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Bio-Based Water-Repellent Coating for Wood
Münstermann, Nils ; Weichold, Oliver
Wood is one of the oldest building materials and is currently becoming increasingly popular again due to the present growth in awareness in society regarding environmental issues. Wood is hygroscopic and porous, i.e. it not only absorbs moisture from the atmosphere, but also actively and quickly sucks up large amounts of water through its capillary system particularly via the end grain. This leads to dimensional changes, but above all the wood becomes susceptible to rot. As a result, for many applications wood needs to be protected from moisture. Besides a large number of well-established petrochemical products, there are still some traditional, natural finishes available. The most prominent ones are linseed oil and tung oil. Due to their large content of linoleic acid, both harden in air via autooxidation. However, to achieve a decent degree of protection, both oils need to be applied in multiple layers and the final coating requires at least several days to harden completely. In addition, linseed oil interferes with the food chain and tung oil is said to be toxic in some publications.
We have recently developed an alternative coating for wood based on chitosan, which can be obtained from food-industry waste. The coating is applied from an aqueous solution and adheres nicely to wood surfaces due to the structural similarity of chitosan and cellulose. The polymerised film reliably seals the end-grain of wood against liquid water. Currently, the polymerisation requires the films to be heated to 70 °C in an oven, but a method for UV curing is being worked on.
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Application of microencapsulation techniques in development of novel controlled-release systems.
Karásková, Iva ; Mravec, Filip (referee) ; Sedláček, Petr (advisor)
This diploma thesis deals with application of microencapsulation techniques in development of hydrogel controlled-release systems in which the main role is played by humic acids, biopolymer chitosan, compound fertilizer NPK and 3-indoleacetic acid. This paper continues my bachelor thesis topic about utilization of polyelectrolyte complexes. The aim of this work was to develop a literature review focusing on the microencapsulation techniques and according to its results optimize the method. Microencapsulation was performed with a commercial encapsulator BUSCHI B-395 Pro and a release of individual components into a water was measured. An amout of released substances was measured by UV-VIS method and HPLC analysis. Practical part also included testing of repeated swelling and drying. It was found that suitable composition and combination of ingredients form hydrogels for further use in agriculture.
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Reactivity-mapping studies on biopolymers in hydrogel forms
Smilek, Jiří ; Kislinger, Jiří (referee) ; Sedláček, Petr (advisor)
The diploma thesis is focused on the study of interactions between biopolymers and model probes in a hydrogel media utilizing diffusion processes. The main aim was to test and to optimize selected combination of diffusion methods (diffusion cells and unsteady diffusion) in study of interactions between biopolymers and organic dyes. Anionic (humic acids) and cationic (chitosan) representatives of biopolymers were utilized and methylene blue and methylene orange were used as a reactivity probe in the case of humic acids and chitosan, respectively. Another appreciable part of the work is represented by in-depth characterization of applied biopolymers and hydrogel samples by a wide range of analytical and physico-chemical methods (rheometry, UV-VIS, FT-IR etc.). Besides particular experimental results on studied systems, the diploma thesis provides both theoretical and practical background for subsequent applications of the innovative and full-automated method for reactivity mapping of biopolymers.
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Disposable sensor of ammonium for intelligent packaging
Nentvichová, Aneta ; Kořínková, Radka (referee) ; Veselá, Mária (advisor)
This diploma thesis is focused on the problematic of the smart packaging and deals with the preparation of disposable ammonia sensors/indicators and the subsequent color measurement of prepared sensors/indicators using the CIE L* a* b* color space. The theoretical part of the diploma thesis focuses on active and intelligent packaging, using ammonia sensors/indicators. The emphasis is placed on the main components of the sensor/indicator, i.e., chitosan as a polymer and curcumin as a dye. The theoretical part also includes the problematic of meat degradation, which plays a very important role in this thesis. The experimental part was divided into two parts. The first part was to prepare layers that will respond in different colors based on the concentrations of ammonia. Prepared layers were sensitive to ammonia across all concentrations, and based on this result, ascorbic acid was applied to compositions to achieve a calibration retention of the selected amount of ammonia. The second minor part of the experiment was the application of selected layers to packages with real meat.
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Hydrogels based on cationic polyelectrolytes
Jarábková, Sabína ; Lehocký,, Marián (referee) ; Pekař, Miloslav (advisor)
This diploma thesis deals with the study of physical hydrogels based on positively-charged polyelectrolyte. The study is to investigate the interaction of selected positively-charged polyelectrolytes with oppositely charged surfactants in water and in physiologicla saline solution (0.15 M NaCl). The influence of the process for preparing hydrogels. Hydrogels were prepared by dry or wet. Were tested solubilization abilities hydrogels prepared using the hydrophobic dye oil red O were also measured rheological properties of the hydrogels prepared using frequency oscillatory tests and flow tests, depending on the concentration of the polymer or surfactant. For the rheological experiments suggest that chitosan is capable of forming rigid hydrogels with better mechanical properties than the dextran in the presence of both surfactants. Selected samples were also carried out experiments using fluorescent sold prodan, nile red and -naphthol as fluorescent probes. And in selected experiments was determined by solids content in percentage depending on the concentration used polyelectrolytes or surfactants.
