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Rheology as a powerful tool for the complex characterization of hydrogels
Kadlec, Martin ; Kráčalík, Milan (referee) ; Smilek, Jiří (advisor)
This diploma thesis investigates the suitability of relaxation tests as a part of complex characterization of hydrogel materials using classical rheology methods. With respect to the current research, creep and three interval thixotropy tests were taken into account. For them, general optimization was done aiming to find an ideal parameter settings. The optimization was performed using physically crosslinked agarose (AG) hydrogel and the tuned tests were also applied to two more samples: hyaluronan (HyA) and polyvinyl alcohol (PVAl) gel. These materials were selected due to their mutually different crosslinking principle. The experiments showed, the AG gel proved to have the best ability to recover after deformation of all studied samples. On the other hand, the HyA gel relaxed the worst. Although the final results of both tests were comparable, the regeneration process itself was different. Hence, the complex relaxation characteristics cannot be described using one of the performed tests alone and both the creep and three interval thixotropy tests have great importance in the scope of complex relaxation behaviour. The obtained results may lead to more precise description of deformation and relaxation, which are frequent phenomena occurring during treatment and application of hydrogel materials.
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Study on relaxation properties of hydrogels by using rheometer
Obrusníková, Klára ; Heger, Richard (referee) ; Smilek, Jiří (advisor)
This thesis deals with viscoelastic (specifically relaxation) properties of a selected hydrogel system using three interval thixotropy tests. Collagen hydrogel was chosen as the investigated material and its viscoelastic properties were studied based on time and different storage temperatures. The collagen gel is thixotropic; its structure is disrupted when subjected to deformation and it is able to reform (relax) to a certain rate afterwards. As for time dependency, the collagen hydrogel shows great stability, there were almost no changes in mechanical properties over two months. The temperature dependency is, however, quite significant. When subjected to temperatures below the freezing point, the structure of collagen stabilises, which is expressed by an increase of the complex modulus, when subjected to temperatures close to the human body temperature, the structure degrades, which is expressed by a decrease of the complex modulus. The results show that the collagen gel relaxes best when kept at room temperature, but it simultaneously exhibits the lowest elasticity. On the contrary, when kept at the temperature around 5 °C, the gel exhibits the highest elasticity and relaxes the worst. The optimal temperature for the storage of the given gel seems to be around 5 °C, according to the results.
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Study on relaxation properties of hydrogels by using rheometer
Obrusníková, Klára ; Heger, Richard (referee) ; Smilek, Jiří (advisor)
This thesis deals with viscoelastic (specifically relaxation) properties of a selected hydrogel system using three interval thixotropy tests. Collagen hydrogel was chosen as the investigated material and its viscoelastic properties were studied based on time and different storage temperatures. The collagen gel is thixotropic; its structure is disrupted when subjected to deformation and it is able to reform (relax) to a certain rate afterwards. As for time dependency, the collagen hydrogel shows great stability, there were almost no changes in mechanical properties over two months. The temperature dependency is, however, quite significant. When subjected to temperatures below the freezing point, the structure of collagen stabilises, which is expressed by an increase of the complex modulus, when subjected to temperatures close to the human body temperature, the structure degrades, which is expressed by a decrease of the complex modulus. The results show that the collagen gel relaxes best when kept at room temperature, but it simultaneously exhibits the lowest elasticity. On the contrary, when kept at the temperature around 5 °C, the gel exhibits the highest elasticity and relaxes the worst. The optimal temperature for the storage of the given gel seems to be around 5 °C, according to the results.
|
|
|
Rheology as a powerful tool for the complex characterization of hydrogels
Kadlec, Martin ; Kráčalík, Milan (referee) ; Smilek, Jiří (advisor)
This diploma thesis investigates the suitability of relaxation tests as a part of complex characterization of hydrogel materials using classical rheology methods. With respect to the current research, creep and three interval thixotropy tests were taken into account. For them, general optimization was done aiming to find an ideal parameter settings. The optimization was performed using physically crosslinked agarose (AG) hydrogel and the tuned tests were also applied to two more samples: hyaluronan (HyA) and polyvinyl alcohol (PVAl) gel. These materials were selected due to their mutually different crosslinking principle. The experiments showed, the AG gel proved to have the best ability to recover after deformation of all studied samples. On the other hand, the HyA gel relaxed the worst. Although the final results of both tests were comparable, the regeneration process itself was different. Hence, the complex relaxation characteristics cannot be described using one of the performed tests alone and both the creep and three interval thixotropy tests have great importance in the scope of complex relaxation behaviour. The obtained results may lead to more precise description of deformation and relaxation, which are frequent phenomena occurring during treatment and application of hydrogel materials.
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