Spray Polyurethane Foam Insulation has two separate liquids that react in order to foam up and harden. The two liquids come in different drums or containers, typically referred to as the “A” side and the “B” side. Each of these liquids sit on a type of spray gun and each side sit next to each other.
The “A” side of the system is typically comprised of methylene diphenyl diisocyanate (MDI) and polymeric methylene diphenyl diisocyanate (pMDI). The “B” side is typically a made up of polyols, catalysts, blowing agent, flame retardant and surfactant.
The polyols of “B” side are a big part of the chemical reaction that makes the foam. The remaining chemicals in “B” side help control the creation of the foam bubbles (the “cells”) in the most functional way and provide various ways to finish the final foam product (etc. flame retardancy). After the the chemicals from the two liquids are mixed and reacted, the foam products then hardens quickly (time for each type of insulation varies). Once the foam is hardened, the insulation is completed in that area it was applied to and simply needs to dry out.