Transverse strain responses in the electrostrictive poly(vinylidene fluoride-trifluorethylene) copolymer

A large transverse electrostrictive strain S (1) with a high elastic strain energy density is observed along the drawing direction in the stretched po ly(vinylidene fluoride-trifluorethylene) copolymer film under a proper elec tron irradiation treatment condition, which results in a ratio of \S (1)/S (3)\ larger than 1 where S (3) is the longitudinal strain. In contrast, uns tretched films generate a relatively small transverse strain with a small r atio of \S (1)/S (3)\ (similar to 0.25). Hence, in this copolymer system, t he ratio of \S (1)/S (3)\ can be varied over a broad range. In addition, a large volume strain, which amounts to about half of the longitudinal strain , is observed in the films investigated. (C) 1999 American Institute of Phy sics.