ELECTROSTATIC PAINTING OF PLASTICS USING METAL BACKING

This paper explains theoretically and experimentally the fundamental differences between spraying metal and plastic panels electrostatically. Mechanisms of charge dissipation from plastic surfaces are discussed and a simple method is proposed for determining the electrostatic sprayability of plastic substrates. Using a one-dimensional analytical model, it is shown that the effect of charge accumulation can be minimized by appropriately placing a grounded metal backing behind the plastic substrate. Experiments were conducted in a spray booth environment and the results showed good agreement to those predicted theoretically. Special metal backings with indentations and gaps were used to study the effect of a mismatch between the plastic substrate and its metal backing on the quality of the paint finish.