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Study of physical gels with hydrophobic domains
Kovářová, Lenka ; Márová, Ivana (referee) ; Mravec, Filip (advisor)
The thesis is focused on physical hyaluronan gels. The object of study is the interaction of hyaluronan (HyA) with oppositely charged surfactants in physiologic solution (0.15 M NaCl), leading to the formation of gel. In the first part of work have been determined the solids´ contents (X) in gels and their supernatants in percentage and their correlation with molecular weight concentration of original HyA solution and the ratio of binding sites on hyaluronan chain and surfactant CTAB. To conclude, decrease in HyA concentration results in higher values of X and vice versa. On the other hand, increase in the value of X with increasing molecular weight of HyA is not so significant. Analogous conclusions have been made for supernatants and the amount of solids in gel. Drying process has been recorded by drying curves. Swelling process has been used for the characterization of gels. The percentage of water that can be absorbed by dried gel, was determined. The results are in agreement with the measurements of solids´ content in gels. In the next part, the correlation between rheological properties of gels and HyA concentration, HyA molecular weight and concentration of CTAB have been studied by the oscillation and flow tests. The samples with the highest molecular weight and concentration have the most viscoelastic character. The flow test confirmed the assumed pseudoplastic behavior of gels. A very interesting trend arose while comparing HyA concentrations and viscosity in stock solutions and gels. Whereas in stock solution viscosity (at low shear rate) is lower with increasing of HyA concentration, the situation was exactly the opposite in gels. The results are in agreement with frequency tests and observed character of gels.
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Effect of lubricant rheology on lubrication film thickness.
Prášilová, Alena ; Šperka, Petr (referee) ; Křupka, Ivan (advisor)
Lubrication is a very important part of mechanical engineering, which ensures high lifetime of machine parts, reduction of friction and wear and also it leads to decreasing of power consumption. In this bachelor`s thesis there is described rheology of newtonian and non-newtonian lubricants and its effect on lubrication film thickness. Measured central film thickness values are compared with theoretical prediction.
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Thermal degradation of hyaluronan
Šimáčková, Marcela ; David, Jan (referee) ; Chytil, Martin (advisor)
This diploma thesis investigated thermal stability and the degradation of hyaluronan (HA) in HA with a molecular mass of 90–130 kDa and in HA with a molecular mass of 1 500–1 750 kDa. The following methods were used for the research: rheology, SEC-MALLS, TGA and DSC. Low-molecular HA was subject to time dependency of degradation investigation, where it was dried at a temperature of 90 °C for a period of 30 minutes and 60 minutes prior to the preparation of the solutions itself. High-molecular HA was investigated not only from the point of view of time but from the point of view of temperature dependency of degradation as well. In the case of investigating the time dependency of degradation, high-molecular HA was dried at a temperature of 75 °C at a time range from 15 minutes to 120 minutes prior to the preparation of the solutions. During the preparation of the solutions for discovering the temperature dependency of degradation, the high-molecular HA was then dried for a period of 30 minutes at a temperature range from 60 °C to 90 °C. For low-molecular HA, thermal stability was proven. Therefore, there is no decrease in the molecular mass and the solutions did not demonstrate a significant decrease of viscosity. For high-molecular HA, thermal stability was not proven. Degradation due to the temperature of drying as well as the time of drying occurred, which was demonstrated by a significant decrease in molecular mass and viscosity of the solutions. While in the case of using a drying temperature of 60 °C, a decrease in the molecular mass occurred by approximately 5 %, the molecular mass decreased by approximately 20 % at a drying temperature of 90 °C compared to undried HA. Due to this reason, high-molecular HA was also further investigated by means of the TGA method, where the decrease of humidity of HA samples in relation to the drying temperature was observed. The DSC method was also used. The objective of the DSC method was to find out temperatures, at which evaporation of humidity contained in an HA sample in relation to its form (undried HA, dried HA and lyophilized HA) occurs. This method further finds out the heat necessary to evaporate humidity from an HA sample. To conclude this research, the results obtained for high-molecular HA were compared with the results of other drying processes – lyophilized proved to be a very gentle drying method because a decrease in the molecular mass for lyophilized HA compared with undried HA almost did not occur.
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Viscosity study of liquid materials
Januš, Petr ; Rozsívalová, Zdenka (referee) ; Frk, Martin (advisor)
Bachelor thesis focuses on the study of viscosity of liquid materials. Its aim is to study the mathematical and physical fundamentals of dynamic viscosity. The thesis presents a correlation between conductivity and viscosity of liquid insulators called Walden rule. Further part of work is a review of methods for measuring viscosity of liquids and classification of insulating liquids. The last section is the practical part in which it is verified Walden rule for available insulating liquids.
