A conventional system of SPF consists of a two-part, or plural-component, chemical formulation contained in a set of two 55-gallon drums, delineated A-side and B-side. The components must be shipped and stored according specific procedures. The A-side component, also called the iso-side, contains isocyanate, while the B-side component contains a polyol resin blend, and is also called the polyol-side or the resin-side. In order to form spray polyurethane foam, the two components must be combined in a one-to-one ratio within a certain temperature range.
In order to be properly proportioned, the SPF components must be transferred into special equipment that keeps the ratio, pressure, and temperature optimal. Once in use on a job site, the components are transported out of the 55-gallon drums via specialized transfer pumps, which feed the material into the spray foam machine.
The spray foam machine, or proportioner, does exactly that: proportions the chemical components to begin the process of manufacturing spray foam. The machine evenly proportions the chemical components by keeping them in an optimal 1:1 ratio by volume (called being “on-ratio”). It also heats the components to their required temperature range, which can be somewhere in the neighborhood of 120 degrees F, and transports them through hoses to the spray gun. The chemical components are kept separate through this entire process. The proportioner is comprised of a number of components, such as electric motors, metering pumps, pre-heaters, electric consoles, pressure switches and gauges. Find out more about these components.
As the chemical components are transported from the spray foam machine to the spray gun, they travel through heated hoses. The hoses function to maintain the components in the optimal temperature range and keep the materials separate once they leave the proportioner and before they get to the spray gun.
When the chemical components reach the spray gun, they remain separated until the installer pulls the trigger. At this point, the materials are atomized and mixed together at the nozzle of the spray gun. The combined materials are sprayed under high pressure, reacting almost instantaneously as they are applied to the substrate as a liquid. As the components continue to react, the liquid material eventually turns into hardened spray polyurethane foam.