Electrostriction of rubber sheets

Electrostriction coefficients were measured for sheets of five commercially important rubbers. The rubbers, polychloroprene, polyisoprene, chlorobutyl, nitrile, and chlorosulfonated polyethylene, were formulated and cured in a way ordinarily used for rubber applications. The electrostriction coefficients were in the range of 0.2 to 1.4 x 10(-17) m(2)/V-2, which is approximately 50 times larger than the electrostriction coefficients reported for the higher modulus polymers used in fibers, films and structures. The electrostriction was measured perpendicular to the sheet, with the electric field in the same direction. All the rubbers contracted along the direction of the electric field as the magnitude of the field increased. Mechanical constraints at the surfaces of the sheets were shown to affect the measured values of the electrostriction coefficients. Relaxation measurements showed that the electrostriction coefficients increased at longer measurement times. Corrections were made for the relatively small decrease in the thickness of the samples due to the attractive electrostatic force between the electrodes. Thermal expansion effects were reduced to negligible levels by choosing samples with high electrical resistivity, and by using short measurement times.