Solution Modified Fumed Silica and Its Effect on Charge Trapping Behavior of PP/POE/Silica Nanodielectrics

Abstract

Various dielectric nanocomposite materials are studied in the frame of the European Commission funded project GRIDABLE. This project has the aim to develop DC cable extruded insulation and medium and low voltage DC capacitor films exhibiting enhanced performance with respect to presently used materials. The nanocomposites intended for cable applications are polypropylene (PP)/polyolefin elastomer (POE) blends filled with surface modified nano-silica particles. The surface modification is carried out via the state-of-the-art solution method using a polar silane as the modifying agent. Thermally Stimulated Depolarization Current (TSDC) measurements were carried out in order to study the charge trapping behavior of the nanocomposite samples. TSDC results indicate that the addition of the treated nano-silica, for most cases, reduces the density of the deep traps significantly. The effect of the addition of silica nanoparticles - both modified and unmodified - on the crystallinity of the samples was studied using X-ray Diffraction (XRD). This is important as the charge trapping properties of the nanodielectrics can be affected by the degree of crystallinity. While more detailed studies are necessary, these results imply that the depth and the density of the deep trap states is profoundly influenced by the level of the silica modification i.e. the amount of the grafted silane on the silica surface.

On the Silica Surface Modification and Its Effect on Charge Trapping and Transport in PP-Based Dielectric Nanocomposites

“…This can be achieved, e.g., by the introduction of polar functional groups at the interface. 23,24 Siddabattuni et al 25 investigated epoxy nanocomposites with TiO 2 and BaTiO 3 nanoparticles, and observed that upon introduction of electron-withdrawing phenyl groups at the polymer−particle interface, the leakage current and dielectric loss was significantly reduced. This also led to an improvement in the dielectric breakdown strength.…”

“…Another phenomenon through which surface modification of the nanoparticles can affect the dielectric properties of the nanocomposites is the alteration of the electron–phonon interactions at the filler–polymer interface. This can be achieved, e.g., by the introduction of polar functional groups at the interface. , Siddabattuni et al investigated epoxy nanocomposites with TiO 2 and BaTiO 3 nanoparticles, and observed that upon introduction of electron-withdrawing phenyl groups at the polymer–particle interface, the leakage current and dielectric loss was significantly reduced. This also led to an improvement in the dielectric breakdown strength.…”

Silica Surface-Modification for Tailoring the Charge Trapping Properties of PP/POE Based Dielectric Nanocomposites for HVDC Cable Application

“…In general, silica-silane modification in most cases is performed in a solvent at various temperatures [15]- [17]. This enables utilization of various functional silanes and versatile conditions resulting in a good control of the silane deposition on the silica surface.…”

Gas Phase Modification of Silica Nanoparticles in a Fluidized Bed: Tailored Deposition of Aminopropylsiloxane

“…For various industrial and scientific applications, there is a need to functionalize the surfaces of nanoparticles in order to achieve a variety of properties. Among different types of powders, silica nanoparticles are widely used in many fields as filler, − catalyst carrier, and biological and medical materials . In order to improve the application performance, their surfaces usually need to be modified by functional chemical groups. , 3-aminopropyltriethoxysilane (APTES) is a commonly used modifying agent because of its versatility and wide application range.…”

“…12,13 One of the fields where the incorporation of functionalized silica nanoparticles is becoming of growing interest, are high voltage direct current (HVDC) cable insulation systems. 2,3,14 In our previous studies, it was shown that treating silica nanoparticles with APTES results in significant reduction of space charge injection in nanodielectrics under DC fields. This improvement can be due to numerous phenomena, for example, improving filler dispersion, 15 altering the electronic structure at the filler−polymer interface, 16 enhancing nucleation and changing crystalline structures in the semicrystalline polymer matrix.…”