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The effect of biopolymers on adhesive and rheological properties of calcium phosphate bone cements
Scholz, David ; Michlovská, Lenka (referee) ; Vojtová, Lucy (advisor)
Tato práce se zabývá kostním cementem složeného z fosforečnanu vápenatého a termosenzitivního kopolymeru. Hlavním cílem bylo vylepšení zejména adhezivních vlastností cementu přídavkem polysacharidu. Teoretická část práce se zabývá charakterizací kostních cementů a jejich aplikací. Dále také popisem polymerních aditiv přidávaných do kostních cementů se zaměřením hlavně na polysacharidy. V praktické části byly připravené cementy charakterizovány pomocí reologie, práškové rentgenové difrakce a statických zkoušek mechanických vlastností na samotném vytvrzeném cementu a slepených kostí. Reologie byla použita na měření rychlosti tvrdnutí cementu v závislosti na čase a teplotě. Dále byla taky reologie zamýšlena pro měření adhezivních vlastností roztoků kopolymeru, ale toto nebylo možné z důvodu nereprodukovatelných výsledků způsobené nehomogenitou roztoků kopolymeru s polysacharidem. Prášková rentgenová difrakce byla použita pro změření vlivu polysacharidu na konverzi fosforečnanu vápenatého na kalcium deficientní hydroxyapatit. Bylo zjištěno, že polysacharid významně neovlivňuje konverzi fosforečnanu vápenatého. Statické zkoušky mechanických vlastností byly použity pro změření maximální pevnosti v tlaku pro samotné vytvrzené cementové vzorky a také pro změření adheze slepených vzorků kostí. Vytvrzené vzorky s nízkou koncentrací polysacharidu vykazovaly vyšší pevnost v tlaku oproti kontrolním vzorkům. Při zkouškách kostí nebylo dosaženo průkazných výsledků z důvodu náročnosti měření. Jedná se zejména o přípravu vzorků kostí a jejich následné lepení kostním cementem.
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Non-newtonian liquids flow
Mašán, Roman ; Klas, Roman (referee) ; Himr, Daniel (advisor)
The bachelor's thesis explores the topic of Non-Newtonian fluids, which behave unusually compared to Newtonian fluids. It characterizes their rheology, clarifies the reasons and mechanisms responsible for their non-standard properties. The thesis also includes a mathematical description of modeling these fluids, which is subsequently applied to elucidate the nature of flow and phenomena occurring in laminar and turbulent regimes.
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PEG-based semi-interpenetrating polymer network hydrogels
Kadlecová, Michaela ; Kalina, Michal (referee) ; Sedláček, Petr (advisor)
This bachelor's thesis deals with optimization of the preparation of hydrogels based on polymer networks of polyehtylene glycol with the incorporation of a semi-interpenetrating polymer networking and the following chemical-physical characterization of the prepared hydrogels. Polyehtylen glycol diacrylate was chosen from the range of polyethylene glycol modifications as a model material for the formation of hydrogels. Based on this, the preparation using UV photopolymerization was optimized. After optimization of the preparation, selections and following incorporation of the polyelectrolyte took place. Sodium polystyrene sulfonate was chosen as a model polyelectrolyte. Then, there was a basic characterization and comparison of the prepared hydrogels based on polyethylene glycol diacrylate with and without the addition of polyecletrolyte. Swelling, rheology, scanning electron microscopy were used for basic characterization and transport characteristics were investigated using diffusion.
