SEARCH

SEARCH BY CITATION

Keywords:

  • petroleum pitches;
  • heat treatment;
  • thermal conductivity;
  • Lc;
  • d-spacings;
  • La

Abstract

Petroleum-based pitches were used as filler materials to study the effects of heat-treatment-induced changes in pitch structure on the thermal conductivity of epoxy-based composites. The heat treatment was performed in two steps: the first involved heating the pitch to 250 °C in order to remove the low-molecular-weight compounds from the pitch, and the second involved heating the pitch to either 430 or 450 °C. There was no significant difference in the curing behavior of the diglycidyl ether of bisphenol A (DGEBA)/pitch composites, regardless of the heat-treatment temperature. However, the thermal conductivity of the DGEBA/pitch composites improved with increasing heat-treatment temperature, and the epoxy composite prepared with pitch heat-treated at 430 °C exhibited the maximum thermal conductivity. This can be attributed to structural changes in the pitch, such as the distance between adjacent planes (d-spacing), crystallite height (Lc) and crystallite width (La). Although Lc of the pitch increased with increasing heat-treatment temperature, the d-spacings and La decreased. These results suggest that the heat treatment of the pitch led to a well-stacked crystalline structure. However, compared with the pitch heat-treated at 430 °C, that heat-treated at 450 °C exhibited lower thermal conductivity in the DGEBA/pitch composite because of the low La, resulting in the loss of basal carbon as a consequence of in situ gasification, and pyrolysis of the low-molecular-weight compounds in the pitch. © 2013 Society of Chemical Industry