Direct carbonization of PBO fiber

Poly p-phenylene benzobisoxazole (PBO) fiber appears to display unusual characteristics during its conversion to carbon fiber. This introductory study focused on specific aspects of the carbonization behavior that differentiate PBO from other materials. Results showed that oxidative stabilization did not affect the tensile properties of carbonized fiber produced from PBO precursor fiber. Unlike other polymeric precursors, unstabilized PBO fibers could be directly converted to carbon fibers with promising mechanical and thermal properties. The carbonization characteristics of unstabilized PBO were found to be similar to those of stabilized PAN-based fibers. However, the PBO-based carbon fibers exhibited a radial texture similar to pitch-based fibers. Surprisingly, the PBO-based carbon fibers exhibited electrical resistivities in the range of commercial pitch-based fibers, implying that their thermal conductivities also will be similar. Low-temperature carbonization studies 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 thermal properties of the final carbon fiber, may make PBO an attractive precursor for some carbon fiber applications.