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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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Rheological properties of gelatin-based gels for ultrasound brain phantom
Bojňanská, Terézia Marianna ; Šnejdrová, Eva (advisor) ; Holas, Ondřej (referee)
CHARLES UNIVERSITY IN PRAGUE FACULTY OF PHARMACY IN HRADEC KRALOVE DEPARTMENT OF PHARMACEUTICAL TECHNOLOGY Author: Terezia Marianna Bojnanska Supervisor: PharmDr. Eva Snejdrova, Ph.D. Title of diploma thesis: Rheological properties of gelatin-based gels for ultrasound brain phantom The diploma thesis deals with the evaluation of the viscoelastic properties of gelatin gels modified by addition of glutaraldehyde and glycerol using a rheometer with goal to verify the suitability of tested materials for their intended use as ultrasound brain phantoms. The theoretical part deals with gels in general and is focused on gelatin gels as a possible basic component of ultrasound phantoms, and the possibilities of characterizing gels as viscoelastic systems using methods of oscillatory rheometry. Gelatin gels of different concentrations (5; 7,5 and 10%) with the addition of glutaraldehyde and glycerol were characterized by complex modulus, complex viscosity, yield stress, phase angle. Temperature stability of the samples in the range from 20 to 50řC was tested. All tested gels were viscoelastic solids with a clearly defined linear-viscoelastic region, which is confirmed by phase angle values close to 0ř. With the increasing concentration of gelatin the values of the complex modulus increased, increasing...
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Rheological properties of silicone gels for scar treatment
Khorsand, Ghazal ; Šnejdrová, Eva (advisor) ; Paraskevopoulos, Georgios (referee)
Charles University, Faculty of Pharmacy in Hradci Králové Department of Pharmaceutical Technology Supervisor: PharmDr. Eva Šnejdrová, Ph.D. Student: Ghazal Khorsand Title thesis: Rheological properties of silicone gels for scar treatment The thesis is focused on testing of the flow and viscoelastic properties of the scar treatment silicone-based gels, either commercially available or newly formulated gels under development. The theoretical part deals with the scar formation, silicone in scar treatment, and characterization of the gels. In the experimental part, rotational and oscillation tests were performed using a rotational rheometer. The obtained flow curves were fitted by Newton or Power law models. The shear viscosity, coefficient of consistency, and index of flow behaviour were used for gel characterization and comparison. The highest viscosity revealed in the ScarEsthetique cream, followed by RejuvaSil gel. Surprisingly, the Stratamed scar gel and Scar gel Dr. Max showed the lowest viscosity, even lower than the formulations at the development stage. Despite the name "gel", they behave as Newtonian fluids. The elastic modulus G', viscous modulus G'', and complex modulus G*, phase angle , the gel point, and linear viscoelastic region LVER were selected to describe the viscoelastic behaviour...
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Rheological properties of agar-based gels for ultrasound brain phantom
Schneiderová, Marie ; Šnejdrová, Eva (advisor) ; Holas, Ondřej (referee)
CHARLES UNIVERSITY FACULTY OF PHARMACY IN HRADEC KRÁLOVÉ DEPARTMENT OF PHARMACEUTICAL TECHNOLOGY Author: Marie Schneiderová Supervisor: Phar Dr Eva nejdrová Ph D Title of diploma thesis: Rheological properties of agar-based gels for ultrasound brain phantom The diploma thesis deals with the evaluation of the rheological properties of agar gels on a rotational rheometer. The theoretical section contains the characterization of gels, their distribution, properties and use in pharmacy, describes agar and its characteristic properties. It also provides brief information on phantoms and describes the agar-based phantom in more detail. The principles of oscillation tests and their evaluation are described. Twelve gels with different agar concentrations were tested: a series of gels without glycerol and a series of gels with glycerol. The structure of the gels was characterized by the test Evaluating product texture using oscillatory testing and te perature stability in the range of 20 ř C to 40 ř C by the Single frequency strain controlled temperature ramp test. The viscoelastic properties of pig brain tissue were characterized by the same tests. The gel structure was confirmed in all samples tested. The stiffness expressed by the value of the complex modulus G * increases with the agar concentration....
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Adhesive and rheological properties of chitosan-based mixtures in media of different pH
Omar, Alaa Abdel Gawad Ahmed Osman ; Šnejdrová, Eva (advisor) ; Mužíková, Jitka (referee)
Title of thesis: Adhesive and rheological properties of chitosan-based mixtures in media of different pH Author: Alaa Omar Supervisor: PharmDr. Eva Šnejdrová, Ph.D. Consultant: Mgr. Juraj Martiška The aim of the diploma thesis is the study of rheological and adhesive properties of tableting materials for matrix tablets based on chitosan. The theoretical part describes in detail the materials used to prepare the matrix tablets, which were chitosan, sodium alginate and hypromellose. The experimental section was focused on the flow and adhesive properties of the chitosan-based mixtures after exposing them to a media of different pH. The flow tests were done on an absolute rotational rheometer. Obtained viscosity curves were analysed by Power law model. Viscosity at 10 s-1 and Power Law model coefficients were used to evaluate and compare the flow behaviour of dispersions with different concentrations of retarding component in different media. The test of adhesion was carried out using a pull away test on a rotational rheometer and evaluated as maximal detachment force. The remarkably high viscosity of 5% dispersions at pH 1.2 is due to the dissolution of chitosan, as sodium alginate is not soluble in acidic media. The increase in viscosity with the concentration of the retarding component is insured...
