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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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Functionalization of polyolefins by grafting
Paulenka, Igor ; Petruš, Josef (referee) ; Petrůj, Jaroslav (advisor)
The theoretical part of the diploma thesis is focused on the funcionalization of polyolefins in order to accelerate their degradation and to increase their carbon content from renewable resources with focus on hydroxyacids. The experimental part is focused on preparing samples and studying the properties of the polypropylene and polyethylene blends with the polylactide with different contents of the initiator and the maleic anhydride. Samples were evaluated by determining the degree of conversion maleic anhydride, differential scanning calorimetry, infrared spectroscopy, melt flow index and mechanical properties.
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Electrical behaviour of polymeric composites with expanded graphite
Šimonek, Michal ; Petruš, Josef (referee) ; Kučera, František (advisor)
Electrically conductive thermoplastic composites made from graphene nanoplatelets or graphene precursors are a promising branch of new functional materials. Graphene nanocomposites were prepared via processing in an internal mixer from four extrusion grade polyethylenes (PE) and expanded graphite (EG). As a method of possible improvement of EG dispersion, compounding in presence of various compatibilizers is examined. Melt compounding was performed for 10 min at 200 °C and 60 rpm. The electrical conductivity of compression-molded samples was determined from a current voltage characteristic or direct resistance measurement. Composite morphology was characterized by scanning electron microscopy. Depending on the PE matrix and compatibilizer structure, different electrical conductivities and morphologies were observed, which corresponded in agreement with either percolation theory or the random-resistor network of Miller and Abrahams models. Substantial reduction of percolation threshold was achieved in compatibilized ultra-low density polyethylene where percolation occurred at 3,92 % vol.
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Application of functional fillers in composites: Effects of fillers content on the mechanical properties
Krhut, Jiří ; Petruš, Josef (referee) ; Poláček, Petr (advisor)
This work deals with the application of selected types of fillers and monitoring their addition to the specific properties of the resulting composite material. The theoretical part of this work includes a general description of composite materials, and selected types of matrices, followed by a brief description of the characteristics of particulate composites and the effect of fillers on selected material properties. In the experimental part, samples of polyester resin were prepared to contain the given content of filler based on aluminium hydroxide (Al(OH)3), expanded glass, hollow glass microspheres, and fillers based on nitrogen and phosphorus compounds. Subsequently, the influence of the used fillers on the rheological properties, flammability of the material, on mechanical and thermomechanical properties was monitored. Flame test methods, bending test methods and dynamic mechanical analysis (DMA) were used to evaluate the samples. Finally, the measurement was supplemented by an analysis of fracture surfaces using a scanning electron microscope (SEM). The addition of additives improved the fire resistance of the prepared materials. The mechanical and thermomechanical properties of the prepared materials differed significantly depending on the applied fillers and their content.
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Application and properties of silicone textile coatings
Bernátová, Silvia ; Petruš, Josef (referee) ; Kučera, František (advisor)
The diploma thesis in the first part deals with a theoretical description of coating technologies, textile materials used in coatings, types of coated polymers and properties of coatings - especially adhesion. The experimental part of the work is devoted to the preparation of textile coatings from polyester fabric and coating based on addition silicone. Using the developed method of sample preparation for T-peel testing of the adhesive strength, the improvement of the adhesion of the coating by chemical adhesion with the support of adhesive agents was studied. The second method studied the change in compactness and adhesion of the coating to the fabric after shaking as a function of breathability. The influence of side reactions of reagents on silicone cohesion was studied by preparing dogbones for testing tensile-deformation properties. The research also included the characterization of silicone samples using ATR-FTIR, monitoring the weight gain and thickness of the fabric after coating, the feel and color stability of the applied fabric and observing the coating under an optical microscope.
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Copolymeric Acrylamide Gels: Preparation and Properties
Nováková, Pavlína ; Petruš, Josef (referee) ; Kučera, František (advisor)
The bachelor thesis deals with the preparation and properties of copolymer acrylamide gels. The theoretical part is focused on the general characteristics of gels, closer look at copolymeric acrylamide gels – preparation methods, various possibilities of initiation, crosslinking, and use of comonomers. Factors influencing swelling of the gel were described. The experimental level focuses on the preparation of neutral polyacrylamide gel and acrylamide copolymeric gel with anionic component, sodium acrylate. First, the formation of the copolymer and the presence of functional groups were verified by infrared spectroscopy with Fourier transformation. Then gels of different concentrations of sodium acrylate and the crosslinking agent, bisacrylamide, were prepared by radical solution polymerisation. The influence of the gel composition on the swelling degree in distilled water was investigated on the prepared samples. The selected samples were then swelled in environments of different pH and ionic strengths to assess the influence of the external environment on the swelling degree.
