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Long-term tests for examination of surface treatments in various adverse environments simulating real effects
Hudečková, Petra ; Vacula, Miroslav (referee) ; Bydžovský, Jiří (advisor)
Cement bonded particleboards contain organic base and as they are set outside, extreme weather condition, such as frost, chemical defrosting substances or sulphates, cause their degradation. The presence of the organic base in the matrix of the material could be the reason why there is higher probability of degrading when compared with materials containing an inorganic base. It could be partially eliminated by an appropriate surface modification of the slab, which main goal is to weaken the impact of an aggressive environment and to extend the lifespan of the board. On the other hand, the surface modifications based on a polymer base are prone to degrade because of other unfavourable conditions such as UV radiation when compared with the cement bonded particleboard. The classification of the surface modifications and the way of their degradation caused by the aggressive environment in real applications are presented in the theoretical part of the thesis. In the experimental part, appropriate methodical ways of testing the resistance of cement bonded particleboard’s coating system were chosen. Then, the testing and comparing of the physical, mechanical and aesthetic properties of different types of coatings were done. Moreover, a spectrophotometric analysis of the colour shade changes for the different aggressive environment were carried out. Furthermore, microstructures of chosen surface modifications were assessed by using an optical and an electron microscope.
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Hybrid Blends of Recycled Plastics
Černý, Miroslav ; Lehocký, Marián (referee) ; Balgová,, Vendula (referee) ; Jančář, Josef (advisor)
Work describes the relationship between structure and mechanical properties in case of hybrid mixtures. They are composed from polyurethane matrices (eventually polyurethane-urea or polyurethane-inorganic filler mixtures), different rubber fractions as filler and eventually reinforcement made from PET monofilaments. Mechanical behaviour was studied by tensile testing. Studied mechanical properties include tensile modulus, ultimate strength and strain and also specific energy need neccessary for ultimate strength achievement. Prepared materials are naturally porous. Therefore their mechanical behaviour has to be described generally for porous composites. The porosity occurence means, that it is difficult to describe them by models valid for mechanical behaviour (mainly elastic modulus) of nonporous composites. Models are also based on idealized structures on microscopic level. In case of porous composites, it is very difficult to create any idealized structure. The structure is changed with modifications of composition (change of components or their rates). These conditions have lead to utilizing of different approach how to describe the relationship between structure and mentioned mechanical properties. The chosen approach comes from knewledge about structural parametres coming from porosity. Structural parameters describe the structure on macroscopic level. They include interspace volume (volume lying between filler particles), interspace filling (how the matrix fills the interspace volume) and matrix volume fraction. Proposed parameters are used in relations, where they are fitted by exponents to interlay values of chosen mechanical properties for composites containing discrete matrix and filler. Found exponents are then described by properties of matrices to obtain relations describing properties of filled porous materials. Very similar approach was chosen for description in the case of reinforced composites. Proposed relation are potentially valid for materials containing binding matrix, infinity count of fillers and one kind of reinforcement.
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The evaluation of properties of fine aggregate for asphalt mixtures
Kadlček, Jakub ; Sychra, Martin (referee) ; Dašek, Ondřej (advisor)
The diploma thesis is focused on evaluation of properties of fine aggregate by means of laboratory tests. Fine aggregate evaluation was performed using sieving test, laser diffraction, delta ring and ball test, bitumen number test, uncompacted void content of fine aggregate according to AASHTO T 304, voids of dry compacted filler (Rigden) test and particle density of filler. Laboratory research has led to the discovery of some properties of fine aggregate and their dependencies.
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Modification of epoxy resin effecting ductility of wood bonds
Hudečková, Petra ; Drochytka, Rostislav (referee) ; Vaněrek, Jan (advisor)
This bachelor thesis is focus on a jointing process of wood parts, the basic kinds of adhesives that are used for wood constructions, and also deals with an important demands on a bonded wood joint. Then there is briefly described an issue of fracture toughness and the ways of epoxy adhesives filling, primarily filling with the rubber, the thermoplastics and other fillers. In the experimental part the reinforcing of epoxy matrix with the different quantity of rubber was carried out. The mixture was prepared by an ultrasound homogenizer. Firstly, the tensile strength test with epoxy samples was carried out. Secondly, the Young modulus was calculated and in the last part the fracture surface was analyzed with the scanning electron microscope.
