Q: We are in need of an electrostatic dissipative (ESD) coating for work furniture to be used in the assembly of electronically sensitive equipment. We have tried carbon black containing liquid paint (alkyds) but wonder if we can get this performance in a powder coating. Also, can we get it in colors other than black?
A: ESD coatings have been typically formulated using very fine carbon pigment (conductive-grade carbon black). The use of this or any conductive agent requires particle-to-particle interaction in order to achieve any level of electrical continuity. Fine-particle-size carbon black by its nature has a very high oil absorption, which poses rheological problems in most coatings.
Liquid coatings can compensate for this by lower solids or lower viscosity resins. With powder coatings, it is a nearly impossible to incorporate enough conductive carbon black to achieve ESD. Levels high enough to reach this level of conductivity have no flow and leveling.
Alternately, you may consider using an antimony-doped tin oxide as the conductive agent. This material is light gray and possesses a reasonable oil absorption. Suppliers offer this material neat or as a coating on mica or titanium dioxide. The mica product can be used at a much lower concentration due to its platy morphology. The titanium dioxide product offers superior opacity.
You may also wish to consider the emerging field of nanofibers and nanotubes. These materials are noted for their conductive performance, but dispersion of them may be difficult to achieve in a powder coating extruder. It’s an interesting technology that bears investigation.
You may also consider inherently conductive polymers such as polyaniline. However, they are very expensive and may be cost prohibitive for your application.