Papers by Keyword: Gelation Time

Abstract: Calcium ions released from calcium-alginate hydrogel can promote inflammatory responses when injected subcutaneously in mice. In this study, a novel alginate hybrid hydrogel was prepared using sodium alginate (SA) and Glycyrrhizic acid (GA) design for reduce calcium concentration in the hydrogel. nanoCalcium carbonate was wrapped in an alginate solution and internal gelling was induced by the Ca²⁺ released from CaCO₃ by adding of GA. As varying of the amounts of GA and CaCO₃ in alginate solution, the gelling time could be controlled within 10 min. Taking advantage of short gelation time and controlled hydrogel shape, GA calcium alginate hydrogel system has great potential for tissue engineering applications.

Abstract: Polymer gel is widely used in water shut-off and profile control. For success of conformance treatment, it is very important to study the dynamic gelation process of polymer gel, especially in porous media. Based on the systems of HPAM/ phenol formaldehyde resin (PFR), the dynamic gelation process in porous media was studied in an unconsolidated sandpack of the circulating device. The results showed that dynamic gelation time was much longer than static gelation time in ampoule bottle and porous media. With permeability increasing or injected speed decreasing, the dynamic initial gelation time increased but the dynamic initial gelation time varied unconspicuously. In dynamic gelation process, the system of HPAM/ PFR could be injected into in-depth of reservoir more easily. The relationship between permeability and apparent viscosity was in accordance with equation y=a (1-e^-bx). The apparent viscosity after dynamic gelation was in contrast with linear velocity of b.

Abstract: The Bombyx mori silk fibroin gel with three dimensional structures is an important form to be developed for tissue engineering materials. In this paper, silk fibroin gels were prepared with adding polyalcohol into silk fibroin solution. The gel structure was analyzed by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The results demonstrated that when adding more than 100% of polyalcohol, both of glycerol and polyethylene glycol 400 (PEG400) can accelerate the gelation process markedly. With the increase of the percentage of PEG400 and glycerol, it promoted silk fibroin molecules to cluster rapidly and inhibit silk fibroin molecules transforming from the random coil or α-helix to β-sheet in a ratio of 900% especially. Silk fibroin gels containing 100% of polyalcohol had more uniform morphology and the pores distributed uniformly.

Abstract: This paper investigates the rheological behaviour of chitosan solutions crosslinked with different concentrations of genipin at body temperature and physiological pH. The effect of the crosslinker concentration on the rheological properties of hydrogels was evaluated. The oscillatory time sweep was used to analyze the dynamics of G’ during in situ gelation experiments enabling the determination of the gelation time. Additionally, the stress and frequency sweeps were employed to measure G’ of cured hydrogels. The solutions of chitosan crosslinked with genipin at physiological conditions were found to form relatively strong elastic gels for all the concentrations, when compared to pure chitosan. A significant reduction on gelation time was achieved. This behaviour shows that these formulations are able to be produced in situ and thus constitute promising matrices for cells and bioactive molecules encapsulation.

Abstract: Zirconia based gels were prepared by the sol-gel route using sodium tris(glycozirconate)complex as precursor synthesized directly from the reaction of inexpensive and readily available compounds via the one step method. Rheological technique was used to investigate the sol-gel transition of zirconium based materials at different water/alkoxide ratios and reaction temperatures. The gelation time was determined from the evolution of the storage and loss moduli versus time at various frequencies using the Winter-Chambon criterion. The effect of an increase of the hydrolysis ratio and /or temperature was an enhancement of the kinetics of crosslink reactions, thus decreasing the gelation time. The variation of the gelation time versus temperature could be described by Arrhenius law. Furthermore, zirconia powders prepared from the thermal treatment at 500°C were analyzed by X-ray diffraction and the BET technique.