The behavior of filler particles in the polymer matrix on a physical model representing the suspension of solid particles in the apolar liquid has been studied. Relative sedimentation volumes of powder components included in the polymer composition for the cable insulation in liquids of different polarity have been identified. The dependence of the effect of hygroscopic powder fillers on the relative sedimentation volume of powders and a ratio of wetting has been studied. It has been found that hydrophobic interactions are not observed at the surface of completely dry materials placed in liquids of different polarity. Consequently, the role of the filler is actually to prevent adsorption of moisture from the air on the surface of the particles, to reduce their hygroscopicity. It is proposed to assess the degree of water-repellency of the particles of powdered fillers by the measurement of their maximum hygroscopicity