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The influence of conditioning on the mechanical properties of polymers produced by injection molding technology
Neužil, Tomáš ; Řehořek, Lukáš (referee) ; Válka, Libor (advisor)
The aim of the thesis is to determine change of mechanical properties of three types of damp polymeric materials (polyamides) depending on the water content inside material. Before testing, specimens of all three types of materials were placed inside the air conditioning chambers until equilibrium (conditioned) state was reached when the specimens received the maximum possible amount of water from the environment. A total of three conditioning levels were set, representing besides the standard level of conditioning both extreme states like state when the material was fully dried and the state where the material content the largest possible amount of water. With the increasing content of water bound in material, there is a characteristic change in the mechanical properties of the material, such as a decrease in strength and modulus of elasticity and an increase in toughness and ductility. To examine material properties change, tensile and Charpy impact tests were performed, Charpy impact tests were performed for both specimens with and without a notch. Besides changes in mechanical properties, the rate of water absorption was also observed depending on the materials and its filling.
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MOISTENING OF COMPONENT MATERIALS AND SPEED OF DEHUMIDIFICATION
Pospíšil, Tomáš ; Tomáš, Bžoněk (referee) ; Starý, Jiří (advisor)
This bachelor thesis deals with process associated with moisture in electrotechnics. The bachelor thesis is focused on the components and basic materials that are sensitive to moisture and defects caused by moisture in the reflow soldering process. The theoretical part describes the principles of measuring humidity and sorts of absorption. Furthermore this work described the basic classification and defects in components, base materials and packaging material sensitive to moisture and selection of standards dealing with this issue. Another theoretical part is focused on the manipulation with components and materials sensitive to moisture. The practical part deals with the methodology and practical measurement of moisture soaking in the components and materials with respect to their level of sensitivity to moisture. The following part is focused on the methodology of drying, practical measurement of drying and comparing two drying cabinets.
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Hydrolytical stability of poly(3-hydroxybutyrate)
Korčušková, Martina ; Petruš, Josef (referee) ; Kučera, František (advisor)
The bachelor thesis deals with the study of hydrolytical stability of poly(3-hydroxybutyrate) in the hydrolysis with excess of water and in the hydrolytic degradation in melt. Theoretical part summarises knowledge about the process, mechanism and kinetics of hydrolysis and contains an overview of further decomposition reactions of poly(3-hydroxybutyrate). Experimental part is focused on degradation of poly(3-hydroxybutyrate) in the presence of water and on comparing the rate of hydrolytical degradation with acidic and alkaline catalysis. In order to comparing the range of hydrolysis, hydrolytic degradation of poly(3-hydroxybutyrate) was investigated in extruder at the temperature of 170 °C. Samples were analyzed to determine the melt volume index, melt temperature, degree of crystallinity, distribution of molecular mass and the structure of poly(3 hydroxybutyrate) using infrared spectroscopy.
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Možnosti nastavování překližek do větších formátů
Lempera, Martin
The bachelor´s work deals with problematics of longitudinal setting of plywood materials, for a purpose of comparing of mechanical features of particular glue mixtures at the connecting at chamfer. The first part of the work deals with characteristics, production and division of plywood boards. Follows the information about connecting and surface finish of plywood boards. The second part of the work contains methodology of carrying out tests and results of particular groups of samples according to glued materials. The main testing of samples was focused on modulus of rupture (MOR) and modulus of elasticity (MOE). Further performed tests were for a purpose of finding out of: moisture, density, durability of edges, their dampness and resistance of surfaces of plywood boards against abrasion.
