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Preparation and characterization of polyhydroxybutyrate-based particles
Kopřivová, Lenka ; Šindelář, Jan (referee) ; Pospíšilová, Aneta (advisor)
This bachelor's thesis deals with the preparation of particles with a modified surface based on poly 3 hydroxybutyrate and the subsequent characterization of both modified and untreated particles. The particles were examined with a vision for future replacement for non degradable commodity microplastics in the cosmetics industry, as they are capable of biodegradation. The following chemicals were used for surface treatment: zinc stearate solution, lipase, hydrophobic silane (hexadecyltrimethoxysilane) and cationic surfactant. Next, the properties of the resulting modified particles were studied in comparison with unmodified poly 3 hydroxybutyrate and polyurethane-based powder, which is currently used in the cosmetic industry, and therefore served as a standard for sensory analysis. All samples were subjected to SEM and EDS analysis, FTIR spectroscopy and sensory analysis. Then, the following properties were measured: wettability, bulk density and particle size distribution by laser diffraction. Wettability was measured on compressed tablets from the powders using static contact angles. It was found that the hydrophobicity of particles treated with silane and zinc stearate increased, whereas the particles treated with cationic surfactant increased in hydrophilicity. The results measured from the contact angle and other analyses led to the conclusion that the surface treatment with lipase was not successful. Sensory analysis showed that the surface treatments did not affect the deterioration of the sensory properties compared to the original untreated PHB powder and that an untrained evaluator cannot tell the differences in pleasantness between the samples therefore, we can consider them as pleasant as the standard we determined.
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Vliv termické úpravy dřeva na jeho navlhavost a smáčivost
Bednář, Jakub
Presented bachelor thesis discusses the effect of wood wettability change and contact weting angle change by heat treatment. Experimental measurements are performed for the wood of beech (Fagus sylvatica) and spruce (Picea abies), wherein three levels of heat treatment in the temperature range 100-180 °C are selected. For samples with this treatment are compiled experimental models of sorption isotherms, which are compared with one another and with the values of the theoretical models taken from literature. In the second part, the change of surface free energy and contact wetting angle for those samples is investigated. Contact wetting angle is taken from transversal section. That can have great influence for example in the case of linear-glued wood panels.
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Plasma discharge generated by surfatron with frequency 2,45 GHz
HOUSER, František
This diploma thesis deals mainly with utilization of plasma in technological aplications. The introductory part is apllied to the theoretical description of plasma generated by the surfatron. This launcher works with the frequency of 2,45 GHz and it is able to excite the surface wave, that sustains plasma column in a quartz tube. Plasma generated by surfatron was used for modification of surface properties of polyethylen to change its surface energy. By changing of surface energy it was reached of higher hydrophilicity. Plasma generated by surfatron was diagnosed in detail during experiments in a continual regime as well as in a pulse one with a help of a single {--} probe and a double {--} probe Langmuir measurement. In this diploma thesis there is discussed influence of pressure, power and other experimental options.
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