Comparison of the length of vapor-grown carbon fiber before and after mixing process

It was found that both ends of the vapor-grown carbon fiber (VGCF) were clearly observed by SEM on the cover glass through dispersing VGCF in a polycarbonate (PC)/tetrahydrofuran (THF) solution and decomposing PC by heat treatment. By using this method, the length of three kinds of VGCF before and after mixing was measured: untreated VGCF (average diameter: 150 nm), VGCF treated for densification, and VGCF which was melt-mixed with PC using a twin screw extruder. SEM analysis suggested that the average length of VGCF has become short by densification treatment or melt mixing from 6.7 mum to 3.9 mum or to 3.0 mum, respectively. The present study proposed a new simple method to evaluate VGCF length, and demonstrated the evidence for breakage of VGCF by mixing.