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Articoli di riviste sul tema "Cellulose-water interactions":
1
De Wever, Pieter, Rodrigo de Oliveira-Silva, João Marreiros, Rob Ameloot, Dimitrios Sakellariou e Pedro Fardim. "Topochemical Engineering of Cellulose—Carboxymethyl Cellulose Beads: A Low-Field NMR Relaxometry Study". Molecules 26, n. 1 (22 dicembre 2020): 14. http://dx.doi.org/10.3390/molecules26010014.
Abstract (sommario):
The demand for more ecological, highly engineered hydrogel beads is driven by a multitude of applications such as enzyme immobilization, tissue engineering and superabsorbent materials. Despite great interest in hydrogel fabrication and utilization, the interaction of hydrogels with water is not fully understood. In this work, NMR relaxometry experiments were performed to study bead–water interactions, by probing the changes in bead morphology and surface energy resulting from the incorporation of carboxymethyl cellulose (CMC) into a cellulose matrix. The results show that CMC improves the swelling capacity of the beads, from 1.99 to 17.49, for pure cellulose beads and beads prepared with 30% CMC, respectively. Changes in water mobility and interaction energy were evaluated by NMR relaxometry. Our findings indicate a 2-fold effect arising from the CMC incorporation: bead/water interactions were enhanced by the addition of CMC, with minor additions having a greater effect on the surface energy parameter. At the same time, bead swelling was recorded, leading to a reduction in surface-bound water, enhancing water mobility inside the hydrogels. These findings suggest that topochemical engineering by adjusting the carboxymethyl cellulose content allows the tuning of water mobility and porosity in hybrid beads and potentially opens up new areas of application for this biomaterial.
2
Stenqvist, Björn, Erik Wernersson e Mikael Lund. "Cellulose-Water Interactions: Effect of electronic polarizability". Nordic Pulp & Paper Research Journal 30, n. 1 (1 gennaio 2015): 26–31. http://dx.doi.org/10.3183/npprj-2015-30-01-p026-031.
3
Voronova, M. I., T. N. Lebedeva, M. V. Radugin, O. V. Surov, A. N. Prusov e A. G. Zakharov. "Interactions of water–DMSO mixtures with cellulose". Journal of Molecular Liquids 126, n. 1-3 (maggio 2006): 124–29. http://dx.doi.org/10.1016/j.molliq.2005.12.001.
4
Chami Khazraji, Ali, e Sylvain Robert. "Interaction Effects between Cellulose and Water in Nanocrystalline and Amorphous Regions: A Novel Approach Using Molecular Modeling". Journal of Nanomaterials 2013 (2013): 1–10. http://dx.doi.org/10.1155/2013/409676.
Abstract (sommario):
The hydrophilic/hydrophobic nature of cellulose is based on its structural anisotropy. Cellulose chains are arranged in a parallel manner and are organized in sheets stabilized by interchain OH–O hydrogen bonds, whereas the stacking of sheets is stabilized by both van der Waals (vdW) dispersion forces and weak CH–O hydrogen bonds. Cellulose has a strong affinity to itself and materials containing hydroxyls, especially water. Based on the preponderance of hydroxyl functional groups, cellulose polymer is very reactive with water. Water molecular smallness promotes the reaction with the cellulose chains and immediately formed hydrogen bonds. Besides that, vdW dispersion forces play an important role between these two reactive entities. They stabilize the cellulose structure according to the considerable cohesive energy in the cellulose network. Hydrogen bonding, electrostatic interactions, and vdW dispersion forces play an important role in determining the cellulose crystal structure during the cellulose-water interactions. As a result of these interactions, the volume of cellulose undergoes a meaningful change expressed not only by an exponential growth in amorphous regions, but also by an expansion in nanocrystalline regions. In addition, the volume change is associated with the swelling material expressed as a weight gain of the cellulose polymer. Molecular modeling using Accelrys Materials Studio allowed us to open a new horizon and is helpful for understanding cellulose-water interactions.
5
Masas, Daria S., Maria S. Ivanova, Gocha Sh Gogelashvili, Alexander S. Maslennikov, Yury B. Grunin e Tatiana Yu Grunina. "Analysis of water state adsorbed by cellulose fibers". Butlerov Communications 58, n. 5 (31 maggio 2019): 24–31. http://dx.doi.org/10.37952/roi-jbc-01/19-58-5-24.