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Analysis and optimization of the dyeing process of surgical instruments
Roušarová, Kateřina ; Jugl, Adam (referee) ; Krouská, Jitka (advisor)
This bachelor thesis deals with the issue of staining of disposable surgical instruments in the corporate facility of the industrial partner with whom the cooperation took place. Within the framework of this bachelor thesis an analysis of the input organic raw materials, which are an essential part of the manufactured dye for instrument staining, was carried out. The basic characterization of the raw materials was carried out by available methods at the Faculty of Chemistry, such as density measurement with a hydrometer, viscosity measurement with an automatic viscometer and viscosity versus shear rate with a rheometer. Subsequently, a visual assessment of the behaviour of the individual liquid feedstocks in water was performed. The tabulated values of the raw materials from the safety data sheets were verified by these methods. It was found that the starting ingredients are insoluble in water, in which they precipitate and thus significantly affect the viscosity of the resulting suspension. The actual laboratory preparation of the paint samples was carried out, where 7 samples were mixed, varying in the volumes of the input liquid organic components. These samples were subjected to rheological measurements, which resulted in the dependence of viscosity on shear rate. A range of 0,4–0,8 Pas at a shear rate of 10 s-1 was specified by the industrial partner for the resulting viscosity of the mixed suspension, within which 4 samples fell. The result of the spout test performed using a Ford spout cup determined the time of suspension discharge from the cup, which can be used to verify the quality and correct consistency of the paint mixed in company operation. All samples were stained with surgical instruments and the quality of staining was evaluated after firing. Based on the requirements of the industrial partner, 4 samples were designed falling within the required viscosity range and suitable for staining surgical instruments. The results have been passed on to the industrial partner, who has the discretion to implement new dye preparation procedures in their operation.
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Preparation and characterization of polysaccharide hydrogel systems with gradient structure
Škutová, Patricie ; Krouská, Jitka (referee) ; Smilek, Jiří (advisor)
This bachelor thesis deals with the preparation of polysaccharide hydrogels with a diffusion gradient and their subsequent characterization in terms of viscoelastic properties, which are used to demonstrate the gradient structure. The main goal was to select a suitable method for the preparation of chitosan hydrogels with different molecular weights (168 kDa - 437 kDa). The biopolymer chitosan is a cationic polysaccharide that is suitable for use in biomedical applications due to its excellent biocompatible properties. First, concentration-uniform hydrogels without gradient structure were prepared, in which the influence of various parameters (chitosan molecular weight, chitosan concentration, sodium hydroxide concentration) was investigated. To prove the created gradient structure, the samples were subjected to the drying method (determination of the dispersion fraction) and determination of mechanical properties by oscillatory rheometry. Increased attention was paid to the search for a suitable preparation method for gradient chitosan hydrogels with higher molecular weight, which showed some problems with the already established method of preparation of hydrogels with gradient structure controlled by diffusion. From the results of the measurements obtained, it can be concluded that the viscoelastic properties of the hydrogels can be modified by changing the selected parameters and the method of preparation. By the controlled diffusion method, it was possible to prepare hydrogels with a gradual gradient of cross-linking density, which confirmed the assumption that the more cross-linked the layer, the higher the values of viscoelastic moduls and therefore the higher resistance to stress was confirmed.
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Biodegradable thermoplastics from renewable resources
Březinová, Štěpánka ; Kučera, František (referee) ; Petruš, Josef (advisor)
The theoretical part of diploma thesis summarizes the state of the art in the field of biodegradable thermoplastic materials, emphasizing polymeric materials made from renewable sources and the possibilities for their processing and for the modification of their useful properties. The experimental part of the thesis is focused on the preparation and characterization of biodegradable polymer blends based on thermoplastic starch (TPS) and poly(butylene adipate-co-terephthalate) (ECX). A suitable type of TPS was selected according to the rheological behavior of the melt for blending with ECX via extrusion technology. The degree of compatibility between TPS and ECX was evaluated by infrared spectroscopy (FTIR-ATR) and by examining the morphology of TPS/ECX blends using scanning electron microscopy (SEM). Affecting the mechanical properties, rheological behavior, and wettability of the prepared TPS/ECX was verified by testing the mechanical properties under tensile stress, determining the melt flow index (MFI), employing the oscillatory rheological test, and determining the maximum wettability. The experimentally obtained results show the possibility of optimizing the mechanical and rheological properties of TPS by blending with ECX. In terms of biodegradability, blends with a majority TPS content can be assumed to be more advantageous.
