Production and properties of flexible sodium silicate films from rice hullash silica

Flexible self-supported films were produced from rice hull ash silica extra ct. Silica was extracted from rice hull ash using 1 N NaOH. This extract wa s concentrated by volume reduction and adjusted to 3 N NaOH. Concentrated s ilica extracts in 3 N NaOH solution were used to produce flexible silicate films. XRD analysis showed that silicate existed in an amorphous form in th e film. The effect of methyl oleate (MO) as a plastisizer in the presence a nd absence of the emulsifier lecithin on the film properties was also inves tigated. FTIR data indicated that the interaction of silicate and MO in the films was mainly due to siloxane groups. This interaction resulted in sign ificant changes in film network and film flexibility. Percent elongations a s measured by a texture analyzer for silicate film, silicate film with MO a nd silicate film with MO and lecithin were 12, 15 and 17, respectively. Mec hanical strength of silicate films was not significantly affected by additi on of MO and lecithin. All the silica based films were permeable to water v apor. However. they were excellent barriers for hexane and iso-octane. (C) 1999 Elsevier Science Ltd. All rights reserved.