Abstract (sommario):
Modernized model of microfibril cellulose layered structure is proposed. This model considers presence of slit-shaped micropores in space between elementary fibrils and cellulose microfibrils. It’s discussed the nature of donor-acceptor hydrogen bonds formation: intra-, intermolecular, and interlayer bonds inherent in each glucopyranous cellulose link. It’s described the mechanism of water molecules specific adsorption interactions in a monolayer with active centers located on the hydrophilic surfaces of elementary fibrils. Dipole-dipole energy transition into energy of hydrogen bond is discussed during adsorption process between active centers of cellulose and water adsorptive molecules. Analysis of water molecules dipole-dipole interactions with surface hydroxyl groups of cellulose showed that at distance of 2.5-3 Å energy of this interaction transforms into energy of hydrogen bond. It is discussed the formation mechanism of water molecules donor-acceptor bonds with cellulose surface hydroxyl groups. Thermodynamic parameters characterizing adsorbate state the in these layers are determined by proton magnetic relaxation and sorption measurements. It’s established the possibility of determining adsorption net heat in bilayer considering Arrhenius nature of adsorbate thermal molecular motions correlation times. Increase in entropy of adsorbed water during adsorption process is revealed basis on Vant Hoff equation and certain adsorption equilibrium constant. The calculation established that distance between nearest active centers of cellulose is 6.5 Å. This leads to disunity of adsorbed water molecules and allows application of Langmuir and BET adsorption theory. Analysis of spin-lattice relaxation times dependence on cellulose moisture content made it possible to establish the cause of its crystallite wedging from adsorbed water molecules at adsorption initial stages. Decline of the spin-lattice relaxation unambiguously indicates the process of cellulose dispersion into its structural elements. It was established that during adsorption a part of the internal regions of crystallites passes to their surface with participation of cellulose hydroxyl groups. During desorption reverse process is observed.
6
Pontoh, Raynardthan, Vania Edita Rarisavitri, Christine Charen Yang, Maximilliam Febriand Putra e Daru Seto Bagus Anugrah. "Density Functional Theory Study of Intermolecular Interactions between Amylum and Cellulose". Indonesian Journal of Chemistry 22, n. 1 (20 gennaio 2022): 253. http://dx.doi.org/10.22146/ijc.69241.
Abstract (sommario):
Amylum is one of the polysaccharides developed into biodegradable plastic bags. However, amylum-based plastics are easily damaged due to their low mechanical strength and hydrophilic properties. Cellulose is used as a support material in amylum-based plastics to increase strength and reduce water damage. This study investigated the molecular interactions between amylum and cellulose computationally. The minimum interaction energy of amylum and cellulose was calculated using in silico modeling using the Density Functional Theory (DFT) method. The B3LYP function and the basis set 6-31++g** were used in the calculations. Simultaneously, D3 Grimme dispersion correction was used as the effect of water solvent in the measures. The results obtained from this study were the interaction energy of amylum and cellulose of –29.8 kcal/mol. The HOMO-LUMO energy gap of the cellulose-amylum complex was lower than cellulose, indicating that the cellulose-amylum complex was more reactive and bonded to each other. Analysis of Natural Bond Orbital (NBO), Quantum Theory Atom in Molecule (QTAIM), Reduced Density Gradient (RDG), Non-covalent Interaction Index (NCI), and Intrinsic Bond Strength Index (IBSI) showed that the cellulose-amylum complex had weak to medium intermolecular bonds. The hydrogen bond at O61···H48 was the strongest in the complex. All data show that cellulose and amylum could interact through non-covalent bonds.
7
Chami Khazraji, Ali, e Sylvain Robert. "Self-Assembly and Intermolecular Forces When Cellulose and Water Interact Using Molecular Modeling". Journal of Nanomaterials 2013 (2013): 1–12. http://dx.doi.org/10.1155/2013/745979.
Abstract (sommario):
Cellulose chains are linear and aggregation occurs via both intra- and intermolecular hydrogen bonds. Cellulose has a strong affinity to itself and toward materials containing hydroxyls groups. Based on the preponderance of hydroxyl functional groups, cellulose is very reactive with water. At room temperature, cellulose chains will have at least a monomolecular layer of water associated to it. The formation of hydrogen bonds at the cellulose/water interface is shown to depend essentially on the adsorption site, for example, the equatorial hydroxyls or OH moieties pointing outward from the cellulose chains. The vdW forces also contribute significantly to the adsorption energy. They are a considerable cohesive energy into the cellulose network. At the surface of the cellulose chains, many intermolecular hydrogen bonds of the cellulose chains are lost. However, they are compensated by hydrogen bonds with water molecules. Electronic clouds can be distorted and create electrostatic dipoles. The large antibonding electron cloud that exists around the glucosidic bonds produces an induced polarization at the approach of water molecules. The electron cloud can be distorted and create an electrostatic dipole. It applies to the total displacement of the atoms within the material. Orbitals play a special role in reaction mechanism. Hydrophilic/hydrophobic nature of cellulose is based on its structural anisotropy. Cellulose-water interactions are exothermic reactions. These interactions may occur spontaneously and result in higher randomness of the system. They are denoted by a negative heat flow (heat is lost to the surroundings). Energy does not need to be inputted in order for cellulose-water interactions to occur.
