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by Rachael Geerts – GBI Composite Materials Engineer
The 105 System is designed with a flexible, mix-and-match approach, like a chemistry set, allowing you to tailor formulations to your specific needs. Starting with the WEST SYSTEM® 105 Epoxy Resin® as a base, cure speed or clarity is determined by hardener selection, and viscosity can be increased by adding fillers. What is lesser known is the WEST SYSTEM additive line. The dry and liquid additives can also be used to modify other properties of your mixed epoxy, including hardness, wear, moisture exclusion, and color.
Dry Additives
The dry additives are beneficial for increasing durability, adding moisture resistance, or decreasing friction when added to mixed epoxy. Since all of the dry additives are opaque particles, they do provide a little UV-stability to the epoxy. The additive particles in the top layer or two of epoxy prevent sunlight from damaging the epoxy below. Please note that the top layers will still become chalky due to UV degradation if no UV-stable finish coat (i.e., paint, varnish, polyurethane, etc.) is applied over the cured epoxy. While these additives do impact the color, their purpose is to increase other properties of the epoxy.
420 Aluminum Powder
As the name suggests, this additive is made of fine particles of aluminum. In fact, the average particle size of the aluminum is only 50-60 microns (or about 0.002″). For scale, the average diameter of a human hair
is around 100 microns (or 0.004″).
We recommend mixing this additive into the epoxy at a loading of 5% to 10% by volume. At this loading, the additive can increase the hardness and abrasion resistance of the surface without significantly impacting the other properties of the epoxy—namely, tensile elongation.
Common applications for this additive include visible or wear surface repairs on aluminum substrates and surfaces where increased hardness and abrasion resistance are desired.
422 Barrier Coat Additive
The 422 Barrier Coat Additive is a blend of aluminum powder and muscovite mica. The muscovite mica is a common mica mineral that tends to have a platelet shape. When mixed with WEST SYSTEM Epoxy, it can improve the epoxy’s already great moisture resistance. Blending the muscovite with aluminum powder further increases the epoxy’s durability.
The 422 Barrier Coat Additive is gray in color. We recommend adding it to mixed epoxy at a rate of 15%-20% by volume.
The most common application for this additive is for use during the blister repair process. Once the blisters have been removed, coating the bottom of a fiberglass boat will help seal the hull to prevent future blisters from forming. For more information about blister repairs, see our Fiberglass Boat Repair Manual.
423 Graphite Powder
The 423 Graphite Powder is made up of fine graphite (carbon) particles. The particles are measured by the size of mesh that they can pass through. Almost all of the graphite particles in our 423 Graphite Powder can pass through a 325 Mesh (0.0017″). This means they can pass through a mesh that has 325 holes in a square inch.
We recommend adding the 423 Graphite Powder into the mixed epoxy at up to 10% loading by volume. Once the epoxy mixture has cured, the surface should be sanded to expose the graphite powder. Now that the wear surface has been “activated”, the small particles can release and act as bearings to create a lower friction surface.
Common applications for the 423 Graphite Powder include running surfaces on the bottom of boats and bearing surfaces. It should be noted that as the graphite particles are exposed, they will act much like pencil lead and can transfer to other surfaces, giving a smeared, black appearance.
Liquid Additives
Liquid additives’ primary purpose is to color the epoxy through the use of pigment particles suspended in an epoxy resin base. The colorants will not make the epoxy UV-stable, so it will still require a UV-stable topcoat over the cured epoxy for applications that will see direct or indirect sunlight. The epoxy resin base of the liquid colorant additives means they have excellent compatibility with all our WEST SYSTEM products.
We recommend adding the pigments to your epoxy at up to a 3% loading by volume. Though they are potent, you may need multiple coats of pigmented epoxy to achieve a truly opaque surface. The exact number of coats will depend on the color of the substrate being coated and the liquid additive selected. Please note that all our epoxy systems should be cured, the amine blush removed (where applicable), and prepped (usually sanded) before applying a finish coat over the epoxy.
501 White Pigment
This is our white colorant. Though the colorants can be used with any of our epoxies, hardeners with strong yellow/amber colors will influence the color of the mixed epoxy. To achieve the whitest surface, you will want to use our 105 Epoxy Resin with 207 Special Clear Hardener®.
Common applications for epoxy with 501 White Pigment include as a finish coat in a bilge or as a primer for light-colored paint.
502 Black Pigment
The 502 Black Pigment is a very rich, dark black. Because of this, it can hide the yellow/amber tones some hardeners have very well.
When mixed with epoxy, the 502 Black Pigment becomes great for many applications. These include coloring the epoxy to fix a black surface, using it as a primer coat for dark-colored paint, and for filling knot holes, cracks, or checks in wood.
503 Gray Pigment
The 503 Gray Pigment can be used in much the same way as the 501 White Pigment and the 502 Black Pigment. Being gray, however, tends to lend itself to being used on applications with stone and concrete to blend in better.
It also works well as a signal layer for fairing applications when used in conjunction with the 501 White Pigment or the 502 Black Pigment.
Final Thoughts
The WEST SYSTEM line of additives further enhance the versatility of the 105 System and give you peace of mind in the compatibility of the products. Whether you are looking for increased hardness, moisture exclusion, wear resistance, or simple color enhancement, the WEST SYSTEM line has products to help make your projects successful. As always, if you have any questions about our products or how to use them, feel free to reach out to our Technical Advisors either over the phone or through westsystem.com.
