The Universal Selection Source: Coatings Ingredients

Wax Emulsions for Coatings: Techno Brief

How to improve specific surface effects using wax emulsions is often a challenge for formulators. This technology brief will describe the mechanisms by which waxes work, their applications, and how to formulate with wax emulsions & dispersions. It also describes the risks and benefits of Wax Emulsions depending on your application.

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 of waxes:
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 stability. 

 The order of component addition:
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

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