ELECTROSTATIC PAINTING OF PLASTICS USING METAL BACKING

This paper explains theoretically and experimentally the fundamental d ifferences 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 spr ayability of plastic substrates. Using a one-dimensional analytical mo del, it is shown that the effect of charge accumulation can be minimiz ed by appropriately placing a grounded metal backing behind the plasti c substrate. Experiments were conducted in a spray booth environment a nd 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 b acking on the quality of the paint finish.