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Characterization of silicone scar treatment gels
Podzimková, Alena ; Šnejdrová, Eva (advisor) ; Miletín, Miroslav (referee)
Charles University in Prague Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Technology Author: Alena Podzimková Title of Thesis: Characterization of silicone scar treatment gels Supervisor: PharmDr. Eva Šnejdrová, Ph.D. This diploma thesis deals with characterization of silicone gels by various methods, specifically measurement of rheological properties, overall characterization of the composition by infrared spectroscopy, identification of volatile compounds by gas chromatography and determination of molecular weight distribution of polymers by gel permeation chromatography. The theoretical part provides information about scars and their treatment options and describes the principles and the evaluation of tests performed in the experimental part. Five commercial gels and three newly formulated scar healing gels were evaluated. Analysis of viscosity curves confirmed newtonian type of flow in commercial gels Scar Gel Dr. Max and Stratamed and in the newly formulated gels. Strataderm, RejuvaSil and ScarEsthetique show a decrease in viscosity under stress. Oscillation tests have shown a gel structure only with the commercial ScarEsthetique and RejuvaSil. Scar Gel Dr. Max, Strataderm, the newly formulated gels and Stratamed contain polymeric polydimethylsiloxane. In case of Scar...
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Characterization of silicone scar treatment gels
Podzimková, Alena ; Šnejdrová, Eva (advisor) ; Miletín, Miroslav (referee)
Charles University in Prague Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Technology Author: Alena Podzimková Title of Thesis: Characterization of silicone scar treatment gels Supervisor: PharmDr. Eva Šnejdrová, Ph.D. This diploma thesis deals with characterization of silicone gels by various methods, specifically measurement of rheological properties, overall characterization of the composition by infrared spectroscopy, identification of volatile compounds by gas chromatography and determination of molecular weight distribution of polymers by gel permeation chromatography. The theoretical part provides information about scars and their treatment options and describes the principles and the evaluation of tests performed in the experimental part. Five commercial gels and three newly formulated scar healing gels were evaluated. Analysis of viscosity curves confirmed newtonian type of flow in commercial gels Scar Gel Dr. Max and Stratamed and in the newly formulated gels. Strataderm, RejuvaSil and ScarEsthetique show a decrease in viscosity under stress. Oscillation tests have shown a gel structure only with the commercial ScarEsthetique and RejuvaSil. Scar Gel Dr. Max, Strataderm, the newly formulated gels and Stratamed contain polymeric polydimethylsiloxane. In case of Scar...
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Adhesive and rheological properties of chitosan-based mixtures in media of different pH
Omar, Alaa Abdel Gawad Ahmed Osman ; Šnejdrová, Eva (advisor) ; Mužíková, Jitka (referee)
Title of thesis: Adhesive and rheological properties of chitosan-based mixtures in media of different pH Author: Alaa Omar Supervisor: PharmDr. Eva Šnejdrová, Ph.D. Consultant: Mgr. Juraj Martiška The aim of the diploma thesis is the study of rheological and adhesive properties of tableting materials for matrix tablets based on chitosan. The theoretical part describes in detail the materials used to prepare the matrix tablets, which were chitosan, sodium alginate and hypromellose. The experimental section was focused on the flow and adhesive properties of the chitosan-based mixtures after exposing them to a media of different pH. The flow tests were done on an absolute rotational rheometer. Obtained viscosity curves were analysed by Power law model. Viscosity at 10 s-1 and Power Law model coefficients were used to evaluate and compare the flow behaviour of dispersions with different concentrations of retarding component in different media. The test of adhesion was carried out using a pull away test on a rotational rheometer and evaluated as maximal detachment force. The remarkably high viscosity of 5% dispersions at pH 1.2 is due to the dissolution of chitosan, as sodium alginate is not soluble in acidic media. The increase in viscosity with the concentration of the retarding component is insured...
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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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Thixotropy test of semisolid preparations
Tenorová, Klára ; Šnejdrová, Eva (advisor) ; Drastík, Martin (referee)
CHARLES UNIVERSITY Faculty of Pharmacy in Hradec Kralove Department of Pharmaceutical technology Name: Klára Tenorová Title of diploma thesis: Thixotropy test of semisolid preparations Supervisor: PharmDr. Eva Snejdrova, Ph.D. This thesis deals with the study of thixotropic properties of selected semi-solid preparations such as Vaselinum album, Adep lanae, Adeps lanae cum aqua, Alcoholis cetylici unguentum and Alcoholis cetylici cremor. The theoretical part deals with characterization of semi-solid preparations and ointment bases, rheology, rheometry and description of the tests used in the measurement. The experimental part deals with the description of viscosity curves and with the measurement of time dependency of flow behaviour by thixotropic test. Model semi-solid samples show only partial recovery, i.e. false thixotropy. The highest recovery of the structure was shown by Adeps lanae, 83 % at 25 řC and 79 % at 32 řC. The flow behaviour are changed by incorporation of the water depending on the character of the semisolid preparation. At 25 ř C, the viscosity recovery rate was lower than at 32 ř C for all samples except Adeps lanae. After the emulsification of 25% water to Adeps lanae, the recovery rate at both temperatures was significantly reduced, which means that lanolin is slower to recover...
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