8
Lee, Hye Ji, Younghyun Cho e Sang Wook Kang. "Formation of Nanochannels Using Polypropylene and Acetylcellulose for Stable Separators". Membranes 12, n. 8 (4 agosto 2022): 764. http://dx.doi.org/10.3390/membranes12080764.
Abstract (sommario):
In this study, a polymer separator with enhanced thermal stability is prepared to solve the problem of thermal durability of lithium-ion battery separators. This separator is manufactured by coating a solution of acetyl cellulose and glycerin on polypropylene. The added glycerin reacts with the acetyl cellulose chains, helping the chains become flexible, and promotes the formation of many pores in the acetyl cellulose. To improve the thermal stability of the separator, a mixed solution of acetyl cellulose and glycerin was coated twice on the PP membrane film. Water pressure is applied using a water treatment equipment to partially connect the pores of a small size in each layer and for the interaction between the PP and acetyl cellulose. SEM is used to observe the shape, size, and quantity of pores. TGA and FT-IR are used to observe the interactions. Average water flux data of the separators is 1.42 LMH and the decomposition temperature increases by about 60 °C compared to the neat acetyl cellulose. It is confirmed that there is an interaction with PP between the functional groups of acetyl cellulose.
9
Tammelin, Tekla, Ramarao Abburi, Marie Gestranius, Christiane Laine, Harri Setälä e Monika Österberg. "Correlation between cellulose thin film supramolecular structures and interactions with water". Soft Matter 11, n. 21 (2015): 4273–82. http://dx.doi.org/10.1039/c5sm00374a.
10
Peydecastaing, J., C. Vaca-Garcia e E. Borredon. "Interactions with water of mixed acetic-fatty cellulose esters". Cellulose 18, n. 4 (11 aprile 2011): 1023–31. http://dx.doi.org/10.1007/s10570-011-9530-2.
Tesi sul tema "Cellulose-water interactions":
1
McCrystal, Conor B. "Characterisation of the fundamental interactions between water and cellulose ether polymers". Thesis, Liverpool John Moores University, 1998. http://researchonline.ljmu.ac.uk/4912/.
2
Lopes, Da Costa Lisa. "Conception d’actionneurs à base de nanofibres de cellulose induits par l’eau". Electronic Thesis or Diss., Nantes Université, 2023. http://www.theses.fr/2023NANU4060.
Abstract (sommario):
Le changement de forme est un phénomène particulièrement observé dans le règne végétal, comme l'ouverture et la fermeture des écailles de pommes de pin sous l'effet de l'humidité. Cette capacité à se mouvoir en fonction d’un stimulus externe est dénommée actionnement. L’objectif de cette thèse est de concevoir des actionneurs inspirés de ce phénomène naturel à partir de nanofibres de cellulose (NFC). Les NFC sont une excellente matière première végétale pour fabriquer des actionneurs grâce à leurs groupes hydroxyles permettant l'introduction de groupes chimiques sensibles à un stimulus, à leur nature hydrophile et à leurs excellentes propriétés mécaniques. Dans cette thèse, les NFC ont été fonctionnalisées et assemblées sous la forme de films bicouches capables de subir des expansions asymétriques lorsqu’ils sont immergés dans l’eau. Ces expansions asymétriques ont permis le mouvement des films (flexion ou/et torsion).La prise d’eau différentielle entre les couches est le moteur de l’actionnement des films de NFC. L’hydratation et la déshydratation ont été contrôlées par le degré de fonctionnalité des NFC et par l’immersion des films dans des solutions aqueuses à différents pH ou des solvants organiques. Les mécanismes liés à l’actionnement ont été étudiés en analysant la structure des NFC fonctionnaliées, en quantifiant les capacités de prise d’eau et les propriétés mécaniques des films et enfin en évaluant les interactions physico-chimiques principales entre les différentes NFC et les milieux d’immersion. Cette thèse est une preuve de concept que les actionneurs à base de NFC ont un grand potentiel pour diverses applications telles que la robotique souple ou les dispositifs biomédicauxShape change is particularly observed in the plant kingdom, such as the opening and closing of pine cone scales driven by humidity. This ability to move in response to an external stimulus is known as actuation. The aim of this thesis is to design actuators inspired by this natural phenomenon using cellulose nanofibers (CNF). CNF are an excellent plant-based raw material for actuators thanks to their hydroxyl groups, which allow the introduction of stimuli- sensitive chemical groups, their hydrophilicity, and their excellent mechanical properties. Herein, CNF were functionalized and assembled into bilayer films undergoing asymmetric expansions when immersed in water. These asymmetric expansions enabled the films to bend and/or twist. The differential water uptake between layers is the driving force behind the film actuation. Hydration and dehydration were controlled by the degree of functionality of the CNF and by film immersion in aqueous solutions at different pH or in organic solvents. The mechanisms of actuation were studied by analyzing the structure of functionalized CNF, assessing the water uptake and mechanical performances of the films, and determining the main physico- chemical interactions between the different CNFs and immersion media. This study is a proof-of-concept that CNF-based actuators have a great potential for various applications such as soft robotics or biomedical devices
3
Lindh, Erik L. "Cellulose-water interaction: a spectroscopic study". Doctoral thesis, KTH, Tillämpad fysikalisk kemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-199200.
