Why special equipment?
Spray polyurea gels within seconds of mixing, so the two components must meet inside the gun, at the right ratio, temperature and pressure, and leave as a spray almost immediately. Viscous resins are heated to lower viscosity for good atomization and mixing.
Main components
- Transfer (feed) pumps move A and B from drums to the proportioner. The B-side is usually agitated so pigments and fillers stay mixed.
- The proportioner uses matched positive-displacement pumps to meter both sides at a fixed ratio, most often 1:1 by volume, and builds spray pressure.
- Primary heaters bring each component to set temperature.
- Heated hoses carry both components to the gun while holding temperature over long runs.
- The impingement gun forces the two streams to collide at high pressure in a small mixing chamber, then sprays the mix. Air-purge or mechanical-purge designs clear the chamber when the trigger releases.
Typical operating window
1 : 1Common volume ratio for spray polyurea
~150–160 °FTypical material and hose temperature (65–71 °C)
~2,000+ psiTypical dynamic spray pressure
SecondsTypical gel time
Always use the settings on the material’s data sheet; products differ.
Signs of trouble
| Symptom | Likely cause |
|---|---|
| Soft, tacky or cheesy spots | Off-ratio (B-rich), pressure imbalance, partially blocked screen or port |
| Brittle, dark or foamy material | Off-ratio (A-rich) or moisture in the A-side |
| Poor pattern, coarse texture | Low temperature or pressure, worn mix chamber |
| Pressure gauges far apart | Restriction, cavitation or viscosity mismatch on one side |
Protect the A-sideIsocyanate reacts with humidity to form solid crystals that block screens and pumps. Fit a desiccant dryer on the A-side drum vent, keep containers sealed, and keep the A-side pump lubricant reservoir maintained.
Spraying isocyanate coatings requires appropriate respiratory and skin protection. See our isocyanate safety guide.