water (O/W) working fluids containing carbon nanocapsules (CNCs) with concentrations ranging from 0 to 1.0 wt.%. For the O/W working fluid, the ratio of oil to water was set as 6%. It was shown that for the water working fluid, the COF decreased by around 20% as the CNC content increased from 0 to 1.0 wt.%. In contrast, the wear volume increased by 50% as the CNC addition increased from 0 to 0.5 wt.%, but it fell to a value slightly lower than that achieved using only pure water (i.e., no CNCs) as the CNC content was further increased to 1.0 wt.%. For the O/W emulsion, the addition of 0.8 wt.% CNCs reduced the COF by around 30% compared to that of the emulsion with no CNCs. Overall, the results showed that while the addition of a small quantity (6%) of oil to the water working fluid had a relatively small effect on the wear performance, the addition of an appropriate quantity of CNCs (i.e., 0.8 wt.%) resulted in a significantly lower COF and an improved wear surface.
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Samat, Noorasikin, Raimi Fariz Nasrudin, Nur Afiqah Mokhtar, and Norzita Yacob. "PRODUCTION OF CELLULOSE NANOCRYSTALS FROM OIL PALM EMPTY FRUIT BUNCH AND PINEAPPLE LEAF FIBRE USING DOUBLE OXIDATION APPROACH." Jurnal Teknologi 84, no. 5 (July 26, 2022): 73–81. http://dx.doi.org/10.11113/jurnalteknologi.v84.18215.
Повний текст джерелаАнотація:
Cellulose nanocrystasl (CNC) were produced from oil palm empty fruit bunch (EFB) and pineapple leaf fibre (PALF) using double oxidation treatment comprising bleaching and ammonium persulfate (APS) treatments. Different techniques were used to characterise the extracted CNC. Fourier transform infrared (FTIR) spectra confirmed the formation of carboxyl group and decreasing fractions of non-cellulosic components. The CNCs from both fibres show a better crystallinity index than the raw fibre, and the CNCs also conform to the crystalline structure of cellulose I. Morphology analysis using transmission electron microscopy (TEM) reveals that the CNCs of EFB and PALF have different shapes and dimensions. Spherical EFB had a 16.33 ± 8.5 nm diameter, while rod-like PALF had 13.07 ± 6.15 nm and 78.67 ± 38.07 nm diameter and length. However, the thermal stability of both CNCs decreased slightly. Hence, the findings indicate that the double oxidation approach using agricultural biomass wastes can work as an alternative route for the preparation of CNCs.
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Feng, Chiao, and Sheng-Sheng Yu. "3D Printing of Thermal Insulating Polyimide/Cellulose Nanocrystal Composite Aerogels with Low Dimensional Shrinkage." Polymers 13, no. 21 (October 20, 2021): 3614. http://dx.doi.org/10.3390/polym13213614.
Повний текст джерелаАнотація:
Polyimide (PI)-based aerogels have been widely applied to aviation, automobiles, and thermal insulation because of their high porosity, low density, and excellent thermal insulating ability. However, the fabrication of PI aerogels is still restricted to the traditional molding process, and it is often challenging to prepare high-performance PI aerogels with complex 3D structures. Interestingly, renewable nanomaterials such as cellulose nanocrystals (CNCs) may provide a unique approach for 3D printing, mechanical reinforcement, and shape fidelity of the PI aerogels. Herein, we proposed a facile water-based 3D printable ink with sustainable nanofillers, cellulose nanocrystals (CNCs). Polyamic acid was first mixed with triethylamine to form an aqueous solution of polyamic acid ammonium salts (PAAS). CNCs were then dispersed in the aqueous PAAS solution to form a reversible physical network for direct ink writing (DIW). Further freeze-drying and thermal imidization produced porous PI/CNC composite aerogels with increased mechanical strength. The concentration of CNCs needed for DIW was reduced in the presence of PAAS, potentially because of the depletion effect of the polymer solution. Further analysis suggested that the physical network of CNCs lowered the shrinkage of aerogels during preparation and improved the shape-fidelity of the PI/CNC composite aerogels. In addition, the composite aerogels retained low thermal conductivity and may be used as heat management materials. Overall, our approach successfully utilized CNCs as rheological modifiers and reinforcement to 3D print strong PI/CNC composite aerogels for advanced thermal regulation.
