Charge Retention of Silica-Agglomerate Electret using Electrostatic Spraying at Elevated Temperatures

抄録

The model electrets where only one silica agglomerate was formed by manual droplet formation (MD) were prepared using a negatively charged syringe as well as the electrets obtained by an electrostatic spraying (ES). The charge retention of the samples was measured in heating test and the dependencies of the initial surface potential and the size of silica-agglomerate on the charge retention at 250℃ (R250) were investigated. The silica-agglomerate electrets prepared by the ES method revealed that the value of R250 was influenced by the initial surface potential though the average diameter and the point density of agglomerate were almost constant. The silica-agglomerate electrets prepared by MD method demonstrated a ring-like shape though thin layer existed at the center of agglomerate. The R250 of the MD electrets was monotonically increased with the diameter of agglomerate. Furthermore, the average value of R250 of ES electrets showed good agreement with the line estimated from the relationship between R250 and the diameter of MD. Consequently, the specific surface area of silica agglomerate might be related to the dependence of R250 on the diameter although further study must be needed to clarify the mechanism of dependence of R250 on agglomerate size.