The electrical and dielectric properties of compression‐molded segregated polyethylene‐carbon black mixtures are described in the frequency range between 10 and 8000 kHz as a function of frequency, temperature, and carbon black loading. The segregated systems investigated exhibit insulator‐conductor transitions in the range 0.25–0.65% (volume/volume) carbon black. The dielectric constant and the dissipation factor of the conductive samples are relatively very high in the frequency range studied. The dielectric constant increased sharply with the carbon black concentration, and then increased moderately beyond the insulator‐conductor transition. The dissipation factor‐concentration curves for different carbon blacks show maximum values in the vicinity of the critical concentration values. The dielectric properties of these systems are discussed in terms of interfacial Maxwell‐Wagner polarization effects.

The dielectric properties of peroxide cross‐linked polyethylene–carbon black composite systems are described in the frequency range between 10 and 107 Hz as a function of frequency and carbon black loading. Very high values for the dielectric constant were obtained when measuring conductive samples. A percolative model gives a suitable explanation, within experimental limits of the properties of the systems studied.

This paper reports results on the dielectric properties of carbon black filled crosslinked polyethylene composites. These systems are shown to follow percolative type models. The dielectric constant increases slowly, with carbon black concentration, up to roughly the percolation concentration and then increases rapidly over the whole concentration ranges studied. The dissipation factor‐concentration curves are bell‐shaped with maximum values at approximately the percolation concentration. The dielectric properties of these systems are discussed in terms of interfacial Maxwell‐Wagner polarization effects.

The dielectric and magnetic properties of polystyrene composites containing barium or nickel‐zinc ferrites were studied as function of the ferrite concentration and field frequency. The composites were prepared by methods yielding a random distribution of the ferrite particles or segregated structures. Barium ferrite‐poly‐styrene composites exhibited a typical insulator behavior, and only above 60% ferrite were high values of the dielectric properties noted at the lower frequencies, decreasing gradually with frequency to the low values typical of the higher frequencies. The mode of barium ferrite particle distribution did not affect the dielectric properties. The nickel‐zinc ferrite systems demonstrated a conductor type behavior. An apparent insulator‐conductor transition was observed, having lower values for segregated than for random distributions. The magnetic permability of barium ferrite‐polystyrene composites above 10% ferrite increases with the ferrite concentration, whereas the magnetic dissipation factor steeply increases with concentration above 40% ferrite.

The dielectric properties of thermoplastic and cross‐linked polyethylene compounds with a low structure medium thermal carbon black are described in the frequency range between 30 and 8000 kHz as a function of frequency, temperature, and carbon black loading. Very high values of the dielectric constant were obtained for the conductive samples. The systems investigated are shown to follow percolative type models with experimental critical exponents in good agreement with the predicted values. The dielectric constant increases slowly with the carbon black concentration up to roughly the percolation concentration, then increases rapidly, and subsequently decreases at the higher black loadings. The dissipation factor‐concentration curves show maximum values in the vicinity of the percolation concentration. The dielectric properties of these systems are discussed in terms of interfacial Maxwell‐Wagner polarization effects.