This spray system is provided in different reactivity profiles to meet varying substrate temperatures previously noted. At the lower end of the recommended temperature range, flash passes are to be avoided. RTC Technical Personnel should be consulted in all cases where application conditions are marginal. Higher wind speeds also retard the exothermic reaction of foam and can lead to poor adhesion and increased density as well as poor surface texture of the foam itself. Moisture in the form of rain, dew, frost or other sources can seriously affect the adhesion of urethane foam to the substrate or to itself.
Water reacts with the mixed foam components, seriously affecting the foam's physical properties.
The gun should be of the internal mix type which provides intensive and thorough blending of the components. Dry nitrogen should be employed to blanket the liquid components, especially when tanks are employed to store the components. Both components are adversely affected by moisture and humidity. The thickness of each pass is dependent upon the temperature of the substrate, the speed of application and the output of the proportioning unit and gun. It is desirable for the foam to be built to the final desired thickness before moving to another area.