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Du Pont

Mylar

Mylar is a type of polyester film (specifically BoPET: biaxially-oriented polyethylene terephthalate), originally developed by DuPont, Imperial Chemical Industries and Hoechst in the 1950s. In the keyboard industry, Mylar found a use as a suitable material for membranes in keyboards of that type.

Products confirmed to use Mylar include:

The patent for General Instrument S700 Series also suggests metallised Mylar for the foil covering on the foam pads.

Kapton

Kapton is polyimide film, also developed by DuPont, in the late 1960s. Kapton was specified for the spacer sheets in Datanetics batch-fabricated array keyboards. It was also used for the membrane layers of prototype Datanetics DC-50 switches, before Datanetics changed to Mylar.

Documentation

All documents scanned by Bitsavers unless otherwise noted.