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Ochilov Tulqin Ashurovich, Candidate of Technical Sciences, Associate Professor, Tashpulatov Salih Shukurovich, Doctor of Technical Sciences, Professor, Gadoev Nuriddin Ergashevich, Senior Lecturer, Muhtarov Jurabek Reyimbergenovich, Doctor PhD., Senior Lecturer, Laysheva Elmira Talgatovna, Senior Lecturer,
Tashkent Institute of Textile and Light Industry E-mail: [email protected]
EFFECT OF STORAGE AND DRYING ON COTTON FIBER SUPRAMOLECULAR STRUCTURES
Abstract. One of the direct methods for studying the supramolecular structure of polymeric materials, including cotton fibers, is the electron microscopy method. This section describes the results of studying the supramolecular structure of Yulduz variety fibers subjected to different drying temperatures. For the study, raw cotton was taken from three sections of the riot: upper, middle and lower parts. To study the change in the supramolecular structure during these transformations, two independent methods ofelectron microscopy were used. These research methods allow you to investigate changes occurring on the surface (replica method) and the secondary wall (hydrolysis method) of fibers.
Keywords. Supramolecular structure, polymeric materials, cotton fibers, microscopy, drying temperature.
Currently, ginneries and procurement centers a key prob- It is known that on cotton seeding with excessive plant
lem is the drying of raw cotton and its storage in the riots. density it is created a microclimate under which the humidity
Analysis of the published work has shown that by drying the of raw cotton becomes higher than in the crops with highest
raw cotton at high temperatures, as well as storage in the ri- density and better ventilated. Procurers of raw cotton take all
ots there is deterioration of important characteristics such as the necessary measures to organize seed collection and ensure
breaking load, tortuosity, length and degree of fiber defects, the preservation of their quality during processing and storage.
and for a variety of breeding cotton varieties and variations Mixed batch of a total fee of quite mature cotton with immature,
are different [1]. The foregoing requires further study fine mi- having a high humidity leads to self-warming and damage to
crostructure because strength and technological properties of seeds, as well as many of the technological quality deteriorates.
cotton fibers, as well as other polymeric materials, are inextri- Storage conditions (in the riots, warehouses, etc.) stimulate the
cably linked with changes in their supramolecular structure. rapid growth of bacteria and fungi on the raw cotton, which
One of the direct methods of investigation of the supramo- absorb oxygen and release carbon dioxide and heat. Therefore,
lecular structure of polymer materials, including cotton fibers, the quality of seeds and fibers deteriorates. is the method of electron microscopy. This section describes On cotton purchasing centers and processing plants it is
the results of studies of the supramolecular structure of fibers kept for about 80% of procuring raw cotton. Drying condi-
of "Yulduz" grade subjected to different drying temperatures. tions to standard moisture, as well as proper storage of raw
To study the raw cotton were taken from three areas of rebel- cotton are key problem of cotton growing and the subject of
lion: the upper, middle and lower parts. To study changes in the many studies [2; 3].
supramolecular structure used two independent methods of The beginning of our research is devoted to the study of
electron microscopy studies with data transformations. These the topography of the surface of the raw cotton fibers, taken
techniques allow the study to explore the changes that occur on from the upper, middle and lower parts of the rebellion. Shelf
the surface (replica method) and a secondary wall (hydrolysis life in the riots was three months. First of all, it should be noted
method) fibers. Detailed procedure for preparing preparations that the topography of the surface of mature cotton fibers har-
described in the methodological part of the work. vested from the field, depending on the variety of grades and
forms of cotton (wild, semi-wild, cultural form) is characterized by multiple folds and protrusions disposed on the surface at an acute angle relative to the fiber axis. In this case, there is also the nature of this picture. However, despite the fact that the study was one fiber grade "Yulduz", depending on the storage conditions in coils, the surfaces are slightly different fibers. Thus, the surface of the fibers subjected to the investigation of the upper portion characterized riot more homogeneous structure. Folds and protrusions are arranged at an acute angle to the fiber axis and the distance between the folds is small. The folds are distributed fairly parallel to each other and to the fiber axis. A somewhat different pattern is found when considering the surface of the fibers taken from the study for the middle and lower parts of the uprising during storage. Despite the fact that both samples belong to class "Yulduz", their surface varies dramatically: conserved folding, but the distance between the pleats is much larger than that of a sample taken from the top of riot that is especially evident in the fibers of the bottom riot at storage. The surface of the fiber has a completely different look: the surface is not uniform, there are some folds between globular and shapeless structural elements. Observed effects appear to contribute to conditions of storage of raw cotton in the bottom of the rebellion. As we noted earlier, the analysis of the technological qualities of fibers from different parts of the riot, in samples taken from the bottom of many technological qualities deteriorate sharply. Between the surface uniformity and technological qualities of fibers found in the relationship and A. Muratova and K. F. Gesos. According to the authors, more uniform surface of the fibers, the higher the quality of the fibers. In this case, more uniform surface of the fiber is observed in samples taken from the top, middle, and lower than. Therefore, the deterioration of the technological qualities of the fibers from the top to the bottom of the revolt is also confirmed by the changes occurring in the topography of the surface of the fibers studied. Similar changes were observed in the study of secondary fiber walls by acid hydrolysis.
