Preparation of PVA/CNTs film with high stability and humidity sensitivity based on multiple process

Abstract

Polyvinyl alcohol (PVA) is a polyhydroxylated water-soluble polymer with rapid response to water molecules in environment. In this paper, a humidity sensitive PVA film with both high stability and satisfactory humidity sensitivity were prepared based on multiple process, i.e., crosslinking, foaming, spin coating and composition with hydroxylated carbon nanotubes (CNTs). The crosslinking of PVA with formaldehyde enhances the stability of the film under cyclic test condition, which exhibits deviation ratio of 1.1 and 1.2 in response and recovery process respectively. The pore structure generated by foaming agent promotes the water vapor exchange efficiency and improve the humidity response and recovery performance. The spin coating speed significantly influences the pore structure and thickness of the prepared films. CNTs facilitate the dissociation of water molecule through hole carriers and hydroxyl groups to reduce the resistance of PVA/CNTs films and enlarge the humidity response range. The spin coating speed and CNTs content jointly determine the final foaming structure and film thickness. Based on the multiple methods, the obtained crosslinked open pore film exhibits satisfactory humidity sensitive properties with the response time of 48 s and equilibrium time of 296 s, which should have good application prospect.