Powder coating additives are chemicals added to the powder coating base material that can help obtain different mechanical properties. So, what should we consider when applying additives in powder coatings?
Compatibility with the Resin
This is the first issue that should be noted when selecting additives. Powder coating additives must exist steadily in the powder coating in a long term in order to play its proper performance. So general additives must have compatibility with different resins, such as epoxy, polyester, acrylic and others.
Usually, the method to compare the compatibility of these additives with resin is based on the similarity of their structures. For example, the leveling agent is the main additive in the production of powder coatings. It can reduce the difference in surface tension of the coating film, make the film more uniform and eliminate porosity so that the cured coating film can obtain a smooth and glossy surface.
More specifically, additives with carriers, such as the E-12 carrier, can not be applied in the formulation with a pure polyester system. Also, the commonly used B-68 type chemical matting agent containing cyclic ether and polyacid is only suitable for the epoxy system. When used in other resins, it will bring a negative impact on the coating film.
Adaptability to the Production Process
When designing the formula for powder coating additives, it should be considered that some harsh conditions like high temperature, low temperature, or high-speed shear, may cause the decomposition and volatilization of powder coating additives, resulting in formula failure.
In the mixing of two or more additives and the base material, the additives must be fully dispersed in the powder coating base material for full effectiveness. They can be mixed with the base material in a different order of addition.
For example, there are 4 ways to add additives A and B to the powder coating.
(1) Base material + A → premix → extruding, crushing + B → sieving, finished product, packaging
(2) Base material + B → premix → extruding, crushing + A → sieving, finished product, packaging
(3) Base material + A + B → premix → extruding, crushing → sieving, finished product, packaging
(4) Base material → premix → extruding, crushing + A + B → sieving, finished product, packaging
If there are 3 or more kinds of additives, there will be more ways of dispersion considering the setting of processing parameters.
Experiment fully proves that the sequence and each step of processing conditions are very important for mixing various additives with base materials, which directly affects the mixing effect and the performance of the finished coating film.
Diversity of the Functions
In addition to the main functions, some powder coating additives also have two or more functions. Thus, we must take this into account and adjust the amount in the formula or simplify the formula when designing the powder coating formula.
For example, zinc oxide is a common chemical. It can replace part of the titanium dioxide as a white pigment. It has specific electrical conductivity for anti-static or electrical conductivity occasions. And it also has the functions of shielding ultraviolet rays, anti-mildew, and sterilization, and can improve the performance of coatings containing carboxyl group resins. As you can see, understanding its various functions is important to choose an effective additive.
Mutual Effects between Powder Coating Additives
The mutual effect of powder coating additives refers to the synergistic effect of two or more additives when used in conjunction with each other. Of course, the opposite of synergistic effect is confrontation effect.
For example, carbon black and thiophenol antioxidants in pure polyester outdoor powder coatings have an excellent synergistic antioxidant effect. However, when used with amine or phenolic antioxidants, the coating film stability is weakened by the antagonistic effect.
Limitation of the Powder Coatings
The application of powder coating additives is often limited to the end use of the coating film. Different kinds of powder coatings have different requirements on the features of the additives, including color, odor, pollution resistance, durability, electrical conductivity, heat and cold resistance, etc.
Summary
Powder coating additives are very important for powder coatings because they have properties that can enhance certain special properties of powder coatings or reduce the appearance of some film defects.
Hoyonn Matting Agent is a excellent additive for powder coatings to achieve a matting finish, which has three type that can be used in indoor, outdoor, and HAA systems. What’s more, our TGIC additive is a very effective curing agent for powder coatings that has great compatibility with polyester resin, and can be applied in the production of various materials.
