Advanced Powder Technology, Vol.18, No.2, 175-186, 2007
Powder characteristics and coating conditions of fresh and reused polyester resins for electrostatic powder coating: powder recycling and loss prevention
Powder characteristics and coating conditions are significant factors in electrostatic powder coating. In this work, powder characteristics of the reused polyester resin or recycled powder particles in terms of shape, size, particle size distribution, moisture content, density, flowability, fluidity and chargeability were compared with those of fresh resin or as-received powder to consider powder recycling. The coating conditions for a metal lantern electrostatic powder coating were studied with fresh polyester resin on a work-piece of 70 x 150 mm using a manual corona spray gun by varying the spray gun voltage, the distance between the spray gun and work-piece, and the gun output. For full utilization of powder particles, the effects of different weight ratios of fresh and reused polyester resins on film thickness were observed using the obtained coating conditions accordingly. The suitable weight ratio of fresh and reused polyester resins was 3:1. In addition, to prevent loss of powder particles in automatic electrostatic powder coating due to over-spraying, the relations between the displacements of the spray guns and conveyor distance were simulated by Microsoft Excel XP on a model metal lantern of 600 x 1216 x 120 mm. No overlapping of the displacements of the spray guns must be considered.