Structural inhomogeneity in cotton cellulose upon its interaction with water

Yakunin, N. A.; Zavadskii, A. E.; Yakunina, E. N.; Moryganov, A. P.

doi:10.1134/s0965545x10020045

Cited by 5 publications

(13 citation statements)

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“…The kinetic curves of moisture absorption by cotton fibres in the range of p/p 0 from 0 to 0.1 does not concern the "Fickian" type but the pseudonormal type which characterizes sorption processes with a diffusion coefficient that diminishes in time. The ratio between the crystalline and amorphous regions changes to the greatest degree precisely in this segment of the isotherm in the cotton cellulose sample investigated [4], and this correspondingly decreases its diffusion permeability and transfer parameters.. Similar characteristics were also observed for the hydrated cellulose-water system in [11].…”

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confidence: 74%

“…We investigated scoured and bleached cotton fabric; samples of this fabric had previously been used in x-ray diffraction studies [4,5]. This make it possible to use the established parameters of the supramolecular structure in calculations of the sorption characteristics.…”

Section: And a P Moryganovmentioning

confidence: 99%

“…For the sample of cotton cellulose investigated, the content of amorphous regions in limiting wetting decreases by 9% [4]. In the swollen state of the fibres, the number of amorphous regions is minimum (22%) and the content of crystallites and degree of completion of their surface layer are maximum.…”

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“…Calculations of the different sorption characteristics using these isotherms usually assume constancy of the content of sorbing regions in the cellulose during water absorption. Moreover, the effect of a change in the supramolecular structure of different cellulosic materials during wetting has been reliably established with different methods of investigation (x-ray structural analysis, IR spectroscopy, dilatometry) [1][2][3][4]. The important effect of the moisture content on the ratio of amorphous and crystalline phases in cellulose should undoubtedly be reflected in the equilibrium and kinetic characteristics of its reaction with water.…”

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“…For quantitatively determining the sections accessible to water, calculating the degree of crystallinity of the cellulose alone is insufficient, since water molecules can also enter defective regions in the crystallites formed during drying. It was proposed in [4] that the change in another structural parameter -the cross section of the crystallites (L 002 ) -be used for this type of evaluation. In contrast to the integral crystal scattering intensity, this index is not only sensitive to a change in the content of crystalline formations in cellulose but is also a function of their defectiveness.…”

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Structural dependence of the features of the sorption behavior of cotton cellulose in reacting with water

2008

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and A. P. MoryganovIt was shown that the increase in the accessibility of cotton cellulose to water in drying is due to perturbations of the long-range order in the surface layer of crystallites. The necessity of quantitatively considering the structural changes in calculations of sorption values was demonstrated. The correlation of some features of the sorption behavior of cellulose materials in processes that include frequently repeated wetting and drying operations with the probable character of formation of accessible sections in the surface layer of the crystalline phase was noted.Studying the cellulose-water system has sustained continuous interest for many years. Information on this is important not only because of its theoretical value, but it also has direct practical significance, since cellulose materials are in close contact with aqueous and water-vapor media, primarily with atmospheric moisture, in all stages of production, processing, and use. Valuable information on the reaction of the components of the system is obtained in analyzing the water-vapor sorption isotherms for cellulosic materials [1]. Calculations of the different sorption characteristics using these isotherms usually assume constancy of the content of sorbing regions in the cellulose during water absorption. Moreover, the effect of a change in the supramolecular structure of different cellulosic materials during wetting has been reliably established with different methods of investigation (x-ray structural analysis, IR spectroscopy, dilatometry) [1][2][3][4]. The important effect of the moisture content on the ratio of amorphous and crystalline phases in cellulose should undoubtedly be reflected in the equilibrium and kinetic characteristics of its reaction with water. In this research, we established the cause of the dependence of these features of the sorption behavior of cotton cellulose which are related to the structural rearrangements that take place when the moisture content changes.The sorption measurements were performed by vacuum gravimetry using a quartz spring. We investigated scoured and bleached cotton fabric; samples of this fabric had previously been used in x-ray diffraction studies [4,5]. This make it possible to use the established parameters of the supramolecular structure in calculations of the sorption characteristics.The reaction of oxidation of cellulose with atmospheric oxygen at 150°C was also used to study the character of the structural changes that take place when cotton cellulose is wet and dried. The degree of thermooxidative degradation of the samples of cotton fabric was evaluated with the yellowness parameter, defined as coordinate b of the color field of the CIE Lab colorimetric system. It was calculated with the spectral reflection curve of thermooxidized samples taken on a reflection spectrophotometer in the 400-700 nm wavelength range.The water-vapor sorption isotherm for the investigated fabric sample at 20°C is shown in Fig. 1. In determining such a sorption value as the average hydration numbe...

