Effect of heat treatment of carbon nanofibers on polypropylene nanocomposites

Carbon nanofibers (CNFs) synthesized at 600 °C were modified at thermal treatment temperatures of 1200, 1800, and 2200 °C. These CNFs were incorporated into polypropylene (PP) at 10 wt% level by intensive mixing. Volume resistivity of composites containing CNFs heat treated at 2200 °C was higher than that of composites containing untreated CNFs. BET adsorption isotherms showed a significant reduction of specific surface area of CNFs after heat treatment, resulting from the decrease of pore volume without a change of surface roughness. In addition, scanning electron microscopy (SEM) micrographs revealed that after mixing, heat treated CNFs had a narrower length distribution (1-10 μm) than that of untreated CNFs (1-30 μm). We believe that these morphological changes of CNFs due to heat treatment contribute to a higher resistivity of composites with CNFs possessing even more graphitic content.