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Functionalization of Poly(Lactic Acid)
Petruš, Josef ; Pospíšil, Ladislav (referee) ; Alexy,, Pavol (referee) ; Petrůj, Jaroslav (advisor)
Teoretická část předložené dizertační práce popisuje princip radikálového roubování a faktory ovlivňující reakční průběh. Radikálové roubování poly(mléčné kyseliny) (PLA) reaktivní modifikací je vhodnou technikou přípravy biodegradabilních polymerních materiálů s rozličnými vlastnostmi. Současný stav problematiky modifikace poly(mléčné kyseliny) radikálovým roubováním v tavenině je obsahem literární rešerše včetně možných aplikací. Experimentální část se zabývá modifikací PLA anhydridem kyseliny itakonové (IAH) radikálovým roubováním v tavenině. Reakce byla iniciována 2,5-bis(tert-butylperoxy)-2,5-dimethylhexanem (L101). V první části je průběh radikálového roubování pozorován “in situ” pomocí diferenciální kompenzační kalorimetrie (DSC) a termogravimetrické analýzy (TGA). Exotermní pík na DSC záznamu odpovídá průběhu radikálové reakce, na jehož základě lze definovat aktivační energii reakce. Průběh TGA křivky “in situ” radikálové reakce umožňil detekovat vedlejší produkty vznikající v průběhu radikálové modifikace. Ve druhé části byla PLA funkcionalizována reakcí v diskontinuálním laboratorním mixéru za reakčních podmínek navržených dle poločasu rozpadu zvoleného iniciátoru a zpracovatelských podmínek PLA. Reakční teplota 190 °C byla stanovena výpočtem z Arrheniovy rovnice pro reakční čas 6 min. Uvedené reakční parametry byly zvoleny s ohledem na kinetiku rozkladu L101 a potlačení degradace PLA. Infračervená spektroskopie (FTIR) potvrdila navázání IAH na PLA řetězec na základě výskytu –CH2 vibrací s absorpčními pásy při vlnočtu 2860 a 2920 cm-1. Vzrůstající intensita absorpčního pásu 1750 cm-1 potvrdila přítomnost minoritních C=O vibrací anhydridového kruhu překrytých dominantními C=O vibracemi PLA řetězce. Nukleární magnetická rezonance (1H-NMR) nepotvrdila roubování oligomerního IAH na PLA. Koncentrace reaktantů ve zvoleném rozsahu (0.5–10 hm % IAH, 0.1–2 hm % L101) byla použita pro posouzení jejího vlivu na obsah naroubovaného IAH a míru vedlejších reakcí, např. -štěpení, větvení a síťování. Při vysoké koncentraci IAH a L101 byla potvrzena homopolymerace IAH i přes její zanedbávání v tématicky podobných studiích. Tvrzení o IAH homopolymeraci bylo podpořena výsledky kolorimetrické analýzy, charakterizací vzorků připravených polymerací IAH za podmínek radikálového roubování a termickou stabilitou frakcí extrahovaných z PLA-g-IAH. Radikálovou modifikací PLA došlo ke zvýšení flexibility polymerních řetězců díky objemné struktuře IAH navázané na PLA řetězci, což se projevilo poklesem teploty skelného přechodu (Tg). Zvýšený obsah amorfní fáze, hydrofilní chování, rozvětvená struktura a štěpení řetězců má pozitivní vliv na zvýšenou biodegradabilitu PLA-g-IAH v porovnání s nemodifikovanou PLA. Neradikálová degradace, probíhající v průběhu zpracování PLA, byla prokázána změnou tokových vlastností taveniny. Tento nežádoucí jev byl potlačen přídavkem tzv. “prodlužovače řetězců” obsahujícího reaktivní epoxy skupiny. Reakce mezi epoxy skupinami a karboxylovými skupinami byla potvrzena pomocí FTIR a změnou reologických vlastností PLA-g-IAH.
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Inflence of technological conditions and polyhydroxybutyrate materials composition on crystallinity
Olšan, Jakub ; Petruš, Josef (referee) ; Kučera, František (advisor)
Diploma thesis is summarizing sources and technology of PHB and its physical and chemical properties compared to other polymers. Thesis mentions usage and function of certain additives in PHB matrix and their impact on the final product. Practical part of the thesis is concerned with technological parameters and degradation of the PHB during extrusion. The thesis also observes behaviour of nucleating agents on crystallinity and crystallization properties of prepared compounds. Degradation was analyzed by MFI and colour difference against standard material, FTIR was not successfully used for the purpose of degradation. Crystallinity and crystallization behaviour was analysed by DSC and optical microscopy with heated operating table. Graphs were created from results of analysis and suitable usage of each nucleating agent was considered. Boron nitride was selected as the most suitable nucleating agent due to creating higher amount of smaller spherulites.
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Composite materials with enhanced coefficient of linear attenuation of ionizing radiation
Novotný, Kamil ; Petruš, Josef (referee) ; Kučera, František (advisor)
Ionizing radiation has many useful applications in the fields of healthcare, food industry, nuclear energy and others but poses a hazard to human health in higher doses. In this work, composite materials with enhanced ionizing radiation attenuation properties were prepared. Unsaturated polyester resin was reinforced with inorganic fillers containing elements such as bismuth or barium. Morphology of the samples was studied using scanning electron microscopy. Theoretical values of mass attenuation coefficients were obtained for photon energies 662 keV and 1253 keV using the XCOM software. The attenuation of ionizing gamma radiation was experimentally measured using radioactive sources 137Cs and 60Co. Linear attenuation coefficients and half value layers of the materials were determined using the obtained data. Addition of the fillers improved the shielding properties of the matrix. Composite containing bismuth oxide achieved the highest values of linear and mass attenuation coefficients. The experimental results were found to be in good agreement with theoretical values. Moreover, influence of the fillers on impact toughness has been evaluated.
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