|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
| |
|
|
Targeted modification of transport and structural properties of biomedical hydrogels
Bayerová, Zuzana ; Kráčalík, Milan (referee) ; Smilek, Jiří (advisor)
The presented diploma thesis deals with a targeted modification of the structural properties of hydrogels, which is closely related to the application properties of these materials (eg transport). Due to the desired pharmacological applications of the use of these materials for targeted drug release, hydrogels based on chitosan and polyvinyl alcohol as substances with good biocompatibility were selected for the study. The combination of these polymers ensured swelling (controlled by the presence of chitosan) and viscoelastic (influenced by the presence of polyvinyl alcohol) properties, which were characterized by a wide range of analytical and physicochemical methods (swelling, tensile strength, rheology, atomic force microscopy or specific surface area, etc.). Information on structural properties played a crucial role not only for a detailed description of the studied materials in terms of whether the structural properties can be changed in a targeted manner, but also served as an explanation for the different release of the active substance diclofenac from the hydrogel matrix. With regard to the literature search, the effect of pH and crosslinking was chosen to modify the properties. From the measured results it was found that even a slight change in pH has an effect on the transport or release of the active substance. The results obtained in this work may be useful in the formation of hydrogel matrices with drugs depending on the intended medical applications.
|
|
|
High-strength macrodefect-free composites for refractory applications
Ryšková, Martina ; Másilko, Jiří (referee) ; Šoukal, František (advisor)
The subject of the bachelor thesis is the study of heat-resistant macrodefect-free (MDF) cements based on calcium-aluminate cement and organic polymer polyvinylalcohol. Macrodefect-free cements are particularly important in excellent mechanical parameters, which include tensile strength in bending. These materials are characterized by their low porosity and the absence of microcracks. The main role of the MDF cements takes binding and non-flush interaction with polymer cement, which affect the chemical and physical-mechanical properties. The main problem in applying the MDF cements is the low water resistance. To prepare macrodefect-free samples were used calcium-aluminate cement (SECAR 51, SECAR 71) and polymer polyvinyl Gohsenol GH 17S. They were observed changes in mechanical properties depend on the type of curing samples were cured at laboratory temperature and 70°C. Samples annealed at 1000 ° C and then tested for tensile strength in bending before and after annealing, compared to mechanical properties. Thermal stress was tested by doping a microscope TGA-DTA-EGA and TMA analysis.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
guest ::
