Bridgestone Corporation

Yoshiki Fukuyama

Tasuku Saito

Takayuki Maruyama

Yasuo Kurachi

Shigeki Endo

Yuichi Ishino

Toshiyuki Osaki

Seisuke Tomita

Ryo Sakurai

An electro-responsive elastomeric material comprising (A) an electrically insulating polymer having a specific modulus of elasticity and (B) a fine powder dispersed in the polymer which electrically polarizes under an electric field independent of water changes its viscoelasticity upon voltage application. The powder has a mean particle size of 0.5 to 500 .mu.m and is (1) a fine carbonaceous powder having a C/H atomic ratio of from 1.2 to 5, (2) composite particles having minute particulates of an insulating material dispersed in a matrix phase of a carbonaceous or carbide material, (3) composite particles having minute particulates of a carbonaceous or carbide material dispersed in a matrix phase of an insulating material, or (4) a fine composite powder of a stratum clay mineral having a two-dimensional stratum structure with a carbonaceous or carbide material incorporated between the strata.

Electro-responsive elastomeric material

A powder having improved oxidation resistance and controlled electrical properties is obtained by dispersing minute particulates in a matrix phase to form composite particles. The minute particulates may be distributed uniformly or non-uniformly such that the particulates are dense near the surface and sparse near the center of each particle or inversely. The matrix phase has a moderate conductivity of 10.sup.-10 to 10.sup.2 Scm.sup.-1, and the dispersed particulates have a low conductivity of up to 1/10 of that of the matrix phase, typically up to 10.sup.-2 Scm.sup.-1. Alternatively, the matrix phase has a lower conductivity and the dispersed particulates have a moderate conductivity. The powder is dispersed in an insulating oily medium to form an electrorheological fluid.

Powder and electrorheological fluid

The electroviscous fluid is a suspension composed of a finely divided dielectric solid dispersed in an electrically nonconductive oil. The viscosity of the fluid increases swiftly and reversibly under an influence of electric field applied thereto and the fluid turns to a state of plastic or solid when the influence is sufficiently strong. The electroviscous fluid of the present invention comprises 1-60% by weight of a dispersed phase of carbonaceous particulates having average particle size of 0.01-100 micrometer, and 99-40% by weight of a continuous liquid phase of an electric insulating oil having a viscosity of 0.65-500 centistokes at room temperature. The electroviscous fluid exhibits an excellent electroviscous effect even at a high temperature with a low electric power consumption together with maintaining the improved electroviscous effect for a long period of time.

Electroviscous fluid

The electroviscous fluid is a suspension composed of a finely divided dielectric solid dispersed in an electrically nonconductive oil. Viscosity of the fluid increases swiftly and reversibly under an influence of electric field applied thereto and the fluid turns to a state of plastic or solid when the influence is sufficiently strong. The electroviscous fluid of the present invention comprises

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Kodaira, Japan

Yoshiki Fukuyama