No abstract
The effect of different regimes for each stage of fabrication of cotton cellulose on its supermolecular structure was evaluated by electron microscopic methods. It was shown that rigorous conditions of fabrication of cotton cellulose cause destruction and loosening of the surface and inner layers of the fibre. This indicates an increase in the reactivity of the cellulose and is promising for processing # into viscose fibres.As a function of the method of separation of cellulose, its structure has special features which are manifested by different reactivity, kinetics of mechanical transformations of the cellulose, and properties of the final product [1][2][3]. There are data which suggest the dependence of the reactivity of wood cellulose on the morphological structure and degree of its breakdown [4][5][6].Cotton cellulose has lower reactivity than the wood cellulose used for fabrication of viscose fibres. For this reason, it is important to select the conditions of separation of cellulose which will maximally increase its capacity for esterification and decrease the viscosity while preserving a high concentration of o~-cellulose.Microfibrils of the primary wall of fibres based on cotton cellulose are known to form an unusual loosely packed network which virtually does not prevent penetration of reagents inside the fibre [7]. The following first layer of the secondary wall has a dense structure with rigorously parallel mutual orientation of packed microfibrils, in turn densely twisted around the axis of the fibre. This layer swells poorly, and the size changes little in delignification. We can hypothesize that the reactivity of the cellulose in this layer is lower than for the cellulose in the basic secondary wall.The effect of the basic stages of processing (preliminary cleaning of linter and cellulose, cooking, bleaching, etc.) in fabrication of cotton cellulose suitable for viscose formation on the supermolecular structure of the surface and inner layers of the fibre was investigated in the present study. Type III cotton linter with an 8% degree of contamination was the starting raw material. The cellulose was obtained by alkaline cooking with subsequent bleaching.The structure of the cellulose was investigated with a PEM-100 electron microscope using a Pt/C replica and ultrasound dispersion methods [8]. The possibility of maximum cleaning of extraneous contaminants from the cotton linter was determined first, since there are high requirements concerning ripeness, degree of contamination, and length for linter intended for chemical processing.Using multistage Centricleaner cleaning (CCC) of linter as the most efficient, it was possible to decrease the degree of contamination from 8 to 2.8%. Maximum elimination of waste contaminants was obtained after 4 cleaning stages.The purpose of cooking is the further removal of lignin from the linter and other substances associated with cellulose, as well as to decrease the viscosity. Cellulose suitable for viscose formation should have a viscosity within the limits of 17...
No abstract
The structure of a gel based on microcrvstalline celhdose (MCC) and the antiprotozoic preparation azidin is studied. Intense ultrasonic irradiation produces a physicochemical reaction in the MCC:azidin system that lengthens the effective I(fetime of the drug.Microcrystalline cellulose (MCC) is promising as a polymeric carrier lbr drugs [1, 2]. This unique material has specific properties owing to its high degree of crystallinity, irregular particle shape, hydrophilic nature, etc.The goal of the present work is to investigate the possibility of reacting the antiprotozic drug azidin [4,4'-(diazoamino)dibenzamidine diaceturate] with the MCC polymeric carrier to produce a gel and to study the MCC properties.We used x-ray diffraction, IR spectroscopy, and dialysis to study the hydrogel obtained by mechanical mixing of MCC, azidin, and water in a given proportion with subsequent irradiation by ultrasound.The x-ray studies of the starting materials showed that both components are distinctly crystalline materials. Four ec~uatorial reflections are clearly observed in the diffraction pattern of MCC (Fig. 1. curve 1). These are characteristic of the cellulose-1 structural modification with 20 = 14.7, 16.5, 22.4, and 34.5 ~ and correspond to reflections from the crystallographic planes (101), (101), (002), and (040). The diffraction pattern of azidin (Fig. 2) contains several reflections (atx}ut 15) of moderate strength that are rather sharp and narrow. This is characteristic of a low-molecular-weight substance. The strongest reflections occur at 20 = 14.0, 26.6. 20.1, 15.7, and 28.4 '~.
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