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Preparation and characterization of highly filled composite materials for dental applications
Gavroňová, Ivana ; Bystřický, Zdeněk (referee) ; Poláček, Petr (advisor)
Master thesis deals with highly filled particulate composite materials for dental applications. In the practical part, the dimetacrylate matrix was filled with a mixture of particles of different types and different sizes to achieve the maximum possible packing. Moreover, filler content and the influence of filler on composite material was studied. Hydrolytic stability was also tested on composite materials. The methods used to characterize composite materials were bending test, thermogravimetric analysis (TGA), differential scanning photocalorimetry (DPC), dynamic-mechanical analysis (DMA) and scanning electron microscopy (SEM). Curing of the matrix was characterized by the degree of conversion, the heat of polymerization and the polymerization rate. Furthermore the polymerization shrinkage was measured. The glass transition temperature, the dynamic modulus at 40 °C and 100 °C, the modulus of elasticity, the strength, the critical value of the stress factor and the critical energy release rate were found in the tested samples.
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Mosaic geopolymeric thin-film plasters for decorative applications
Svidroňová, Barbora ; Šiler, Pavel (referee) ; Šoukal, František (advisor)
This bachelor thesis deals with preparation of mosaic geopolymeric plasters, used fillers and it observes their influence on the final properties of geopolymeric plaster. The aim of the study is the selection of proper raw materials for filler, the determination of optimal filler-to-sand ratio and the preparation of plaster with proper shade of colour. In experimental part, during the detection of adequate ratio of raw materials, there were prepared beams from several types of metakaoline, sand, water and water glass. The beams were tested for compressive strength and bending. The blasters themselves were watched for their applying, hardness, shades of colour and efflorescence.
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Filling of Polyurethanes
Bečka, Filip ; Poláček, Petr (referee) ; Kučera, František (advisor)
Bachelor thesis focuses on preparation of filled polyurethanes, determination of tensile properties, hardness and measurement of IR spectra. Theoretical part is devoted to main components of polyurethane systems and the most common inorganic, particulate filler and summarises knowledge about application of mineral fillers into polyurethane matrix. In experimental part was developed method of application of fillers into polyurethane and test specimens were prepared. Dispersion of fillers into polyol and affected workability was investigated. For examination of test specimens 3 methods were used: FTIR spectroscopy, tensile testing and hardness measurement. FTIR spectroscopy was used to investigate conversion of free isocyanate groups an OH groups. Tensile testing proved toughness of material and tensile modulus was determinated. Conformity of strength and stress at break and also conformity of strain at strength and strain at break was found. No yield point was observed for the specimens. Hardness of specimens was measured by the Shore A method.
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Brickmaking grogs and their thermo-dilatometric determination
Hladík, Václav ; Skotal, Zbyněk (referee) ; Sokolář, Radomír (advisor)
Main focus of the bachelor´s thesis is use of rock waste fraction as an alternative raw material to traditional quartz sand. Effect of this substitution on ceramic produts properties is outlined. Key properties are water absorption, flexural strength and compressive strength. The practical part traces the potential of alternative grogs. Their behavior is monitored by DKTA analysis, water absorption tests and strength tests. Thesis includes author´s suggestion of an optimal grog based on publications and results of the practical part.
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Heat insulating moulded refractory concretes
Bednárek, Jan ; Bartoníčková, Eva (referee) ; Šoukal, František (advisor)
The thesis deals with the possibility of specific weight lowering of kaolin suspensions using air-entraining agents. These agents are usually used as concrete admixtures. The goal of the thesis is to verify an alternative possibility of creating porous structure in kaolin suspensions in order to prepare heat insulating moulded refractory concretes without using lightweight fillers. The effect of several air-entraining agents was compared, after that the dosage of agent and mixing conditions were optimized. The stabilization of prepared foams and practical application of selected agents were also part of the thesis.
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