http://www.scprod.com/product_bulletins/PB%20Cloisite%2020A...

来自 : www.oalib.com/references/13881 发布时间：2021-03-24

ABSTRACT: The evolution of the space charge and conductivity with DC poling of two types of polypropylene-(PP-) based nanocomposites (PNCs) was investigated. The PNCs were manufactured with different concentrations of synthetic and natural organoclays. The optimal concentrations of nanofiller that can efficiently mitigate the space charge with DC aging time were 2-wt% for PP-natural-clay and between 2 and 4？wt% for the PP-synthetic-clay. Above these percentages charge transport through overlapping of nanoparticles can occur due to the interaction zone of double layers formed at the nanoparticle/host material interfaces. Under DC field the overlapping increases the conductivity of PNCs and minimizes the benefit of incorporating nanofillers into PP. The total charge stored in unfilled PP increased continuously with time reaching a maximum around 5000？h before decreasing but it also changed slightly in all filled specimens. It was perceived that the smaller the size of nanofiller platelets the more efficient the charge mitigation. The conductivity of specimens containing 6？wt% of natural clay and 8？wt% of synthetic clay reached ≈6 times the level of the unfilled PP. This observation could be related and due to the crossing of the percolation threshold for these composites. 1. Introduction Polymers such as polypropylene (PP) are extensively used as electrical insulation in power capacitors, cable wraps, and phase separators for rotating electrical equipment. The impact of filling polymers with a small quantity of nanoparticles is currently the most active subject of research for universities, research centers, and industrial institutions. The main objective of these activities is to develop the next high-performance industrial materials with superior properties compared to unfilled polymers. This can only be realized if the resulting polymer nanocomposites (PNCs) possess as many as possible of the following features: more discharge endurance, better thermal and mechanical properties, lower quantity of accumulated space charges, longer lifetime, and so forth. ≈ It was reported that the mechanical and thermal properties of polypropylene (PP) [1–3] and Epoxy resin [4] were improved after being loaded with a small weight percentage (wt%) of organoclay. The electrical breakdown strength, surface and volume resistivity to erosion and Partial Discharges (PDs) were superior to the unfilled materials [5–8]. It was also stated that the polyamide-aluminum-nitride composites are more tolerant to high working temperatures [9]. In addition to that, polymer materials can provide