Dielectric properties of upright carbon fiber filled poly(vinylidene fluoride) composite with low percolation threshold and weak temperature dependence

Upright carbon fiber (CF) filled ferroelectric poly(vinylidene fluoride) (PVDF) composites were prepared via a simple blending and hot-molding technique. The dielectric properties of the CF/PVDF composites as a function of the volume fraction of CF, the temperature, and the frequency were studied. The dielectric constants decrease slowly with increasing frequency and rise gradually with increasing CF contents in the composites. As the volume fraction of the CF is up to 0.074, an abrupt increase in the dielectric constant occurs, which is attributed to the formation of the conductive network in the matrix. The percolation theory, the microcapacitor model, and the simple concept of polarization in the capacitors are employed to explain these experimental results. (C) 2007 American Institute of Physics.