Fine Chemical Technologies (E-Journal) / Тонкие химические технологии
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ВЛИЯНИЕ ОСТАТОЧНЫХ КОЛИЧЕСТВ ЭМУЛЬГАТОРА В БУТАДИЕН-НИТРИЛЬНЫХ КАУЧУКАХ НА СВОЙСТВА ЭЛАСТОМЕРНЫХ МАТЕРИАЛОВ
Get PDFThe paper considers the properties of a number of commercially available Russian nitrilebutadiene rubbers (NBR) containing approximately the equal acrylonitrile amount (from 26 to 33%) in the macromolecule, but differing in the method of synthesis and isolation. The assessment ofthe influence of residual emulsifier content and also such surfactants as rosin and stearic acid introduced as technological additives on some NBR properties was performed. The technological properties of model compounds based on these NBR, in particular, Mooney viscosity, minimal and maximal torques during curing, and scorching time were determined. It was shown that both residual emulsifier amounts and introduced surfactants decrease the viscosity of the compounds and increase the curing time. It was noted that rosin acts in a different manner in comparison with stearic acid. In particular, stearic acid acting as an interstructural plasticizer affects viscosity decrease in a greater degree. The mechanical performance of vulcanizatesbased on rubber compounds considered in the paper was also determined. It was shown that the surfactants effect on the mechanical properties is negligible and is within the measurement accuracy. Nevertheless, the NBRs obtained with various emulsifiers differ essentially and can’t be replaceable without revising both the rubber compounds recipes and processing parameters. The vulcanizates resistance to some organic solvents and water was also studied. It was shown that the acrylonitrile content in the rubber macromolecule is the key factor affecting the resistance to non-polar solvents. At the same time it was found that the vulcanizates containing residual emulsifier amounts tend to the swelling index increase. In general, the surfactants effect on the swelling index is ambiguous, and it requires deeper research
АНАЛИЗ СТЕХИОМЕТРИЧЕСКИХ ЗАКОНОМЕРНОСТЕЙ, ОГРАНИЧИВАЮЩИХ СТАЦИОНАРНЫЕ СОСТОЯНИЯ РЕАКЦИОННО-РЕКТИФИКАЦИОННЫХ ПРОЦЕССОВ
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РАСТРЕСКИВАНИЕ ЛИСТОВОГО МОНОЛИТНОГО ПОЛИКАРБОНАТА В НАПРЯЖЕННОМ СОСТОЯНИИ
Get PDFThe accelerated stress cracking of monolithic polycarbonate sheets was investigated. Cracking of polycarbonate organic glasses during operation leading to a drop in impact strength and transparency is their main disadvantage. The main role in the acceleration of the process of cracking is played by the stresses that arise when they are formed and mounted. The aim of this work was to investigate the dependence of the cracking start time on the stress applied to the sheet monolithic polycarbonate. This makes it possible to predict the lifetime of polycarbonate products. The experiments were carried out in air and in contact with an adsorption-active medium (a mixture of toluene and n-propanol). The stresses applied to the samples varied in the range from 25 to 55 MPa. It is shown that the dependence of the cracking start time of a polycarbonate on the applied stress can be described by Zhurkov exponential equation. The coefficients of this equation for the processes of cracking in air and in contact with the adsorption-active liquid are calculated. It is established that the activation energy of the polycarbonate cracking process (129.5 kJ/mol) is close in magnitude to the activation energy of the thermal-oxidative destruction (about 145-155 kJ/mol). In contact with the adsorption-active mixture of toluene (25% mass.) and n-propanol, the activation energy of the cracking is reduced to 98.5 kJ/mol. At the same time, the structural coefficient in the Zhurkov equation ("activation volume") increases from 1.45 to 2.45 nm3. The analysis of the obtained results made it possible to predict the lifetime of monolithic polycarbonate sheets and products made of them at various operating stresse
ПРОВОДИМОСТЬ НА ПЕРЕМЕННОМ ТОКЕ ТОНКИХ ПЛЕНОК ПОЛИХЛОРОПРЕНА, СФОРМИРОВАННЫХ В ЭЛЕКТРИЧЕСКОМ ПОЛЕ
