Proper pigment selection is very critical in determining optimum performance and production efficiency of the finished coating. While understanding the specific types and chemical properties of pigments helps coming up with the most appropriate coat, it’s equally important to learn what are the processes involved for achieving effective pigment dispersion for high performance coatings. In other words, pigments have to be wetted, dispersed or de-agglomerated, distributed and stabilised properly. This is crucial to achieve excellent hiding power, optimal gloss and colour intensity.
Wetting Phase
The more effective the wetting will become if there is less air that’s trapped in the system. This is all because of surface tension. The surface tension of the liquid should be lower than that of the solid it has to wet. By that it means liquids that have lower surface tension will provide much more effective to use for wetting. This is why wetting additives become very important in pigment dispersion. They help adhere and coat the pigment by reducing the surface tension, creating proper interface of additive and the liquid. Typically, solvents are commonly preferred than water due to their lower surface tension.
Deagglomeration or Grinding Phase
During this phase, the particles agglomerate and separate into smaller aggregates. Lower energy will be required to disperse the pigment if there’s lower surface tension involved. This is achieved by using mechanical energy through high-speed grinding equipment. High shear blades are well suited for dispersion to ensure high efficiency and good laminar flow. However, the kind of media mill to use depends on the type of high performance coatings and to the specific level needed to disperse it.
Stabilization Phase
This process is needed to stabilise the increased surface area of the deagglomerated pigments during the grinding step. Stabilization is very essential to prevent major issues like sedimentation, colour shift, flocculation and loss of stability. This happens by integrating some additives into the pigment and can be achieved through different mechanisms such as steric and electrostatic stabilization.
All of these processes are very important to high performance coatings and should be done properly for a successful dispersion of the pigments for various applications.