Q: Is it possible to create that liquid look with a metallic pigment in a powder coating? I’ve heard a lot of grumbling among powder coat companies that it’s just not possible. What research has your lab completed on the topic, if any, and do you have any positive results you can share?
If not, do you think it will take new technology on the part of the resin/pigment suppliers to achieve the liquid look in powder, or a new type of gun, or maybe both? Or are we all just a little too “pie in the sky” to think it’s possible?
A: This is a problem that has to do with rheology, viscosity, and open time of a curing binder system. Metallics tend to orient themselves randomly in a viscous powder binder. The metal flakes are distributed onto particles via bonding or — worse — just mixed into the bulk powder.
Electrostatic application doesn’t help, either. The charging characteristics of a metal flake are vastly different than a nodular organic particle.
Consequently, the “lay-down” of the flakes is indeed random. Then the only time the flakes can “lay down” to establish any degree of regular orientation is in the oven after the powder melts, coalesces, and is fluid.
The vast majority of powders are thermosetting so soon after the powder melts that they start to build molecular weight and therefore increased viscosity. Low-viscosity binders (some epoxies and polyurethanes) are somewhat better but never approach the low viscosity of a solventborne paint.