The basics of Spray Polyurethane Foam
Spray Polyurethane Foam (SPF) is a mixture of chemicals that react and make a foam. When the chemicals are mixed the reaction occurs very fast. The mixture expands many times its original size and fills gaps and cracks in construction making it a very effective insulation and air seal. This also helps create a barrier that will help keep out moisture. SPF is very good at resisting heat transfer which makes it a great insulation and it seals very well as an added benefit.
In both new home construction and heavy renovations home owners are finding that SPF insulation is a very effective way to save on energy and greatly improve the comfort of their homes. The spray application creates a continuous barrier on any surface, corner, or contour. The SPFs installed by professionals is typically high or low pressure foam and can be either open or closed cell. There are many differences that translate to advantages and disadvantages between every type. Your application requirements will dictate which foam will be used.
How is it made?
Two different liquids are put together to cause a chemical reaction to form the SPF. The liquids both come in their own containers which are generally referred to as the "a" and "b" side. The A side of the SPF system is usually methylene diphenyl diisocyanate (MDI) and polymeric methylene diphenyl diisocyanate (pMDI). The other side is a blend of polyols, catalysts, blowing agent, flame retardant, and surfactant. The polyols are essential to creating the foam while the other ingredients in the B side are used to control how the foam is made and are also to make the foam flame retardant.
Material Safety Data Sheets (MSDS) are available for all materials used in the process.
During the SPF installation:
Once both parts are mixed and the reaction has occurred, SPF tends to harden very quickly. How long it takes for the reaction to be completed depends on many factors including the type of foam and other variables. The exact time it takes for the foam to harden is specific to each application and can be discussed prior to installation.
Two component foam will be applied using specific personal protective equipment (high pressure foam is installed with a respirator, for example). This equipment, coupled with certain work practices and engineering practices including ventilation, are used to minimize exposures to the chemicals used to make SPF during the job. As a homeowner, you can minimize or eliminate exposure to the chemicals used to create spray foam by carefully following the guidelines given about how long to leave the home during the installation, job completion, and cleanup.
To install the foam in your home requires special equipment. Some foams require a respirator along with other equipment to be safely installed. This equipment along with special ventilation and work methods are used to cut down on exposure to the chemicals that make up SPF during the installation process. As the homeowner you can be sure your family is safe by following the guidelines for reentering your home after the installation is finished.