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Foam Building Materials
By
Thomas Morva
Although there are many metal foams made up of solid metals like aluminum, their high price prevents them from being used in normal household constructions Commonly used foams are plastics, which are primarily made up of polyurethane and polystyrene. Most of these materials are low density elastomers, polymers and other materials with various porosities. Foam building materials are characterized by their high density, tensile strength and thermal conductivity and dielectric strength. They are used in roofing membranes, insulation, pipe covers, vapor barriers, crack suppressant membranes and as installed flooring protection.
Polyurethane is polymer with bubbles produced at the time of foaming from one polyols and one isocyanate -- usually TDI (Toluene diisocyanate). There are rigid and flexible polyurethane foams available.
The most simple and common process to manufacture foams is by adding water to the liquid precursors of polyurethane. Water will react with the isocyanate of TDI. This will result in the production of carbon dioxide, which can create relatively uniform bubbles that harden through the polymerization process producing solid foam.
One other important polymer used to make household foams is polystyrene. Most polystyrene foams are made by adding little amounts of volatile materials known as blowing agents. The commonly used blowing agents in the past were CFCs (Chlorofluorocarbons). Other agents like acetone and methylene chloride have replaced this.
When polyurethane foams are required in soft form, they are mixed with resin. These soft foams are generally heavier than rigid foams. Forcing a pressurized gas, usually nitrogen or carbon dioxide, into the polymerizing mixture, produces large amounts of polyurethane and polystyrene foams. Some surfactants are also used for reducing the surface tension of foams, which are mainly silicone-based.
The machinery used to produce polyurethane foam depends on the application of foam. The most commonly used machinery is a spray foam gun, which are available in different sizes.
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