Abstract (sommario):
The human society of today has a significantly negative impact on the environment and needs to change its way of living towards a more sustainable path if to continue to live on a healthy planet. One path is believed to be an increased usage of naturally degradable and renewable raw materials and, therefore, attention has been focused on the highly abundant biopolymer cellulose. However, a large drawback with cellulose-based materials is the significant change of their mechanical properties when in contact with water. Despite more than a century of research, the extensively investigated interaction between water and cellulose still possesses many unsettled questions, and if the answer to those were known, cellulose-based materials could be more efficiently utilized. It is well understood that one interaction between cellulose and water is through hydrogen bonds, established between water and the hydroxyl groups of the cellulose. Due to the very similar properties of the hydroxyl groups in water and the hydroxyl groups of the cellulose, the specific interaction-induced effect on the hydroxyl groups at a cellulose surface is difficult to investigate. Therefore, a method based on 2H MAS NMR spectroscopy has been developed and validated in this work. Due to the verified ability of the methodology to provide site-selective information regarding the molecular dynamics of the cellulose deuteroxyl groups (i.e. deuterium-exchanged hydroxyl groups), it was shown by investigating 1H-2H exchanged cellulose samples that only two of the three accessible hydroxyl groups (on the surface of cellulose fibrils) exchange with water. This finding was also verified by FT-IR spectroscopy, and together with MD simulations we could establish that it is O(2)H and O(6)H hydroxyl groups (of the constituting glucose units) that exchange with water. From the MD simulations additional conclusion could be drawn regarding the molecular interactions required for hydrogen exchange; an exchanging hydroxyl group needs to donate its hydrogen in a hydrogen bond to water. Exchange kinetics of thin cellulose films were investigated by monitoring two different exchange processes with FT-IR spectroscopy. Specific information about the two exchanging hydroxyl/deuteroxyl groups was then extracted by deconvoluting the changing intensities of the recorded IR spectra. It was recognized that the exchange of the hydroxyl groups were well described by a two-region model, which was assessed to correspond to two fibrillary surfaces differentiated by their respective positions in the fibril aggregate. From the detailed deconvolution it was also possible to estimate the fraction of these two surfaces, which indicated that the average aggregate of cotton cellulose is built up by three to four fibrils. 2H MAS NMR spectroscopy was used to examine different states of water in cellulose samples, hydrated at different relative humidities of heavy water. The results showed that there exist two states of water adsorbed onto the cellulose, differentiated by distinct different mobilities. These two states of water are well separated and had negligible exchange on the time scale of the experiments. It was suggested that they are located at the internal and external surfaces of the fibril aggregates. By letting cellulose nanofibrils undergo an epoxidation reaction with a mono epoxide some indicative results regarding how to protect the cellulose material from the negative impact of water were presented. The protecting effect of the epoxidation were examined by mechanically testing and NMR spectroscopy. It was proposed that by changing the dominant interaction between the fibril aggregates from hydrophilic hydrogen bonds to hydrophobic π-interactions the sensitivity to moisture was much reduced. The results also indicated that the relative reduction in moisture sensitivity was largest for the samples with highest moisture content.QC 20161229
4
Shetty, Pramod. "Study on Supramolecular Gel Lubricants". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-76007.
