Powder coatings are prepared by dispersion of the solid ingredients in a molten resin in an extruder. Paint dispersions must be stabilized to prevent pigment agglomeration and settling. Flooding, floating and pigment agglomeration are not problems in powder coatings.
Powders have only a short time after melting to coalesce and flow before cross-linking starts.
Therefore, the melt viscosity, functionality and reaction rate of powder coatings must be carefully controlled. In simple terms, this is the temperature at which solid polymeric materials start to soften and flow. Some powders will remain completely free-flowing, while others will sinter into a solid lump. The T g of a powder coating is affected by all the resinous and polymeric ingredients present. This is the reason most resins have a higher T g than absolutely necessary to prevent resin sintering and clumping.