Electrostrictive Response of Elastomeric Polymers

Abstract : It is well known that the electrostrictive response of all materials is small at low applied electric fields. However, the electrostrictive strains (S) are related to the square of the applied field (E). It therefore appeared reasonable to assume that for a soft polymeric material, a large thickness response, d sub T(d sub T = partial derivative of S/partial derivative of E), might be obtained by application of sufficiently high D.C. bias fields (approx. 20MV /m) to a film while driving the film with an A.C. signal. Under such high electric fields, d sub T values greater than 3 A/V were obtained for a low crystallinity poly(vinylidene fluoride) (PVF2) film containing 65% by weight of a plasticizer tricresyl phosphate (TCP). Values of 6 A/V were obtained for certain classes of thermoplastic elastomers, i.e., polyurethanes. These values are considerably greater than those obtained from conventional piezoelectric ceramic materials and an order of magnitude greater than the 0.25 A/V obtained from polarized PVF2. In addition, large elastic strains (>3%) were observed as a function of applied D.C. field.