Abstract (sommario):
Most of the rolling element bearings are lubricated with Grease lubricant. Generally, the grease is expected to serve for life. The major causes of the bearing failure are due to the failure of the lubrication. The grease will experience creeping, oil permeation, oil separation etc. The separated oil will be lost permanently from the bearing. The widely used grease for general application is the lithium grease. The thickener of the grease consists covalent bond. When the grease is sheared, the breakage of the covalent bond will be permanent, resulting in the permanent loss of the rheological properties. The gels have unique properties such as thermal reversibility, viscoelasticity and thixotropy. They become mobile under shear stress and solidify again when the shear stress is removed. This property can be harnessed to avoid the base oil creeping, oil permeation, leakage in gears and bearings. Due to the presence of the polar group in the gels, they form a good tribo film and prevent the wear. Under the shear stress, weak supramolecular interactions will be distorted, and this leads to the release of the oil and they re-form the structure after a certain period of rest. When the gel is in the solid-state, it will avoid creeping and evaporation. Many classes of gels are either derived from natural sources or from environmentally friendly materials. Thus, the lubricant formed out of gel would effectively solve both environmental as well as lubrication problems. In this work, supramolecular gel lubricants were prepared out of fully green, cellulose derivatives and starch hydrolysates. The non-ionic hydroxyethyl cellulose (HEC) and anionic sodium carboxymethyl cellulose (NaCMC) were chosen to understand the effect of ionic and non-ionic gelators on the rheological and the tribological parameters. Traditionally fat was used as a lubricant, now, in food industry various fat replacers are being used. To study whether the fat replacers can act as a thickener, Dextrin and maltodextrins were chosen. Dextrin and maltodextrin with the different DE values were selected to understand the influence of molecular weight on gelation and tribological performance. Inspired by the recent developments and advantages of aqueous lubrication, mixer of water and poly(ethylene glycol) 200 (PEG 200) is chosen as the base fluid. It was found that a very small amount of gelator can increase the viscosity of the PEG/water to several orders. The thermal stability of the gels was studied using thermogravimetric analysis (TGA) and found that gels can increase the thermal stability of the base fluid. FTIR results showed the formation of a non-covalent bond between the PEG molecules and water. It is shown that anionic gelator will result in producing low friction and wear in comparison to non-ionic gelator. The possible tribo-film formation due to the negative charge in the NaCMC molecules is attributed to these results. The very low friction and low wear was exhibited by the dextrin and maltodextrin gels. It is proposed that this could be due to the microspherical particles of gels which can act as nano bearings. It was found that choosing the optimum concentration of the gelator is important to reduce friction and wear. The higher gelator concentration will form the hard gel, which cannot flow and replenish the sliding contact, resulting in the starved lubrication. This will cause high wear and friction. These gel lubricants can be used in food, pharmaceutical and biomedical industries.
5
Lin, Ching-Yuan, e 林清源. "Interaction between hydrophobically modified hydroxyethyl cellulose and nonionic surfactant in pyridine and water mixed solvent". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/58663985218382211338.
Abstract (sommario):
碩士國立成功大學
化學工程學系碩博士班
94
Hydrophobically modified polymer and surfactant system have been applied in industry many years. So, interaction between hydrophobically modified polymer and surfactant has attracted growing attention. In this experiment, we study the interaction between nonionic polymer (hydrophobically modified hydroxyethyl cellulose) and nonionic surfactant (Tergitol 15-S-5). The first step in my experiment is preparation of hydrophobically modified hydroxyethyl cellulose with lauroyl chloride. The second step in my experiment is to discuss interaction between hydrophobically modified hydroxyethyl cellulose and Tergitol 15-S-5 and to compare my results with literatures. We observe interaction with viscosity (η)、dissociation energy (Em)、hydrodynamic radius (RH).
Capitoli di libri sul tema "Cellulose-water interactions":
1
Miyamoto, Hitomi, Keita Sakakibara, Isao Wataoka, Yoshinobu Tsujii, Chihiro Yamane e Kanji Kajiwara. "Interaction of Water Molecules with Carboxyalkyl Cellulose". In Cellulose Science and Technology, 127–41. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2018. http://dx.doi.org/10.1002/9781119217619.ch6.
2
Costa, Carolina, Bruno Medronho, Björn Lindman, Håkan Edlund e Magnus Norgren. "Cellulose as a Natural Emulsifier: From Nanocelluloses to Macromolecules". In Cellulose [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.99139.
Abstract (sommario):
During the last decade, cellulose structural features have been revisited, with particular focus on its structural anisotropy (amphiphilicity) and interactions determining its recalcitrance to dissolution. Evidences for cellulose amphiphilicity are patent, for instance, in its capacity to adsorb at oil–water interfaces, thus being capable of stabilizing emulsions. This behavior is observable in all its forms, from cellulose nanoparticles to macromolecules. This chapter is divided into two main parts; first, the fundamentals of emulsion formation and stabilization will be introduced, particularly focusing on the role of natural emulsifiers. Secondly, the emerging role of cellulose as a natural emulsifier, where the ability of cellulose to form and stabilize emulsions is revisited, from cellulose nanoparticles (Pickering-like effect) to macromolecules (i.e., cellulose derivatives and native molecular cellulose).
Atti di convegni sul tema "Cellulose-water interactions":
1
Forsström, Jennie, Malin Eriksson e Lars Wågberg. "Molecular Interactions between Model Cellulose Surfaces and Ink – Influence of Surface Energy and Surface Structure on Adhesion". In Advances in Paper Science and Technology, a cura di S. J. I’Anson. Fundamental Research Committee (FRC), Manchester, 2005. http://dx.doi.org/10.15376/frc.2005.2.1379.
