Sprayed Polyurethane Foam (SPF):- is produced by a chemical reaction when two liquid components are combined, an isocyanate,  known as the "A" component, and a polyol resin, known as the "B" component. When the two liquids  are mixed together (typically at a one-to-one ratio), a chemical reaction occurs creating rigid closed cell  foam.

The mixed liquid starts to react in seconds, expanding 20 to 30 times its liquid state. Once cured  it solidifies and becomes polyurethane foam. SPF conforms to the surface to which it is applied and forms a seamless layer of insulation.