ELECTROSTRICTION OF RUBBER SHEETS

Electrostriction coefficients were measured for sheets of five commerc ially important rubbers. The rubbers, polychloroprene, polyisoprene, c hlorobutyl, nitrile, and chlorosulfonated polyethylene, were formulate d and cured in a way ordinarily used for rubber applications. The elec trostriction 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 electrostricti on coefficients reported for the higher modulus polymers used in fiber s, films and structures. The electrostriction was measured perpendicul ar to the sheet, with the electric field in the same direction. All th e rubbers contracted along the direction of the electric field as the magnitude of the field increased. Mechanical constraints at the surfac es of the sheets were shown to affect the measured values of the elect rostriction coefficients. Relaxation measurements showed that the elec trostriction coefficients increased at longer measurement times. Corre ctions were made for the relatively small decrease in the thickness of the samples due to the attractive electrostatic force between the ele ctrodes. Thermal expansion effects were reduced to negligible levels b y choosing samples with high electrical resistivity, and by using shor t measurement times.