Development of Clay-Based Films

Phyllosilicate (clay) is used as a filler to improve the thermal stability and gas barrier properties of plastic films. However, few film preparation trials used clays as the main component. Many researchers have studied clay-based films (CBFs) that are heat-resistant and have high gas barrier properties against various gases (such as oxygen, water vapor, and hydrogen) over a wide range of temperatures. An organic binder improves the film toughness, but increases gas permeation. CBFs are obtained by solution casting and show excellent incombustibility and electrical insulation. Moreover, transparent films, e.g. for optoelectronic applications, can be prepared using synthetic clay, which does not contain colored impurities. The water vapor barrier properties of CBFs were achieved using reduced-charge smectite. Applications of CBF materials include food packaging, solar cell back sheets, hydrogen tanks, gaskets, water vapor barrier display films, substrates for printed electronics, thermal insulation, and electric insulation. Recent achievements in the field and future prospects are discussed.