Preparation of PVA/ SOL-Jel deri̇ved biosilicate gel composite films

In this thesis, various PVA/wet silica gel composite films were prepared. TEOS, TMOS or sodium silicate solution silica sources are generally used in preperation of silica films. In this study, rice hull ash which is an agricultural waste and a cheap material was used as a silica source. Moreover, silica was added to films as a gel for the first time in this study which is different than other studies in the literature. Sodium silicate solution was produced from rice hull ash with alkali extraction method. Sodium silicate solutions were gelated at pH 7 with HCl addition by sol-gel method. Composite films were prepared by using obtained gels and three different viscosity grades PVA. PVA, has different viscosity; 5:88, 26:88 and 40:88 was used. PVA/silica gel films were obtained by drying at room temperature for 24 hours and in vacuum at 40 °C for 9 hours. Structural characteristics of prepared PVA/silica gel films were determined by FT-IR analysis, and its morphology by SEM. Further, swelling properties of films in water was studied by keeping them in water for 72 hours. The films obtained with high viscosity PVA were found slightly high absorption capacity and more homogenous films were obtained. The obtained films dried at 40 ° C in vacum were found to be more durable and stable compared to films dried at ambient conditions Keywords: Composite films, polyvinyl alcohol, rice hull ash, silica gel