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KHUMALO, NDUDUZO, MASULUBANYE S. MOHOMANE, LINDA Z. LINGANISO, CEBISA E. LINGANISO, SANDILE SONGCA, and MOTAUNG E. TSHWAFO. "EFFECT OF ACID HYDROLYSES ON PROPERTIES OF CELLULOSE/POLY FURFURAL ALCOHOL (PFA) COMPOSITES FROM MAIZE STALK." WOOD RESEARCH 68(1) 2023 68, no. 1 (February 28, 2023): 96–111. http://dx.doi.org/10.37763/wr.1336-4561/68.1.96111.
Повний текст джерелаАнотація:
The study investigated morphology and thermal properties of cellulose/poly furfural alcohol (PFA) composites prepared from maize stalk through acid mixtures. The cellulose nanocrystals (CNCs) were extracted from maize stalk via acid hydrolysis using mixtures of various acids.The prepared CNCs were encapsulated in a PFA matrix via in situpolymerization process using p-toluene sulfonic acid as catalyst. The properties of untreated maize stalk, cellulose and their nanocomposites were analysed by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transmission infrared (FTIR) and thermogravimetric analysis (TGA). The crystallinity of maize stalk was generally increased after an acid hydrolysis dominated by H2SO4/HNO3 and H2SO4/HCl. The same trend was observed from TGA, except that H2SO4/H3PO4and H2SO4/HClO4dominated thermal stability trailed by H2SO4hydrolysed CNC nanocomposite. The surface breakage of fibers observed in SEM images was depended on the strength of acids used tohydrolysed the CNC. There was also evidence of aggregation and cracked PFA surface with addition of acid hydrolysed CNCs, dependent on the acids strength. The H2SO4/HClO4hydrolysed CNC/PFA displayed afairly good dispersion of CNCs in the PFA matrix with no surface breakage.
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Park, Ji-Soo, Chan-Woo Park, Song-Yi Han, Eun-Ah Lee, Azelia Wulan Cindradewi, Jeong-Ki Kim, Gu-Joong Kwan, et al. "Preparation and properties of wet-spun microcomposite filaments from cellulose nanocrystals and alginate using a microfluidic device." BioResources 16, no. 3 (July 2, 2021): 5780–93. http://dx.doi.org/10.15376/biores.16.3.5780-5793.
Повний текст джерелаАнотація:
Cellulose nanocrystals (CNCs) were wet-spun in a coagulation bath for the fabrication of microfilaments, and the effect of sodium alginate (AL) addition on the wet-spinnability and properties of the microcomposite filament was investigated. The CNC suspension exhibited excellent wet-spinnability in calcium chloride (CaCl2) solution, and the addition of AL in CNC suspension resulted in the enhancement of the wet-spinnability of CNCs. As the AL content increased from 3% to 10%, the average diameter of the microcomposite filament decreased, and its tensile properties deteriorated. The increased spinning rate caused an increase in the orientation index of CNCs, resulting in an improvement in the tensile properties of the microcomposite filament.
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Dinçel Kasapoğlu, Ekin, Sibel Kahraman, and Fatih Tornuk. "Extraction Optimization and Characterization of Cellulose Nanocrystals from Apricot Pomace." Foods 12, no. 4 (February 8, 2023): 746. http://dx.doi.org/10.3390/foods12040746.
Повний текст джерелаАнотація:
Apricot pomace (AP) is lignocellulosic agro-industrial waste that could be considered a good source for cellulose-based, value-added compounds. In this study, conditions for cellulose nanocrystals’ (CNCs) extraction from apricot pomace (AP) were optimized using Response Surface Methodology (RSM) based on the extraction yield, and the resulting CNC was characterized using Fourier transform infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Transmittance Electron Microscopy (TEM), Thermogravimetric Analysis (TGA), and X-Ray Diffraction (XRD). The maximum CNC yield (34.56%) was obtained at a sulfuric acid concentration of 9.5 M within 60 min. FTIR analysis showed that noncellulosic components were gradually removed from the pomace. A morphological analysis of the nanocrystal was performed using SEM and TEM. CNCs were in the range of 5–100 µm in diameter and appeared as individual fibers. TGA analysis of the CNC sample revealed good thermal stability around 320°C. The crystalline index (%CI) of the CNC obtained from AP was determined to be 67.2%. In conclusion, this study demonstrated that AP could be considered a sustainable source for value-added compounds such as CNCs to contribute to a circular economy.
