Space charge dynamics in silica-based polyethylene nanocomposites

Abstract

Space charge formation is a well known phenomenon that affects the overall dielectric properties of insulation systems. Space charge occurs when the rate of charge accumulation is different from the rate of removal and involves moving and trapped charges, which modify the electric field distribution within the material. As a result of this, the internal field within the dielectric is locally increased, which then leads to faster degradation and premature failure. Several techniques have been used to probe the space charge behavior of novel dielectric materials, especially in connection with the emerging topic of polymer nanocomposites -material systems that exhibit unique insulation characteristics due to the presence of nanometer-sized inclusions. In this paper, we report on an investigation into space charge dynamics in silica-based polyethylene nanocomposites, where the nanofiller has been modified with respect to its surface chemistry. For this, the pulsed electro-acoustic technique has been used. Experimental observations indicate that the incorporation of nanosilica into polyethylene results in homocharge development near both electrodes. However, with appropriate surface treatment of the filler, homocharges formation was successfully suppressed. Possible relationships between the space charge development and dielectric breakdown properties of the nanocomposites are discussed.

The role of the filler surface chemistry on the dielectric and thermal properties of polypropylene aluminium nitride nanocomposites

“…However, the C8-M and C8-E treated nanoparticles show weaker abilities to increase the crystallisation temperature than both MPTS treated and untreated nanoparticles. These results are consistent with works that use non-polar SCAs [6,12]. Since the untreated nanoparticles can be considered to have polar groups on the surface, like -OH and -NH2, it can be concluded that the polar surface of nanoparticles can provide a stronger nucleating effect.…”

“…All nanocomposites have a decreased melting enthalpy and present dependency on the loading ratio rather than on the surface chemistry. This observation has been explained by the hindrance effect of nanoparticles on the growth of the crystalline structure [6,19].…”

“…Therefore, the dispersion of nanoparticles and how to reduce the agglomerations to maximise surface area are considered to be essential issues for nanodielectrics. This leads to a broad application of surface functionalisation in nanodielectrics research [6][7][8]. It is considered that the surface functionalisation can improve the nanoparticles dispersion by reducing the surface energy or by forming chemical bonding with the matrix material.…”

“…However, polymers like polyethene (PE) and polypropylene (PP) with a carbon chain structure, which is nonpolar, functional group free and low unsaturation, are unlikely to interact chemically with any SCA. It is generally believed that alkyl silanes, such as propyl (C3) and octyl (C8) silanes can thermodynamically increase the compatibility between the nanoparticles and carbon chains due to their similar carbon chain structures [6,12]. Although some studies believe methacrylate silanes can form covalent bonds with PP [10,13], there is no convincing evidence to show that any SCA can durably bond to PP.…”

Evaluation of polypropylene/polyolefin elastomer blends for potential recyclable HVDC cable insulation applications

“…With the increase of POE content, a large amount of trapping sites can be introduced at the interface between POE particles and PP matrix. Also the semicrystalline nature of PP leads to the presence of trapping sites at the interface between the crystalline and amorphous phases [24]. As a result, the injected charges are captured by the trapping sites so that there are large amount of hetero space charge that accumulates near the electrode.…”