Fosroc Nitoseal MS300
A one-part, high-modulus silyl-modified polymer sealant built for floor and pavement joints that take forklift and wheel traffic — fast-curing, abrasion-resistant, and tolerant of damp substrates.
What is it?
A single-component, moisture-curing sealant based on hybrid silyl-modified polyether (SMP) technology that cures to a tough, high-modulus elastomer.
Where is it used?
Trafficked floor joints in factories, warehouses, distribution depots, shopping centres, car parks and stadia terracing — saw-cut, movement and perimeter joints.
Why use it?
It resists abrasion, picking and wheel loading where softer PU or silicone sealants would tear or extrude, while still accommodating joint movement.
How is it applied?
Gun-extruded from a 600 ml sausage into a prepared square-profile joint over a backing rod, then tooled flush within five minutes; primer-less on most substrates.
About Fosroc Nitoseal MS300
Nitoseal MS300 is Fosroc’s answer to a specific problem on industrial floors: the joint sealant usually fails long before the concrete does. Foot traffic, pallet trucks and forklifts pick at, abrade and compress joint sealant relentlessly, and a conventional polyurethane or silicone simply does not have the surface toughness to survive it. MS300 is formulated from hybrid silyl-modified polyether, a chemistry that cures on contact with atmospheric moisture into a hard yet still flexible elastomer. The result is a seal you can drive over, that shrugs off scuffing and vandalism, and that holds its line in busy plant rooms and loading bays for years.
For engineers and applicators working across Delhi NCR and the rest of India, its practical appeal is how forgiving it is on site. It is a genuine one-part product — no mixing, no pot-life race against the clock — and it will bond to concrete that is merely damp rather than bone-dry, which matters when you are sealing floors that were power-floated only days earlier. On the vast majority of substrates it needs no primer at all. Space Arc Engineering supplies MS300 as an authorised Fosroc distributor and applicator, and we position it precisely: it is the tough-floor sealant in the Nitoseal range, not a general-purpose facade product, and specifying it for the right joint is where its value shows.
The technical insight
The performance of MS300 comes from its silyl-modified polyether backbone. Unlike polyurethanes, which cure by reacting isocyanate groups and can foam or bubble when they meet moisture too quickly, and unlike pure silicones, which stay very soft and cannot take abrasion, the SMP hybrid cures through silane end-groups reacting with ambient humidity to form a dense, cross-linked network. That network is what gives MS300 its high modulus and roughly Shore A 45 hardness — firm enough to resist a forklift wheel driving across a flush joint, yet elastic enough to accommodate ±25% movement in a butt joint (up to 50% in a lap configuration). Because the cure is moisture-driven rather than solvent-driven, the sealant tolerates damp concrete and develops strength from the surface inward, reaching a tack-free state in two to three hours and a functional cure in about 24 hours. The same isocyanate-free chemistry is why it needs no primer on sound, dry concrete: the silane groups couple directly to the substrate. Primer MS2 is reserved for the one case where moisture attacks the bond line — joints that are intermittently or permanently saturated.
