Paint type - Binder
The binder in the paint system plays a key role in terms of determining the pigment
and the type of solvent in which it is dissolved. A common choice for a solvent
is water as it is compatible with most polymers, except some toners.
White spirit is a commonly used solvent for long oil alkyd paints, which are widely
used in decorative gloss paints. A large majority of pigments are insoluble, or
almost insoluble in white spirit, so it rarely narrows the choice of pigments.
Industrial finishes can be based on broad variety of solvents. To take an example,
solvents such as xylene, ketones, and esters are very powerful and can dissolve
pigments with poor or only moderate resistance to solvents. If such paints are dried
by stoving, the high temperature poses even greater demands on the pigment used.
It is also necessary to consider whether the coating will be overcoated. For example,
in the case of a car getting repaired, the pigment used on the original finish will
have to be fast to overcoating.
In powder coatings crosslinking agents can affect the pigment. For this reason,
the pigments must be compatible with these agents at temperatures employed during
It is therefore evident that the type of resin and solvent used remain key factors
in the choice of pigment.