Nitoseal MS250: UV Resistant Elastomeric Joint Sealant

Product Overview

Nitoseal MS250 is a high-performance elastomeric joint sealant based on Silyl Modified Polymers (Polyurethane hybrid) technology, replacing the previous Duraflex® formulation. It combines the weathering and adhesion performance of a silicone sealant with the toughness of a polyurethane sealant, making it an ideal solution for various construction applications.

Key Applications

Nitoseal MS250 is designed for sealing moving or static joints in high-performance applications across multiple building types and materials:

• Structural Systems: Precast or insitu concrete, tilt-up slabs
• Building Facades: Curtain walls and lightweight cladding systems
• Masonry Work: Brick and blockwork applications
• General Construction: Most building materials and joint types

Technical Specifications

Physical Properties

Property	Value
Form	Smooth, non-slump paste
Skin Time	65 minutes @ 23°C and 50% RH
Tooling Time	35 minutes @ 23°C and 50% RH
Cure Time	>2mm / 24 hours @ 50% RH at 25°C
Typical Hardness	34 Shore A
Elongation at Break	520%
Modulus @ 100%	0.75 MPa
Specific Gravity	1.45

Joint Movement Capability

• Total Movement Capacity: ±25% (total 50%)
• Designed Joint Width: 10mm to 35mm
• Extended Range: 5mm to 50mm under suitable conditions
• Minimum Depth: 10mm for joints 10-20mm wide; 2:1 ratio for joints >20mm

Environmental Performance

Property	Specification
Continuous Service Temperature Range	-15°C to +70°C
Minimum Application Temperature	5°C
VOC Content	12g/L (ASTM D3960)
Shelf Life	12 months in original unopened packaging
Storage Conditions	+10°C to +25°C, 55% relative humidity

Key Advantages

Nitoseal MS250 offers numerous performance benefits:

• Outstanding UV Resistance: Maintains colour and integrity under prolonged exposure
• Easy Application: Extrudes smoothly even at low temperatures with low stringing
• Excellent Adhesion: Primerless adhesion to concrete, timber, masonry, aluminium, metal, and ceramics
• Aesthetic Properties: Will not stain masonry surfaces
• Moisture Performance: Blister-free cure in high humidity or on SSD (Saturated Surface Dry) surfaces
• Low Environmental Impact: Very low VOC content of 12g/L
• Safety: Contains no isocyanate; solvent-free formulation
• Local Manufacturing: Made in Australia

Material Composition & Safety

Nitoseal MS250 is formulated with isocyanate-free components, eliminating safety concerns associated with isocyanate exposure. The product is also solvent-free, contributing to its low VOC profile and environmental compliance.

Substrate Compatibility & Adhesion

Nitoseal MS250 provides excellent primerless adhesion to a wide range of construction materials:

• Concrete (precast and insitu)
• Masonry (brick, blockwork, masonry surfaces)
• Timber
• Metals (aluminium, steel)
• Ceramics
• Most coating surfaces

On some specialized surfaces (such as FC sheet), adhesion can be improved using Primer 10.

Application & Installation

Surface Preparation

Joint surfaces must be:

• Clean and dry (SSD - Saturated Surface Dry condition)
• Free from frost
• Cleared of all dirt, laitance, loose materials, and foreign matter
• Non-porous surfaces degreased using Fosroc Solvent 10

Bond Breaker Requirements

Bond breaker materials must be used in all joints to prevent sealant contact with the joint back and optimize performance:

• Shallow Joints (< 10mm depth): Self-adhesive polyethylene tape
• Deep Joints: Expandafoam Backing Rod or similar backing strips

Application Method

The sealant is applied using a suitable sausage gun:

1. Insert 600ml sausage into gun
2. Cut slit at top of sausage
3. Replace end cap and nozzle
4. Extrude sealant firmly into joint ensuring complete contact with joint faces
5. Tool sealant to smooth finish

Tooling Characteristics

Nitoseal MS250 can be easily tooled to a smooth finish without the use of soapy water or tooling aids. If tooling aids are required, they must only be applied after the sealant has been initially tooled into the joint to prevent contamination.

Cleaning

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

Paintability Features

Nitoseal MS250 is paintable with water-based paints typically after a thick skin has developed. Key paintability guidelines:

• Optimal Timing: Painting should occur no later than 7 days after sealant application
• Flexibility Consideration: Applied coatings must have sufficient flexibility to accommodate expected joint movement
• Not Compatible: Do not paint over Nitoseal MS250 with solvent-based paints (such as enamels)

This paintability feature makes Nitoseal MS250 a preferred alternative to Nitoseal PU250 when painting is required.

Limitations & Restrictions

Nitoseal MS250 has specific application limitations:

• Do not apply to bituminous surfaces
• Prevent bitumen contact with the sealant
• Not suitable for underwater or continually immersed applications
• Do not apply to wet surfaces where free water is present

Product Supply & Coverage

Packaging Options

Nitoseal MS250 is supplied in 600ml foil sausages in cartons of 12, with multiple color variants available:

Color Variant	Product Code
Pale Brown	FC920169-600ML
Black	FC920170-600ML
Pipeline Grey N43	FC920171-600ML
Off White	FC920172-600ML
White	FC920173-600ML
Dark Grey	FC920174-600ML
Beige	FC920175-600ML
Brick Red	FC920176-600ML
Redwood	FC920177-600ML
Dark Earth	FC920178-600ML
Sandstone	FC920179-600ML
Original Grey	FC920185-600ML
Special Colour (Made to Order)	FC930223-600ML

Made-to-Order Colors: Minimum order quantity of 360 units with 14-21 day lead time.

Coverage Rate

One 600ml sausage will supply 6 metres of 10mm x 10mm sealant bead.

Storage & Shelf Life

• Shelf Life: 12 months when kept in original unopened packaging
• Storage Temperature: Between +10°C and +25°C
• Humidity: 55% relative humidity
• Location: Away from direct sunlight and moisture
• Conditions: Dry storage environment

Safety Information

A Safety Data Sheet (SDS) is available from the Fosroc website and should be read carefully before use. In case of emergency, contact:

• Poisons Information Centre: 13 11 26 (within Australia)
• Medical Professional: Doctor for advice

Manufacturer Information

Nitoseal MS250 is manufactured and sold under license from Fosroc International Limited. The product is distributed in Australia by Parchem Construction Supplies Pty Ltd.

---

References

• [1] Fosroc_Nitoseal_MS250_TDS.pdf
• [2] Fosroc_Nitoseal_MS400_TDS.pdf
• [3] Fosroc_Nitoseal_PU250_TDS.pdf
• [4] Fosroc_Flamex_XT_TDS.pdf