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Durairaj, Arulppan, Moorthy Maruthapandi, Arumugam Saravanan, John H. T. Luong, and Aharon Gedanken. "Cellulose Nanocrystals (CNC)-Based Functional Materials for Supercapacitor Applications." Nanomaterials 12, no. 11 (May 26, 2022): 1828. http://dx.doi.org/10.3390/nano12111828.
Повний текст джерелаАнотація:
The growth of industrialization and the population has increased the usage of fossil fuels, resulting in the emission of large amounts of CO2. This serious environmental issue can be abated by using sustainable and environmentally friendly materials with promising novel and superior performance as an alternative to petroleum-based plastics. Emerging nanomaterials derived from abundant natural resources have received considerable attention as candidates to replace petroleum-based synthetic polymers. As renewable materials from biomass, cellulose nanocrystals (CNCs) nanomaterials exhibit unique physicochemical properties, low cost, biocompatibility and biodegradability. Among a plethora of applications, CNCs have become proven nanomaterials for energy applications encompassing energy storage devices and supercapacitors. This review highlights the recent research contribution on novel CNC-conductive materials and CNCs-based nanocomposites, focusing on their synthesis, surface functionalization and potential applications as supercapacitors (SCs). The synthesis of CNCs encompasses various pretreatment steps including acid hydrolysis, mechanical exfoliation and enzymatic and combination processes from renewable carbon sources. For the widespread applications of CNCs, their derivatives such as carboxylated CNCs, aldehyde-CNCs, hydride-CNCs and sulfonated CNC-based materials are more pertinent. The potential applications of CNCs-conductive hybrid composites as SCs, critical technical issues and the future feasibility of this endeavor are highlighted. Discussion is also extended to the transformation of renewable and low-attractive CNCs to conductive nanocomposites using green approaches. This review also addresses the key scientific achievements and industrial uses of nanoscale materials and composites for energy conversion and storage applications.
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Liu, Xuehua, Rue Yang, Mincong Xu, Chunhui Ma, Wei Li, Yu Yin, Qiongtao Huang, Yiqiang Wu, Jian Li, and Shouxin Liu. "Hydrothermal Synthesis of Cellulose Nanocrystal-Grafted-Acrylic Acid Aerogels with Superabsorbent Properties." Polymers 10, no. 10 (October 19, 2018): 1168. http://dx.doi.org/10.3390/polym10101168.
Повний текст джерелаАнотація:
In this work, we applied a fast and simple method to synthesize cellulose nanocrystal (CNC) aerogels, via a hydrothermal strategy followed by freeze drying. The characteristics and morphology of the obtained CNC-g-AA aerogels were affected by the hydrothermal treatment time, volume of added AA (acrylic acid), and the mass fraction of the CNCs. The formation mechanism of the aerogels involved free radical graft copolymerization of AA and CNCs with the cross-linker N,N′-methylene bis(acrylamide) (MBA) during the hydrothermal process. The swelling ratio of the CNC-g-AA aerogels was as high as 495:1, which is considerably greater than that of other polysaccharide-g-AA aerogels systems. Moreover, the CNC-g-AA aerogels exhibited an excellent methyl blue (MB) adsorption capacity and the ability to undergo rapid desorption/regeneration. The maximum adsorption capacity of the CNC-g-AA aerogels for MB was greater than 400 mg/g. Excellent regeneration performance further indicates the promise of our CNC-g-AA aerogels as an adsorbent for applications in environmental remediation.
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Parajuli, Sanjiv, Mohammad Jahid Hasan, and Esteban E. Ureña-Benavides. "Effect of the Interactions between Oppositely Charged Cellulose Nanocrystals (CNCs) and Chitin Nanocrystals (ChNCs) on the Enhanced Stability of Soybean Oil-in-Water Emulsions." Materials 15, no. 19 (September 26, 2022): 6673. http://dx.doi.org/10.3390/ma15196673.
