直接通電加熱による炭素繊維の熱処理

抄録

A continuous process for heat-treating a carbon fiber tow by directly passing electric curren through the tow was developed, and by this process a polyacrylonitrile-based carbon fiber tow which was prepared at a highest temperature of about 1250°C was heat-treated. Heat-treatments of two types were made; one employing a reflector covering the heat-radiating zone of a tow, and the other without a reflector. The structural parameters characterizing the stacks of carbon layer, such as interlayer spacing, sizes and orientation, and the mechanical propertie of the carbon fibers heat-treated by direct currenting were evaluated as a function of surfac temperature of tow during heat treatment over the range of 1000 to 2000°C. A considerable heat-loss by radiation from the tow surface is expected during heat-treatment by direct currenting. Therefore an effective heat-treatment temperature in the inside of tow will be lower for the heat-treatment with a reflector than that without a reflector if the surface temperature of tow is constant. The structural parameters versus surface temperature relations for the tow heat-treated with a reflector differed from those for the tow heat-treated without a reflector. These results were explained by considering an effective heat-treatment temperature of tow. Differences in density and linear density between the tows heat-treated with and without a reflector could not be explained by the effective heat-treatment temperature, and seemed to be caused by a certain factor proper to the present heat-treatment method. The tensile modulus after making a correction on density increased almost linearly with increasing orientation of the stacks. The tensile strength decreased with increasing heat-treatment temperature in a similar manner reported for carbon fibers heat-treated by a conventional method.