Matting agent properties
Matting agents with smaller average particle size do not give a quality matting
effect, but they produce smooth paint films. In contrast, products with larger particle
sizes are stronger in matting efficiency but the paint film surface is not so smooth.
Matting additives with large particles show a tendency to build up separation and
sedimentation in clear paint systems during storing time. Untreated silicas and
fillers, in particular, need to be combined with anti-settling agent or fine particle
size waxes to avoid these phenomena. Fine particle size waxes and easy to disperse
hydrophobic pyrogenic silicas are recommendable, as they have a similar refractive
index to these additives.
The equal refractive index of silica, wax and organic matting to resin systems which
are commonly used in paints are one reason for their popularity. Substrates like
wood, foils, and leather (natural & artificial) must be coated with transparent
coating systems. It is of prime importance to select an application that has little
influence on transparency, and also to choose a resin and matting agent which have
similar ‘refractometers’, as this also improves the transparency of
the system. The amount of matting agent added to the paint film also impacts upon
transparency. More efficient matting agents require lower dosing levels and therefore
provide better transparency.