Nitoseal PU250: High Performance Polyurethane Joint Sealant

Overview

Nitoseal PU250 is a high-performance elastomeric joint sealant based on polyurethane technology. It is specifically formulated for vertical interior and exterior applications, providing excellent weather resistance and durability. When cured, Nitoseal PU250 forms a waterproof and durable seal, making it ideal for exterior applications where protection from environmental elements is essential.

Key Features and Advantages

Nitoseal PU250 delivers several important performance characteristics:

• Excellent primerless adhesion to concrete, timber, masonry, bricks, aluminium, metal, and ceramics
• Low stringing for clean, professional application
• Low odour formulation for improved working conditions
• Weather resistant performance for long-term durability
• Easy to gun out using standard sealant equipment
• Suitable for use in contact with drinking water, making it appropriate for potable water applications
• Low modulus elastomeric properties allowing significant joint movement accommodation

Technical Specifications

Physical Properties

Property	Specification
Form	Smooth, non-slump paste
Movement Accommodation Factor (MAF)	±25% (total 50%)
Tack-Free Time	90 minutes (±10 minutes) at 23°C, 50% RH
Cure Rate	3mm per day at 23°C, 50% RH
Hardness (Shore A)	25 (±5) (ISO 868)
Modulus at 100% Elongation	0.20 - 0.30 MPa (ISO 8339)
Elongation at Break	>500%
Continuous Service Temperature Range	-40°C to +70°C
Application Temperature Range	5°C minimum to 35°C maximum
VOC Content	103.6g/litre

Joint Design Criteria

Nitoseal PU250 is designed for sealing movement joints between 10mm and 35mm wide. However, under suitable conditions, joints as small as 5mm and as large as 50mm can be sealed effectively.

The sealant width to depth ratio should be maintained at:

• Minimum depth of 10mm for joint widths between 10mm and 20mm
• 2:1 ratio for joint widths greater than 20mm

Applications and Uses

Nitoseal PU250 is suitable for sealing joints in:

• Concrete panels and precast concrete structures
• Fibrous cement products
• External cladding panels and facade systems
• Blockwork and brickwork construction
• Metal or concrete water tanks requiring waterproof sealing
• Joints around aluminium and timber door and window frames
• Between metal structural elements
• Movement joints in various construction materials

Application Instructions

Surface Preparation

The joint surfaces must be thoroughly dry, clean, and frost-free. Preparation includes:

• Remove all dirt, laitance, loose materials, and foreign matter
• Remove all rust, scale, and protective lacquers from metal surfaces
• Degrease non-porous surfaces using Fosroc Solvent 10
• Ensure joint surfaces are free from contamination

Bond Breaker Requirements

In all joints, a bond breaker must be used to prevent sealant contact with the back of the joint, allowing optimum sealant performance.

• Shallow joints: Use self-adhesive polyethylene bond breaker tape to eliminate adhesion to the joint base (3-sided adhesion)
• Deep joints: Incorporate a backing strip such as Expandafoam Backing Rod or Hydrocell to support the sealant while acting as a bond breaker

Priming

Good adhesion can be achieved to clean, dry, uncontaminated concrete, timber, metals, ceramics, brickwork, and most coating surfaces without primers. However:

• Primer 21 is recommended for optimum adhesion to concrete and porous materials
• Primer 13 must be used on concrete in applications subject to semi-permanent or long-term water immersion
• For non-porous materials such as aluminium, stainless steel, and galvanised metals, consult Fosroc for specific advice

Application Method

• Apply using a suitable 600ml sealant gun
• Extrude the sealant firmly into the joint to ensure complete contact with joint faces
• Smooth finish if necessary with a suitable spatula
• Do not spray detergent solution onto the sealant surface, as this will promote surface blisters

Cleaning

Tools should be cleaned immediately after use with Fosroc Solvent 10.

Limitations and Restrictions

Bituminous Surfaces

Do not apply Nitoseal PU250 to bituminous surfaces, nor allow bitumen to contact the sealant. Nitoseal MB175 is recommended as an alternative for these applications.

Paintability

Although polyurethane sealants generally accept painting with acrylic coatings, plasticizers may migrate over time and stain the surface of the coating. Fosroc does not recommend painting over Nitoseal PU250 and recommends using Nitoseal MS250 in applications where painting is required.

Standards Compliance

Nitoseal PU250 has been tested to comply with AS4020:2018, the Australian standard for joint sealants. Refer to AWQC Report 339139 for detailed compliance information.

Supply and Coverage

Product Availability:

• Supplied in 600ml foil sausages in cartons of 12
• Product code: FC920112-600ML (Concrete Grey)

Coverage: As a guide, one 600ml sausage will seal 3 metres of 20mm x 10mm joint.

Storage and Shelf Life

• Shelf life: 18 months from date of manufacture
• Storage conditions: Original, unopened packaging in dry conditions
• Temperature range: +10°C to 25°C
• Humidity: 55% relative humidity
• Protection: Store away from direct sunlight and moisture

Related Products and Alternatives

• Nitoseal PU400: An alternative polyurethane sealant for wider joints and trafficable applications
• Nitoseal MS250: Recommended alternative when paintability is required
• Nitoseal MB175: Alternative for bituminous surface applications
• Expandafoam Backing Rod or Hydrocell: Supporting materials for deep joints
• Primer 13, Primer 21: Primer products for enhanced adhesion
• Fosroc Solvent 10: Cleaning and surface preparation solvent

Safety and Additional Information

A Safety Data Sheet (SDS) is available from the Fosroc website and should be read carefully prior to use, as application or performance data may change over time. In emergencies, contact the Poisons Information Centre (phone 13 11 26 within Australia) or a doctor for advice.

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References

• [1] Fosroc_Nitoseal_PU250_TDS.pdf
• [2] Fosroc_Nitoseal_PU400_TDS.pdf
• [3] Fosroc_Nitoseal_MS250_TDS.pdf
• [9] Fosroc_Expandafoam_Open_Cell_TDS.pdf