|
|
Functional polymer foams
Hána, Tomáš ; Pospíšil, Ladislav (referee) ; Jančář, Josef (advisor)
Functional polymer foams are considered as a promising field which could potentially produce foams with added value. Specifically, functionally graded foams are materials which are expected to provide better mechanical properties while preserving low density in comparison with regular foams. In this thesis, a preparation process of such foams is designed, examination of prepared structure and comparison of mechanical properties with regular foams is performed. The obtained results are discussed and further research in this field is proposed.
|
|
|
The gelation of hydroxyethylcellulose and hyaluronan using citric acid
Martinková, Martina ; Krouská, Jitka (referee) ; Hurčíková, Andrea (advisor)
This master's thesis deals with gelation of hydroxyethylcellulose and hyaluronan crosslinked with nontoxic crosslinking agent – citric acid. First of all, the optimalization of gelation process of hydroxyethylcellulose took place. After obtaining the product insolube in the ultrapure deionized water, a reaction mixture of hyaluronan and hydroxyethylcellulose in two different weight ratios were prepared. There was prepared solution containing only hyaluronan as the polymeric part too. Citric acid was used in concentrations of 5 %, 10 % and 20 % (w/w of polymer). These solutions of polymers and citric acid were gelated under the same conditions and the products were compared to each other using Differential Scanning Calorimetry, Thermogravimetry and Fourier Transform Infrared Spectroscopy. The products containing hydroxyethylcellulose and hyaluronan with hydroxyethylcellulose in weight ratio equal to 3 : 7 were considered crosslinked.
|
|
|
Use of starch and glycerin in polymer films with controlled life span
Almásyová, Zuzana ; Pospíšil, Ladislav (referee) ; Jančář, Josef (advisor)
This diploma thesis deals with preparation and testing of biodegradable materials for use in the packaging indrustry. The task of this work is to prepare set of laboratory made films based on wheat starch, glycerol, polyvinyl alcohol with the addition of a suitable additive, which has been selected as citric acid. A suitable composition meeting the requirements of the packaging foils has been found. Quaternary blends from all components achieve the best results. It has been found that citric acid can influence the chemical structure and thus affect the mechanical and thermal properities and also the degree of solubility. The films were characterized in terms of mechanical properities by tensile testing and thermal stability by means of thermogravimetric analysis with respect to the phase structure. The structure was characterized by Fourier transform infrared spectroscopy and confocal laser scanning microscopy. The biodegradability of the film was tested by its solubility in aqueous medium.
|
|
|
Solubility control of biodegradable starch-based packaging
Krobot, Štěpán ; Ondreáš, František (referee) ; Lepcio, Petr (advisor)
This bachelor thesis deals with the preparation and testing of biodegradable films based on starch. The aim of the thesis is laboratory preparation of foils based on various types of starch, glycerol, polyvinylalcohol and with the addition of plasticizer – citric acid. Four different types of starch and two types of polyvinyl alcohol were used. In the first series of samples, the ratio of added glycerol to starch content was varied. Samples in the second series were prepared in the same ratios, but with different PVA. A citric acid solution was added into the last series of samples. The second aim of the thesis, after pressing the films, was to determine their solubility and stability in aqueous media depending on the ratio between added glycerol to starch content, the type of polyvinylalcohol used, and the addition of citric acid to the mixture. It has been found that citric acid appears to affect the chemical structure of the films and thus their solubility in aqueous media as well as their mechanical properties. Fourier-transform infrared spectroscopy (FTIR) was used to study the structure of the films and to elucidate its effect on solubility.
|
|
|
Optimization of condition of procedure of gelation hydroxyethylcellulose using citric acid
Burešová, Natálie ; Krouská, Jitka (referee) ; Hurčíková, Andrea (advisor)
The bachelor thesis dealt with hydrogels, which have the advantage detention large quantities of water, it allows large potential applications, such as in medicine. Hyaluronan and hydroxyethylcellulose were the reactants of crosslinking reaction. Citric acid was crosslinking agent which is nontoxic and inexpensive. Hydroxyethylcellulose and hyaluronan for crosslinking reaction were selected on the finding from available publications. The resulting gels can be used mainly in medicine because they are nontoxic. The main aim of the thesis was optimalizacion process of gelation and hydroxyethylcellulose and finding a suitable gelation process. Selected gelation procedure is applied to a mixture of hydroxyethyl cellulose and hyaluronan in two different weight ratios and hyaluronan. Chemicaly cross-linked were considered samples, which contained hydroxyethylcellulose and then a mixture of hyaluronate and hydroxyethyl cellulose in a weight ratio of 3:7.
