Waterproofing concrete pipe and vessels.

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 ultra violet degradation.

The development of Liquid EPDM Rubber resulted in a high solids, two components chemically reactive product capable of polymerizing at ambient temperatures( 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.

Liquid EPDM 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 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.

PRODUCT COMPARISON
	Liquid EPDM	Liquid Neoprene
Product Description	Two component ambient temperature cure	One component solution or emulsion
Solids content( by Volume)	60-65 %	less than 30 %
Flash Point	105 F ( 40 C )	50 F ( 10 C)       (solvent solution)
Tensile strength	600-800 psi ( 42-46 kg/cm)	1600 psi (112 Kg/cm)
Elongation	150 – 200 %	450 %
Temp. tolerance range	-60 to 300 F              -76 to 149 C	-40 to 200 F           -40 to 93 C
Max dry film per coat	30 mils                 .76 mm	4-6 mils            .1 to .15 mm
Ultra violet stability	Excellent	Recommended top              coatings
Water resistance fresh water sea water	excellent to 275 F (135 C) excellent to 180 F (82 C ) Very good to 200 F ( 93 C)	excellent to 212 F (100 C) excellent to 70 F (10 C )
Oil resistance	Poor	Very good
Hydrogen sulfide (wet) resistance	Very good	Very good
Coverage	960 sq.ft/gal/mil          8.57 sq.m/l/mm	417 sq.ft/gal/mil          3.7 sq.m/l/mm
Specific gravity	1.05
volatile organic compounds	333 gr/l	600-610 gr/l

Coating Cast Concrete

Concrete which has not been  trowel finished will have a surface that is more porous   than one which 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 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.