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Possibilities of clay plasters shrinkage elimination
Melichar, Jindřich ; Koplík, Jan (referee) ; Opravil, Tomáš (advisor)
Earth plasters which are applicated in interiers don´t have just an estetic, but mainly heat storage function. To accomplish better storage properties the plaster has to be laid on the wall in sufficient thick ply. But this use to be accompained by creating of cracks during dehydration of the plaster. This bachelor work will be considering possibilities of elliminating this negative event by additing suitable components to suppress shrinkage and cracks by creating ettringite.
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Preparation of MDF composites of increased moisture resistance
Žůrová, Marcela ; Šiler, Pavel (referee) ; Šoukal, František (advisor)
The subject of the thesis is to improve the moisture resistance of MDF (macro-defect-free) composites prepared on the basis of aluminous cement and polyvinyl alcohol. These materials are characterized by the absence of defects in the structure and high mechanical performance. These features make MDF composites a promising type of material that could be used in the future for construction purposes. The basic deficiency of MDF composites is insufficient resistance to water or moisture, accompanied by a significant decrease in strength. Therefore, this work deals with increasing of moisture resistance using organotitanate agent and modification of the polymer. Two types of polyvinyl alcohols differing in hydrolysis degree and degree of the polymerization has been modified. Based on the results of the measurement the effect of storage conditions on the properties and structure of prepared MDF composites was observed. The characterization of MDF composites were realized by measurement of flexural strength in bending, scanning electron microscopy with EDS analysis, TG-DTA-EGA, water absorption and consequently the porosity of all prepared MDF composites.
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Synthesis of High-Strength Composites Based on Inorganic Cement and Polymer
Másilko, Jiří ; Palou, Martin (referee) ; Drábik, Milan (referee) ; Havlica, Jaromír (advisor)
The subject of the doctoral thesis is the study of moisture resistance of macro-defect-free (MDF) composites based on calcium-aluminate cement and polyvinylalcohol used as polymer. MDF cements are perspective materials providing unique properties relative to traditional cement pastes with great potential to incoming constructional utilization. But it is known that MDF cements exhibit sensitivity to water, with swelling and reduction of strength. Therefore the work is aimed in monitoring of an organic polymer effect on the moisture resistance of MDF materials and phase changes. The effects of three different organotitanate cross-linking agents on the properties were investigated. The organotitanate-modified MDF cement samples exhibited improved moisture resistance as compared to the standard samples when exposed to 100 % relative humidity or water at laboratory conditions. The influence of composition at different curing on the properties of model MDF cement samples was observed. The characterization of MDF samples was based especially on test of flexural strength, XRD, DTA/TGA and EGA, EDS and scanning electron microscopy analyses.
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Polymer-cement composites for refractory aplications
Zbončák, Marek ; Ptáček, Petr (referee) ; Šoukal, František (advisor)
This bachelor thesis deals with preparation of high-strength polymer-cement composites based on the calcium aluminate cement and polyvinylalcohol. MDF composites are interesting because of their mechanical properties which exceed strengths of the common materials based on the cement and inorganic binders. So they represent perspective kind of material which could be used for construction purposes. Thermal degradation of the polymer leads to structure changes of the composite and reduction of mechanical properties. Therefore thesis is aimed to characterize the influence of the temperature on mechanical properties, structural changes and material composition. Temperature dependence of flexural strength was examined during the work. Changes of composition and structure were characterized by XRD, DTA-TGA in combination with EGA, SEM and EDS analyses. Due to requirement of the material refractoriness there were also tested options of preparation of MDF composites based on phosphates binders which are used in refractory manufacture.
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Optimization of the hardening and drying process of non-cement refractory castables based on colloidal SiO2
Zbíral, Roman ; Koplík, Jan (referee) ; Švec, Jiří (advisor)
Thesis deals with drying and its effect on refractory materials based on materials with zero cement content. Heat-resistant materials prepared by the sol-gel method, i.e., a process where the input raw materials are first formed into a colloidal solution, in our case already prepared by the manufacturer, and then a gel is formed with gelation reagent. This sol must be poured into a mold before gelation processes start and gel mesh formation occur. These materials can have better mechanical properties and better firing possibilities than standard cement materials, and a shorter preparation time. These refractory materials will be examined from the point of view of drying result gel, but also with the effect of subsequent firing and mechanical properties. Samples of sol, aluminate cement, model and real mixture will be analyzed using thermal methods (DSC, TG, DTA and thermal microscope). XRD technique was used to determine content of crystalline phases.
