Polyurea is applied using commercially available plural-component proportioning equipment. It should be applied by trained, professional contractors.
The amine resin blend and isocyanate material components are typically supplied in 55-gallon drum sets. The materials must be shipped and stored according specific procedures. Once in use on the jobsite, they are transferred from 55-gallon drums to the machine using special pumps called transfer pumps.
Typical equipment used to apply Polyurea has two metering, or proportioning pumps (one for each component) that heat and proportion the isocyanate and polyol resin through heated hoses to the spray gun in a 1:1 ratio. The two materials are kept separate through this entire system until they come together in the gun, where they are mixed and spray applied to the substrate.
Here you'll find some additional basic information about each of the parts of the application equipment systems -- proportioning pumps, spray guns, and mobile spray rigs.
Proportioning machines come in all shapes and sizes from several manufacturers. There are several major distinctions to consider when specifying and purchasing a machine: type of drive system, output and pressure capacity, heating capacity, and electrical system are the majors. Maximum and minimum hose lengths may be affected by the choices made in these major component areas.
Pump Drive System
The drive system is what forces the metering pumps to go up and down, or back and forth. The metering pumps are the pumps that proportion, or ratio, the materials and move them out through the machine and hoses to the gun. Most drive systems are pneumatically, electrically, or electric-hydraulically driven. Pneumatically driven machines are typically less expensive, but because air is compressible, hydraulic drives are considered to be of higher performance.
Output & Pressure Rating
A machine's output rating is a measurement of how much mixed foam the machine will dispense in any given time period. Output is typically classified in pounds per minute, gallons per minute, or kilograms per minute. The machine's pressure rating is a measurement of how much pressure the machine will generate to mix the chemicals at the spray gun. Pressure is typically classified as pounds per square inch (psi.) or bar for metric pressure measurement. Keep in mind that equipment manufactures often classify their machine's maximum pressure rating as a static pressure. Operating pressure is often less than what is rated. It is important to make sure that your spray gun's output and pressure ratings are matched to your machine.
Most high pressure thick film polyureas are commonly processed at 140°F-160°F. This temperature requirement is primarily to lower the viscosity of the liquid chemical components to assist in pumping and mixing. Often times the temperature of the material can affect spray pattern development and the physical properties of the finished polyurea product, so it is very important to assure the machines heating system is in good working order, and of enough capacity to keep up with the output of the machine.
Most proportioning machines have heaters and control systems which require an electrical connection. Hydraulic machines use an electric motor to power the hydraulic drive system, which also requires electricity. Proportioning machines can typically be ordered by the manufacturer to operate anywhere in the world. Common electrical voltages are single-phase 220v, three-phase 220v and 380v. Know where your machine will be used and be sure it is compatible with the available electrical system.
Polyurea Spray Guns
Most every commercial Polyurea Spray Gun uses impingement-mixing technology to mix the chemicals inside the gun. Pouring and injection applications can incorporate a variety of different mixing technologies including static and dynamic mix, however, in this section we will focus on spraying.
It is important to understand that once the two materials come together inside the gun to mix, they begin to react immediately as they mix and exit the spray gun. If the all of the reacted material is not expelled from the gun once the trigger is released, the material will set-up and harden inside the gun, rendering it non-usable. The design function within the spray gun that assures this does not happen is called purging. There are three basic purge systems offered by the various manufactures that offer different degrees of advantages and disadvantages, mechanical purge, air purge and solvent purge. Solvent purge is not that common in spraying foams as it is in coatings.
Mechanical purge serves two functions in a spray gun. A valving rod is set inside the mixing chamber of the gun. When the gun is not triggered, the valving rod remains static and closes off the two chemical ports. When the gun is triggered, the valving rod withdraws, opening up the two chemical ports to let the amine resin blend and isocyanate materials into the gun to mix and spray. When the trigger is released, the rod comes forward closing off the two chemical ports and mechanically purges the remaining mixed material from the gun chambers.
Air purge guns work similar to mechanical purge guns, except they purge the material from mixing chamber and gun block using a quick blast of air.
Solvent purge is typically less common and requires flushing of a cleaning solvent through the gun to neutralize the chemical reaction and the wash out the inside of the gun. This not favorable due to the fact that solvents cost additional money, they need to be properly disposed of (costing more money), and they can be harmful to the operators and the environment.
Mobile Spray Rigs
These mobile all-in-one packages of polyurea spray machine, tools, compressor and generator have fast become the standard for polyurea and spray foam contractors.
Mobile polyurea spray rigs with built-in generators allow contractors to arrive on the jobsite and get to work quickly. There is no lost time running around looking for power and wasting time hooking it up everyday.
Mobile spray rigs allow contractors to keep all valuable tools equipment and material supplies in one locked and secure place. They also protect all of these from the harsh weather and jobsite environment.
Many polyurea spray rigs are set-up with work benches and other support tools so you can service equipment when in need. But best of all, a mobile spray rig help to build brands, grow businesses, and sell more jobs by using those huge outside walls for placing company logos, and color graphics.