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Usage of of common reclaimed asphalt in asphalt mixtures
Přívara, Jakub ; Coufalíková, Iva (referee) ; Dašek, Ondřej (advisor)
The bachelor thesis is focused on adding of RAP (reclaimed asphalt pavement) to the wearing asphalt courses flexible pavements. Specifically it is SMA 11S asphalt mixture. The theoretical part describes issues of ecology and recycling. The practical part deals with bitumen recovery from SMA mixtures with different added ratios of RAP and assessment of basic empirical and functional tests on the bituminous binder. The verification of properities of modified bituminous binder used in this quality SMA mixtures is also introduced.
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3D printing of complex structures using light cured resins
Vozárik, Andrej ; Zbončák,, Marek (referee) ; Jančář, Josef (advisor)
This bachelor thesis deals with preparation of acrylate photopolymer resins for 3D printing with emphasis on complex structures. The work deals with the curing characteristics of resins with gradually increasing CN966H90 oligomer content. Subsequently the effect of composition and individual print settings on the quality of the created complex structures is observed. For the basic characterization of photopolymer resins, Jacobs working functions were created, the structure of the cured resins was observed with CLSM and rheologically determined the effect of composition on viscosity. Part of the work is also devoted to the influence of composition on the mechanical properties in compression and tension for cured resins. The effect of exposure time on print quality was observed on calibration bodies. Finally, from the results obtained from previous measurement the printing process was adapted for print of the complex structures.
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Optimization of preparation and characterization of hybrid hydrogels with respect to viscoelastic and flow properties
Zhurauliova, Darya ; Kalina, Michal (referee) ; Smilek, Jiří (advisor)
This bachelor thesis focuses on the study of hybrid hydrogels that combine the properties of the hydrogel system together with oleogels, which is a gel on the base of oil. The aim of the thesis is to carry out a study of the current state of the solved issue on the topic of preparation of hybrid hydrogels, on this basis to design and optimize the appropriate procedure of preparation and in the form of viscoelastic measurements to perform the basic reological characterization of the prepared systems. A system based on sodium alginate dissolved in deionized water and meshed with calcium chloride solution was chosen as a suitable hydrogel system, and a system based on beeswax dissolved in sunflower oil was chosen as oleogel. Sodium alginate has been chosen because it is used as a thickener, emulsifier, stabilizer or gelling agent in the creams and preparation of pharmaceutical forms. By mixing hydrogels and oleogels of different proportions, a hydrogel/oleogel system, also called bigel, was created, the properties of which were tested in terms of flow and viscoelastic properties. In the practical part, amplitude, frequency and flow tests of both the hydrogel itself and the hybrid hydrogel with a ratio of 50:50 (hydrogel vs. oleogel) were measured. These tests provided information on gel preparations, i.e. what is their character, what are the mechanical properties and how it depends on the amplitude of deformation. By comparing the measurement results, it was possible to determine how oleogel acts on the properties and structure of the hydrogel.
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Nanofluids
Cabúk, Matej ; Kárník, Jan (referee) ; Fic, Miloslav (advisor)
Nanomaterials are phenomena of present time in science and technology. Nanofluids are fluids with original characteristics. In this thesis are presented production methods and effect of nanoparticles onto basic thermophysical properties. Applications of nanofluids are attractive. It is used mainly in heat transfer systems, but can be used in wide area. It can increase the performance a efficiency, save energy and money but also rescue human lives.
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Study on flow and viscoelastic properties of laboratory prepared synovial fluids by macrorheological techniques
Veldamonová, Aneta ; Heger, Richard (referee) ; Smilek, Jiří (advisor)
This bachelor thesis deals with preparation and characterization of synthetic synovial fluid. Preparation was focused mostly on finding proper ratios of substances existing in real synovial fluid which have influence on viscoelastic properties. Based on study of literature, these substances are hyaluronic acid, lubricin, phospholipids and proteins. Samples of real synovial fluid from horse hock acquired from University of veterinary and pharmaceutical sciences Brno were tested for comparation with synthetically prepared synovial fluid. Both synthetic and real synovial fluid were characterized by macrorheological techniques. The experimentally obtained data were then compared with data from the patent on which the preparation of synthetic synovial fluid was based on. Thermogravimetry and isothermal thermogravimetry were used as additional method for the study of moisture and water binding of synovial fluids.
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The Rheological Behavior of Polymer Solutions Suitable for Electrospinning
Divínová, Nikol ; Voráč,, Zbyněk (referee) ; Chamradová, Ivana (advisor)
This diploma thesis deals with preparation and characterization of aqueous solutions of polyvinyl alcohol suitable for electrospinning. In the theoretical part method of electrospinning is described, including parameters which influence this process. Literary research also includes a chapter about rheology, which deals with the rheological properties of polymers, specifically PVA. The experimental part describes the preparation and rheological study of of aqueous solutions of polyvinyl alcohol, which were then spun. The morphology of prepared nanofibers was studied by using scanning electron microscopy (SEM). The effect of molecular weight, the solvent, concentration of solution, rheological properties, electrical conductivity and surface tension on the spinability, diameter and morphology of nanofibers is discussed.
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