Corona Compared with Triboelectric Charging for Electrostatic Powder Coating

Abstract

ABSTRACT: The purpose of this research was to compare electrostatic and nonelectrostatic coating and determine the improvement between corona and triboelectric charging systems. Graham crackers were coated with food powder at 0, −50, or −95 kV or by tribocharging with teflon or nylon. Five sizes of sucrose from 13 to 138 μm were coated onto the crackers to determine the effect of particle size on coating efficiency. Three proteins, three carbohydrates, and one salt between 35 and 58 μm were analyzed to determine the effect of composition. Electrostatics improved transfer efficiency (TE) up to 27%, adhesion up to 40%, and reduced dust up to 99% over nonelectrostatic coating. Particle size and composition significantly affected the improvement produced by each charging method. As particle size increased, nonelectrostatic TE and adhesion increased, while dust decreased. Electrostatic TE increased and leveled off and adhesion and dust decreased with increasing particle size. Generally, corona TE, adhesion, and dust reduction was the highest, followed by teflon triboelectric, nylon triboelectric, and nonelectrostatic coating. For proteins, teflon produced higher charge to mass, TE, and adhesion than nylon. Although the corona system was most efficient, the teflon triboelectric system produced comparable results for some powders and may be necessary to produce a thick coating while minimizing back ionization and alleviating Faraday Cage effects.