ETFE copolymers are known in the art. U.S. Pat. No. 4,123,602--Ukihashi et al. (1978) discloses such polymers with about 40 to 60 mole % of each comonomer, using modifiers such as 1% perfluoro butylethylene. Such modifiers and other adjuvants are common in the art and are considered to be part of the copolymer.
Films of various fluoropolymers including ETFE, which can have various fillers including mica, are used for cladding metal substrates in Japanese Kokai 4-229246--Sahara et al. (1992). There is no focus in this kokai on minimizing permeation or on using mica in ETFE, or on what proportions would be needed.
Mica coated with oxides to produce sparkling optical effects is the subject of U.S. Pat. No. 3,087,829--Linton (1963).
Mica is used in fluoropolymer coatings for cookware to minimize stain formation, as in U.S. Pat. No. 4,353,950--Vassiliou (1982).
The disclosure of the previously identified patents and patent publications is hereby incorporated, by reference.