Modeling Dielectric Constant Variability in Aggregate Polymers from CV Measurements

Recently a new technique based on capacitive sensing has been developed and used to estimate the amount of moisture in polymers by means of the deviation of the dielectric constant. This technique is expected to be used for in-line monitoring of aggregate polymers. Despite its interest for industry, only a few papers have been published on modeling these systems in which the material has a granularity in the mm range. In this paper the problem of variability of the dielectric constant extracted in aggregate polymers was addressed. It was demonstrated that, while keeping the same average density of the material, the orientation of the elementary rod may be critical. In particular, assuming that rods can have two orientations, below a given population, the variance of the dielectric constant induced by random arrangement of rods could exceed the change in the dielectric constant arising from the content of water. In addition, guidelines were proposed to estimate the confidence interval for these CV-based humidity sensors.