Bonded and non-bonded powders are terms usually used when referring to metallic powders. All metallics used to be non-bonded, which meant that a powder base coat was manufactured and then the metal flake was mixed with the powder to create a metallic. In bonded powders, the base coat is still manufactured separately, then the powder base coat and the metallic pigment are placed in a heated mixer and heated just enough to soften the powder. As the powder is mixed the metallic pigment “bonds” to the powder particle, hence the phrase bonded.
Here is the big difference between bonded and non-bonded powders:
imagine the metal flake as a corn flake shaped object. In non-bonded, the electrostatics of the gun make the metal flake either stand on it’s side (as opposed to laying flat) or it makes the metal flakes “bunch” together. You part will end up with alot of different shades (some flakes on edge and some flat), or with alot of metallic in one area and none in another area. Bonded metallics don’t allow this to happen.
You are now asking “why would anyone ever use non-bonded?” and “how can I tell if my powder is bonded or not”. The only reason anyone uses non-bonded is because they are much cheaper. Powder manufacturers generally aren’t creating new, unbonded formulations, but they have several stock colors that they may continue to make that way because customers continue to buy them (some customers never figure out the difference…i.e., they may have a part too small to notice the inconsistencies). However, a few manufacturers might still be developing unbonded powders due to the fact that not all of the effects required by their customers are possible from bonded powders.
If you need to know if a powder is bonded, simply call the manufacturer. They can tell you. If the person on the phone won’t answer the question, MAKE THEM put you through to a lab tech who can.
Joey R. Golliver
Powder-X Coating Systems