Get PDFThe temperature dependences of conductivity at alternating current (a frequency of 1 kHz) were studied for thin polychloroprene films formed from a solution on metal electrodes having different polarities: anode, cathode and zero potential. It was found that the nature and form of the temperature dependence of the conductivity of the investigated polymer film depends on the method of sample formation. Temperature regions of maximum conductivity were detected. The realization of the heating cycle followed by the film cooling in a limited region between the electrodes under the action of an alternating electric field leads to an increase in the specific conductivity and a shift of the extreme values to the region of lower temperatures. This effect is manifested to the greatest extent for films formed at the cathode. The process of heating and subsequent cooling is of hysteresis nature both for permittivity and for the dielectric loss tangent. The dependence of dielectric loss tangent on permittivity in a rather wide temperature range is inversely proportional. During the analysis of temperature dependences the mechanism of conductivity was studied for polychloroprene thin films at direct and alternating current. The determined activation energies of the polymeric system conductivity change enable concluding that the mechanisms of electric conductivity at direct and alternating current are of similar nature. The extreme values of permittivity may be due to structural alterations in the process of heating. This is confirmed by the data on the temperature dependence of dielectric loss tangent. In order to explain conductivity at direct current a model of dipole traps is offered
О ВЗАИМОСВЯЗИ РАЗНОСТЕЙ РАЗЛИЧНЫХ СВОЙСТВ ФРЕОНОВ НА ЛИНИЯХ НАСЫЩЕНИЯ ПРИ ФАЗОВОМ ПЕРЕХОДЕ ЖИДКОСТЬ-ПАР
Get PDFИСПОЛЬЗОВАНИЕ АЭРОБНЫХ СИНТРОФНЫХ АССОЦИАЦИЙ МИКРООРГАНИЗМОВ ДЛЯ ДЕЗАКТИВАЦИИ ЖИДКИХ РАДИОАКТИВНЫХ ОТХОДОВ
Get PDFThe primary objective of the study was to test the possibility of cesium-137 transmutation into a stable barium isotope in contact with an aerobic syntrophic association (SA - a conglomerate of several thousands of different species of bacteria, protozoa and fungi living in symbiosis with each other) together with a set of macro- and microelements. The study was performed sequentially on two different SA. In the course of the work, the transmutation of cesium-137 into stable barium with the use of SA was not experimentally revealed, but the phenomenon of cesium-137 biosorption by both SA was detected to different degrees. In the course of the experiment the possibility of cesium-137 sorption by SA from the solution in the pH range of 7.7 - 8.6 was shown. In the process of the work, the time dependence of cesium-137 distribution in the liquid phase and the phase of SA was determined. The time dependence of the sorption capacity of the syntrophic association was revealed. With further continuation of the study, it is possible to obtain a mixture of SA capable of selectively extracting and concentrating prescribed radionuclides from the liquid phase.The result of this work may be the development of a technology for processing and conditioning low-level liquid radioactive waste (RW) by transferring the bulk of radioisotopes in the phase of SA (the so-called "nanosorbent of biological origin"), with multiple volume reduction.The cost of such a technology compared to existing technologies using synthetic sorbents should be several times less due to the cheapness of the SA and the reagents required for it. Besides, the new technology is more environmentally friendly. The process of biotechnologyoxidation of sulfide ores and concentrates based on the activity of chemolitotrophic bacteria that translate insoluble metal sulfides into soluble metal sulfates can serve as analogue for hardware design of RW purification technology using nanosorbent of biological origin
АНАЛИТИЧЕСКИЕ РЕШЕНИЯ ГИПЕРБОЛИЧЕСКИХ МОДЕЛЕЙ НЕСТАЦИОНАРНОЙ ТЕПЛОПРОВОДНОСТИ