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The long-term stability and properties of a skin cream with addition of liposomes
Müllerová, Kristýna ; Pekař, Miloslav (referee) ; Enev, Vojtěch (advisor)
The aim of the thesis was to design a formulation and subsequently prepare a native skin cream and skin creams enriched with liposomal particles with encapsulated vitamin E. After preparation of the skin creams, their stability and rheological properties were studied at given time intervals during storage for 12 weeks. The stability of the prepared samples was determined using a LUMiSizer analytical centrifuge with STEP-Technology. Among the rheological properties, changes in the rate of structure recovery of the formulations were monitored, as well as changes in zero and infinite viscosity, which can be presented as changes in viscosity during product storage and changes in viscosity during application and spreading on the skin. All stability and rheological tests were performed for a temperature of 25 °C, which also corresponded to the storage temperature, and for a temperature of 37 °C, which approximately corresponds to the human body temperature. According to the results, the sample without the addition of liposomes showed the highest stability and the skin cream with the addition of 10 wt.% liposomes at 1 week of age showed the best spreadability. Next, the characterization of liposomal particles was performed. Finally, a sensory analysis was performed where the evaluators compared the fresh native skin cream, the native skin cream at 12 weeks of age, the fresh skin cream with the highest liposome content and the skin cream with the highest liposomal particle content at 12 weeks of age.
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Effect of different type and crosslinking density of polyethylene glycol hydrogels on transport and sorption properties
Janáková, Kristýna ; Pekař, Miloslav (referee) ; Krouská, Jitka (advisor)
The main goal of this work was to study the transport and sorption properties of polyethylene glycol (PEG) hydrogels with different types and densities of cross-linking. Before characterizing these properties it was necessary to optimize the preparation of selected hydrogels including the study of mechanical properties using rheological measurements. A significant part of the work, therefore, consists of the optimization of PEGDA-thiol hydrogels created from 4-arm polyethylene glycol-thiol (PEG-4SH) and polyethylene glycol diacrylate PEGDA by step-growth polymerization. To compare the transport and sorption properties of another type of crosslinking, PEGDA hydrogels were prepared using radical polymerization. In the transport experiments, the sorption and desorption of the Rhodamine 6G dye were monitored using free diffusion. Molecular absorption spectrometry (UV/VIS) was used to characterize the course of these experiments. The structure of these gels was compared using scanning electron microscopy.
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Characterization of Mechanical Properties of semi-IPN Hydrogels Based on Poly(vinylalcohol)
Přibyl, Jiří ; Pekař, Miloslav (referee) ; Kalina, Michal (advisor)
This diploma thesis deals with the issue of mechanical properties of semi-IPN hydrogels based on poly(vinylacohol). The prepared poly(vinylalcohol) hydrogels were modified by the addition of sodium alginate, dextran, DEAE-dextran, chitosan, and poly(ethyleneglycol). The mechanical properties were studied by various methods, such as the oscillatory amplitude rheological test, dynamic mechanical analysis, swelling experiments and drying characteristics. Microcalorimetry was used to study the interactions between poly(vinylalcohol) and biopolymers in solution using the ITC method and the morphology of prepared hydrogels was visualized using cryo-SEM. The main concept for semi-IPN hydrogels is that there is minimal influence on the mechanical properties but leads to the modification of the binding sites present in the hydrogel structure, which has a high potential in transport properties. From the experimental results, the effects of each biopolymer on the mechanical properties were determined. The obtained results showed that the additions of biopolymers do not have a significant impact on the mechanical properties of PVAl hydrogels, but in the case of swelling experiments, there is a significant influence of the number of freezing/thawing cycles, ionic strength of the environment, and the used biopolymer.
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Simulation of nonlinear response of construction materials and problem of identitifaction of material parameters
Hokeš, Filip ; Kala, Zdeněk (referee) ; Krejsa,, Martin (referee) ; Kala, Jiří (advisor)
The issue of parameter idenetification within numerical simulations can be considered a necessary step in the use of mathematical models, such as complex material models of building materials utilized in finite element method. The problem is particularly epmhasized in the case of anisothropic materials but also in the case of concrete, which behaves differently in tension and compression and which shows different response under rapid-dynamic and long-term loading. Correct capture of the concrete response in the computation requires usage of plasticity theory, damage theory, visco-elasticity and visco-plasticity or their mutual combinations. It results in development of material models and rheological schemes with large amount of parameters that are not commonly available in standards. The disseration presents application of meta-heuristic algorithm Particle Swarm for parameter identification. The success of the method is demonstrated in a pair of cases, first on the identification of elastoplastic material model parameters from stress strain diagram and then to identify the values of stiffness constants and viscosities of the rheological scheme from a creep curve.
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