Influence of water on PE — SiO2 nanocomposites dielectric properties

Polymers filled with inorganic nanoparticles have been extensively investigated in recent years because of their improved mechanical and electrical properties compared with the unfilled polymers. The most commonly used inorganic particles are oxides, particularly silica, because of their good properties and low cost. However, oxides have a hydrophilic nature, which leads to presence of water at the interface between particles and matrix. Due to the predominance of the particle-matrix interfaces in the case of nanocomposites, the presence of water in the interlayer region can become problematic. Moreover, the hydrophobic nature of most polymers, particularly polyolefins such as polyethylene, may make difficult the movement of this interfacial water. In this paper, dielectric spectroscopy was used during drying isothermal treatment at 80°C. The Maxwell - Wagner - Sillars relaxation peak sharpens and shifts to lower frequencies by three decades with time, translating into a modification of the interface between silica and polyethylene by drying.