The Laboratory for Film Chemistry (LMC) of the National Institute of Advanced Industrial Science and Technology (AIST), an independent administrative institution, has succeeded in developing a flexible, translucent and self-supported gas barrier film through compact lamination of clay crystal platelets. The newly developed gas barrier film is expected as gas barrier materials used under wide range of temperatures, which had been hardly available up to now.
In the prior art, heat-resistant gas barrier film was prepared by the use of engineering plastic, or if necessary, through composite processing, surface modification or lamination. The usage of the conventional gas barrier material, however, was limited up to 350 °C.
The LMC-AIST successfully prepared a gas barrier film of uniform thickness without a pinhole nor other defects at a high degree of reproducibility, by using clay which was added to engineering plastics for upgrading the gas barrier performance as main ingredient of the film, and by optimizing composition of clay materials and additives, as well as preparation process. A flexible and translucent gas barrier film can be prepared through the compact lamination of clay crystal layers of thickness around 1 nm each (1 nm = 1/1,000,000,000 m). A clay crystal layer of nanometer thickness is adequately flexible and transparent. The compact lamination of clay layers provides a translucent film with light scattering suppressed. The thickness of resultant film is comparable to that of copy paper, 3~100 μm (1 μm = 1/1,000,000 m), and can be made much thicker by layering the film together. The size of the film is unlimited. Besides, it is also possible to create a protective film by coating metal surface with the clay film. The gas permeability of the film at room temperatures to hydrogen, oxygen, nitrogen and other inorganic gases is lower than the detection limit: much lower than the oxygen permeability of conventional engineering plastic (18, for Nylon 6) and comparable to that of aluminum foil (0). Besides, the gas barrier performance of the film remains unchanged up to temperatures as high as 1000 °C, much higher than the melting point of aluminum foil (660 °C).
The heat-resistant gas barrier film will be useful as gaskets around automobile engine, sealant materials for piping in chemical plant, fuel-sealing materials around rocket and jet engines, separating film solid electrolyte fuel cell, constituting hopeful heat-resistant gas barrier materials.