Hydrophobic additives like solid or liquid organic
UVA or solid inorganic MS need to be emulsified
(emulsions) or dispersed (solid state dispersions) in
water, using emulsifiers or dispersing agents. Although
such products offer the coating formulators the full
freedom to apply the desired concentration levels,
there are some drawbacks in the use of such preparations.
One challenge of solid UVA dispersions is to
prevent reagglomeration and sedimentation which
occurs after relatively short storage periods in the
product delivery form or the wet paint. Also for solid
particles, another difficulty is to have a homogeneous
distribution of the active component throughout the
coating and the size of the particles. Furthermore, they
might affect the transparency or reduce gloss levels
because of light scattering effects. The high levels of
emulsifiers/dispersants typically used in this case
increase the risk of the water sensitivity of the coating
being increased.