マイクロ波法による導電性ゴムの配向測定
Measurement of Orientation for Conductive Rubber by Microwave Method
永田紳一・小山清人
Nagata, Shinichi / Koyama, Kiyohito
The orientation dependence of the electrical characteristics of conductive rubber is strongly influenced by the shape of the carbon black particulates. This anisotropy of the electrical properties of conductive rubber is considered to be due to the shape of the carbon particulates in the continuous rubber matrix. The change in anisotropy for various extrusion conditions was investigated by using a microwave method based on dielectric anisotropy. The degree of orientation increased with an increase in the extrusion rate and the dielectric constant showed a maximum in the extrusion direction. It is conjectured that the shear stress orients the carbon black in the extrusion direction. On the other hand, a pressed vulcanized rubber was found to be almost isotropic. Although an electron microscope was used for observing the carbon structure of both a pressed rubber and an extruded one, we could not see much difference between them. Nonetheless it can be stated that the anisotropy in the conductive rubber is caused by alignment of the carbon particles in rows. This assumption is based on the facts that the unevenness of electrical response decreased with a decrease in orientation, and the anisotropy of dielectric constant is too great in comparison with that of rubber itself. To confirm this assumption, an estimation for the carbon structure was also studied by using both the dielectric constants measured by the microwave method and the theoretical equations which show the dielectric constants in the island-sea structure.
Key words: Orientation / Conductive rubber / Carbon structure / Microwave method / Island-sea structure