Formation of a compatible composite of silica/poly(vinyl alcohol) through the sol-gel process and a calcinated product of the composite

A transparent composite film of poly(vinyl alcohol) (PVA) and silica was obtained through the sol-gel process using tetraethoxysilane (TEOS). By ESCA and X-ray diffraction measurements on the composite, it is confirmed that the PVA and silica were intimately mixed together. The Young's modulus increased with increasing silica content in the PVA, but the tensile strength decreased from 84 for pure PVA to 40 MPa (as the PVA content reaches 50 wt%). A maximum value of 145 MPa was observed for the 80% PVA composite. The composite could be drawn to 2 similar to 3 times its original length under saturated humidity conditions. The modulus and the tensile strength were increased by a factor of two by the drawing of the as-cast composite film. The residuals created by the removal of PVA from the composite films were transparent and showed a surface area of about 500 m(2) g(-1) (in the case of 80% PVA as the original material). The residuals showed permeability for gases. The gas permeability of the residuals rapidly increased with the PVA content in the original materials.