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WEST SYSTEM epoxy is often used to provide a moisture barrier for applications that are in frequent or constant contact with water.  In order to gain a more complete understanding of the moisture resistance properties of WEST SYSTEM, Gougeon Brothers Inc use accelerated testing to measure the ability of a coating applied in a relatively thin film to resist water transmission. This test is call Moisture Exclusion Effectiveness ( MEE), based on a method developed by the USDA Forest Products Laboratory. 

The Moisture Exclusion Effectiveness Test

The MEE test begins with Douglas fir plywood blanks with corners and edges sanded round.  A small cup hook is installed in each end.  The sample blanks are then conditioned in the Arizona room, a hot/dry room kept at 38^oC with a relative humidity close to 0%, for 2 weeks or until the moisture content of the blanks levels out close to 0%.

The blanks are then removed from the hut, allowed to assume room temperature, and weighed very accurately to 4 decimal places.  This is recorded as the dry weight.

Next, the blanks are coated with whatever product is being tested - WEST SYSTEM and also competitors including other epoxies, paints, polyesters, vinylesters, etc.  Generally 5 samples of each are made with 1,2 and 3 coats for a total of 15 pieces for each test material.  Five samples generate an acceptable average, and the increasingly thicker coating allows for a curve to be generated for each test material. 

After the coatings are completely cured, the weight is recorded again.  Samples are then hung in a rack and placed in the Florida room, a hot/wet hut that is kept at 38^o C and 100% relative humidity.  The weight gain is measured each week for 6 weeks or until the test curves begin to flatten out.  As with any good test procedure, control samples left uncoated, are run alongside the test samples.

Because all coatings are semi-permeable membranes, GBI can generate curves that compare the relative permeability of various coatings.  As shown in chart below, WEST SYSTEM R105/H205 performs well relative to the other materials tested, provides a superior moisture barrier, combined with excellent mechanical properties.