Instructions for Nitrogen Gas Purging of Polyurethane Resin Components
1. Importance of Nitrogen Gas Blanketing Polyurethane raw materials—especially isocyanates (Part A)—are highly sensitive to moisture. Even minimal exposure to atmospheric humidity can lead to contamination, causing undesirable reactions such as foaming, softening, or incomplete curing. To prevent this, it is critical to blanket the headspace of the container with dry nitrogen gas immediately after opening or dispensing.
2. Sourcing Nitrogen Gas Dry nitrogen gas is readily available from industrial gas suppliers. Cylinders are typically leased and can be exchanged when empty. For most small operations, a single nitrogen cylinder can last a long time, making it an efficient and economical solution.
3. Safe Handling of Nitrogen Cylinders Nitrogen is a non-flammable gas, but it is stored under high pressure. Cylinders must be handled with care and secured upright to prevent tipping. Always follow the safety instructions provided by your supplier. For small-scale applications, start with the smallest available cylinder to monitor usage efficiently.
4. Regulator Use A pressure regulator is recommended for controlling nitrogen flow and monitoring pressure. While not always required for simple purging, it provides better control and reduces the risk of over-pressurization. Check with your supplier for a regulator suitable for your system.
5. Nitrogen Purging Procedures
A. General Guidelines
• Purge the headspace of containers immediately after dispensing to minimize moisture exposure.
• Ensure lids, caps, and grooves are clean before sealing to prevent dried material from compromising the airtight seal.
• For improved sealing and easier reopening, consider placing a layer of plastic wrap (e.g., Saran Wrap) over the opening before closing.
B. Small Containers (Quart and Gallon Sizes)
• Quart containers: Purge for 10–20 seconds.
• Gallon containers: Purge for 30–60 seconds.
• Insert the nitrogen tube while keeping the lid slightly open. Purge the headspace, then seal the lid promptly.
NOTE: For a very small quantity, you may use an aerosol paint preserver type products such as this: http://www.bloxygen.com/
C. 5-Gallon Pails
• Purge for 15–60 seconds, depending on headspace.
• Insert the nitrogen tube through the dispensing hole, purge, then close the screw cap quickly.
• Clean screw threads to prevent the cap from sticking due to residue or dried material. D. 55-Gallon Drums Option 1: Nitrogen Blanketing
• Store drums on their side with the dispensing hole at the bottom.
• Install a shut-off valve on the dispensing hole to prevent air backflow.
• Connect the nitrogen line to the vent hole at the top to displace air with nitrogen as material is dispensed.
Option 2: Desiccant Filtering
• Install a desiccant filter at the vent hole to dry incoming air to a dew point of –40°C or lower. Handling Tip: Use drum cradles or drum trucks for safe handling and positioning of the drum. These allow for easy dispensing into smaller containers while maintaining nitrogen blanketing. 6. Final Notes
• Always reseal containers immediately after purging. • Store polyurethane resin components in airtight conditions with proper nitrogen blanketing to ensure product stability and shelf life.
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Suppliers Reference Supplier Website
Praxair http://www.praxair.com/ Airgas http://www.airgas.com/
McMaster-Carr http://www.mcmaster.com/
BASCO http://www.bascousa.com/
Wesco http://www.wescomfg.com/
For Small Test Material Quantities:
Bloxygen (Argon gas in aerosol form) – http://www.bloxygen.com/
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Document Prepared by:
Tandem Products, Inc. DBA Northstar Polymers
3444 Cheatham Avenue, Minneapolis, MN 55406 USA
Tel: 612.721.2911 ext. 119
Email: info@northstarpolymers.com
Website: www.northstarpolymers.com
Revised: June 19, 2025
