| TOKYO--Kyoto
University chemical engineering professor Masahiro Ohshima and Mitsubishi
Plastics Inc. (TSE:4213) have developed a way to manufacture plastic sheets
with a number of tiny, uniformly sized holes.
Such plastic sheets are expected
to make fuel cells more efficient. Mitsubishi Plastics hopes to commercialize
the technology within a year.
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.
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