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Modification of polyurethane by biodegradable poly(hydroxybutyrate)
Kupka, Vojtěch ; Žídek, Jan (referee) ; Vojtová, Lucy (advisor)
Cílem předložené bakalářské práce byla syntéza elastomerního polyuretanu plněného biodegradabilním polyhydroxybutyrátem. Vzorky byly podrobeny analýze morfologie pomocí rastrovací elektronové mikroskopie, mechanické vlastnosti byly testovány jednoosou tahovou zkouškou. Práce se taktéž zabývá předpovědí mechanických vlastností na základě teorií kaučukové elasticity. Bylo zjištěno, že výsledný materiál je částicový kompozit, kde se vzrůstajícím hmotnostním obsahem plniva v materiálu vzrůstá modul pružnosti. Predikce tahových křivek pomocí softwaru SEC.exe ukazovala pro reálný průběh křivky nereálné hodnoty hustot polymerních řetězců. U modelů, které vykazovaly reálné hodnoty hustot, byly naopak hodnoty napětí vyšší, než ve skutečnosti naměřené.
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Rheological properties and biodegradation of Poly (3-hydroxybutyrate-co-4-hydroxybutyrate)
Černeková, Nicole ; Obruča, Stanislav (referee) ; Kovalčík, Adriána (advisor)
This diploma thesis deals with the characterization of rheological properties and biodegradation of a poly(3-hydroxy-co-4-hydroxybutyrate), a copolymer produced by a strain of Cupriavidus malaysiensis. The theoretical part focuses on the rheology and degradation of polymers in general. It also contains the basic characteristics of polyhydroxyalkanoates and deals in more details with the description of the studied copolymer, its properties, synthesis, decomposition and possibilities of its applications. In the experimental part, the given copolymer was investigated in its native form and also in the form of copolymer mixtures filaments, which were enriched with additives (stabilizers and plasticizers). In terms of rheology, the samples showed pseudoplastic behaviour, which was slightly limited by the plasticization of the material. The highest thermal stability observed as a function of changes in complex viscosity over time was observed in a sample of a copolymer mixture containing stabilizers and plasticizer Citrofol BII. The plasticization also caused significant changes in thermal properties, especially crystallinity, which decreased compared to the native copolymer. In vitro degradation studies of samples in the form of films prepared by dissolving copolymer mixtures in chloroform were performed in phosphate buffer with lipase, in simulated body fluid and in synthetic gastric juice. The course of the process itself was characterized by the method of determining the molecular weight (SEC-MALLS) and the weight loss over time (gravimetrically). The results showed that the analysed samples are subject to degradation in all used environments. The most considerable molecular weight loss after 105 days (76 %) was observed in the sample containing stabilizers and plasticizer Citrofol BII in the environment of synthetic gastric juice. The most extensive gravimetric weight loss was attributed to the sample with stabilizers and without plasticizers, in the environment of phosphate buffer with lipase, specifically by 79%.
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Microbial Degradation of Polycaprolactone-based Materials
Damborský, Pavel ; Stratilová, Eva (referee) ; Hermanová, Soňa (advisor)
Diplomová práce se zabývá vlivem nutričních a aeračních faktorů na produkci lipáz bakterií Bacillus subtilis (CCM 1999). Produkce lipáz byla studována zejména z hlediska katalytického působení lipáz při degradaci polyesterových řetězců. Mezi studované parametry patřily: růst bakterií, lipolytická aktivita, pH optimum, teplotní optimum, tepelná stabilita, proteolytická aktivita, množství bílkovin, atd. a to v různých typech živných medií zaočkovaných Bacillus subtilis. Jedna série vzorků kultivačních médií pro BS na bázi: pepton a kvasničný extrakt (NB), pepton, kvasničný extrakt s 2% přídavkem (w/v) glukózy (NBG) a minerální médium s kvasničným extraktem (MS-YE) obsahovala jeden PCL vzorek o definovaných rozměrech (Mn = 10 kDa, = 1.4). Experimenty probíhaly po dobu 21 dnů pří rychlosti třepání 160 a 200 rpm. Přítomnost PCL způsobila v obou typech médií (NB, NBG) inokulovaných BS zvýšení lipolytické aktivity, což naznačuje, uvolnění a následné uplatnění se nízko-molekulekulárních řetězců PCL jako substrátů pro BS. BS kultivovaný v MS-YE medium vykazoval ve srovnání s NB a NBG médii nízké hodnoty lipolytické aktivity a to i v přítomnost PCL. Během experimentů se hodnota pH posunula z neutrální (pH 7.0) do alkalické (pH 8.5-9.3) oblasti a to ve všech typech médií s i bez přítomnosti PCL vzorku v důsledku metabolických pochodů BS využívajících různé substráty. Lipolytické enzymy stanovené v supernatanech bez bakteriálních buněk vykazují dvě pH optima v přítomnosti PCL, pH 7 a 9. V nepřítomnosti polymeru vykazují pouze jedno pH optimum při pH 7. Na základě měření tepelné stability bylo prokázáno, že extracelulární lipázy jsou relativně termostabilní enzymy, zejména v nepřítomnosti polymeru. Dále byla provedena základní proteomická analýza lipáz produkovaných bakterií Bacillus subtilis v NBG médiu pomocí metody peptidového mapování (PMF). Byla ověřena přítomnost proteinů s molární hmotnosti (19.3 kDa) pomocí FPLC. SDS-PAGE a IEF-PAGE prokázaly přítomnost těchto proteinů v obou studovaných mediích inokulovaných BS (NBG vs. NBG/PCL). Zásadní rozdíly proteinového složení v přítomnosti PCL nebyly potvrzeny a identifikace pomoci MALDI-TOF hmotnostní spektrometrie nestanovila žádnou lipázu. Proces degradace v PCL vzorcích byl vyhodnocen také na základě hmotnostních úbytků, které byly zjištěny ve všech typech médií inokulovaných BS pravděpodobně v důsledku synergického účinku enzymaticky-katalyzované a biotické hydrolýzy v alkalickém prostředí. . Modelová degradační studie PCL a jeho kompozitu s oxidem grafenu (2.7 hm.%, GO) byla provedena v přítomnosti bakterie Bacillus subtilis v NBG při 30 °C a počátečním pH 7 po dobu tří týdnů. Hmotností úbytky PCL filmů se postupně zvyšovaly během celého degradačního testu až ke 12 hm%. Degradace PLC/GO kompozitu probíhala pomaleji, což je prokázáno maximální hmotnostním úbytkem 5 hm%. Podobný charakter elučních křivek PCL a jeho kompozitu stanovený pomocí SEC potvrzoval snížení molární hmotnosti po degradaci.
