How to Formulate with Wax Emulsions?
Wax emulsions are now well established and extensively used in various aqueous formulations
such as paints, coatings, inks and OPV's, textile and leather treatments, paper
and corrugated coatings, etc. These ready-to-use wax emulsions can be easily incorporated
into a formula by simple mixing. Their very fine particle size ensures thorough
homogeneous incorporation with other ingredients.
The wax properties that have the greatest impact on formulation performances are
described hereunder. When selecting a wax, it is important to consider:
The regulatory aspects
If the emulsion is intended for food contact use (in a coating or in a package),
both the wax and other incorporated additives (emulsifiers, antifoams, biocides
etc.) must be in compliance with applicable statutes and regulations (FDA, BfR,
European Directives, Kosher Certification etc.).
The melting point
When curing is required, it is important that the wax has a lower melting point
than the curing temperature. Thus, the wax can melt, migrate to the surface of the
coating, re-crystallize as the coating cools and, eventually, form a continuous
film that encourages blooming.
The coating thickness layer
In order to maximise the wax effects, it is important to have the highest dried
wax density to be at dried film surface. Hence, the wax emulsion should have a particle
size as closest as possible to the thickness of the coating layer. Sometimes a wax
emulsion with a smaller particle size performs equally well, provided that the concentration
is correctly adapted.
pH of the wax emulsion
should be within approximately one unit of the system to which it is added. If necessary,
the pH of the emulsion can usually be adjusted using aqueous ammonia or acetic acid.
The type of surfactant
can also influence compatibility with the other components, as well as the overall
formulation stability. Matching the emulsion charge with the coating charge enhances
The order of component
In water-based formulations, the order of component addition can be a critical factor
in maintaining stability. Agglomeration can be prevented and overall stability maximized
by adding the wax emulsion last. A further dilution of the emulsion with soft or
demineralized water before incorporation can also reduce the shock.
Determination of Wax content
in a formulation
Click here to see an example that demonstrates how to calculate the solids