Fire-retardant gel
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Fire-retardant gel (also known as fire-blocking gel, fire protection gel, anti-fire gel and by a number of trade names) is a liquid concentrate made of absorbent polymers that is sprayed through hoses and designed to protect structures and form firebreaks in wildland fires. These absorbent polymers are similar to those used in diapers.
The polymers soak up hundreds of times their weight in water creating millions of tiny drops of water surrounded by and protected by a polymer shell. The result is a "bubblet" or a drop of water surrounded by a polymer shell in contrast to a bubble which is air surrounded by liquid.
As the gel and water are sprayed onto an exposed surface, millions of tiny "bubblets" are stacked one on top of another. The stacking of the water "bubblets" form a thermal protective "blanket" over the surface to which it is applied. In order for the heat of the fire to penetrate the protected surface, it must burn off each layer of the gel "bubblets" coating. Each layer holds the heat away from the next layer of bubblets beneath. The polymer shell of each bubblets and their stacking significantly prevent water evaporation. The manufacturer of one such product, Barricade gel, claims it "can provide thermal protection from fire for extended periods even at 3500° Fahrenheit".
The stacking of the bubblets is similar to aspirated fire fighting foam or compressed air foam systems, except that bubblets are water filled, whereas foam bubbles are only filled with air. Because it takes more heat to raise the temperature of water than air, the water filled bubblets will absorb more heat than the air filled foam bubbles which are more effective for vapor suppression. When barricade gel is applied to a surface such as an exterior wall the water filled bubblets will absorb the heat given off by the fire and prevent it from reaching the wall.
[edit] References
- James H. Meidl: "Flammable Hazardous Materials", Glencoe Press Fire Science Series, 1970.
