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Study on relaxation properties of hydrogels using rheological techniques
Lorenc, Pavel ; Klučáková, Martina (referee) ; Smilek, Jiří (advisor)
Submitted bachelor’s thesis deals with the study of relaxation and time stress of viscoelastic substances (hydrogels) using selected rheological techniques, especially with regard to oscillation tests. Hydrogels with different types of crosslinking were prepared and their properties were compared during the measurement. Agarose hydrogels (physically), alginate hydrogels (physicochemically), polyvinyl alcohol hydrogels (chemically) and hyaluronic acid hydrogels (ionically). In this bachelor's thesis, methods for measuring the relaxation properties of these hydrogels using a rheometer were designed and subsequently applied. We examined the relaxation properties of hydrogels using time-dependent tests that examined changes in amplitude over time. We performed a test that had 3 intervals, in which we monitored the response of hydrogels to the changes by changing the amplitudes of deformation with time. The relaxation properties of these hydrogels were studied, which showed significant differences in the behavior of hydrogels in measurements.By these methods, it was found that the structure of hydrogels and concentrations have an influence on relaxation. From the measured results, it was shown that the best relaxing properties have chemically crosslinked polyvinyl alcohol hydrogel, the lowest ability to relax was shown by physico-chemically crosslinked alginate hydrogel.The results from the measured data were finally compared, assessed and commented on the differences between the individual hydrogels.
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Utilization of various methods of porosimetry in investigation of internal structure of biopolymer hydrogels
Zahrádka, Jan ; Pekař, Miloslav (referee) ; Sedláček, Petr (advisor)
The main aim of the thesis was to select, optimize and test suitable methods for studying inner structure of hydrogel materials. The study of the size of pores with potential use in fundamental and applied research of these materials is the central focus of the thesis. Firstly, a literature search was done in order to collect basic information about usefulness of the individual methods. On the basis of this literature search, the experimental part of the work was divided into several steps. First, selected methods of conventional porosimetry (mercury intrusion porosimetry, BET analysis and DSC thermoporometry) were applied on reference porous materials and the results obtained by the individual methods were compared. The methods optimized with the use of these reference materials were then utilized in the analysis of porosity of model hydrogels based on polyvinyl alcohol. Based on the results of this analysis, the usability and benefits of the individual methods were discussed with respect to the sample preparation, time and financial demands, and also from the viewpoint of compliance of the determined pore sizes with the range of sizes declared for the physical PVA gels.
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Preparation of chitin film
Debnáriková, Michaela ; Abdelrahman, Rasha (referee) ; Abdellatif, Abdelmohsan (advisor)
Predložená bakalárska práca sa zaoberá extrakciou, čistením, rozpúšťaním a prípravou filmu na báze chitín/ polyvinylalkoholu (PVA). Čistý chitín bol úplne charakterizovaný rôznymi metódami, ako je potenciometrická titrácia, FT-IR, TGA, XRD, SEM a pevná NMR. Rozpustnosť a čistota extrahovaného chitínu sa skúmala a hodnotila meraním obsahu proteínov, pomocou reológie a skúmaním času potrebného na rozpustenie. Filmy chitín / PVA boli pripravené použitím rôzneho pomeru roztoku chitínu a PVA. Merané a vyhodnotené boli morfológia povrchu, reologické a mechanické vlastnosti filmu.
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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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Synthesis of High-Strength Composites Based on Inorganic Cement and Polymer
Másilko, Jiří ; Palou, Martin (referee) ; Drábik, Milan (referee) ; Havlica, Jaromír (advisor)
The subject of the doctoral thesis is the study of moisture resistance of macro-defect-free (MDF) composites based on calcium-aluminate cement and polyvinylalcohol used as polymer. MDF cements are perspective materials providing unique properties relative to traditional cement pastes with great potential to incoming constructional utilization. But it is known that MDF cements exhibit sensitivity to water, with swelling and reduction of strength. Therefore the work is aimed in monitoring of an organic polymer effect on the moisture resistance of MDF materials and phase changes. The effects of three different organotitanate cross-linking agents on the properties were investigated. The organotitanate-modified MDF cement samples exhibited improved moisture resistance as compared to the standard samples when exposed to 100 % relative humidity or water at laboratory conditions. The influence of composition at different curing on the properties of model MDF cement samples was observed. The characterization of MDF samples was based especially on test of flexural strength, XRD, DTA/TGA and EGA, EDS and scanning electron microscopy analyses.
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MDF composites AC-PVAl with increased moisture resistance
Repka, Martin ; Brandštetr, Jiří (referee) ; Šoukal, František (advisor)
Polymerem impregnované cementové materiály představují zajímavou a perspektivní alternativu klasických portlandských cementových past. Hlavním zástupcem těchto materiálů jsou macrodefect-free (MDF) kompozity, složené z anorganického pojiva a organického polymeru. I přes řadu vynikajících mechanických vlastností je plné zavedení MDF kompozitů na trh omezené především z důvodu jejich relativně nízké odolnosti vůči vlhkosti. Jednou z možností jak zvýšit odolnost výsledného MDF vůči vlhkosti je „in situ“ síťování polymeru. V této práci byla připravena počáteční série MDF kompozitů na bázi hlinitanového cementu a polyvinylalkoholu se třemi typy organo-titanátových síťovacích činidel (Tyzory). Efekt modifikace MDF kompozitů byl hodnocen na základě zkoušek pevnosti v tahu za ohybu po uložení materiálů v různých vlhkostních podmínkách.
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Determination of additives in multicomponent electrospinning systems
Gajdová, Barbora ; Petr, Knotek (referee) ; Knotková,, Kateřina (advisor)
This bachelor thesis deals with methods of producing nanofibres from mixture of different polymers. Different methods of preparation and production nanofibres by 4SPIN® are described in theoretical part. Experimental part deals with incorporation of additives into fibred layer. There were four different dyes used in this thesis: brilliant green, erythrosine, riboflavin and eriochrom black. UV – VIS spectrophotometry was used to measure volume of additives in nanofiber layer.
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Homogenity of aditives in nanofibres
Linha, Vojtěch ; Pokorný,, Marek (referee) ; Knotková,, Kateřina (advisor)
The goal of this thesis was to summarize basic options of fiber spinning and incorporation of additives. Options for nanofiber production by 4SPIN® are described along with particular electrodes for spinning in theoretical part. The experimental part was focused on influence of molecular structure of additives to incorporated volume of the substance. For this research four dye was used: erythrosine, riboflavin, briliant blue and eriochrom black. UV-Vis spectroscopy was used for evaluation of volume of aditives in nanofiber layer.
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Dependence of adherence on viscosity for water-based polymeric glues.
Kotrlová, Janka ; Novák,, Igor (referee) ; Kapusta, Jozef (advisor)
There was examined wet tack and dynamic viscosity of mono adhesives and found out their interdependence in the thesis. Adhesives containing PVAl hydrolyzed from 85 % and various types of acrylic copolymers neutralized with alkaline agents were compared. The purpose of the measurements was to determine the polymer with the highest wet tack at the lowest dynamic viscosity at the desired level of wet tack. Furthemore, the impact of the degree of neutralization of acrylic copolymer, the impact of used alkaline agent for apparent viscosity and wet tack of acrylic copolymer was detecting and also was determined limit viscosity number of PVAl.
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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.
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