Liquid EPDM Rubber vs. Neoprene Rubber
for waterproofing concrete pipe and vessels.

EPDM rubber was not available in liquid form until relatively recently, so liquid neoprene rubber became the material of choice for protecting concrete against both fresh and salt water. The liquid neoprene products are simple solvent solutions or water-based emulsions, and therefore have low solids content and relatively low molecular weights. These limitations made multiple-coat applications necessary and required top-coating with other polymers to prevent ultraviolet degradation.

The development of Liquid EPDM Rubber resulted in a high-solids, two-component chemically reactive product capable of polymerizing at ambient temperatures of 55 F, (13 C) and higher. This product can be applied at a 30 mil dry film (.76 mm) in a single application because of the high solids content. Its chemical cure feature then results in a high-molecular-weight film with protective and performance properties exceeding those of liquid-applied neoprene films.

EPDM Liquid Rubber can withstand boiling water or live steam and is inherently UV and ozone stable. The product is safer to use because of its higher flash point, and the two-component packaging permits extended storage at higher temperatures than liquid neoprene. The non-polar characteristic of the EPDM also gives it advantages over neoprene in saltwater environments, as well as better resistance to cathodic disbondment.

EPDM rubber has poor resistance to oils, fats, waxes and aliphatic solvents, but possesses very good resistance to ketone solvents, alcohols, polar compounds, salts, most acids at up to 50% concentration, alkalies, and water.

Advantage of Liquid EPDM Rubber

• One-coat application.
• UV and ozone stability.
• Higher flash point (105 F, 40 C).
• Storage stability at higher temperatures .
• Can be used in extreme environments.

Coating Cast Concrete

Concrete that has not been  trowel finished will have a surface that is more porous   than one that has been trowelled. When Liquid Rubber is applied directly to such a porous surface, it will produce a high density of small craters in the resulting membrane. This is caused by the fact that Liquid Rubber actually penetrates into the pores, leaving a crater on the surface. The following  procedure is recommended to prevent formation of surface craters:

1) Apply a light coat of one of the following products to seal the surface:

       a.) Water-based acrylic elastomeric coating (primer or base-coat version).

        b.) Solvent-based chlorinated rubber or Hypalon product.

        c.) Solvent-based neoprene product.

The choice of water-  or solvent-based product should be based on temperature and  humidity conditions. For water-based products, relative humidity should be less than 70% and temperature 60 degrees or higher. Solvent-based products should be used  at low temperatures and high relative humidity.

2) Liquid Rubber may be applied when primer application is sufficiently dry. Water-based products should be allowed to dry thoroughly, as any surface moisture will interfere with  the adhesion of the rubber. A single coat of Liquid Rubber is preferable to multiple coats.

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