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Synthesis of High-Strength Composites Based on Inorganic Cement and Polymer
Másilko, Jiří ; Palou, Martin (referee) ; Drábik, Milan (referee) ; Havlica, Jaromír (advisor)
The subject of the doctoral thesis is the study of moisture resistance of macro-defect-free (MDF) composites based on calcium-aluminate cement and polyvinylalcohol used as polymer. MDF cements are perspective materials providing unique properties relative to traditional cement pastes with great potential to incoming constructional utilization. But it is known that MDF cements exhibit sensitivity to water, with swelling and reduction of strength. Therefore the work is aimed in monitoring of an organic polymer effect on the moisture resistance of MDF materials and phase changes. The effects of three different organotitanate cross-linking agents on the properties were investigated. The organotitanate-modified MDF cement samples exhibited improved moisture resistance as compared to the standard samples when exposed to 100 % relative humidity or water at laboratory conditions. The influence of composition at different curing on the properties of model MDF cement samples was observed. The characterization of MDF samples was based especially on test of flexural strength, XRD, DTA/TGA and EGA, EDS and scanning electron microscopy analyses.
|
|
|
Preparation of MDF composites of increased moisture resistance
Žůrová, Marcela ; Šiler, Pavel (referee) ; Šoukal, František (advisor)
The subject of the thesis is to improve the moisture resistance of MDF (macro-defect-free) composites prepared on the basis of aluminous cement and polyvinyl alcohol. These materials are characterized by the absence of defects in the structure and high mechanical performance. These features make MDF composites a promising type of material that could be used in the future for construction purposes. The basic deficiency of MDF composites is insufficient resistance to water or moisture, accompanied by a significant decrease in strength. Therefore, this work deals with increasing of moisture resistance using organotitanate agent and modification of the polymer. Two types of polyvinyl alcohols differing in hydrolysis degree and degree of the polymerization has been modified. Based on the results of the measurement the effect of storage conditions on the properties and structure of prepared MDF composites was observed. The characterization of MDF composites were realized by measurement of flexural strength in bending, scanning electron microscopy with EDS analysis, TG-DTA-EGA, water absorption and consequently the porosity of all prepared MDF composites.
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Polymer-cement composites for refractory aplications
Zbončák, Marek ; Ptáček, Petr (referee) ; Šoukal, František (advisor)
This bachelor thesis deals with preparation of high-strength polymer-cement composites based on the calcium aluminate cement and polyvinylalcohol. MDF composites are interesting because of their mechanical properties which exceed strengths of the common materials based on the cement and inorganic binders. So they represent perspective kind of material which could be used for construction purposes. Thermal degradation of the polymer leads to structure changes of the composite and reduction of mechanical properties. Therefore thesis is aimed to characterize the influence of the temperature on mechanical properties, structural changes and material composition. Temperature dependence of flexural strength was examined during the work. Changes of composition and structure were characterized by XRD, DTA-TGA in combination with EGA, SEM and EDS analyses. Due to requirement of the material refractoriness there were also tested options of preparation of MDF composites based on phosphates binders which are used in refractory manufacture.
|
|
|
Possibilities of clay plasters shrinkage elimination
Melichar, Jindřich ; Koplík, Jan (referee) ; Opravil, Tomáš (advisor)
Earth plasters which are applicated in interiers don´t have just an estetic, but mainly heat storage function. To accomplish better storage properties the plaster has to be laid on the wall in sufficient thick ply. But this use to be accompained by creating of cracks during dehydration of the plaster. This bachelor work will be considering possibilities of elliminating this negative event by additing suitable components to suppress shrinkage and cracks by creating ettringite.
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