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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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Biodegradation of bioplasts in compost environment
Vodička, Juraj ; Kovalčík, Adriána (referee) ; Obruča, Stanislav (advisor)
This master’s thesis focuses on biodegradation of polyhydroxybutyrate (PHB) and polylactic acid (PLA). The theoretical part discusses an origin, properties and applications of investigated biopolyesters, and so the enzymology of their biodegradation. The experimental part deals with biodegradation of these polymers in liquid medium using several pure thermophilic bacteial strains and controlled composting of these bioplastics. Amongst six tested thermophilic bacterial strains only one showed PHB-biodegradation activity – strain Schlegelella thermodepolymerans. No degradation degree of amorphous or semi-crystalline PLA was observed. Mainly disintegration of both forms of PLA articles was observed in compost environment, thus the abiotic mechanism of its decomposition was indicated. After 4 weeks of composting, the relative weight loss of 99 % and 63 % was detected in amorphous and semi-crystalline PLA respectively. On the contrary, the weight loss of PHB after 4 weeks of composting reached 36 %, moreover, a half decrease of molar mass was observed using SEC. The surface erosive mechanism of PHB-biodegradation was stated using SEM. By monitoring of esterase, lipase and protease activities, no influence on the compost by polymer presence was concluded at statistical significance.
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In vitro biodegradation of biopolyesters exposed to synthetic gastric juice
Sobková, Markéta ; Skoumalová, Petra (referee) ; Kovalčík, Adriána (advisor)
This bachelor’s thesis is focused on the study of in vitro biodegradation of biopolyesters exposed synthetic gastric juice and phosphate buffer saline with lipase for 81 days. The theoretical part summarises the necessary information about characteristics of biodegradable biopolyesters, deals with their possible applications in medicine. The experimental part deals with the biodegradation of prepared biopolyesters films. in this work, poly(lactic acid), amorphous poly(hydroxy alkanoates), poly(3-hydroxybutyrate), poly(butylene adipate terephthalate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), filament poly(lactic acid) and filament poly(lactic acid)/poly(hydroxybutyrate) were used for the experiment. The films were prepared by dissolving of the biopolyesters in hot chloroform. The dissolving agent was evaporated, and prepared films were dried. Prepared films had different properties depending on the used biopolyesters. Their appearance was formed transparent to milky cloudy. Also, trey differed in their plasticity. During biodegradation, the morphology changed, and the samples gained higher fragility. The effect of biodegradation was monitored by changes in 1) molecular weights (SEC-MALLS), 2) chemical structure (FTIR) and 3) weight loss changes (gravimetrically). The analysed biopolyesters were demonstrably susceptible to biodegradation in simulated body conditions. The degree of biodegradation depends on the type of biopolyester. The most significant weight loss was recorded for the sample of amorphous polyhydroxyalkanoate (PHA). The PHA´original weight was reduced about 84.28 ± 0.03 % after the 81 days of biodegradation in the phosphate-buffered saline with lipase.
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Modification of concrete elements for cooling towers
Mohelská, Lucie ; Šoukal, František (referee) ; Opravil, Tomáš (advisor)
This master´s thesis deals with the suppression of the growing of algae in cooling towers. Subject of the work is suggestion and testing surface modification of the existing mature concrete in order to suppress the growth of algae. In the frame surface modification, several commercially available and newly developed systems were tested. Testing systems are based on the basis of portland cement, geopolymers or formation of insoluble complex compounds containing metal elements (Zn, Cu). Experimental methods were applied in the real environment of cooling towers of Dukovany Nuclear power plant.
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Processing optimalization of biodegradable starch based packaging and its characterization for adaptation on production technology
Krahulová, Veronika ; Ondreáš, František (referee) ; Lepcio, Petr (advisor)
This diploma thesis focuses on the problematics of preparation of biodegradable starch based packaging. The aim of the thesis is to optimize the preparation and verify the characteristics for further adaptation and production technologies. The films consisted of starch, PVA and glycerol. Four types of starches, three types of PVA and different ratios of glycerol were tested. Films were prepared by casting with glycerol as a plasticizer, instead of distilled water, to reduce the energy cost of the preparation. The mechanical properties of the films were tested as well. The experimentally determined values of elongation at break and tensile strength of the wheat starch films were compared with a semiempirical model. Results revealed that the preparation of thermoplasticization of starch with glycerol leads to a considerable increase in elongation at break but at the same time to a marked decrease in tensile strength compared to the preparation from solution. The rheological properties of the prepared films were also investigated. Infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to study the structure of the films.
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