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Možnosti snížení navlhavosti dřeva a přestupu vlhkosti do dřeva užitého v konstrukci rezonanční desky hudebního nástroje
Zatloukal, Petr
This theses is focused on possibilities of sorption properties decrease of musical instruments soundboards. This task should be solved with respect to sustainability of previous acoustics properties or their improving. The resonance wood specimens has been fabricated and conditioned to the relative humidity of 40 % The specimens were divided into three groups. The first one with natural properties, the second one treated by the temperature of 180 °C and the last one was treated by 200 °C. Specimens were conditioned all together to the relative humidity of 60 % and at the last step at 80 %. The conditioning was isothermal with the temperature of 20 °C. Swelling and hygroscopicity establishment was based on dimensions and weight measurement during conditioning of specimens. The first, second and longitudinal natural oscillation frequency of the specimens were determined by free-free resonant frequency method. Longitudinal and transversal sound propagation velocity were measured using Fakopp Ultrasonic Timer. Dynamic Young’s modulus (E´L,E´RT), dynamic bend Young’s modulus (Eb), acoustic constant (KL, KRT), characteristic impedance (ZL, ZRT), acoustic conversion efficiency (ACEL, ACERT), relative acoustic conversion efficiency (RACEL, RACERT) and damping coefficient (tan δ) were determined using the measured data. The treatment by 180 °C caused the decrease of volume swelling, which was 7,4% lower after the treatment. The hygroscopicity decreased by 2,8%. The treatment by 200 °C decreased swelling by 8,5% and the hygroscopicity by 4,3%. The different results of both treatments were observed in case of longitudinal sound velocity. In case of 180°C treatment the value of longitudinal sound velocity decreased by 1,6 %, whereas after treatment by 200 °C the increase by 2,1% was found. Acoustical properties E´, Eb, K, Z, ACE, RACE were decreasing due to the higher moisture content and tan δ was increased. Heat treatment by 180 °C has not significantly affected acoustical properties and sound velocity but the treatment by 200 °C caused their increase.
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The influence of conditioning on the mechanical properties of polymers produced by injection molding technology
Neužil, Tomáš ; Řehořek, Lukáš (referee) ; Válka, Libor (advisor)
The aim of the thesis is to determine change of mechanical properties of three types of damp polymeric materials (polyamides) depending on the water content inside material. Before testing, specimens of all three types of materials were placed inside the air conditioning chambers until equilibrium (conditioned) state was reached when the specimens received the maximum possible amount of water from the environment. A total of three conditioning levels were set, representing besides the standard level of conditioning both extreme states like state when the material was fully dried and the state where the material content the largest possible amount of water. With the increasing content of water bound in material, there is a characteristic change in the mechanical properties of the material, such as a decrease in strength and modulus of elasticity and an increase in toughness and ductility. To examine material properties change, tensile and Charpy impact tests were performed, Charpy impact tests were performed for both specimens with and without a notch. Besides changes in mechanical properties, the rate of water absorption was also observed depending on the materials and its filling.
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Hydrolytical stability of poly(3-hydroxybutyrate)
Korčušková, Martina ; Petruš, Josef (referee) ; Kučera, František (advisor)
The bachelor thesis deals with the study of hydrolytical stability of poly(3-hydroxybutyrate) in the hydrolysis with excess of water and in the hydrolytic degradation in melt. Theoretical part summarises knowledge about the process, mechanism and kinetics of hydrolysis and contains an overview of further decomposition reactions of poly(3-hydroxybutyrate). Experimental part is focused on degradation of poly(3-hydroxybutyrate) in the presence of water and on comparing the rate of hydrolytical degradation with acidic and alkaline catalysis. In order to comparing the range of hydrolysis, hydrolytic degradation of poly(3-hydroxybutyrate) was investigated in extruder at the temperature of 170 °C. Samples were analyzed to determine the melt volume index, melt temperature, degree of crystallinity, distribution of molecular mass and the structure of poly(3 hydroxybutyrate) using infrared spectroscopy.
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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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MOISTENING OF COMPONENT MATERIALS AND SPEED OF DEHUMIDIFICATION
Pospíšil, Tomáš ; Tomáš, Bžoněk (referee) ; Starý, Jiří (advisor)
This bachelor thesis deals with process associated with moisture in electrotechnics. The bachelor thesis is focused on the components and basic materials that are sensitive to moisture and defects caused by moisture in the reflow soldering process. The theoretical part describes the principles of measuring humidity and sorts of absorption. Furthermore this work described the basic classification and defects in components, base materials and packaging material sensitive to moisture and selection of standards dealing with this issue. Another theoretical part is focused on the manipulation with components and materials sensitive to moisture. The practical part deals with the methodology and practical measurement of moisture soaking in the components and materials with respect to their level of sensitivity to moisture. The following part is focused on the methodology of drying, practical measurement of drying and comparing two drying cabinets.
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