Improvements in the long-term stability of a LiCl dew-point sensor using cross-linked porous poly(vinyl alcohol) film

A novel sensing film for a LiCl dew-point sensor was prepared by incorporating LiCl into the cross-linked porous PVA film. Their impedance characteristics and long-term stability was examined. The porous PVA film cross-linked with formaldehyde exhibited superior stability for more than 50 days, even when the film was stored in 50% RH atmosphere where dewdrops appear on the surface of the film. FTIR analysis, dielectric measurements, and SEM observation suggested that this superior stability may be attributed to the unique layered morphology of the coating, which is composed of a cross-linked PVA exterior layer and a primarily porous PVA interior layer that holds LiCl inside.