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Water Expansion Rubber: Best Seal ™EW
【Rubber type】
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Today's civil engineering and construction work must meet increasingly advanced reliability demands. They must provide perfect water sealing that protects the internal structure of facilities and that prevents their deterioration.

Denka Elastlution has developed a new type of water expandable sealant, Best Seal ™EW, based on its long experience in the production of sealants.Best Seal ™EW has a feature not found in conventional sealing materials. When it contacts water, Best Seal ™EW expands under its own self-expansion pressure to completely block water routes through joints in tiles and concrete, resulting in a new water sealing capability.

Types and Shapes.

Model Expansion magnification Typical cross-section
Best Seal ™EW-8B Approx. 8 times its volume
Best Seal ™EW-5B Approx. 5 times its volume
Best Seal ™EW-3B Approx. 3 times its volume

* The expansion magnification represents the volumetric expansion magnification.

●Status before and after expansion

●Product photo

Basic properties

Test item Unit EW-8B EW-5B EW-3B Test method
Specific gravity - 1.3 1.3 1.3 JIS K 6268
Hardness Hs・A 50±5 50±5 50±5 JIS K 6253
Tensile strength MPa 2.5 or more 2.5 or more 2.5 or more JIS K 6251
Elongation ％ 500 or more 500 or more 500 or more JIS K 6251
Resilience ％ 95 or more 95 or more 95 or more Internal standard

Compression rate

Expansion magnification

Water pressure resistance results

●Test method

Test sample: EW-3B 3 mm x 20 mm
(1) Glue an EW-3B test sample onto the test equipment using CRK Bond™.
(2) Place 4 mm spacers in the test equipment and then flow water through the equipment for 48 hours to see if water leaks during a 10 minute pressure retention time while changing the water pressure in steps of 0.1 MPa.

●Test equipment

Model Pressure (MPa) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
EW-3B Water pressure resistance results No water leakage No water leakage No water leakage No water leakage No water leakage No water leakage No water leakage No water leakage

Construction method


Base surface treatment
If the base surface is contaminated with sand, rust, dust or other materials, remove them using a cloth, wire brush or other tool.
The photo demonstrated drying the surface of the segment using a gas torch.

Placing the adhesive
Place and spread the CRK Bond™ C-41B adhesive uniformly using a brush.

Bonding the sealant
After placing the adhesive, touch it with a finger. When it no longer sticks to the finger,* put the sealant in place.
* Allow approximately 10 to 30 minutes for bonding.

Storing the sealant
Protect unused portions of the sealant with a sheet or other material to prevent it from expanding due to rain or other sources of moisture.