Синтез и медико-биологические свойства низкозамещенных фосфатов целлюлозы

The process of cellulose fiber esterification by dilute (0.3-0.8 mol/dm3) orthophosphoric acid water solutions in presence of urea under various conditions has been investigated. Low-substituted cellulose phosphates containing 0.25-0.5 mmol/g of phosphorus, have been prepared . Physical, chemical and medico-biological properties of cellulose phosphates obtained have been studied. It has been shown that they fit the medico-biological safety criteria, including biocompatibility indicators and possibility of use as medicine materials .Исследован процесс этерификации целлюлозы в виде нитей разбавленными водными растворами ортофосфорной кислоты (0,3-0,8 моль/л) в присутствии мочевины при различных условиях. Получены низкозамещенные фосфаты целлюлозы с содержанием фосфора 0,25-0,5 ммоль/г. Изучены физико-химические, механические и медико-биологические свойства полученных фосфатов целлюлозы. Показано соответствие медико-биологическим критериям безопасности, в том числе по показателям биосовместимости и возможности использования материалов на их основе в медицине

Improving the Structural Characteristics of Heavy Concrete by Combined Disperse Reinforcement

The development of perspective concrete mixes capable of resisting the action of external loads is an important scientific problem in the modern construction industry. This article presents a study of the influence of steel, basalt, and polypropylene fiber materials on concrete’s strength and deformation characteristics. A combination of various types of dispersed reinforcement is considered, and by methods of mathematical planning of the experiment, regression dependences of the strength and deformation characteristics on the combination of fibers and their volume fraction are obtained. It was shown that the increase in compressive strength was 35% in fiber-reinforced concretes made using a combination of steel and basalt fiber with a volume concentration of steel fiber of 2% and basalt fiber of 2%; tensile strength in bending increased by 79%, ultimate deformations during axial compression decreased by 52%, ultimate deformation under axial tension decreased by 39%, and elastic modulus increased by 33%. Similar results were obtained for other combinations of dispersed reinforcement. The studies carried out made it possible to determine the most effective combinations of fibers of various types of fibers with each other and their optimal volume concentration

Investigation of Integral and Differential Characteristics of Variatropic Structure Heavy Concretes by Ultrasonic Methods

The article develops methods and methodology for experimental studies of centrifuged and vibro-centrifuged concrete products of annular cross-section. They assess the real variatropy of the structure and confirm the correctness of the accepted research. An original technique for experimental studies of the variatropy of the cross-sections of vibrated, centrifuged and vibro-centrifuged concretes is proposed to determine their integral (common) and differential (differing in layers) strength and strain characteristics and deformation diagrams. It has been proved that with vibro-centrifugation it becomes possible to obtain concretes with improved structure and higher characteristics compared with centrifugation and vibration techniques. Experimental studies of the differential characteristics of centrifuged and vibro-centrifuged concretes under compression and tension revealed that the outer layer of concrete had the best characteristics after centrifugation and vibro-centrifugation, and the inner layer had the worst ones. The three-layer model of the variatropic structure for centrifuged and vibro-centrifuged concrete has been experimentally confirmed. The concrete of the outer layers had the highest strength and modulus of elasticity and the least deformability; the concrete of the inner layers had the lowest strength and modulus of elasticity and the highest deformability; and the concrete of the middle layers had average characteristics. The deformation diagrams of centrifuged and vibro-centrifuged concretes were also differentiated by layers, confirming the variatropy of the structure of such concretes. The deformation diagrams for the outer concrete layer demonstrated the highest strength; the diagrams for the inner concrete layer showed the lowest strength; and the diagrams for the middle concrete layer corresponded to mean characteristics