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Study of interactions of pigments with biopolymer chitosan
Kolesa, Pavel ; Kalina, Michal (referee) ; Klučáková, Martina (advisor)
This master's thesis was focused on the study of interaction of some organic azo dyes (model diffusion probes) with cationic biopolymer chitosan. This interactions were realized via diffusion processes in hydrogel media based on thermoreversible agarose. The main aim was study of influence of pH of solution on the diffusion process. Interactions of used dyes are based on electrostatic character. The aminogroup of chitosan interacts with the functional group of chosen dyes (anionic sulfonic group) and thus affects the process of diffusion. The model diffusion compounds were chosen organic anionic dyes Chicago sky blue 6B (C.I. 24 410), Sirius red (C.I. 35 780) and Reactive blue 49 (C.I. 621 526). The important content of this diffusion method is a monitoring of the time progression of diffusion profile by UV-VIS spectrophotometry. The presented work follows the bachelor thesis and shows comprehensive view of the reactivity of chitosan and its behavior in different systems. Unsteady diffusion in cuvettes appears to be a universal method for the study of reactivity of biopolymers and for the study of transport processes in hydrogel media. The diffusion method is universal, easy and cheap.
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Preparation and characterization of hydrogels based on cationic biopolymer
Tesařová, Barbora ; Mravec, Filip (referee) ; Smilek, Jiří (advisor)
Presented thesis deals with the preparation and characterization of hydrogels based on positively-charged biopolymer and negatively-charged tenside. As an appropriate representative of positively-charged polymer was chosen chitosan, because of his biocompatibility and biodegrability, and N,N,N-trimethylchitosan, which was synthetised from chitosan in this diploma thesis. The final product of synthesis was characterised by SEC-MALS, elemental analysis, infrared spectroscopy and nuclear magnetic rezonation. Interactions between these polymers and representatives of negatively-charged tensides, which are sodium dodecylsuphate and sodium tetradecylsulphate, were investigated. The main method used in this thesis was rheology, through it were investigated prepared hydrogels based on chitosan and tensides and also prepared microgels based on N,N,N-trimethylchitosan and tensides. The interactions between polymers and tensides have been proved.
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Utilization of thermal and structural analyses in study on the formation of polyelectrolyte complexes
Řiháčková, Barbora ; Sedláček, Petr (referee) ; Krouská, Jitka (advisor)
This bachelor thesis deals with a study of the polyelectrolyte complexes made by chitosan and humic acids. The work was motivated by the research in the field of new materials which can be potentially useful for agricultural and medical applications. A degree and a character of the interactions were studied by isothermal titration calorimetry and dynamic light scattering method. The calorimetric experiments proved that decreasing concentration of samples causes decreasing of reaction enthalpy. Moreover, the temperature changes during the titration are not influenced by water molecules as environment but mostly by the interactions between the functional groups of chitosan and humic acids. The formation of polyelectrolyte complexes was proved also by measurements of intensity of scattered light and Z-average of particle size.
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Use of microcalorimetry in the study of hydration of biopolymers
Bola, Tomáš ; Smilek, Jiří (referee) ; Krouská, Jitka (advisor)
This master thesis deals with the using of microcalorimetry in the study of hydration of biopolymers. Lactose has been selected together with the other biopolymers although it is not among biopolymers but disaccharides. Selected biopolymers are alginate, dextrane, chitosan and hyaluronan of two molecular weights. Lactose has been selected for these purposes mainly because it is a model example to determine whether or not the reaction to moisture between the other samples and the saturated salt solution occurs. The biopolymer hydration study, as opposed to the commonly used perfusion calorimetry method using the possibility of measuring with adjustable moisture has been used an isothermal microcalorimetry method where at two constant temperatures the reaction of the sample to the different moisture released by the saturated salt solution was monitored.
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Preparation and characterization of chitosan-based materials
Puchírová, Simona ; Kalina, Michal (referee) ; Kovalčík, Adriána (advisor)
The presented diploma thesis focuses on the characterization of the rheological properties of hydrogels based on agarose, alginate, polyvinyl alcohol and the study of the antimicrobial effect of chitosan added to selected hydrogels. The theoretical part is focused on the creating a literature research dealing with the description of the basic characteristics of hydrogels in general, describes the nature, properties, structure and possibilities of its use. In the experimental part, hydrogels without added active substance and hydrogels modified with chitosan were prepared. Based on rheological measurements, suitable combinations of hydrogels with chitosan were selected. A part of the hydrogel was taken from the samples and monitored in a drying and re-swelling process in distilled water. The hydrogels were tested by Ftir analysis, which verified the presence of chitosan in the samples. Monitoring of the antimicrobial effect of chitosan was performed by the hole diffusion method. Efficacy was tested on bacterial strains of Escherichia coli, Candida glabrata, Micrococcus luteus, Serratia marcescens. Most excised hydrogel disks have formed zones of inhibition of various sizes. Inhibition zones were also formed around hydrogels without chitosan, where the sensitivity of individual microbial cultures to acetic acid is assumed. The antibacterial active of chitosan was verified by studying the separate sensitivity of chitosan solutions and acetic acid.
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