Abstract (sommario):
The influence of surface roughness and surface hydrophobicity on ink detachment of water-based flexographic ink was studied. It was shown that increased surface roughness and an increased surface hydrophobicity both had a negative effect on ink detachment. The increased surface roughness was suggested to increase the molecular contact area between ink and cellulose and thereby also to decrease ink detachment. Ink cellulose interaction was evaluated from interfacial energies and contact angle measurements. A new technique in which the adhesion properties between ink and the model cellulose surface were directly measured using a Micro Adhesion Measurement Apparatus (MAMA) was also used. Upon increasing the hydrophobicity of the model cellulose surface it was shown that the work of adhesion between ink and model cellulose surfaces decreased. At the same time the interfacial energy between cellulose and ink increased, as did the interfacial energy between cellulose and water resulting in a lower degree of ink detachment.
2
Neuman, Ronald D. "Surface Force Measurement in Papermaking Systems". In Products of Papermaking, a cura di C. F. Baker. Fundamental Research Committee (FRC), Manchester, 1993. http://dx.doi.org/10.15376/frc.1993.2.969.
Abstract (sommario):
The surface force technique, whereby the forces acting between two solid surfaces immersed in liquids or in adhesive contact are directly measured, represents a novel approach for both fundamental and application-oriented studies of the surface and colloid science of papermaking. The nature and measurement of surface forces are briefly discussed, and some results reported for mica surfaces are reviewed in order to illustrate the surface chemical information obtainable using a conventional Israelachvili-type surface force apparatus. In the case of cellulose surfaces immersed in water and aqueous electrolyte solutions the measured force vs. distance profile is characterized by three regimes. Significantly, conventional DLVO theory cannot explain the interaction forces measured between cellulose surfaces. Electrostatic double-layer forces, as anticipated, dominate the long-range interactions. However, as the two cellulose surfaces begin to “contact” each other, there is an interplay of steric and electrostatic forces due to dangling tails of cellulose chains. The observed force curves, therefore, are interpreted in terms of a new model — the “dangling tail” model — of the cellulose surface, namely, the water-swollen cellulose surface has long and weakly charged cellulose chains or “molecularfibrils” which extend into the aqueous solution. In addition, the application of the surface force technique to basic problems in the adsorption of polymers, both cationic polyelectrolytes and hemicelluloses, and the colloidal stability of kaolin suspensions is illustrated. The advantages of using a new type of surface force apparatus in future studies of surface and physicochemical phenomena relevant to paper manufacturing, coating and recycling are also briefly discussed.
3
Simion, Demetra, Carmen Gaidau, Jianzhong Ma e Zhang Wenbo. "New nanostructured composite obtained by innovative technologies". In The 8th International Conference on Advanced Materials and Systems. INCDTP - Leather and Footwear Research Institute (ICPI), Bucharest, Romania, 2020. http://dx.doi.org/10.24264/icams-2020.ii.22.
Abstract (sommario):
The paper is focused on obtaining a new nanostructured composite by innovative technologies based on: fibrillar cellulose/titanium dioxide/surfactants (bolaform- dodecandioyl-diglycine and surfactant classic-collagen hydrolysate)/ethanol/water, for improved surface properties. Innovation consists in technologies for obtaining new nanostructured composites, solubilisation/compatibilisation of their component substances for the conditioning of supports processed with the film created by evaporation of the emulsion nanocomposites. Fibrillar cellulose/titanium dioxide nanocomposites have been stabilized with bolaform surfactants in a 1:1 ratio of ethanol/water solvents in order to increase the uniformity of titanium dioxide shell nanocomposites. Nanostructured “cauliflower”-like composites developed as a result of biopolymer-surfactant interactions for fibrillar cellulose/titanium dioxide/bolaform couple in ethanol/water system are reported by SEM microscopy. The analysis by FTIR-ATR spectroscopy of bolaform, fibrillar cellulose and dynamic light scattering of 2 types of nanocomposites emulsions (with bolaform and classic surfactant emulsions) were reported. The new nanocomposites could provide the hybrid film with increased mechanical resistance to water and heat. Supports processing with the composite film improve wet/dry friction resistance, water resistance and tensile strength. Environmentally-friendly supports with smart multifunctional features are obtained for various applications.
4
Lindström, Tom. "Some Fundamental Chemical Aspects on Paper Forming". In Fundamentals of Papermaking, a cura di C. F. Baker e V. Punton. Fundamental Research Committee (FRC), Manchester, 1989. http://dx.doi.org/10.15376/frc.1989.1.311.
Abstract (sommario):
The fundamental physico-chemical aspects of retention chemistry are reviewed in the light of basic concepts in colloid chemistry. Special emphasis has been paid to the surface chemistry of cellulose and cellulosic materials, their origin of charge, dispersion force interactions as well as the implication of certain aspects of peculiar cellulosic surfaces, e.g. the influence of their porosity on polymer adsorption. Charge neutralization, patch flocculation, heterocoagulation, bridging and complex flocculation phenomena are discussed as well as polymer adsorption phenomena at the cellulose/water interface
5
Wang, Ying, e Youping Chen. "An Atomic Model of Cellulose Network in Wood Cell Wall". In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-67603.