Повний текст джерелаАнотація:
Chitin nanocrystals (ChNCs) and cellulose nanocrystals (CNCs) have been recently used to stabilize emulsions; however, they generally require significant amounts of salt, limiting their applicability in food products. In this study, we developed nanoconjugates by mixing positively charged ChNCs and negatively charged CNCs at various ChNC:CNC mass ratios (2:1, 1:1, and 1:2), and utilized them in stabilizing soybean oil–water Pickering emulsions with minimal use of NaCl salt (20 mM) and nanoparticle (NP) concentrations below 1 wt%. The nanoconjugates stabilized the emulsions better than individual CNC or ChNC in terms of a reduced drop growth and less creaming. Oppositely charged CNC and ChNC neutralized each other when their mass ratio was 1:1, leading to significant flocculation in the absence of salt at pH 6. Raman spectroscopy provided evidence for electrostatic interactions between the ChNCs and CNCs, and generated maps suggesting an assembly of ChNC bundles of micron-scale lengths intercalated by similar-size areas predominantly composed of CNC. The previous measurements, in combination with contact angles on nanoparticle films, suggested that the conjugates preferentially exposed the hydrophobic crystalline planes of CNCs and ChNCs at a 1:1 mass ratio, which was also the best ratio at stabilizing soybean oil–water Pickering emulsions.
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Ruppert, Judith. "Edge: Lokale Intelligenz digitalisiert die Fertigung." Konstruktion 70, no. 09 (2018): 18–21. http://dx.doi.org/10.37544/0720-5953-2018-09-18.
Повний текст джерелаАнотація:
Zwischen CNC und Cloud: Mit „Sinumerik Edge“ von Siemens werden hochfrequente CNC-Massen- daten anhand von Softwareapplikationen direkt vor Ort erfasst, vorverarbeitet und analysiert. Die daraus generierten Maßnahmen verbessern die Produktivität von Maschinen und Linien, ohne deren CNCs zu belasten.
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Sun, Yanzhen, Xiaoli Ma, Xiaodong Jing, and Hao Hu. "PAMAM-Functionalized Cellulose Nanocrystals with Needle-Like Morphology for Effective Cancer Treatment." Nanomaterials 11, no. 7 (June 22, 2021): 1640. http://dx.doi.org/10.3390/nano11071640.
Повний текст джерелаАнотація:
Gene therapy is used to correct or compensate for diseases caused by gene defects and abnormalities. Improving the transfection efficiency and reducing the toxicity of gene carriers are the keys to gene therapy. Similar to a typical cationic gene carrier—polyethylenimine (PEI, 25 kDa)—the polyamidoamine (PAMAM) dendrimer also has a large number of amino groups. These amino groups can be complexed with nucleic acids after protonation under physiological conditions. However, the concentrated positive charge can cause undesirable cytotoxicity. Cellulose nanocrystals (CNCs) have good biocompatibility and unique needle-like morphology, and have been proven to be efficiently taken up by cells. In this article, three-dimensional spherical PMAMA dendrimers are conjugated onto the surface of CNCs to obtain a kind of needle-like cationic carrier (CNC-PAMAM). PAMAM dendrimers act as anchors to bind the plasmid DNAs (pDNA) to the surface of the CNC. The prepared CNC-based carrier showed high transfection efficiency and low toxicity. The CNC-PAMAM can effectively deliver the suicide gene to the tumor site, enabling the suicide gene/prodrug system (cytosine deaminase/5-fluorocytosine (CD/5-FC)) to play an effective anti-tumor role in vivo. This research demonstrates that the functionalization of CNCs with PAMAM dendrimers is an effective method for developing novel gene delivery systems.
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Xu, Xin, Ze Ma, Zekun Su, Danqing Li, Xufeng Dong, Hao Huang, and Min Qi. "The Synthesis of Carbon Black-Loaded Pt Concave Nanocubes with High-Index Facets and Their Enhanced Electrocatalytic Properties toward Glucose Oxidation." Nanomaterials 12, no. 21 (October 26, 2022): 3761. http://dx.doi.org/10.3390/nano12213761.
