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

Amirhossein Mathabani,Kari Lahti,Xiaozhen He,Rafal Anyszka,Anke Blume,Wilma Dierkes,Mika Paajanen,Ilkka Rytöluoto,Eetta Saarimäki

doi:10.5324/nordis.v0i26.3292

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.

Highlights

A European project called GRIDABLE (Polymer Nanocomposite Insulation Material Enabling Integration of Renewables and DC Storage Technologies in the AC Energy Grid) was inaugurated under the HORIZON 2020 framework co-funded by the European Community
Thermogravimetry Analysis (TGA) results, depicted in Figure 1, show a higher weight loss for the modified silicas compared to the untreated one, which is an indication of the successful modification of the silica surface
Based on the results presented in this report, modifying the surface of the silica nanoparticles has a profound effect on the charge trapping properties of the PP/polyolefin elastomer (POE)/silica nanocomposites without altering the crystalline structure of the nanocomposites

Summary

Introduction

A European project called GRIDABLE (Polymer Nanocomposite Insulation Material Enabling Integration of Renewables and DC Storage Technologies in the AC Energy Grid) was inaugurated under the HORIZON 2020 framework co-funded by the European Community. The goal of GRIDABLE is to develop polypropylene-based nanocomposites with proper nanoparticle functionalization and dispersion quality This novel material can bring about significant improvements for the state of the art DC cable insulations and film capacitors. Nanodielectric composites containing filler particles of size lower than 100 nm in one dimension, may exhibit significant enhancements in e.g. dielectric strength and voltage endurance [5] These improvements can be due to various phenomena, which mainly stem from the high interfacial area implemented by nanofillers incorporated to the polymer matrix [6] as well as the alteration of the features of the polymer/filler interphase [5]. This paper is based on preliminary results of the study, and further elaborations are planned to be done in future publications

Silica Modification

Preparation of the Nanocomposites

Results and Discussion

Conclusions