Dielectric response and breakdown strength improvement of LDPE/TiO2 nanocomposites by using POSS as compatibilizing agent
In this paper, two types of nanocomposites were prepared by ball milling techniquee The first type consists of 5% untreated titanium dioxide (TiO2) incorporated into LDPE. For the second one, 5% commercial TiO2 chemically treated with trisilanol phenyl polyhedral oligomeric silsesquioxane (TSP-POSS) as dispersant was ball-milled with LDPE. The microscopic observation by Atomic Force Microscopy (AFM) showed a better dispersion into polymer matrix of the TiO2 treated with POSS as compared to untreated TiO2. It was found that LDPE/treated TiO2 nanocomposite exhibited lower relative permittivity and dielectric losses compared to LDPE/untreated TiO2. The surface treatment of LDPE/TiO2 by TSP-POSS also affects the dielectric strength. The LDPE/treated TiO2 revealed highest breakdown strength of 82 kV/mm, compared to 78 kV/mm and 71 kV/mm of LDPE neat and LDPE/untreated TiO2, respectively.
Dielectric properties of epoxy/alumina nanocomposite influenced by control of micrometric agglomerates
Introduction of metal oxide nanoparticles to polymer material is known to have unique dielectric behavior and significant advantages in electrical insulation performance in power apparatus. This paper presents an attempt to clarify the influence of dispersibility of nanoparticles, especially focusing on agglomerates, on dielectric properties of a nanocomposite system by changing particle dispersion processes. Experiments were carried out in epoxy/alumina nanocomposites with the particle dispersion techniques by applying ultrasonic wave and centrifugal force. For the dispersibility control of nanoparticles, we changed the duration of ultrasonic wave and centrifugal force. The experimental results clarified the effect of centrifugal force on the separation of agglomerates and the effect of ultrasonic wave on the disruption of agglomerates. Next, we examined the dielectric properties such as relative permittivity and tan δ of the nanocomposites. As the result, we verified that the permittivity of epoxy/alumina nanocomposites became low due to separation and disruption effects of the agglomerates.
Space Charge Distribution Behavior of Nano-SiOx and Low-density Polyethylene Composite
The composite of nano-SiOx and low-density polyethylene is prepared with the double-solution method. Space charge distribution in the composite with various nano-SiOx contents is carried out by pulsed electro-acoustic method. It is shown that the amount of space charge in the composite increases with the nano-SiOx content. The space charge in the composite under 50 kV/mm dc stress is mainly hetero, which is very different from that in the pure polyethylene. However, after electrically stressed at 50kV/mm for one hour, homo space charge is found while the composite being short-circuited. It is believed that the homo space charge injects and accumulates during the dc stressing process, which mainly contributes to the formation of the space charge