Change in Surface Morphology and Water Vapor Permeation with Elongational Deformation of Silicate/PVA Thin Layer on Nylon 6 Film by Sol-Gel Method

Silica/poly (vinyl alcohol) (PVA) layers with various PVA ratios were coated on nylon 6 films by sol-gel method. Damage of Silica/PVA layer on the nylon 6 film caused by elongation was examined by an atomic force microscope (AFM) and scanning electron microscope (SEM) observations and measurements of water vapor permeation rate. At 1% elongational strain, pure silica layer no longer follows the deformation of nylon film and the linear cracks perpendicular to the stretching direction were produced. Consequently water vapor permeability of silica coated films increased drastically. However, critical elongational strain at which linear cracks were produced increased with PVA ratio in silica/PVA layer and only mild deterioration of barrier property was observed. Such durability of silica/PVA layer to the elongational strain is due to the flexibility of silica/PVA layer which can follow the deformation of nylon film. Further PVA seems to fill the micropores of silica prepared by sol-gel method.