3350 W. 48th Pl. Chicago, IL 60632-3000. Phone 773-927-3484, FAX 773-650-5853.
Source for liquid thermosets: silicones, moldmaking urethanes, casting urethanes, polyester resins, epoxy.
Fiberglass fabrics, release agents, fillers and dyes.
All products available in small quantity.

Shelf Life of Urethane

Moisture contamination is detrimental to liquid urethane systems and is the reason for the short shelf life once the containers are opened. Factory packaged liquid urethanes are typically top-filled with an inert dry gas that allows for uponed containers to be stored for 18-24 months and still be usable once opened.

It is at this time, when the containers are opened for the first time, that the shelf-life of liquid urethanes begins to rapidly decrease. Moisture present in air enters the container above the liquid and once the cap is closed, the moisture chemically reacts with the liquid urethane. The shelf-life can drop to as little as 2 weeks in humid environments, and the result is castings that appear foamed or bubbled. The severity of this effect varies with system, but are usually most pronounced in crystal clear systems.

It is, however, possible to avoid this moisture contamination by spraying Eager Plastics' dry gas blanket in the container prior to putting the lid back on. This works for liquid urethane rubbers, plastics, paints, coatings and other products to significantly lengthen the shelf-life once the containers are opened and the factory seal is broken.

If you suspect that you have a urethane system that has already been contaminated with moisture, it is sometimes possible to alter the chemistry and reverse the effect through the addition of Molecular Sieves.

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