Using our Polyurethanes:
Coatings, Sealants and Adhesives
Polyurethanes are polymer compounds, as are epoxies. As commercial products, polyurethanes are more versatile and form a much broader group than epoxies. Polyurethane products you are familiar with include high and low density foams, sealants, surfacing compounds, some elastomeric liquids, sport shoe soles, molded structures such as auto body/interior parts, truck bed lining, golf ball coatings as well as many others.

Our interest in polyurethanes comes from their bonding affinity with epoxies. We were looking for surfacing elastomeric liquids that were flexible, waterproof, almost indestructible, and could be used on wood, fiberglass, concrete and asphalt. Applications for these polyurethane compounds would include home decks, stairways, boat decks and hulls, walkways, ramps, garage floors, patios, cement blocks, tennis courts, swimming pools -- whatever needed waterproofing or sealing from the weather and once in place would stay there indefinitely.

We found what we were looking for.

Types of Surfacing Polyurethanes
Surfacing polyurethanes can be very generally divided into those that are composed of 100% solids, and those that are diluted, and into those that are aromatic and those that are aliphatic.

100% solids polyurethane coatings are usually composed of an isocyanate-rich solution and a polyol-rich solution. There are no solvents to dissolve or dilute any of the resins, and there are no added fillers. A fast and exothermic chemical polymerization takes place and a very strong film is formed. Polyurethane coatings that are less than 100% solids are simply not as tough.

Almost all 100% solids polyurethanes are aromatic, meaning that they are based on aromatic isocyanates and polyether polyols. They are thick, flowing, and very strong, but will eventually be surface-degraded by UV light, as are epoxies. If aromatic polyurethanes are to be used outdoors, a topcoating is usually applied for color and UV protection. The topcoatings can be another polyurethane (usually aliphatic), acrylics, epoxies, or acrylic/epoxy combinations.

Aliphatic polyurethanes are based on aliphatic isocyanates and mostly polyester and/or acrylic polyols. The term "aliphatic" means open-chain (non-cyclic) hydrocarbons, and it can also apply to open-chain hydrocarbon subunits of larger organic molecules. The end result of being "aliphatic" is toughness, high resistance to UV degradation, and color stability. They apply as a thick film and will flow slowly in temperatures above 50°F. It is nearly impossible to get a easily workable 100% solids aliphatic polyurethane, and as far as we know impossible to have one that is of 100% solids and roller-grade. This is why roller-grade aliphatic polyurethanes are not 100% solids. Aliphatic polyurethanes can be used as topcoats for aromatic polyurethane bases or as coating compounds themselves. Although aliphatic polyurethanes are only about 70% solids, their particular chemistry makes them as tough or tougher than the 100% solids aromatic surfacing polyurethanes. For the products we are offering the tensile strength of the aliphatic polyurethanes is 3200 psi vs. 1500 psi for the aromatic polyurethanes, and tear strength is 350 lbs. per inch for the aliphatic vs. 200 lbs. per inch for the aromatic.

The advantages of using the 100% solid aromatic polyurethanes as a base are that they are VOC free, thicker for a quicker build, do not require a primer on good clean surfaces, and are slightly less expensive. They are also the ideal basecoat for surface coatings.

Our Testing and What We Have Learned
Polyurethanes adhere particularly well to epoxies and polyesters. Polyurethanes are flexible and very strong and very long-lasting. What we wanted were surface coatings that would waterproof the surface and would adhere under the most adverse conditions, and that could be applied by roller or brush. These are not easy to find, but we did. We wanted to sell only the best.

When we found what we thought we were looking for we reviewed the technical specifications and visited the factory that manufacturers them. We saw them after severe test conditions, and on all types of surfaces.

We purchased sample lots of the products and applied them to 2' X 8' X 3/4" plywood panels and to concrete in various combinations, after pre-treating the plywood/concrete with a penetrating epoxy sealer as recommended by the manufacturer. We then put these panels outdoors and subjected them to foot traffic, vehicular traffic, rain, sun, and below freezing temperatures. We also tested panels of restored deteriorated wood with the ELASTUFF 120 and the UNIFLEX 255 Aliphatic*. The results of these tests were evaluated and are what allow us to make the recommendations we do. We are continuing our testing by applying to decks, boat hulls and decks, walkways, fiberglass boat hulls and decks, and asphalt. We will be showing pictures of these applications as these tests are completed.

The product test sheets we show are developed from those of the manufacturer, who puts very stringent requirements on surface preparation for industrial application to a variety of substrates. They should be reviewed thoroughly before applying any of these products.

All of the products work very well indeed, with performance and durability linked directly to product cost. These are not the type of products you will find at retail outlets and they are substantially different from all normal paints or coatings. We'll give you some bottom line thoughts here on each product, and encourage anyone considering using these products to e-mail or call us if you have questions.

*UNIFLEX 255 Aliphatic is no longer available from the manufacturer. We have found a product of equal quality in the Elasta-Tuff™ 6000-AL-HS which we now sell.