The effect of adsorbed water on the dielectric properties of CaCO₃ filled polyethylene composites

Abstract

The dielectric dispersion and loss of a polyethylene–CaCO3 composite have been investigated in the 50 Hz–100 kHz frequency and 20–140°C temperature ranges, and compared with those for a normal mechanical mixture. The different theoretical interpretations are reviewed and compared with the data. The observed dispersion and loss are probably due to adsorbed water at the PE‐CaCO3 interface; both disappear on heating. The high‐frequency permitivities can be well approximated by theoretical models, but the frequency‐dependent phenomena cannot be interpreted in terms of a simple interfacial polarization mechanism. The universal response theory provides a useful tool for interpreting the measurements.

Dielectric properties of moist CaCO3 filled polyethylene composites

“…The 10 kHz losses of D62 and D48 upon cooling are compared in Figure 6. As previously observed [1] D48 shows far less dielectric loss than D62. This smaller dielectric loss of D48 cannot be explained solely by the difference in the filler content; it is probably due to a difference in the surface pre-treatment of the materials.…”

“…The qua- The effect of exposure to humid air on the samples was studied. Most of the measurements were performed using D62, because this sample proved to be most sensitive to water adsorption [1] but D48 and the mechanical mixtures were also studied. The rest of the dielectric measurements were performed at room temperature.…”

“…Samples containing 10-60 wt % filler will be designated as H10-H60. Further details of sample preparation have been described previously [1].…”

“…Evaporated metal layers could influence water vapor diffusion and their surface chemistry could change under the effect of water, so they were omitted. For further details of data processing see Reference [1].…”

“…Preliminary studies on the dielectric properties of polyethylene-calcium carbonate composites have been described in a previous publication [1]. It was established that samples stored under ambient conditions exhibit dielectric loss which disappears on heating or vacuum treatment.…”