To provide a pitch-based graphitized staple fiber slight in the possibility of causing the setting inhibition of a thermosetting resin even if kneaded with the resin.
The pitch-based graphitized staple fiber has the following characteristics: (i) The average fiber diameter observed by optical microscope is larger than 2 m but not larger than 20 m, and the fiber diameter distribution percentage based on the average fiber diameter is 3-20%. (ii) The fiber surface observed by scanning electron microscope is substantially flat. (iii) When the five fibers' ends, whose graphene sheet edge faces have the whole length of longer than 50 nm but shorter than 300 nm, are observed by transmission electron microscope, the average value of the closure percentage represented by formula (1), closure percentage (%)=B/A100 (A is the whole length (nm) of the graphene sheet edge face of the fiber end; and B is the length (nm) of portion where the edge face is curved U-shaped fashion), is greater than 80% but less than 100%.
HARA HIROSHI
TAKAGI SHOICHI
Taizo Shiraishi