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confidence: 74%

Section: And a P Moryganovmentioning

confidence: 99%

mentioning

confidence: 91%

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confidence: 99%

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confidence: 99%

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Structural dependence of the features of the sorption behavior of cotton cellulose in reacting with water

2008

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Current achievements in the mechanically pretreated conversion of plant biomass

Bychkov

Podgorbunskikh

Bychkova

et al. 2019

Biotech & Bioengineering

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At present, “mechanochemistry” is synonymous with “grinding,” according to the views of a significant number of scientists and technologists. Often, one comes across the opinion that “the less the particle size, the better.” The cases of considering chemical reactions occurring during pretreatment, as well as considering changes in the ultrastructure of cell walls are extremely rare. Also, the wrong choice of the type of mechanical impact and the equipment used in most cases leads to excessive consumption of electrical energy and reduce economic efficiency. The review presents the currently available published data on mechanically activated processes for the pretreatment of plant materials and shows that when using mechanical treatment, it is necessary to look more closely at the phenomena occurring, rather than reducing everything to the production of fine and ultrafine powders. As a result of mechanical action, active surface radicals can form, hydrothermal chemical processes can occur, and mechanocomposites can form. The role of interphase processes, changes in surface chemistry, related dimensional effects, and the disordering of the crystal structure and amorphization should be taken into account. In addition, the physicochemical insights in mechanical pretreatment make it possible to more efficiently use the energy delivered to the material, and, consequently, increase the economic efficiency of the activation process.

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Effect of the drying temperature on the structural nonequilibrium of cotton cellulose

Yakunin

Barannikov

2011

Fibre Chem

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A method for quantitatively evaluating the least mobile fraction of moisture sorbed by cotton fibres with the kinetic curves of the change in the desorption process parameters is proposed. The hypothesis that the separated form of the most slowly removed water is localized in sections of the surface layer of crystallites decrystallized on drying is substantiated. Based on an analysis of the temperature curve of the amount of difficult-to-remove moisture, the temperature of the relaxation transition (120-125°C) related to the cooperative mobility of the kinetic elements in the amorphous regions of cellulose was determined.The urgency of studying the reaction of cellulose with water is due to the wide practical importance of cellulose materials and the dependence of their properties on the moisture content. The causes of the important effect of the drying conditions on the reactivity and processability of cellulose are still insufficiently clear. In addition to the "keratinization" effect [1], the changes in the supramolecular structure of cellulose materials when their moisture content is varied can also play a certain role in this phenomenon [2,3]. Together with X-ray structural analysis (XPA), important information on the change in the structural state of dried polymers can also be obtained with sorption measurements [4]. We investigated the kinetic features of the final stage of desorption of water from cotton cellulose in the 20-100°C temperature region and established their correlation with the structural rearrangements in the polymer.The sorption measurements were conducted on a TG 209 F1 thermal microbalance from Netzsch. Moistened samples of cotton fibres were placed in a thin-walled platinum crucible with a perforated lid which ensured removal of desorbed water vapors. At the beginning of the experiment, the measurement cell was heated to the given temperature at the rate of 15°/min and then operation of the furnace in the isothermal mode was ensured. The error of measuring the sample weight and temperature was 5 . 10 -3 mg and 0.1°, respectively. The experimental data were processed with software for thermal analysis (Proteus Software).The curves in Fig. 1 illustrate the character of the change in the process parameters of desorption of water from cotton fibres at 60°C. Due to the cooling effect of evaporation of the moisture, the temperature of the moist sample (curve 7) during drying was always lower than the temperature of the heat carrier (argon) which is only attained at the end of drying. Due to this interdependence of mass and heat transfer processes, the temperature curves can more finely reflect all of the features of binding of moisture with the fibre in comparison to the integral sample weight loss curve (TG curve). For this reason, they are frequently used together with the drying rate curves (DTG) to determine the position of the critical points corresponding to the boundaries of the periods of removal of different forms of sorbed water from the investigated polymer materials [5].According t...

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Structural inhomogeneity in cotton cellulose upon its interaction with water

Cited by 5 publications

References 1 publication

Structural dependence of the features of the sorption behavior of cotton cellulose in reacting with water

Structural dependence of the features of the sorption behavior of cotton cellulose in reacting with water

Current achievements in the mechanically pretreated conversion of plant biomass

Effect of the drying temperature on the structural nonequilibrium of cotton cellulose

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