No abstract

The finding a filler for the creation of polymer composite (PC) for constructional purposes, which is able not only for improving the level of polymer matrix properties, but also significantly for reducing its price was conducted. It was determined that such fillers are silicas of various modifications, which due to the developed surface and active "silanol" groups on it are capable of physical and chemical interaction with the polymer matrix. The most common industrial brands of silicas, such as aerosіl, white soot and silica gel were selected for research. As a result of microscopic investigations it was obtained, that particles of silica of such brands as aerosil and white soot, both in the initial form and in the polymer matrix are actively aggregated, and create agglomerates up to tens of microns. This phenomenon is not observed when using silica gel. Therefore, it is more appropriate to be used as the fillers for PC for construction purposes than other investigated materials. The method of synthesis of silica gel with a high degree of chemical purity was presented. Comparative investigations of the physico-mechanical, thermophysical and tribotechnical properties of constructural polymer composites, based on aromatic polyamide, filled by industrial and synthesized silica gel were performed. It was obtained that PCs with synthesized silica gel have higher level of properties than industrial ones. This is due to the fact that the primes presented in industrial silica gel reduce its reinforcing effect on the polymer matrix and adversely affect the friction process during the friction interaction of the obtained PC with steel. АнотаціяПроведено аналіз щодо визначення наповнювача для створення полімерних композиційних матеріалів (ПКМ) конструкційного призначення, який здатний не тільки покращити рівень властивостей полімерної матриці, а і значно здешевіти її. Визначено, що такими наповнювачами є силіцій (IV) оксиди різних модифікацій, які за рахунок розвиненої поверхні та активних силанольних груп на ній здатні до фізичної та хімічної взаємодії із полімерною матрицею. Для досліджень вибрані найбільш розповсюджені промислові марки силіцій (IV) оксидів: біла сажа, аеросил, силікагель. В результаті мікроскопічних досліджень встановили, що частинки силіцій (IV) оксидів марок «біла сажа» і «аеросил», як у вихідному вигляді так і у полімерній матриці активно агрегатуються, створюючи агломерати розмірами до десятків мкм. Таке явище не спостерігається при використанні силікагелю. Тому силіцій (IV) оксид марки «силікагель» доцільніше використовувати в якості наповнювачів для створення ПКМ конструкційного призначення, ніж інші матеріали, що досліджували. У роботі було приведено метод синтезу силікагелю із високим ступенем хімічної чистоти. Проведені порівняльні дослідження показників фізико-механічних, теплофізичних та триботехнічних властивостей конструкційного полімеру на основі ароматичного поліаміду фенілон С1 при наповненні промисловим та синтезованим силікагелями. Встановлено, що ПКМ із синтезованим силікагелем мають...

Without the employment of new equipment, with units functioning at high levels of weights, sliding speeds and temperatures, the current growth of the sector is all but impossible. High levels of labour intensity have a detrimental impact on the dependability and durability of the product. Moving joints, which comprise friction units, frequently fail at the same time. It is vital to increase their dependability and durability. This can be accomplished by substituting more recent materials with higher-quality qualities for the friction pair materials. To create such materials, the researchers created an aromatic polyamide polymer that was filled with silicon- (silica gel, bentonite) and carbon-containing (technical carbon, graphite) components. It was determined that depending on their nature, structure and content in the polymer matrix, the addition of these fillers enables the reduction of the coefficient of friction and wear of the produced polymer composites by 1.5–2.5 and 20–40 times, respectively, during frictional interaction with steel. It was found that 10–15% by weight of the examined fillers in aromatic polyamide is the ideal concentration. It has been proven that polymer composites filled with layered materials (bentonite, graphite) perform better in terms of tribological qualities when in contact with steel than those filled with spherical elements (technical carbon, silica gel). The improvement of the tribological properties of the developed polymer composites in comparison to the original polymer was determined based on the microphotographs of steel surfaces and the study of their morphological (roughness) and physical (microhardness) properties. It was determined that the change in the friction nature was due to the creation of an antifriction coating on the metal friction surface from the products of tribochemical reactions occurring during friction.

Until recently, vertical-axis wind turbines are less extensively developed in wind energetics. At the same time, there are a number of advantages in turbines of such type like their independence from the change of wind direction, lower levels of aerodynamic and infrasound noises, higher structural reliability (compared to horizontal engines), etc. With these advantages, vertical-axis wind turbines demonstrate promising capacities. Inter alia, the productiveness of such turbines can be refined through the aerodynamic improvement of the structure and comprehensive optimization of the rotor geometry. The main purpose of the presented paper is to aerodynamically improve vertical wind turbine in order to increase the efficiency of wind energy conversion into electricity. Within the framework of the classical theory of impulses, this article presents a study of the effect of variation in Reynolds number on the general energy characteristics of a vertical-axis wind turbine with two blades. The integral approach makes it possible to use a single-disk impulse model to determine the main specific indicators of the system. The power factor was calculated based on the obtained value of the shaft torque factor, which in turn was determined by numerically integrating the total torque generated by the wind turbine. To calculate the test problem, we used the classic NACA airfoils: 0012, 0015, 0018 and 0021. The proposed calculation algorithm makes it possible not to indicate the Reynolds number and corresponding aerodynamic coefficients at the beginning of the calculation, but to recalculate it depending on the relative speed, position of the airfoil and the linear speed of the airfoil around the circumference. Proposed modern design techniques can be helpful for optimization of vertical wind turbines.

No abstract