In most parts of the country, there is a period of the year when ambient temperatures fall below the minimum recommended storage temperatures for your polyurethane chemicals. In these conditions applicators can run into problems keeping their chemicals at recommended storage temperatures of 65° – 85° F. Some polyurethane systems are more sensitive to pressure and temperature settings than others. If the applicator’s chemicals are a little on the cool side and their equipment is not able to raise the temperature of the chemicals to recommended application temperatures, the applicators can experience poor mixing at the gun and poor polyurethane quality.
As the weather begins to cool, we recommend contractors review their procedures to avoid problems which can be directly attributed to lower temperatures.
Keep Your Material Warm
Material storage issues are the most common causes for problems in cold weather foam application. Spraying material that has dropped below 65°F can cause cavitation in the proportioner, off-ratio foam production, and loss of yield.
If chemicals are slightly too cold, the options are:
- Gradually warming the chemicals up to recommended storage temperatures is the best option. Just as it takes some time to cool off 55 gallons of material, it takes some time to warm up 55 gallons of material. The problem with trying to heat the material up too fast with jet burners and band heaters is you run the risk of boiling off the blowing agent, pressurizing the containers, and making it very difficult to open the drums to insert your drum pump.
- Putting a smaller tip in the gun is also an option as this allows the material more dwell time in the heaters, and thus increasing the amount of heat the machine can add to the material during application. For example, depending on your machine you may be able to raise the temperature if incoming material by 70° F with an 02 chamber in a Fusion AP gun. By switching to an 01 chamber, you may raise the delta to 90° F. The extra 20° window may allow you to continue spraying, versus having to pull off the job and let the chemicals warm up over night.
As a rule of thumb, it is always more efficient to maintain your chemical storage area at a constant temperature rather than letting the material get cold and trying to warm up the material prior to application.
Watch Transit Times
Attention to common carrier transit times should be given to prevent material from being stranded on a freight dock over the weekend in extremely frigid areas. As much as possible, material orders should be entered early in the week to allow delivery prior to the weekend.
Colder Temperatures Reduce Yield
Cold ambient temperatures and substrate temperatures rob the heat of reaction from the foam upon application. Without the heat of reaction, the blowing agent is not efficiently “boiled off” resulting in a higher overall density of the foam. Higher densities translate into lower yield, sometimes significantly lower yields.
Watch Out For Condensation
Contractors have often used high output heaters to warm up a space to be sprayed with polyurethane foam. Heating up a space can improve yields and the increased operator comfort level translates into a more efficient professional application. During cold weather foam application, however, extra care must be taken as whenever hot moist air is injected into a cold environment, the threat of condensation on substrate is present. Further, adding heat to a frigid environment may thaw out ice that has built up in construction materials. As with foam application any time of the year, introducing moisture to the chemical reaction is to be avoided. In any case, ventilation requirements still must be followed which can overtax attempts to warm areas, so proper matching of system speed to conditions is important to maintain yield and performance.
Do Not Recirculate
NCFI does not recommend using re-circulation as a means to preheat the A and B side components of TerraThane Geotechnical systems prior to use. Pre-heating or recirculation can cause the following issues if left un-checked:
- Though no one raw material may be heat sensitive, however in combination, degradation may occur at high heat for an extended period of time.
- Extended exposure to heat can shorten the shelf life of the B side.
- 140F (60C) is the maximum recommended processing temperature for most of our TerraThane geotechnical polyurethanes.
- Some TerraThane specialty B side systems contain an HFO which by itself boils at 89F (31.6C). During the re-circulation process, if allowed to escape to the atmosphere, the HFO loss can increase density and decrease performance of the system resulting in possible project failure.
Re-circulation is typically thought of when the chemical has been allowed to get cold, 50F to 60F (10C to 15.5C) or additional mixing is required. This is not the case with TerraThane systems. Proper planning is the best way to keep the stored chemical up to recommended temperature for the next day’s projects.
Always consult with NCFI for proper chemical handling and storage recommendations.