Get PDFPractically important problems of non-stationary heat conduction for hyperbolic transport models are considered. An analytical approach based on contour integration of operational solutions of hyperbolic models is developed. This leads to new integral relationships convenient for numerical experiments. The equivalence of new functional constructions and known analytical solutions of this class of problems is shown. On the basis of the obtained relations, the wave character of the nonstationary thermal conductivity is described taking into account the finite velocity of heat propagation. The jumps at the front of the heat wave are calculated. The proposed approach gives effective results when studying the thermal reaction to heating or cooling regions bounded from within by a flat surface, either a cylindrical cavity or a spherical surface.Рассмотрены практически важные задачи нестационарной теплопроводности для гиперболических моделей переноса. Развит аналитический подход, основанный на контурном интегрировании операционных решений гиперболических моделей, приводящий к новым интегральным соотношениям, удобным для численных экспериментов. Показана эквивалентность новых функциональных конструкций и известных аналитических решений данного класса задач. На основе полученных соотношений описан волновой характер нестационарной теплопроводности с учетом конечной скорости распространения теплоты; рассчитаны скачки на фронте тепловой волны. Предложенный подход дает эффективные результаты при исследовании тепловой реакции на нагрев или охлаждение областей, ограниченных изнутри плоской поверхностью, либо цилиндрической полостью, либо сферической поверхностью
ОСОБЕННОСТИ ВЗАИМОДЕЙСТВИЯ ИЗОЦИАНАТОВ С ПРОИЗВОДНЫМИ ГИДРАЗИНА
Get PDFThe results of studies on chemical transformations of organic and organosilicon isocyanates in their interaction with hydrazine derivatives have been summarized in this review. It is shown that hydrazine and its derivatives including organosilicon compounds reacting with organic isocyanates form corresponding semicarbazides readily enough. The reaction conditions that effect the composition, structure and yield of the resulting target products are presented. A significant difference in the interaction of trimethylsilyl isocyanate with organic and organosilicon derivatives of hydrazine is demonstrated. It is demonstrated that the reason for the impossibility to isolate trimethylsilyl derivatives of semicarbazide is their low hydrolytic stability, as well as high silylating ability. Peculiarities of the reaction of trimethylsilyl isocyanate and dimethylchloromethyl isocyanate silane with 1,1-dimethylhydrazine, its trimethylsilyl analog and isoniazid are given. Possible schemes for the formation of a previously unknown O-trimethylsilyl-1,1-dimethylhydrazinecarboximidoate are presented. The results of using carbofunctional organosilicon isocyanates in these processes are discussed. Basic trends in practical use of the prepared compounds as physiologically active preparations in polymer chemistry and agriculture are shown
ВЫБОР ОПТИМАЛЬНОЙ СХЕМЫ РАЗДЕЛЕНИЯ СМЕСИ УГЛЕВОДОРОДНЫХ ГАЗОВ МЕТОДОМ РЕКТИФИКАЦИИ
Get PDFThe heat costs in distillation columns were determined for the purpose of separating a four-component gas mixture in gas fractionators with various component selection sequences. A method for selecting the optimal scheme was developed. It is based on the concept of “internal energy saving” upon rectification. Internal energy saving means multiple steam operation on the plates of a distillation column, namely, its condensation on each plate with the release of the heat of condensation, which is used for the evaporation of the liquid entering the plate to obtain a new steam composition. It was shown that when binary and three-component mixtures are separated and products of equal purity are obtained, the heat costs are related to the internal energy saving. The calculation of the internal energy saving in a three-column system for the separation of a four-component mixture was carried out. The calculation confirms that, as the internal energy saving increases and, accordingly, the average internal energy saving in the system of columns increases, the total heat consumption is reduced. The results of calculating three separation schemes of the four-component mixture were compared using the program Aspen Plus with different methods for describing the phase equilibrium (NRTL, Peng-Robinson, Chao-Seader) was carried out. It was shown that the calculations with the use of Peng-Robinson and Chao-Seader methods match