DIELECTRIC MONITORING OF WATER-ABSORPTION IN GLASS-BEAD-FILLED HIGH-DENSITY POLYETHYLENE

Model composites of spherical glass particles dispersed in a matrix of high-density polyethylene (HDPE) were prepared. Samples of the composite material were, after careful drying, exposed to several relative humidities at room temperature. The dielectric properties and the mass gain of the composite samples were monitored during the water absorption from the environment. The dielectric measurements covered the frequency range from 0.1 Hz to 50 kHz. A theoretical model for the dielectric properties of composites with an interlayer describes the detected dielectric loss processes due to the electrically conducting layer of adsorbed water at the filler-matrix interface. A quantitative relationship between the amount of absorbed water and the frequency of maximum dielectric loss can be established by taking into account the thickness dependence of the conductivity of the interfacial water layer.