Повний текст джерелаАнотація:
Catalysts with high catalytic activity and good stability are desirable in the electrocatalytic oxidation of glucose. Herein, Pt concave nanocubes with high-index facets (HIFs) supported by carbon black (Pt CNC/CB) are prepared through a hydrothermal method. The experimental results demonstrate that the peak current densities in different potential regions on the Pt CNC/CB anode are 0.22, 0.20, and 0.60 mA cm−2. The catalytic process of the glucose oxidation reaction is investigated in electrolytes with different pH values. Better stability is achieved by Pt CNC/CB than by Pt concave nanocubes (Pt CNCs). Abundant surface defects with low-coordinated atom numbers, such as steps, kinks, and edges, served as active sites in the electrocatalytic oxidation of glucose. With the addition of carbon black, the catalytic activity can be improved by facilitating the full exposure of the active surface defects on the HIFs of the Pt CNCs. Moreover, to address the aggregation of Pt CNCs, caused by the high surface energy of HIFs, the introduction of carbon material is an effective way to preserve the HIFs and thus enhance the stability of the catalyst. Hence, the prepared Pt CNC/CB electrocatalyst has great potential to be applied in the electrooxidation of glucose.
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Wan Ishak, Wan Hafizi, Oo Yong Jia, and Ishak Ahmad. "pH-Responsive Gamma-Irradiated Poly(Acrylic Acid)-Cellulose-Nanocrystal-Reinforced Hydrogels." Polymers 12, no. 9 (August 27, 2020): 1932. http://dx.doi.org/10.3390/polym12091932.
Повний текст джерелаАнотація:
A pH-sensitive poly(acrylic acid) composite hydrogel was successfully synthesized via gamma irradiation and reinforced with cellulosic materials of different sizes. Cellulose was extracted from rice husks via alkali and bleaching treatment, and an acid hydrolysis treatment was performed to extract cellulose nanocrystals (CNCs). Morphological observation of cellulose and CNCs using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed diameters of 22–123 μm and 5–16 nm, respectively. The swelling properties of the fabricated poly(acrylic acid)/cellulosic hydrogels were found to respond to changes in pH, and CNC-reinforced hydrogels performed better than cellulose-reinforced hydrogels. The highly crystalline CNC provided a greater storage modulus, hence acting as a better reinforcing material for poly(acrylic acid)-based hydrogels. SEM showed that hydrogels reinforced with the CNC nanofillers contained a homogeneous pore distribution and produced better interfacial interactions than those reinforced with the cellulose microfillers, thus performing better as hydrogels. These findings demonstrate that gamma-irradiated poly(acrylic acid) hydrogels reinforced with CNCs exhibit a better stimuli response toward pH than poly(acrylic acid) hydrogels reinforced with cellulose.
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Thiruganasambanthan, Theivasanthi, Rushdan Ahmad Ilyas, Mohd Nor Faiz Norrrahim, Thiagamani Senthil Muthu Kumar, Suchart Siengchin, Muhammad Syukri Mohamad Misenan, Mohammed Abdillah Ahmad Farid, et al. "Emerging Developments on Nanocellulose as Liquid Crystals: A Biomimetic Approach." Polymers 14, no. 8 (April 11, 2022): 1546. http://dx.doi.org/10.3390/polym14081546.
Повний текст джерелаАнотація:
Biomimetics is the field of obtaining ideas from nature that can be applied in science, engineering, and medicine. The usefulness of cellulose nanocrystals (CNC) and their excellent characteristics in biomimetic applications are exciting and promising areas of present and future research. CNCs are bio-based nanostructured material that can be isolated from several natural biomasses. The CNCs are one-dimensional with a high aspect ratio. They possess high crystalline order and high chirality when they are allowed to assemble in concentrated dispersions. Recent studies have demonstrated that CNCs possess remarkable optical and chemical properties that can be used to fabricate liquid crystals. Research is present in the early stage to develop CNC-based solvent-free liquid crystals that behave like both crystalline solids and liquids and exhibit the phenomenon of birefringence in anisotropic media. All these characteristics are beneficial for several biomimetic applications. Moreover, the films of CNC show the property of iridescent colors, making it suitable for photonic applications in various devices, such as electro-optical devices and flat panel displays.
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Asohan, Anusha Wei, Rokiah Hashim, Ku Marsilla Ku Ishak, Zuratul Ain Abdul Hamid, Nurshafiqah Jasme, and Yazmin Bustami. "Preparation and Characterisation of Cellulose Nanocrystal/Alginate/Polyethylene Glycol Diacrylate (CNC/Alg/PEGDA) Hydrogel Using Double Network Crosslinking Technique for Bioprinting Application." Applied Sciences 12, no. 2 (January 13, 2022): 771. http://dx.doi.org/10.3390/app12020771.
