Kyoto University chemical engineering professor Masahiro Ohshima and Mitsubishi Plastics Inc. have developed plastic sheets to make fuel cells more efficient. The duo has invented a way to manufacture plastic sheets with a number of tiny, uniformly sized holes. Under the new method, a plastic sheet is made by letting a composite sheet made from polypropylene fiber and rubber absorb carbon dioxide under supercritical pressure. When the resulting sheet is heated in a lower-pressure environment, CO2 vaporizes, leaving minute holes. By changing the amount of CO2 and heating conditions, hole size can be varied between 40 and 500 microns.
An electrolyte membrane based on this plastic sheet can be made thinner than a conventional polypropylene-based electrolyte membrane, resulting in lower electrical resistance and higher efficiency. Such plastic sheets are expected to make fuel cells more efficient. Mitsubishi Plastics hopes to commercialize the technology within a year.