Deposition of Ureido and Methacrylate Functionalities Onto Silica Nanoparticles and its Effect on the Properties of Polypropylene-Based Nanodielectrics

Amirhossein Mahtabani,Ilkka Rytoluoto,Xiaozhen He,Eetta Saarimaki,Wilma Dierkes,Rafal Anyszka,Kari Lahti,Mika Paajanen,Minna Niittymaki,Anke Blume

doi:10.1109/access.2021.3112849

Abstract

Surface modification of nanoparticles is often utilized to tailor the interfacial properties in dielectric nanocomposites. Introducing different functional groups to the nanoparticles’ surface may induce localized states (traps) that can enhance the dielectric performance of the material depending on their density and energy levels. Furthermore, surface modification of the filler can affect the dispersion quality and crystallization of the nanocomposites which can ultimately alter the dielectric response of the material. In this study, functionalization of silica nanoparticles is demonstrated using 3-(trimethoxysilyl)propyl methacrylate (TMPM) and 1-[3-(trimethoxysilyl)propyl]urea (TMPU) as modifying agents. The effect of such modifications on the crystallization behavior, dispersion quality of the nanoparticles, as well as charge trapping and transport under a medium DC field is studied in nanocomposites based on polypropylene (PP)/ethylene-octene-copolymer (EOC) blends at 1% and 5% of filler concentrations. The results show that both ureido and methacrylate functional groups introduce localized states, but with different energy levels. Nitrogen containing ureido groups in TMPU tend to introduce deeper traps to the filler-polymer interfaces, compared to the methacrylate silane modification. Comparing the two types of surface functionalization, the ureido-functionalized silica resulted in a suppression of space charge formation at the interfaces under a medium DC electric field, despite the relatively larger mean cluster size of nanoparticles.

Highlights

Nanodielectric materials attracted immense attention in the past few decades, being studied in a wide range of applications such as insulating materials, electronics, sensors etc. [1,2,3,4,5]
The results show that both ureido and methacrylate functional groups introduce localized states, but with different energy levels
Polypropylene/ethylene-octene copolymer (PP/EOC) blends are among the best candidates, due to their susceptibility to reduce space charge accumulation under high DC electric fields [13,14,15]

Summary

Introduction

Nanodielectric materials attracted immense attention in the past few decades, being studied in a wide range of applications such as insulating materials, electronics, sensors etc. [1,2,3,4,5]. The absence of crosslinking by-products in PP-based nanodielectrics results in an improved space charge accumulation, and their thermoplastic nature allows for a more sustainable end-of-life for these materials [6,7,8,9] This class of dielectric nanocomposites exhibit good mechanical properties, comparable to XLPE, which makes them a reliable candidate for high voltage direct current (HVDC) cable insulation systems [10,11,12]. Recent studies have been focusing on different types of thermoplastic elastomers to be blended with PP for HVDC applications In this regard, polypropylene/ethylene-octene copolymer (PP/EOC) blends are among the best candidates, due to their susceptibility to reduce space charge accumulation under high DC electric fields [13,14,15]. Studying the morphological aspects of nanodielectrics is of great importance for tailoring their macroscopic dielectric properties

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Conclusion