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Optimization of optical and transport properties of PVA based hydrogels
Zahrádka, Jan ; Kalina, Michal (referee) ; Sedláček, Petr (advisor)
The main goal of this bachelor thesis is to design and optimize a suitable method for preparation of transparent physically crosslinked hydrogels with manipulable transport properties. Polyvinyl alcohol (PVA) crosslinked by cyclic freezing and thawing was chosen as the model gel-forming material. From the originally proposed three mechanisms of influencing optical properties of thus prepared PVA gels, the influence of freezing rate was selected on the basis of pilot screening experiments for a deeper follow-up analysis. The mechanical properties of prepared hydrogels were analyzed by rheology using strain sweep test. The internal structure was visualized by scanning electron microscopy (SEM). The optimized technique for preparation of transparent PVA gels was subsequently used for preparation of gels with an interpenetrated polyelectrolyte component (poly (styrene sulfonate)). It was then experimentally verified by diffusion pair method with methylene blue as diffusion probe that the hybrid hydrogel network has modified transport properties.
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Experimental study of artificial articular cartilage friction
Kulíšek, Vlastimil ; Ranuša, Matúš (referee) ; Rebenda, David (advisor)
Many conventional materials are used to replace damaged articular cartilage, which are beginning to be replaced by innovative biomimetic materials that mimic cartilage properties. One of these materials are poly(vinyl alcohol) (PVA) hydrogels crosslinked by freeze-thawing and cast-drying method. These hydrogels possess similar mechanical as articular cartilage. In order to clarify the effect of kinematic conditions on the friction of hydrogels, three levels of sliding speed and load and a uniform lubricant – PBS were chosen. The coefficient of friction of the FT hydrogel decreased with increasing load. The dependence of the sliding speed did not show a uniform trend and corresponded to the adsorption-repellent model for PVA gels. The coefficient of friction of the CD hydrogel increased with increasing sliding speed according to the repulsion-adsorption model for PVA gels. The increase in load at low sliding speeds of CD hydrogel caused a slight decrease in the coefficient of friction. At the highest speed, there was an optimal load at which a low coefficient of friction was achieved. The CD hydrogel showed a lower coefficient of friction than cartilage. The FT hydrogel achieved a lower coefficient of friction than cartilage only at 5 N and 10 mm s- 1. This work contributes to the understanding of the tribological properties of PVA hydrogels.
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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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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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In vitro testing of carrier system based on nanofibres for vitiligo treatment
Kodedová, Barbora ; Amler, Evžen (advisor) ; Kuželová Košťáková, Eva (referee)
Vitiligo is a skin disease with 2 % prevalence in a worldwide population. It is characterised by loss or decrease in activity of epidermal melanocytes, which lead to skin and hair depigmentation. It has negative impact on psyche, social relationships of patients and reduces the protection of the organism against UV radiation. One of the treatment methods is autologous transplantation of melanocytes or suspension of melanocytes with keratinocytes. Use of the biocompatible membrane, which allows the cultivation of these cells with resulting transplantation on the depigmented lesion, could improve treatment and make it more efficient. The main goal of this work was to create the biocompatible membrane from nanofiber layers of polyvinylalcohol (PVA) which can stand as a carrier for cell transplants in vitiligo therapy. PVA scaffolds were prepared by electrostatic spinning and later on modified by cold methane plasma (CH4) for lowering their hydrofility. Samples of modified nanofiber carriers were analysed according to their physical and chemical characteristics (visualization fiber morphology by SEM, XPS and surface Zeta potential analysis and contact angle). Consequently, adhesion, proliferation and metabolic activity of cultivating mice cell lines of melanocytes (Melan-a) and keratinocytes (XB2) were examined...
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The Rheological Behavior of Polymer Solutions Suitable for Electrospinning
Divínová, Nikol ; Voráč,, Zbyněk (referee) ; Chamradová, Ivana (advisor)
This diploma thesis deals with preparation and characterization of aqueous solutions of polyvinyl alcohol suitable for electrospinning. In the theoretical part method of electrospinning is described, including parameters which influence this process. Literary research also includes a chapter about rheology, which deals with the rheological properties of polymers, specifically PVA. The experimental part describes the preparation and rheological study of of aqueous solutions of polyvinyl alcohol, which were then spun. The morphology of prepared nanofibers was studied by using scanning electron microscopy (SEM). The effect of molecular weight, the solvent, concentration of solution, rheological properties, electrical conductivity and surface tension on the spinability, diameter and morphology of nanofibers is discussed.