Where it is used
- Saw-cut and stress-relief joints in industrial and warehouse floor slabs
- Movement and isolation joints in factory floors subject to forklift and pallet-truck traffic
- Perimeter and bay joints in distribution depots and logistics hubs
- Trafficked joints in shopping-centre floors, malls and public concourses
- Floor and hardstanding joints in car parks and vehicle-maintenance areas
- Terracing and step joints in sports stadia and grandstands
- External hardstanding and pavement joints where abrasion resistance is required
- Sealing over sound residual silicone, PU or polysulphide in refurbishment work
Key advantages
- Cures to a genuinely tough, abrasion-resistant elastomer that withstands wheel and forklift loading
- High modulus and Shore A ~45 hardness resists picking, scuffing and vandalism at the joint edge
- Single-component and ready to gun — no mixing, no pot life, less site wastage
- Bonds to damp and surface-wet concrete, so floors can be sealed sooner after casting
- Primer-less on most sound substrates, cutting an entire step from the workflow
- Fast rate of cure — tack-free in 2-3 hours, functionally cured in 24 hours
- Isocyanate-free SMP chemistry with good UV and weathering resistance
- Adheres over many residual sealants, easing refurbishment of old joints
Limitations & considerations
- Do not apply below 5°C — the moisture cure slows and adhesion suffers in cold conditions
- Not for permanently immersed joints; specify Nitoseal MS600 where continuous water contact is expected
- Not suitable for contact with bituminous materials, which can bleed and destroy the bond
- Large joints need extended cure before trafficking — a 40 mm joint may require up to 10 days
- Its high modulus suits durable floor joints, not high-movement facade or glazing joints where a low-modulus sealant is correct
- Good adhesion to old sealant is not a substitute for proper joint preparation
Selection & best practice
Design the joint as a square slot with a minimum depth of 10 mm and control the depth-to-width ratio with a closed-cell polyethylene backing rod, which also prevents three-sided adhesion. Clean the joint faces back to sound, dust-free concrete; the surface may be damp but not standing wet. Skip the primer on normal dry or surface-dry concrete — MS300 is primer-less for most floor applications — but where the joint will be intermittently or permanently saturated, brush on mixed Fosroc Primer MS2 and gun the sealant between 30 minutes and 4 hours later. Load a 600 ml sausage into a Fosroc GX gun, cut the nozzle at 45°, extrude firmly to fill the joint fully, and tool flush within five minutes to force intimate contact with both faces. Keep traffic off until the sealant has cured through — a few days for typical widths, and up to about 10 days for the widest 40 mm joints. Clean tools immediately with Fosroc Equipment Cleaner before the sealant skins.
Specifications
| Base chemistry | One-part, moisture-curing hybrid silyl-modified polyether (SMP) |
| Form and colour | Paste, grey (special colours on request) |
| Hardness | Shore A approx. 45 at 20°C |
| Movement accommodation | ±25% in butt joints; up to 50% in lap joints |
| Joint width | 6-20 mm trafficked; up to 40 mm non-trafficked / recessed |
| Minimum joint depth | 10 mm, square cross-section |
| Tack-free / cure | 2-3 hours tack-free; approx. 24 hours functional cure |
| Application temperature | 5°C to 50°C (do not apply below 5°C) |
| Standards | EN 14188-2:2004; ISO 11600 Type F 25HM |
| Packaging | 600 ml sausages, 10 per box; Primer MS2 in 500 ml packs |
| Shelf life | 12 months in original containers, cool and dry |
Industry use cases
Warehousing & Logistics
Saw-cut and movement joints in distribution-depot slabs stay intact under constant forklift and pallet-truck traffic, avoiding the ragged, picked-out joints that softer sealants leave behind.
Manufacturing Plants
Bay and isolation joints in factory floors are sealed with a hard-wearing elastomer that resists chemical splash, abrasion and heavy point loading in production and maintenance areas.
Retail & Malls
Trafficked floor joints in shopping-centre concourses hold a clean, flush line under continuous foot traffic and cleaning-machine wheels, in special colours where finish matters.
Car Parks & Hardstanding
Deck and pavement joints in car parks and external hardstandings take vehicle wheel loads while accommodating slab movement, with good UV resistance for exposed areas.
Sports & Public Infrastructure
Terracing and step joints in stadia and public spaces are sealed with a tough, vandal-resistant material that survives crowd traffic and impact at the joint edge.
Frequently asked questions
Is Nitoseal MS300 a floor sealant or a facade sealant?
Do I need a primer before applying MS300?
How much MS300 does one sausage cover?
Can it be applied to damp concrete?
How long before the joint can take traffic?
What if the joint is permanently under water?
How we position Fosroc Nitoseal MS300
Within the Fosroc Nitoseal range, MS300 is the tough-floor specialist: choose it for trafficked slab joints, and step up to Nitoseal MS600 when the joint sees permanent or intermittent immersion or needs a more general-construction MS polymer. Pair it with Fosroc Primer MS2 for saturated joints and a compatible closed-cell backing rod for correct joint geometry. Where the requirement is actually a high-movement expansion or facade joint rather than a trafficked floor joint, a low-modulus gun-grade polyurethane such as Nitoseal PU sealants is the honest fit. For the joint itself in heavy-duty industrial floors, Fosroc’s Nitoflor and Nitomortar floor systems complete the specification. Across our other brands we can offer equivalent MS polymer and PU joint sealants from Sika and MC-Bauchemie where a project standard or approved-vendor list calls for them — Space Arc supplies all of these Pan-India and can advise on the correct grade for the exposure.
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