Evolution of space charges and conductivity with DC aging of polyethylene-synthetic and natural clay-composites

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Journal titleJournal of Nanomaterials
Subjectpolypropylene nano-composites (PNC); dc field conductivity; space charge evolution; PEA technique; natural and synthetic organoclay
AbstractTo develop new materials with better dielectric properties for electric equipment, such as power capacitors, two types of polypropylene (PP)-based nanocomposites (PNC) were manufactured. The PNCs were composed of PP with different concentrations of synthetic and natural organoclays. The evolution of the space charge density and dc conductivity with dc poling of these composites were investigated. It was observed that the optimal concentration of nanofillers for space charge mitigation with aging time was 2-wt% for PP-natural clay composite and between 2 and 4 wt% for the PP-synthetic clay. Above these percentages, charge transport through overlapping of nanoparticles can occur. This fact is due to the interaction zone of double layers formed at the nanoparticle/host material interfaces. Under dc field the overlapping increases the conductivity of polymer nanocomposite (PNC), which could reduce 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. However, the total charges in all filled specimens only changed slightly. The effect of platelet size on space charge mitigation reported by other authors is confirmed here, i.e. nanofillers with smaller platelets such as natural clay can mitigate space charge more efficiently than nanofillers with larger platelets such as synthetic clay. The conductivity with -25 kV/mm dc field of the specimens containing 6-wt% of natural clay and 8-wt% of synthetic clay reached ≈ 6 times the level for unfilled PP. This observation could be related to crossing the percolation threshold of these composites. At least 1000 h of aging with -25 kV/mm dc field is required before correctly evaluating the impact of filling the PP with nano-particles.
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AffiliationMeasurement Science and Standards; National Research Council Canada
Peer reviewedYes
NPARC number20955689
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Record identifier9a96cb74-ab02-4a37-910d-e96762e3bddc
Record created2012-11-14
Record modified2016-05-09
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