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Mechanical activation of chemical reactions at interfaces of MDF composites
Matoušek, David ; Másilko, Jiří (referee) ; Šoukal, František (advisor)
The thesis deals with study of mechnochemical activation of chemical reactions at interphase of MDF composites. MDF composites are high-perspective composite materials on polymer-cement base. They excel especially in terms of flexural strengths. High flexural stregth is caused by binding interactions between the polymer and the cement. This interactions arise due to mechanochemical activation of raw material mixture at the stage of production. This work focuses on the creation of artificial cement-polymer interphase by contacting the surfaces of two molded tablets (polyvinyl alcohol and monocalcium aluminate), activation of chemical reactions at interphase by means of specially designed appartus, which achieves good plane-parallelism of activation surfaces and good definability of activation conditions (shear rate, pressure). After experiments under different conditions, the activated surfaces are analyzed by SEM, EDS, XPS and FT-IR.
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The Synthesis and Characterisation of Biocomposite Materials for Potential Application in Medicine
Balgová, Zuzana ; Plešingerová,, Beatrice (referee) ; Bakoš, Dušan (referee) ; Palou, Martin (advisor)
Dizertační práce se zabývala syntézou a studiem kompozitních materiálů pro potenciální lékařské využití. Teoretická část je zaměřena na biomateriály, zejména na kompozity složené z polyvinylalkoholu a hydroxyapatitu(PVA/HA). Byly připraveny kompozitní membrány složené z polyvinylalkoholu s různým hmotnostním zastoupením hydroxyapatitu - 0%, 10%, 20%, 30%, 40% a 50%. Hydroxyapatit (HA) byl připraven srážecí metodou z hydrogenfosforečnanu amonného a tetrahydrátu dusičnanu vápenatého ve vodném alkalickém prostředí. Vzniklá suspenze se smísila s roztokem polyvinylalkoholu, který byl připraven rozpuštěním ve vodě o teplotě 85° C. Jednotlivé směsi byly odlity do formy a sušeny po dobu 7 dní při teplotě 30 ° C, vzniklé 0,5 mm tenké membrány byly analyzovány ATR-FTIR spektroskopií k identifikaci funkčních skupin v kompozitu, dále byla provedena XRD analýza. Zkouška tahem a TGA měření byly realizovány k určení vlivu HA na mechanické vlastnosti, respektive změnu tepelné odolnosti kompozitů ve srovnání s čistým PVA. Byla provedena zkouška bioaktivity v simulovaném krevním roztoku (SBF) po dobu 2h, 7 a 28 dnů. SEM byla použita k charakterizaci povrchové mikrostruktury biocompositních membrán před a po ponoření do SBF. Na povrchu testovaných membrán vznikla vrstva apatitu, která je charakteristická pro bioaktivní materiály. Bylo zjištěno, že s rostoucím množstvím HA částic docházelo ke vzniku aglomerátů v kompozitu, které vznikly mimo jiné jako důsledek růstu krystalů HA během sušení membrán. Bioaktivita rostla s delším působením SBF na vzorky.
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Polymer-cement composites of increased refractoriness
Ryšková, Martina ; Opravil, Tomáš (referee) ; Šoukal, František (advisor)
The subject of the diploma thesis is the preparation of macro-defect-free (MDF) composites based on calcium-aluminate cement and organic polymer polyvinylalcohol. Attention focused on the optimization of the dose, the degree of hydrolysis and molecular weight of the polymer with respect to the heat resistance of the material. Thermal degradation of polyvinyl alcohol leads to changes in the structure of MDF composite. The study was mainly focused on the characteristics of polyvinyl alcohol dosage associated with the resultant mechanical properties of the material. During the work were monitored for changes in the mechanical properties of samples were cured at 60 °C and subsequently fired at 180 °C, 600 °C, 1000 °C and 1400 °C. It was tested in flexural strength, heat microscopy, TGA-DTA-EGA and SEM analysis.
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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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