Using the method of hydrolysis with diluted acid and subsequent dispersion ultrasonically different cotton varieties can detect the presence and quality of aggregates of elementary fibrils micro fibrils fibers. Such micro fibrils units can be regarded as the real morphological units of cotton fibers, interconnected elementary fibrils or bundles of macromolecules with a low order. Hydrolyzability drug dependence on its structure is widely used for fiber quality characteristics determination of crystalline and amorphous materials.
In electronic micrographs clearly revealed the mass of thin and fairly uniform micro fibrils and their aggregates, or so-called crystallites. Their width varies from 100 to 150 A0, depending on the storage space in a riot fiber. It was found that all crystallites aggregated and aggregation is most clearly
manifested in the study of drugs fibers taken from the upper and middle parts of the rebellion. When studying the fibers obtained from the bottom riot (relatively lower strength) together with asymmetric particles observed shapeless particles. The foregoing suggests that these samples are subjected to greater and faster hydrolysis process. From this we can conclude that hydrolyzability associated with fiber strength.
Thus, one can conclude that storage of raw cotton in coils substantially influences not only the processing characteristics, but also on the structure of the fiber, both on the surface and on a secondary wall.
Equally important is the drying of the fibers prior to storage and processing. The process of drying the raw cotton in the first period is done in general by removing the free water from the fiber surface and peeled seeds. When drying occurs in dryers rapid heating and dehydration, and the heating process is much more intense than dehydration. The mechanism of drying wet materials is determined primarily in the drying regime and forms of moisture due to the material, as a basis for the classification which adopted P. A. Rebindera scheme. According to the scheme distinguish: a bond (in the exact proportions); Physicochemical bond (in different, not strictly defined ratios), which is divided into an osmotic and adsorption.
It is known that the raw cotton is a thermo sensitive material and intensifying its drying process at high temperatures, usually accompanied by a change of mechanical properties of fibers and presentation. The scientific literature contains information on studies and the properties of the cotton fiber structure at drying. It should be noted that the difference between types of communication cotton components with moisture leads to a difference of their hygroscopic properties. According to the authors, the sorption capacity of cotton fiber depends on the presence of hydroxyl groups in the cellulose. The energy of hydrogen bonds between water molecules arising and the hydroxyl groups of cellulose is insufficient to destroy the crystal lattice. Therefore, the water sorption occurs only in amorphous regions and crystalline regions are not affected. There are conflicting views on the impact ofwax surface layer on their sorption properties. So, Korolev V. K. and Schekoldin M. M. believe that the existence wax layer makes the liquid pervious fiber surface. With regard.to sorption capacity peel and seed kernels, most researchers believe that skin it is higher than that of the seed core.
Thus, raw cotton is a material having hygroscopicity as sorption properties of raw cotton are different components, the uneven moisture removal occurs between the components. In particular it is shown that the fiber drying process is faster than that of seeds. Despite the importance of cotton for the drying process, storage and processing, some aspects
of the problem remains poorly understood. Especially, it concerns the changes of the supramolecular structure of cotton fibers, originating in the process of drying the temperature of raw cotton in the riots.
We have investigated in detail the changes of the supra-molecular structure of the variety of cotton fibers "Yulduz" taken from the upper, middle and lower parts of the riot, and dried at 160 and 200 °C.
First of all, look at the at drying the fibers taken from the top of the riot trial.
The topography of the surface of the fibers dried at 160 °C a little differ from sources not dried, but by the nature of the arrangement of the elements on the surface is almost identical to other mature form fibers G. Hirsutum varieties. A little different picture can be observed when drying fibers at 200 °C. Unlike the original, and dried at 160 °C, the topography of the surface is characterized by the numerous folds of the distance between them varies between 0.2-1.3 ^m. Along with a smooth surface structure observed gross structural alterations, especially, dramatically changing the angle between the folds and the fiber axis.
The reason for such a violation of the structural heterogeneity of the surface is the effect of high temperature. From the literature it is known that even a short fiber drying (7-30 s) at 150-200 °C leads to structural changes in varying degrees, which confirmed a significant change in density of the cellulose fibers. Another study indicated that the intermittent heating of cellulose to 120-170 °C is no significant structural change, while heating to a temperature above 160-180 °C leads to rapid degradation of the cellulose molecules. The authors argue that this is due to thermal decomposition of the cellulose molecules. In this case also found that the drying temperature compared with the 160-200 °C substantial surface topography does not change.