Abstract (sommario):
Wood is composed of parallel columns of long hollow cells which are made up of layered composite of semi-crystalline cellulose fibrils embedded in an amorphous matrix of hemicellulose and lignin. The extraordinary mechanical performance of wood is believed to result from a molecular mechanism operated through hydrogen bond connection. However, the molecular interactions, the assembly method of cell-wall components, as well as the molecular mechanisms responsible for the deformation of wood, are not well understood yet. Progress in studying the superior mechanical properties of wood cell is severely hindered because of this fact. To overcome this barrier, the foremost step is to build up an atomic model of the native cellulose fibril network, which is the dominant polysaccharide in wood cell walls. Then, in this work, we proposed the atomic models to study the cellulose network which includes a single cellulose microfibril (MF), and a thin film which is built up by first secondary layers (S1) and second secondary layers (S2) composed of cellulose MF with periodic boundary conditions. Additionally, we investigated the length effect of the microfibril and compared the effect of explicit water solvent environment with the vacuum environment. Moreover, the spatial arrangements of these atomic models have been determined by molecular mechanics simulation (energy minimization). The hydrogen bond length of the crystalline part of the inner cellulose was evaluated using first principle calculation.
6
Paajanen, A., P. Penttilä, A. Zitting e J. A. Ketoja. "New Tools to Study Water Interactions of Microfibril Bundles: Molecular Modelling Based on Nanoscale Characterization". In Advances in Pulp and Paper Research. Pulp & Paper Fundamental Research Committee (FRC), Manchester, 2022. http://dx.doi.org/10.15376/frc.2022.1.483.
Abstract (sommario):
The picture of the smallest structural units of wood fibres, that is, cellulose microfibrils and their bundles, has become more accurate during the last couple of decades, when information gained from several experimental characterisations has been drawn together. This work has been supported by computational methods that allow one to test the behaviour of postulated structures on the nanometre scale, and thus help in interpreting the experimental data. Bound water is an essential component in these models, as it affects both the structural swelling and the mechanical properties of the fibre wall nanostructure. Moreover, mechanisms on this scale can be expected to drive similar properties of macroscopic fibres. We suggest that several large-scale problems in papermaking and converting could be approached with atomistic molecular dynamics simulations for varied chemical compositions and external conditions. We demonstrate this by first showing that simulated moisture diffusion rates agree with measured ones at room temperature, and then determine diffusion rates at elevated temperatures that lack reliable experimental data. These predictions provide key knowledge for further development of high-temperature drying and pressing processes. The results are important also when linking material performance at varied external conditions to the composition of the fibres.
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Jaya Prakash, Nirmala, Rejish Ramakrishnan, Senthil Vadivu Kulandhaivelu e Anantha Janani Vellaisamy Singaram. "Preparation and characterisation of carboxymethyl cellulose/carrageenan/jackfruit seed starch blend film for packaging applications". In 11th International Symposium on Graphic Engineering and Design. University of Novi Sad, Faculty of technical sciences, Department of graphic engineering and design, 2022. http://dx.doi.org/10.24867/grid-2022-p8.
Abstract (sommario):
In this study, carboxymethyl cellulose, carrageenan-based films and a blend film with 1:1 concentration were prepared using the solvent casting method and the influence of various concentrations of jackfruit seed starch (0, 0.5, 1.0, 1.5, and 2 g) on its functional properties were investigated. The effect of jackfruit seed starch on strength properties such as tensile strength and elongation, as well as waterrelated characteristics such as water contact angle, water vapour permeability, and moisture content, were evaluated and compared with the results of the control blend films. FT-IR, TGA, SEM, XRD were performed to identify the functional group and its potential interactions, thermal stability, surface morphology and crystallinity of prepared films. The results suggests that addition of jackfruit seed starch from 0 to 1.5 g enhanced the tensile strength from 26.62 MPa to 33.26 MPa, but thereafter the tensile strength drops to 32.58 MPa and the elongation decreases. When compared to the carboxymethyl cellulose carrageenan control film, some physical parameters of the film, such as water vapour permeability and moisture content, decreased while thickness and contact angle increased significantly. The results of scanning electron microscopy exhibited rough and heterogeneous morphology for films with more starch content, while the control films exhibited smooth and homogenous structure. The presence of starch increased the crystallinity of all films, which attributed to improved thermal and mechanical stability of the prepared films.
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Quigley, Connor, e Md Ahasan Habib. "3D Co-Printability of PCL and Hybrid Hydrogels". In ASME 2022 17th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/msec2022-85685.
