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Physical foaming of fluorinated ethylene-propylene (FEP) copolymers in supercritical carbon dioxide: Single-film fluoropolymer piezoelectrets

: Voronina, O.; Wegener, M.; Wirges, W.; Gerhard, R.; Zirkel, L.; Münstedt, H.


Applied physics. A 90 (2008), No.4, pp.615-618
ISSN: 0340-3793
ISSN: 0721-7250
ISSN: 0947-8396 (Print)
ISSN: 1432-0630 (Online)
Journal Article
Fraunhofer IAP ()

Cellular polymer foams with significant piezoelectric activity were prepared from fluorinated ethylene-propylene (FEP) copolymers. The required void structure is obtained by saturation of FEP films with supercritical carbon dioxide and a subsequent heat treatment for controlled inflation. After bipolar electric charging of the voids and evaporation of electrodes, the FEP films show piezoelectric d(33) coefficients up to 50 pC/N. The present physical foaming process generates cellular fluoropolymer piezoelectret films with usually only one single void across the film thickness.