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When an expansion joint must move with the building, perform in challenging conditions, and meet strict certifications, the right sealant is non-negotiable. Bostik Seal 'N' Flex One P390 provides this assurance. It is engineered for high-movement applications in concrete, masonry, and precast panels, ensuring seals remain intact where flexibility and compliance are paramount.
Bostik Seal 'N' Flex One P390 is a low modulus, one-component polyurethane sealant formulated for the demands of Australian construction. It maintains a durable, flexible seal across an impressive ±50% joint movement. This capability prevents common joint failures, especially in dynamic structures like tilt-up panels or concrete slabs. With over 900% elongation at break, it provides a substantial safety margin, absorbing thermal shock and minor settlement that could compromise lesser sealants. This product was developed to deliver reliable performance where AS4020 potable water approval or acoustic rating is required for expansion and construction joints.
Bostik Seal 'N' Flex One P390 is supplied as a one-component system, requiring no mixing, simplifying on-site application. It can be applied in temperatures ranging from 5°C to 35°C using a standard caulking gun. For optimal performance, ensure all surfaces are clean and dry, free from contaminants. While the sealant offers good adhesion to many substrates without a primer, critical or high-performance applications, especially on porous surfaces or those subject to periodic immersion, benefit from Bostik N49 Primer. For non-porous plastics and metals, Bostik N40 Primer is recommended using a two-cloth method. Tooling should occur within the tack-free time to achieve a smooth, concave finish. Once cured (minimum 7 days), the sealant can be painted, though a field test for compatibility with solvent-based coatings is always recommended. Always use a compatible backer rod to control sealant depth and prevent three-sided adhesion.
Bostik Seal 'N' Flex One P390 is the go-to for expansion and construction joints requiring robust ±50% movement and specific certifications like AS4020 potable water approval and acoustic rating. It is a proven performer for standard high-movement applications on dry substrates. In contrast, for joints demanding extreme movement capacity, exceeding ±50% (up to +100%/-50%), or where application on damp or even wet concrete substrates is necessary, Seal 'N' Flex One Plus P590 offers a more advanced solution. The choice between them hinges on the precise movement profile and substrate conditions of the project.
Yes, this sealant is approved to AS4020 for use in contact with potable water. This makes it suitable for sealing joints in tanks or other structures that will hold drinking water.
No, Bostik Seal N Flex One P390 is not recommended for use in trafficable joints. Selecting a product specifically designed for pedestrian or vehicle traffic loads will prevent premature failure.
Joints must be at least 5 mm wide and 6 mm deep. The maximum allowable joint width is 50 mm. Maintaining these dimensions is critical for the sealant to perform to its ±50% movement rating.
Yes, the sealant can be painted after a minimum of 7 days cure. Conduct a field test for compatibility, as solvent-based coatings may cause tackiness, and cyclical movement can cause cracking in the paint layer.
| Application | Key benefit | Primary trades |
|---|---|---|
| Expansion joints in concrete & masonry | Accommodates ±50% joint movement, preventing cracking and bond failure. Maintains integrity in construction and precast panels. | Concreters, commercial builders, precast installers |
| Perimeter sealing for aluminium windows | Forms a durable, flexible seal to withstand building movement without compromising the window system. | Window installers, façade contractors |
| Sealing plasterboard & fibre cement sheets | Acoustic rated to AS 2253 / 1276. Prevents sound transmission through joints and provides a durable, paintable finish. | Plasterers, acoustic installers, dryliners |
| Sealing joints in potable water structures | AS4020 certified for drinking water contact, ensuring health and safety compliance for water storage and supply systems. | Plumbers, water infrastructure contractors |
| Sealing GRC and fibreglass panels | Low modulus and high elongation (>900%) handle the dynamic movement often found in specialty panel systems. | Façade specialists, panel installers |
Signal word: Warning
Wear safety glasses with side shields, lightweight protective clothing, long-sleeved clothing, and impervious gloves (nitrile rubber recommended). Use appropriate respiratory protection, such as a respirator conforming to EN 140 with Type A/P2 filter or better, for organic gases and vapours.
Use only outdoors or in a well-ventilated area. Ensure adequate ventilation and consider showers and eyewash stations.
Keep containers tightly closed in a dry, cool, and well-ventilated place between 5°C and 30°C. Protect from moisture, oxidizing agents, and acids. Shelf life is 12 months in original unopened containers. Dispose of waste and empty containers in accordance with local regulations; do not dispose down drains or into waterways.
Proper surface preparation and primer selection prevent bond failure, ensuring the sealant performs as specified for cyclic movement.
Surface prep: Clean and dry surfaces. Remove laitance, oil, dust, grease, and any curing agents. Vacuum loose particles.
Primer: Not required for standard concrete or mortar that is clean, dry, and uncontaminated. For high-stress joints, extreme weather exposure, or overly porous surfaces, a primer is required. For periodically immersed or submerged applications, use Bostik N49 Primer.
Surface prep: Clean and dry. Remove any protective coating (wax or plastic) from composite panels before application.
Primer: Not required for bare aluminium. Always conduct a Pre-tested Adhesion to Substrate (P.A.T.S.) test beforehand.
Surface prep: Surfaces must be clean, dry, and free of contaminants. Absorbent surfaces that soak up water require careful priming.
Primer: Required for maximum performance, especially in periodically immersed or submerged applications. Use Bostik N49 Primer. Vertical expansion joints in masonry or concrete may not require priming if clean and dry.
Surface prep: Clean and dry surfaces where water beads as a droplet. Includes u-PVC, brass, copper, and stainless steel.
Primer: Required. Use Bostik N40 Primer, applied with the two-cloth method. Conduct P.A.T.S. to confirm adhesion.
| Property | Value |
|---|---|
| Product Type | One Component Polyurethane Sealant |
| Modulus | Low |
| Joint Movement Capability | ±50% |
| Shore A Hardness | 30 |
| Tensile Strength | > 1.3 N/mm² |
| Elongation at Break | > 900% |
| Application Temperature | 5 to 35°C |
| Service Temperature | -40 to 75°C |
| Tack Free Time | 6-12 hours |
| Cure Rate | 2 mm/24 hours (on porous substrates) |
| Full Cure Time | 7 days (on porous substrates), 14 days (joints >20mm wide) |
| Maximum Joint Width | 50 mm |
| Minimum Joint Depth | 6 mm |
| Specific Gravity | 1.25 g/ml |
| VOC Content | 74 g/L (TDS), 64 g/L (SDS) |
| Cure Method | Moisture curing |
| Shelf Life | 12 months |
Here are some common examples on where Bostik Seal 'N' Flex One P390 used by our customers.
