To clearly exhibit a PTC characteristic by which electrical resistance sudden ly increases in a narrow area accompanying by a a temperature rise, and make it suitable for gas piping through constituting it by blending a hyperfine structure carbon material and/or an inorganic substance containing hyperfine structure carbon material at a specific rate with a high polymer material.
A hyperfine structure carbon material is blended by 2 to 100 pts.wt. with 100 pts.wt. of a high polymer material. These carbon materials preferably have a single-layer or multilayered structure of a cylindrical carbon material, which has the average particle size of 10 nm to 10 μm and has a spherical shape or an elliptic spherical shape or an outside diameter of 10 nm to 10 μm, and the carbon content is set not less than 99%, and the spacing of a layer structure in X-ray diffraction of a graphitization degree is set to 0.3354 to 0.36 nm. Since the carbon component concentration and crystallinity are high, a conductive percolation path can be formed easily at a room temperature of a composition, and resistivity increase rate increases greatly, and a PTC characteristic is improved, and electrical conductivity is also good. When hyperfine structure carbon containing an inorganic substance such as metal or its oxide or carbide is blended, a thermal expansion coefficient and heat conductivity of the composition also increase.
YAMAGUCHI CHIHARU
MATSUI TAKEO
YASUDA AYUMI
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