Poly p-phenylene benzobisoxazole (PBO) fiber appears to display unusua
l characteristics during its conversion to carbon fiber. This introduc
tory study focused on specific aspects of the carbonization behavior t
hat differentiate PBO from other materials. Results showed that oxidat
ive stabilization did not affect the tensile properties of carbonized
fiber produced from PBO precursor fiber. Unlike other polymeric precur
sors, unstabilized PBO fibers could be directly converted to carbon fi
bers with promising mechanical and thermal properties. The carbonizati
on characteristics of unstabilized PBO were found to be similar to tho
se of stabilized PAN-based fibers. However, the PBO-based carbon fiber
s exhibited a radial texture similar to pitch-based fibers. Surprising
ly, the PBO-based carbon fibers exhibited electrical resistivities in
the range of commercial pitch-based fibers, implying that their therma
l conductivities also will be similar. Low-temperature carbonization s
tudies showed that PBO fiber can be carbonized at rapid rates without
adversely affecting the tensile properties of the carbonized material.
Its ability to be directly carbonized, combined with the unusual ther
mal properties of the final carbon fiber, may make PBO an attractive p
recursor for some carbon fiber applications.