To achieve a good water seal there are several factors, the most important is selecting the proper material. Sealing sheet metal or plastic enclosures very often need soft, expanded rubber materials that can be readily compressed. Many of the rubber gasket materials like silicone, urethane, neoprene, EPDM are available in expanded form; an analogy is like adding yeast in bread, a blowing agent is mixed with these polymers to make them expand creating pockets of air. Most water sealing applications requires these pockets to be closed off from each other, called closed cell foam or closed cell sponge. When the pocket are open to one another, they are called open cell foam or open cell sponge.
Open Cell Example: A kitchen sponge has open cells; the open, connected cells allow water to pass from one cell to the other, allowing it to hold water used for cleaning.
Closed Cell Example: A scuba diver’s wetsuit, where the adjacent cells are closed off from one another. The trapped air in the neoprene make it soft and lightweight yet does not absorb water even under pressure of being submerged.
The video below shows two expanded silicone products, an open cell silicone foam and a closed cell silicone sponge. Aside from the water picked up from the cut cells on the edges, the close cell gasket material does not absorb water.
For more information on closed cell rubber for water gaskets and open cell foams for dust and light spray gaskets. Please visit www.stockwell.com, email firstname.lastname@example.org or call 1-800-523-0123.