SOME FACTORS FOR THE HIGH PERFORMANCES OF MESOPHASE PITCH-BASED CARBON-FIBER

The tensile strength and Young's modulus of the carbon fibres prepared from naphthalene derived mesophase pitch were studied by varying the spinning temperature, heating rate and final temperature of the stabilization and graphitization temperatures to find the best properties obtainable from the particular pitch. The heating rate was very influential on the tensile strength of the fibre; a slow heating of 0.5-degrees-C min-1, provided the highest strength, as high as 5 G Pa at the optimum final temperature of stabilization. A higher or lower final temperature reduced the strength. Insufficient oxygen uptake or decomposition of oxygen groups at the surface of the fibre could induce defects, reducing the strength. In contrast, Young's modulus of the fibres was rather insensitive to preparation conditions. The carbonization and graphitization temperature influenced the mechanical properties as follows: the strength increased stepwise with the carbonization temperature, whereas the modulus increased sharply with the graphitization temperature. The structural factors most influential differed with these properties.