|
|
|
Jakostní parametry majonéz s obsahem přídatných látek
Hartmanová, Sabina
The thesis entitled „Quality parameters of mayonnaise with additives“ aimed to perform model production of mayonnaise samples according to different recipes (combination of additives – lactic acid, citric acid, sodium sulphate) with different levels of additives and to determine the basic quality characteristic (pH, dry matter content, titratable acidity content) and sensory properties. The pH of model samples ranged from 3.52 (sample with citric acid and lactic acid combination) to 4.03 (sample with lactic acid). The dry matter content ranged from 53.59 % (sample with sodium sulphate and lactic acid) to 59.86 % (sample with citric acid). The titratable acidity content of the model samples ranged from 42 mmol·l−1 (sample with lactic acid) to 56 mmol·l−1 (sample with citric acid). In the sensory analysis, the sample with combination of citric acid and lactic acid got the best results. The results obtained confirm that the additives in the mayonnaise did not have a negative effect on the quality and sensory characteristics.
|
|
|
Preparation and characterisation of selected d and p elements carbides
Nižňanský, Matěj ; Tyrpekl, Václav (advisor) ; Vilémová, Monika (referee)
This thesis is focused on carbide ceramics synthesis, more specifically on the synthesis of a Ti2AlC MAX Phase carbide using solution chemistry rather than powder metallurgy. Chloride and nitrate precursors have been used as a source of metals and citric acid as a source of carbon for carbothermal reduction and as a complexing agent. A new route of precursor synthesis has been developed based on peroxo-titanic acid, which helps retain aluminium. The syntheses were performed using the SPS facility to ensure high heating rates. Al4C3 and TiC carbides and their mixtures were prepared successfully. However, the Ti2AlC phase was not synthesized under used conditions. The phase composition, structure and grain sizes of the samples were investigated by powder X-ray diffraction, X-ray fluorescence and electron microscopy. The contents of carbon in the precursors were determined by thermogravimetric analysis.
|
|
|
Solubility control of biodegradable starch-based packaging
Krobot, Štěpán ; Ondreáš, František (referee) ; Lepcio, Petr (advisor)
This bachelor thesis deals with the preparation and testing of biodegradable films based on starch. The aim of the thesis is laboratory preparation of foils based on various types of starch, glycerol, polyvinylalcohol and with the addition of plasticizer – citric acid. Four different types of starch and two types of polyvinyl alcohol were used. In the first series of samples, the ratio of added glycerol to starch content was varied. Samples in the second series were prepared in the same ratios, but with different PVA. A citric acid solution was added into the last series of samples. The second aim of the thesis, after pressing the films, was to determine their solubility and stability in aqueous media depending on the ratio between added glycerol to starch content, the type of polyvinylalcohol used, and the addition of citric acid to the mixture. It has been found that citric acid appears to affect the chemical structure of the films and thus their solubility in aqueous media as well as their mechanical properties. Fourier-transform infrared spectroscopy (FTIR) was used to study the structure of the films and to elucidate its effect on solubility.
|
|
|
Functional polymer foams
Hána, Tomáš ; Pospíšil, Ladislav (referee) ; Jančář, Josef (advisor)
Functional polymer foams are considered as a promising field which could potentially produce foams with added value. Specifically, functionally graded foams are materials which are expected to provide better mechanical properties while preserving low density in comparison with regular foams. In this thesis, a preparation process of such foams is designed, examination of prepared structure and comparison of mechanical properties with regular foams is performed. The obtained results are discussed and further research in this field is proposed.
|
|
|
Use of starch and glycerin in polymer films with controlled life span
Almásyová, Zuzana ; Pospíšil, Ladislav (referee) ; Jančář, Josef (advisor)
This diploma thesis deals with preparation and testing of biodegradable materials for use in the packaging indrustry. The task of this work is to prepare set of laboratory made films based on wheat starch, glycerol, polyvinyl alcohol with the addition of a suitable additive, which has been selected as citric acid. A suitable composition meeting the requirements of the packaging foils has been found. Quaternary blends from all components achieve the best results. It has been found that citric acid can influence the chemical structure and thus affect the mechanical and thermal properities and also the degree of solubility. The films were characterized in terms of mechanical properities by tensile testing and thermal stability by means of thermogravimetric analysis with respect to the phase structure. The structure was characterized by Fourier transform infrared spectroscopy and confocal laser scanning microscopy. The biodegradability of the film was tested by its solubility in aqueous medium.
|
guest ::