Повний текст джерелаАнотація:
In this study, we aimed to prepare and characterise hydrogel formulations using cellulose nanocrystals (CNCs), alginate (Alg), and polyethylene glycol diacrylate (PEGDA). The CNC/Alg/PEGDA formulations were formed using a double network crosslinking approach. Firstly, CNC was extracted from oil palm trunk, and the size and morphology of the CNCs were characterised using TEM analysis. Secondly, different formulations were prepared using CNCs, Alg, and PEGDA. The mixtures were crosslinked with Ca2+ ions and manually extruded using a syringe before being subjected to UV irradiation at 365 nm. The shear-thinning properties of the formulations were tested prior to any crosslinking, while the determination of storage and loss modulus was conducted post extrusion after the Ca2+ ion crosslink using a rheometer. For the analysis of swelling behaviour, the constructs treated with UV were immersed in PBS solution (pH 7.4) for 48 h. The morphology of the UV crosslinked construct was analysed using SEM imaging. The extracted CNC exhibited rod-like structures with an average diameter and length of around 7 ± 2.4 and 113 ± 20.7 nm, respectively. Almost all CNC/Alg/PEGDA formulations (pre-gel formulation) displayed shear-thinning behaviour with the power-law index η < 1, and the behaviour was more prominent in the 1% [w/v] Alg formulations. The CNC/Alg/PEGDA with 2.5% and 4% [w/v] Alg displayed a storage modulus dominance over loss modulus (G′ > G″) which suggests good shape fidelity. After the hydrogel constructs were subjected to UV treatment at 365 nm, only the F8 construct [4% CNC: 4% Alg: 40% PEGDA] demonstrated tough and flexible characteristics that possibly mimic the native articular cartilage property due to a similar water content percentage (79.5%). In addition, the small swelling ratio of 4.877 might contribute to a minimal change of the 3D construct’s geometry. The hydrogel revealed a rough and wavy surface, and the pore size ranged from 3 to 20 µm. Overall, the presence of CNCs in the double network hydrogel demonstrated importance and showed positive effects towards the fabrication of a potentially ideal 3D bioprinted scaffold.
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Shi, Shih‐Chen, Chi-Feng Lin, Chi-Fan Liu, and Tao-Hsing Chen. "Tribological and mechanical properties of cellulose/PMMA composite." Polymers and Polymer Composites 30 (January 2022): 096739112211409. http://dx.doi.org/10.1177/09673911221140935.
Повний текст джерелаАнотація:
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.
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Abushammala, Hatem. "Nano-Brushes of Alcohols Grafted onto Cellulose Nanocrystals for Reinforcing Poly(Butylene Succinate): Impact of Alcohol Chain Length on Interfacial Adhesion." Polymers 12, no. 1 (January 4, 2020): 95. http://dx.doi.org/10.3390/polym12010095.
Повний текст джерелаАнотація:
Despite the many interesting properties of cellulose nanocrystals (CNCs), their hydrophilicity is one of the main challenges for their processing with hydrophobic polymers and matrices. To overcome this challenge, this paper describes the preparation of brush-like CNCs with tailored surface properties by grafting alcohols of different chain lengths onto their surfaces. Ethanol, 1-butanol, 1-hexanol, and 1-octanol were grafted on the CNC surface using 2,4-toluene diisocyanate (TDI) as a linker. The CNCs were characterized for their structural, morphological, surface, and thermal properties. Because of the grafting, the water contact angle of the CNCs significantly increased from 32° to up to 120°, which was dependent on the chain length of the grafted alcohol. The thermal stability of the CNCs was also improved, mainly as a result of the reaction of TDI with the CNC hydroxyl groups. Later, the CNCs were used to reinforce films of poly(butylene succinate) (PBS), which were then characterized using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). An increase of up to two-fold in the storage modulus was observed using DMA, which was dependent on the chain length of the grafted alcohol. However, no change in the glass transition temperature or degradation temperature of PBS was detected. This approach is proved efficient for tailoring the surface properties of CNCs towards excellent interfacial adhesion in their composites.