High Thermal Conductivity Fibers from PBO.

The objective of this project is to examine the conversion of poly p-phenylenebenzobisoxazole PBO to carbon fiber. The production of polymer-based carbon fibers usually involves heating the precursor fiber to approximately 300 deg C to crosslink the polymeric structure, thus rendering it infusible, and then heating the crosslinked fiber to much higher temperatures to drive off most non-carbon elements. Because stabilization occurs as a separate step, establishing its influence on the structure and properties of the final carbon fiber is relatively straightforward. A series of three stabilization trials were performed, and then all three stabilized fiber samples were heated to 2000 deg C at 20 deg C per minute. A carbonized length of as-received PBO fiber served as a control. The results showed that stabilization did not improve the tensile characteristics of the final carbon fiber. In Dows production of PBO fiber, the fiber is heat treated to a temperature of 550 deg C for 10-30 seconds. This additional heat treatment reduced the fibers tensile strength, but increased its modulus and compressive strength. Future research will be conducted upon the carbonized fiber to determine its thermal conductivity, crystallinity and orientation, and the kinetics of the carbonization process. p2