Experimental Study on Electrostatic Spark Ignitability of Coating Polymer Powders in Electric Field with Corona Discharge

Abstract

This paper is a report of the ignitability of coating polymer powders due to an electrostatic spark in an electric field with a corona discharge. The ultrasonic vibration-type apparatus for measuring the ignitability of an electrostatic spark of coating polymer powders was used in this study. The dust concentration in all tests was always 0.60 kg/m3. Polyester powder with grains of 32 µm used in practical electrostatic powder-coating plants was employed as the powder material. The corona discharger, which was located in the explosion chamber, was controllable in the range of DC 5 to 8 kV (bipolar). As a result, the ignitability of coating polymer powders was confirmed to decrease in an electric field created by corona discharge. The reduction was dependent on the voltage applied to the wire electrode of the corona discharger. This result was attributed to the changes in the dispersion of the powder and the free ions produced by the corona discharge. Therefore, the influence of the corona discharge must be considered in the minimum ignition energies of powder paints when using electrostatic powder coating systems.