Interfacial effects on dielectric properties of ethylene propylene rubber–titania nano- and micro-composites

Abstract

The influence of titania particle size on dielectric properties of ethylene-propylene rubber (EPR) composites was investigated, with an emphasis on the chain dynamics in the interphase region. We hypothesized that a reduction in the conformational entropy of rubber chains in the interphase region would make the restricted chains more prone to orient along the applied electric field and increase dielectric permittivity than the chains in the bulk. The morphology and microstructure of the composites was characterized using scanning electron microscopy and atomic force microscopy, and a notable difference was detected in the average aggregate size and microstructure of the interphase between the nano-and microcomposites. We predicted that the physical attraction between nano-and micro-fillers and polymer, as characterized by the surface energy of fillers, would be similar. However, differences in the chain dynamics investigated by dynamic mechanical thermal analysis and dielectric spectroscopy confirmed the presence of more restricted chains, quantitatively and qualitatively, in the interphase region of the nanocomposites compared to the micro-composites. We concluded that the higher dielectric properties of the nanocomposites could be explained by the lower conformational entropy of chains in these composites compared to those in the micro-composites.

Improvement of insulation effectiveness of natural rubber by adding hydroxyl-functionalized barium titanate nanoparticles

“…Therefore, the addition of nanoparticles results in better dielectric performance than the addition of microparticles [12]. The improvement of the dielectric behavior is in part owing to the greater nanofiller surface area, and in part because of the slower dynamics of the polymer chains surrounding the minuscule aggregates [13].…”

Enhancement of mechanical strength associated with interfacial tension between barium titanate and acrylonitrile–butadiene rubber with different acrylonitrile contents by surface modification

“…The dielectric loss factor of NBR composites was also much different from BR composites. In the low frequency region (around 100 Hz), a large dielectric loss factor was observed, mainly due to the lag in the interfacial polarization resulted from migration and entrapment of charge carriers at the interfacial area between polar and nonpolar . The response time of interfacial polarization is very long.…”

Identification of natural rubber samples for high-voltage insulation applications

“…Therefore, the addition of well dispersed particles of reduced size tends to improve the dielectric performance of the polymer composite [22]. This improvement owes to the greater superficial area of the small aggregates, and the slower dynamics of the polymer chains wrapping the small particles [23].…”