Abstract (sommario):
Abstract 3D bioprinting has recently gained popularity due to its inherent capability of releasing cell-seeded and cell-laden biomaterials in a defined location to fabricate patient-specific scaffolds. Multi-nozzle extrusion-based 3D bio-printing allows the fabrication of various natural and synthetic biopolymers and the investigations of material to material and cell to material interactions, and eventually with a high percentage of cell viability and proliferation. Although natural hydrogels are demanding candidates for bio-printing because of their biocompatibility and high-water content, ensuring the scaffold’s fidelity with only natural hydrogel polymers is still challenging. Polycaprolactone (PCL) is a potential synthetic bioprinting material that can provide improved mechanical properties for fabricated scaffolds, especially bone and cartilage scaffolds. In this paper, application-oriented structural viability such as 3D printability, shape fidelity, and mechanical properties of the scaffolds fabricated by PCL and other natural hydrogel materials will be investigated. Scaffolds will be fabricated using various natural hybrid hydrogels such as Alginate-Carboxymethyl Cellulose; Alginate-Carboxymethyl Cellulose-TEMPO NFC, and PCL simultaneously using various infill densities, applied pressures, print speeds, and toolpath patterns. Shape fidelities of printed scaffolds will be analyzed. This research can help identify optimum natural-synthetic polymer combinations based on the materials interaction, external and internal geometries, and mechanical properties for large-scale multi-material bio fabrication.
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Niazi, Erfan, Mehrzad Shams, Arash Elahi e Goodarz Ahmadi. "Simulation of Gas – Non-Newtonian Liquid Flow in a Rectangular Bubble Column by Considering Bubbles Interactions". In ASME 2012 Fluids Engineering Division Summer Meeting collocated with the ASME 2012 Heat Transfer Summer Conference and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/fedsm2012-72361.
Abstract (sommario):
In this article a CFD model of a three-dimensional Eulerian-Lagrangian is developed for a gas - non-Newtonian liquid flow in a rectangular column. The model resolves the time-dependent, three-dimensional motion of gas bubbles in a liquid to simulate the trajectory of bubbles. Our model incorporates drag, gravity, buoyancy, lift, pressure gradient and virtual mass forces acting on a bubble rising in a liquid, and accounts for two-way momentum coupling between the phases. Population balance equation is solved to model bubble coalescence and break up. In bubble coalescence, Prince and Blanch model is used which can consider the effect of fluid rheology. Luo and Svendosen model was selected for bubble break up. The standard k-e turbulence model is selected for calculating turbulent flow properties. Power-law non-Newtonian liquid is selected for analysis of effect of different solutions of carboxy methyl cellulose in water. The effect of changing fluid to non-Newtonian is discussed in terms of velocity profile and gas hold up.
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JAYATILAKA,, GEHAN, MOHAMMAD MOEIN MOHAMMADI e MEHRAN TEHRANI. "INVESTIGATING STRESS TRANSFER AND FAILURE MECHANISMS IN GRAPHENE OXIDE-CELLULOSE NANOCRYSTALS FILMS". In Thirty-sixth Technical Conference. Destech Publications, Inc., 2021. http://dx.doi.org/10.12783/asc36/35862.
Abstract (sommario):
Graphene oxide (GO) films have great potential for aerospace, electronics, and renewable energy applications. GO sheets are low-cost and water-soluble and retain some of Graphene’s exceptional properties once reduced. GO or reduced GO (rGO) sheets within a film interact with each other via secondary bonds and cross-linkers. These interfacial interactions include non-covalent bonds such as hydrogen bonding, ionic bonding, and π-π stacking. Stress transfer and failure mechanisms in GO and rGO films, specifically how linkers affect them, are not well understood. The present study investigates the influence of inter-particle interactions and film structures, focusing on hydrogen bonds introduced via cellulose nanocrystals (CNC), on failure and stress-transfer of the GO and rGO films. To this end, GO films with CNC crosslinkers were made, followed by a chemical reduction. The few-micron thick films were characterized using tensile testing. All tested films exhibited a brittle failure and achieved tensile strengths and modulus in the ~40-85 MPa and ~3.5-9 GPa ranges, respectively. To reveal stress transfer mechanisms in each sample, tensile in-situ Raman spectroscopy testing was carried out. By monitoring the changes in bandwidth and position of Raman bands while stretching the film, useful information such as sheet slippage and cross-linker interactions were gathered. The addition of CNC enhanced modulus but degraded strength for both GO and rGO films. Interestingly, the Raman G-peak shift at failure, indicative of stress transfer to individual GO/rGO particles, is commensurate with the films’ strengths. Correlating these results with the structure and composition of different films reveals new understanding of stress transfer between GO/rGO particles, paving the way for the scalable manufacturing of strong and stiff GO-based films.