Preparation of hydrogel composites containing sepiolith and investigation of the properties

Hydrogels are polymer networks which uptake a large amount of water. Hydrogels have been used in many fields due to response capacity to different stimuli such as temperature, pH, light and magnetic field. In the first part of this thesis, hydrogels were synthesized using acrylic acid and sodium acrylate as monomer, respectively. In the second part, hydrogel composites were prepared with adding sepiolite as a filler. In the last part, hydrogel composites were prepared with the addition of alkyl ammonium salt modified sepiolite. Characterization of the synthesized hydrogels was performed by TGA, FTIR, SEM and XRD analyses. TGA analysis showed that the addition of sepiolite or modified sepiolite into the hydrogel network slightly increased thermal stability of the hydrogels. According to SEM analysis, uniform dispersion of the fillers in hydrogel structure was observed. XRD analysis indicated that the hydrogels were amorphous structure. Swelling behaviour of the hydrogels was evaluated with tea-bag method. Swelling percentage of the hydrogels in distilled water, FeCl3, NaCl, CaCl2 and different pH solutions was calculated. Based on the swelling tests in distilled water, the highest swelling percentage of Aa hydrogel, Aa+SP hydrogel composite and Aa+MSP hydrogel composite was 3503%, 3208% and 3186%, respectively. For Sa hydrogel and Sa+SP hydrogel composite, the highest swelling percentage in distilled water was determined as 10047% and 10397%, respectively. When considered swelling percentage of the hydrogels in different pH solutions, the swelling percentage was specified as 3916% and 11055% for Aa+SP and Sa+SP hydrogel composites at pH 9, respectively. In distilled water, an increase in temperature provided synergistic effects on the swelling capacity and the highest swelling percentage value was observed at 50 °C. It was revealed that the hydrogels were sensitive to pH and temperature. As a result of repeated swelling tests, an increase in the swelling capacity and reusability of the hydrogels for many times.