Development of Clay‐Based Films

Abstract

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.

Shear orientation of nematic phases of clay nanosheets: processing of barrier coatings

“…8 Such high aspect ratio nanosheets are perfectly suited for high-performance polymer nanocomposites as needed for a wide variety of applications, ranging from food packaging all the way to encapsulation of optoelectronic devices like organic photovoltaic and organic light emitting devices. 10 As pointed out by Cussler's theory of the tortuous path 11,12 for optimization of the barrier properties, perfect parallel alignment of the impermeable nanosheets on the substrate is crucial. Parallel aligned (textured) nanosheets are the key to achieve low gas permeabilities as the diffusion pathway for a gas permeant is hereby maximized and the tortuosity strongly decreases once nanosheets become tilted with respect to the diffusion direction (Fig.…”

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

“…The hybrids of water-soluble polymers and smectites have been prepared using preformed polymers and smectites by mixing in aqueous media. Thanks to the homogeneous mixing of water-soluble polymer and smectite in an aqueous media, several forms of the products such as suspension, gel, and solid (powder and film) are available. , Clay-polymer intercalation compounds where polymers are intercalated in the nanospace as molecular thick layers have also been investigated, and the clay-polymer intercalation compounds have been applied as solid-electrolyte (clay-poly­(ethylene oxide)), − gas barrier film for food packaging, gasket and optoelectronics devices (clay-poly­(vinyl alcohol)), , precursor of graphitic carbon (clay-polyacrylonitrile), and so on. The superior gas barrier, ionic conduction, chemical stability and/or thermal stability of waterborne polymers were achieved by the intercalation of poly­(acrylic acid) or carboxymethyl cellulose sodium salt, poly­(ethylene oxide), poly­(vinyl alcohol), ,,− and polyvinylpyrrolidone into the interlayer space of smectite with keeping the regular layer stacking.…”

Preparation of a Chitin/Clay Hybrid Film by a Mechanochemical Method

“…The smectite clay mineral accommodates water in the interlayer space to swell spontaneously, giving a stable aqueous colloidal suspension of anionic clay nanosheets. , Mixing of the pigment with smectite clay minerals in water often results in the stable and homogeneous dispersion, which is useful for paint, cosmetic, and coating application. For example, it was reported that mixing of the clay nanosheet suspension with TiO 2 and subsequent drying resulted in a hybrid film possessing photocatalytic activity, where the clay worked as a binder of TiO 2 . , The smectite clay mineral is also known as an additive/filler to improve material performances such as optical, mechanical, and gas barrier ones of polymers as polymer-clay nanocomposites . Herein, the mixing of chitin with the aqueous colloidal suspension of a smectite clay mineral (synthetic saponite) using a wet-type jet milling is reported to obtain a stable chitin suspension.…”

“…35,36 The smectite clay mineral is also known as an additive/filler to improve material performances such as optical, mechanical, and gas barrier ones of polymers as polymer-clay nanocomposites. 37 Herein, the mixing of chitin with the aqueous colloidal suspension of a smectite clay mineral (synthetic saponite) using a wet-type jet milling is reported to obtain a stable chitin suspension. A free-standing chitin/clay hybrid film was successfully prepared by drying the suspension on the polytetrafluoroethylene (PTFE) plate and subsequent peeling off from the substrate.…”