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Spraying Plural Component Coatings – A Guide

If your coating s made up of more than a single component than you are spraying a plural component coating. Plural Component Coatings are found in a variety of applications with common coatings that are made of multiple components including polyurethanes, polyureas, and epoxies. The following factors are all things to understand and research about your plural component coating as each factor will contribute to how you will potentially spray your plural component coating.

Pot Life of the Coating

Pot life refers to the amount of time for a coating to double or quadruple in viscosity.  Pot life is a critical factor when considering plural component coatings.  In particular short pot lifes (especially 30 minutes or less) will often require plural component application equipment. Short pot lifes are problematic if not sprayed with plural component equipment because the coating will either become to viscous to spray or in some cases completely harden which can ruin non plural component systems. If your plural component coating has a longer pot life (like an hour or more) you can consider spraying the coating with a pressure pot and spray gun or an airless paint sprayer.  Airless and air spray both have advantages and drawbacks which you can learn more about here.

Percent Solids of the Coating

The percent solids of the coating refers to the ratio of thinner to pigment and resin. Higher solid coatings will have a high viscosity.  Depending on how high of solids the coating consists of you may need particular features available in your spray equipment. With high solids your coating may require heat in the paint system. Heat helps to lower viscosities which can help material flow. Additionally, it can improve  the way material sprays which can be critical depending on your coating and finish requirements. Certain High Solids Material may also require circulation as the solid components of the coatings may need to be continuously moving so that they stay in suspension. Often times heat and circulation will be combined. To be able to implement heat and or circulation in a coating system you will require specific equipment like a Binks Fluid Heater or a recirculating pump. A final reason that the percent solids of a coating matters is that if the coating has really high solids you may not be able to spray it well using an air spray gun and may need to consider airless spraying as your application method.

The Mix Ratio Requirements

The mix ratio refers to the proportions that your coating will be combined in.  Various proportions exist depending on the coating. There are two primary ways which a plural component spray system will potentially mix coatings. First is a mechanical proportioner. A mechanical proportioner depends on the pumps integrated and using differences in the pumps to appropriately mix components.  Mechanical proportioners are offered in variable or fixed ratios which is important to consider.  If you will only spray a single plural component coating a fixed ratio proportioner could help keep costs down. However, if you need to be able to utilize a variety of mix ratios, you will typically want to evaluate a variable mechanical or digital plural component system. An additional important factor to evaluate is the accuracy and precision that your plural component coating will require. A mechanical proportioner will have limited verification of a mix ratio and less ability to provide reports on the mix being provided. Mechanical proportioners may also have less precision in mixing due to relying on mechanical systems to mix which due to wear over time can have slight variance in their mix precision.  If you need to be able to work with multiple plural component coatings, need very precise measurements of the mix being provided, or need mix ratios that are not readily available in a mechanical system you will often need an electrical plural component system. The challenge with digital plural component systems is they can be sensitive to air in the paint lines and in general can be difficult to keep running regularly.  Before deciding between the two it can be a good idea to speak to companies who have used both along with your coating provider and the paint equipment provider. By checking all these sources you should be able to gather a good overall picture of mechanical vs electric plural component systems.

Where does the Material need to Be Combined?

Depending on the plural component coating, the way it mixes will vary. Common plural component mix options include external mix and internal mix.  The way the two components come together is most often determined by the pot life of the coating, which your coating provider will help you know which mix type is right for your application. In an external mix set up, the second component is introduced into the first material after it has left the fluid nozzle. This is often required for coatings with very short pot life’s like fast curing adhesives. An additional option is internal mix. Internal mix allows the two coatings to be combined at the gun or just prior to the gun. This can be beneficial as often times you will have a mix manifold that will support supplying multiple coatings to the manifold and allow for quick change between coatings by including a solvent flush system. There are limitations though if the coating has a short pot life or other characteristics like being too viscous after being mixed that may require the use of an external mix spray gun.

What are the materials requirements for mixing?

Certain plural component coatings will require mixing of the individual components or mixing of the components after they are combined. Plural Component systems can provide this mix using static mixers. Depending on if your coatings will require mixing before being combined, after, or both will also contribute to the requirements of your plural component system. Different coatings may also require different extents of mix as well as different line size which will play into the size of the static mixer.


Ultimately spraying plural component coatings can be one of the most complex applications in painting. By talking with your coating provider and having a thorough understanding of your coatings requirements you can also speak with a spray equipment company. By considering the factors we have mentioned you can be better prepared to select a plural component solution that will meet your application needs while not spending more than necessary. If you want insight on whether plural component can be sprayed without the expense of a plural component system talk to us today for a free consultation.


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