Composition-Dependent Thermal Stability and Water-Induced Self-Healing Behavior of Smectite/Waterborne Polymer Hybrid Film.

By casting an aqueous suspension containing a water-soluble polymer, polyvinylpyrrolidone, and a layered silicate, synthetic hectorite, on the solid substrate, films with varied interlayer expansion were obtained depending on the composition. The thermal stability, water resistance, water-induced self-healing behavior, and adhesion were examined to find their composition dependence, which is thought to be originated from the nanostructure variation. Polyvinylpyrrolidone was thermally stable up to 300 °C for the hybrid with the polymer/clay weight ratio of 0.36 and 260 °C for the weight ratios of 1.08 and 1.80 as shown by the changes in the appearance and structure after heat treatment. The hybrid film with the polymer/clay ratio of 0.36 maintained the film shape when it was soaked in water for 24 h. The hybrids with the polymer/clay ratios of 1.08 and 1.80 were re-dispersed/dissolved into water after the immersion, while the water resistance of the films was enhanced by the thermal treatment at 200 °C for 2 h and showed very fast water-induced self-healing.