Electrical and thermal properties of composite of liquid crystalline polymer filled with carbon black

The electrical resistivity and thermal conductivity of a liquid crystalline polymer (LCP) filled with a commercial carbon black (CB) of various volume fractions (phi) is investigated. The percolation threshold (phi (c)) is fo und at about 3%, and the resistivity (rho) as a function of (phi - phi (c), ) satisfies the exponential function. Although the pure LCP is highly aniso tropic in thermal and mechanical properties after processing, the composite samples exhibit no preferential direction for electrical conduction. Sampl es of phi below phi (c). exhibit a negative temperature coefficient of resi stivity while those above phi (c) show almost no temperature dependence fro m room temperature to 200 degreesC. In addition, the samples at lower phi h ave higher thermal conductivity in the LCP flow direction than those measur ed in the transverse and thickness directions, and they approach the same v alue at higher phi. This result indicates that preferential molecular align ment of the matrix LCP is responsible for the behavior of the thermal condu ctivity of the composites. (C) 2001 John Wiley & Sons, Inc.