When considering the hydrolyzed preparations fibers taken from the top of the storage riot also it has been found that the drying temperature is less 1600 s affect pulp fibers crystallites than 200 °C. The crystallites have the same size and shape of the aggregation, and that the original sample. In contrast, the samples dried at 200 °C along with asymmetric particles observed shapeless and globular particles.
The degree of aggregation in this case is much smaller than the previous sample. Such a sharp change of shapes and sizes at drying facilitates effect of elevated temperature.
And substantial changes in the surface of the crystallites exposed fibers, dried at 200 °C. The changes, apparently, is promoted by two factors: if the first temperature; the second is the changes taking place in different parts of the riots themselves, we have described above. However, studies have shown that between the picture surface topography and the initial
fiber crystallites (the middle part of the sample) and dried at 1600 s (especially at 200 °C), there is a sharp contrast. In particular, it is well reflected in the size, shape and aggregation of hydrolyzed products.
The long sample very well distinguished small globular education and lesotsiatsity (by the way, they are also dense patches of micro fibrils). Compared with previous samples of their number is much higher than, and in size - much inferior. From the literature it is also known correlation between the crystallite size and strength characteristics of cotton fibers. Based on these considerations, this sample has less strength compared to the previous and original samples. That is, less strong fibers easily subjected to acid hydrolysis in comparison with strong fibers. Reductions of strength on the one hand contribute to the action of thermopiles fungi, which are in the middle riot storage, on the other hand increased temperature.
In the analysis of fiber samples taken from the bottom of the storage riot, very well observed the merger of the above factors impact on the variability of the supramolecular structure. It should be noted that the changes taking place on drying (160 and 200 °C) sharply reflected on the surface topography and the nature of the allocation of the crystallites, which is especially evident on the surface of the fiber. Apparently, to the formation it is mainly contributed storage conditions (place), as these conditions are very well for microorganisms developing, destroying the fiber structure and properties. Further drying at high temperature also affects to the mentioned properties, but less than microorganisms which are present in the layer riot. It should be noted that the globular particles observed in the sample were not detected in samples, samples which were taken from the top and middle portions riot. Therefore, the formation of globular particles, particularly at the surface, the influence of microorganisms promoted more than the drying effect.
It is undergoing profound changes and the secondary wall fibers that where the crystallites size and extent of aggregation differ sharply (decrease) from all investigated cotton fibers.
In addition to the asymmetric particles it is observed globular formation, the size of which varies from 10-200 A°, ie this sample is very easy exposed to dilute acid. Consequently, the strength of this sample is also slightly lower than the initial and dried at 160 °C.
Thus, we can conclude that the high temperature drying, regardless of the position in space for storing fiber coils in cotton is a significant structural change. Moreover, the higher the temperature, the greater the change. In particular it is shown that the temperature increase of the drying agent leads to increased defect microstructure on the surface, and the secondary fiber wall. It has been shown that by dry-
ing the raw cotton at temperatures above 1600 s decreases the angle between the fiber axis and the folds are formed globular particles of various sizes, as well as a sharp decrease in the crystallite sizes of micro fibrils.
It was found that the observed structural changes occurring at different storage conditions in the riots, as well as high-temperature drying of raw cotton are mandatory and must be reflected in their physical and mechanical characteristics. Conclusions
1. Experimental study of the kinetics of destruction of fibers technological transition from rebellion to drying processes, cleaning, ginning, pressing post ginning cleaning to show:
a) the nature of the destruction of the fiber has a dual characteristic fracture occurs at a total loading of the fibers when stored in the riots, and the points of contact with the working bodies of machines;
b) the kinetics of the process is subject to the law of fatigue failure when gradually around the cracks, defects and stress raisers occur macroscopic fracture, mechanical and biomechanical nature;
c) the degree of destruction of the fibers depends on technological effects on cotton, their size and number; Therefore, the main share of growth damages the fibers accounted for ginning, ginning and post ginning cleaning; and when ginning is developing the greatest load, but the multiplicity of its small, but clean load below, but repeated many times and it is in good agreement with the theoretical model;
d) the degree of damage depends on the raw state, its moisture content, the terms and conditions of its storage and drying conditions that directly affect the characteristics of cotton material science - without destroying the ability to withstand the required number of cycles of loading technology.
References:
1. Hadzhinova M. A. Investigation of the Properties and cotton fiber structure during drying.- Tashkent: Fan 1966.
2. O'zDst 633-95. Cotton fiber. Methods of determining the length.
3. Muratov A., Gesos K. F., Sharapova R. Z. Comparative electron microscopic study of the supramolecular structure of some cotton fibers varieties // Cytology and Genetics 1983.- No. 5.- P. 18-23.
