Fosroc Nitoseal PU220
Two-part, pitch-modified polyurethane gun-grade sealant for high-movement joints in water-retaining, below-ground and chemically aggressive structures.
What is it?
A two-part, cold-applied polyurethane joint sealant blended with high-grade pitch, supplied as a black, non-sag gun grade for vertical and horizontal movement joints.
Where is it used?
Expansion and construction joints in reservoirs, sewage treatment works, subways, basements, retaining and sea walls, and floors exposed to fuel or chemical spillage.
Why use it?
Combines the chemical, fuel and bio-degradation resistance of a pitch-modified system with the elasticity and recovery of polyurethane, accommodating 25% joint movement while staying watertight.
How is it applied?
Joints are primed with Nitoprime 25, fitted with Expancell backer cord or bond-breaker tape, then the mixed base and hardener are gun-applied and tooled to the correct width-to-depth profile.
About Fosroc Nitoseal PU220
Fosroc Nitoseal PU220 is a two-component, cold-applied joint sealant built on a polyurethane formulation that is blended with high-grade pitch. The pitch component delivers the chemical, fuel and effluent resistance traditionally associated with bituminous and tar-based compounds, while the polyurethane backbone supplies the elasticity, recovery and durability those older materials lack. The result is an elastomeric, highly resilient seal that does not embrittle, soften or cold-flow over time, and that remains watertight under continuous water contact and below-ground exposure.
The product is supplied as a black, gun-grade (non-sag) sealant, so it can be applied to both vertical and horizontal joints from a standard sealant gun without slumping. It is mixed on site from separate base and hardener containers and cures by chemical reaction to a tough, flexible rubber. Once cured it tolerates a service temperature range of -30 deg C to +80 deg C and accommodates joint movement up to 25% of the joint width, meeting ISO 9047 at MAF 25% and US Federal Specification TT-S-00227E, Type 2, Class A.
Nitoseal PU220 sits in the heavy-duty end of the Fosroc Nitoseal joint-sealant family. Where a general building-facade sealant only has to resist weather and UV, PU220 is engineered for structures that also see immersion, hydrostatic pressure, sewage and hydrocarbon contact, which is why it is widely specified on water and wastewater infrastructure, transport tunnels and industrial flooring across India. For Space Arc Engineering customers in Delhi NCR and Pan-India, it is the go-to choice when a joint must stay both flexible and chemically robust for the design life of the structure.
The technical insight
The defining technical feature of Nitoseal PU220 is the pitch-modified polyurethane chemistry. Conventional coal-tar and bitumen joint compounds resist hydrocarbons and effluent well but are thermoplastic, so they soften in summer heat, embrittle in winter and cold-flow out of wide joints over time. By cross-linking the pitch into a two-part polyurethane matrix, PU220 keeps the chemical resistance but converts the material into a thermoset elastomer that recovers elastically after extension and compression. This is what allows it to carry a genuine 25% movement accommodation factor verified to ISO 9047, rather than the much lower effective movement of a plain bituminous seal. Mix discipline is critical to realising this performance: base and hardener must be combined in the correct ratio and mixed thoroughly with a slow-speed paddle (typically 400-500 rpm) for the full mixing period, scraping the container sides so no unmixed material remains, otherwise the sealant will cure unevenly or stay tacky. After mixing, the usable application life is short, roughly 1-2 hours at 20 deg C and only 30-60 minutes at 35 deg C, so on Indian sites in summer the material must be mixed in workable batches and gunned promptly. Cure is moisture- and temperature-dependent; tack-free time runs around 24-48 hours at 20 deg C, shortening to about 16-24 hours at 35 deg C, with full elastic properties developing over several days. A key practical advantage is that the matching primer system, principally Nitoprime 25, gives reliable adhesion even on damp concrete, which is decisive on water-retaining and below-ground structures where a bone-dry substrate is rarely achievable.
Where it is used
- Expansion and movement joints in water-retaining structures such as reservoirs, water and sewage treatment tanks and clarifiers
- Construction and contraction joints in basements, subways, underpasses and below-ground retaining walls
- Joints in sea walls, docks and other marine or tidal structures (with the special accelerator for tidal conditions)
- Floor joints in industrial areas, plant rooms and bunds subject to fuel, oil and chemical spillage
- Joints in sewage treatment works where resistance to bio-degradation and effluent is required
- Horizontal trafficked and vertical wall joints needing a single non-sag, gun-grade sealant
Key advantages
- Pitch-modified polyurethane gives both elasticity and the fuel, chemical and effluent resistance of a bituminous system, without the embrittlement, softening or cold-flow of tar-based compounds
- Accommodates 25% joint movement (MAF 25% to ISO 9047; TT-S-00227E Type 2 Class A) with excellent recovery
- Watertight cured seal suitable for continuous water contact and below-ground use
- Gun-grade non-sag consistency works on both vertical and horizontal joints from one product
- Outstanding adhesion to damp concrete via the Nitoprime primer system, ideal for water-retaining structures
- Wide service temperature range of -30 deg C to +80 deg C and good resistance to weathering and ageing
- Resists bio-degradation in sewage treatment environments and common mineral acids, alkalis, fuels and oils
- Can be accelerated for application in tidal conditions
Limitations & considerations
- Black colour only, so it is a functional/below-ground sealant rather than an architectural facade sealant where colour matching matters
- Two-part material requiring accurate on-site mixing; poor mixing leads to uneven cure or permanent tackiness
- Short application life (about 1-2 hours at 20 deg C, 30-60 minutes at 35 deg C) demands prompt use, especially in Indian summer conditions
- Substrate temperature must be at or above 5 deg C and rising at application
- Requires the correct Fosroc primer (e.g. Nitoprime 25) and a backer rod or bond-breaker; not a simple prime-free, single-part product
- Where hydrostatic pressure exists, bond-breaker tape must be used rather than foam back-up strips
- Not intended as a trafficked floor-joint sealant for heavy point-loading or forklift wheels where a harder Colpor-type grade is specified
Selection & best practice
Design the joint before specifying the sealant. For movement (expansion) joints, target a width-to-depth ratio of roughly 2:1, with a practical minimum width around 10 mm and minimum sealant depth around 10 mm; PU220 can be applied vertically up to a 25 mm joint width in one pass without slumping, with wider joints filled in multiple passes. Always install a bond-breaker so the sealant bonds only to the two joint faces and not the base: use Expancell closed-cell backer cord or debonding tape to control depth, and where hydrostatic pressure is present use bond-breaking tape only, never a foam back-up strip. Saw or grind the joint arrises clean, remove laitance, dust, oil and curing-compound residue, and prime the dry or damp concrete faces with Nitoprime 25, observing the stated drying window (allow the primer to dry before sealing and re-prime if the window is exceeded). Mix the full base and hardener together with a slow-speed paddle for the complete mixing time, scraping the sides, then gun and tool the sealant promptly within its application life, working in shaded conditions and avoiding mixing more than can be placed before the pot life expires. Confirm substrate temperature is 5 deg C or above and protect fresh joints from rain and traffic until tack-free.
Specifications
| Product type | Two-part, cold-applied joint sealant |
| Chemistry | Polyurethane blended with high-grade pitch (pitch-modified PU) |
| Grade / consistency | Gun grade, non-sag (vertical and horizontal joints) |
| Colour | Black |
| Movement accommodation factor (MAF) | 25% (to ISO 9047) |
| Standards | ISO 9047 (MAF 25%); US Federal Spec TT-S-00227E, Type 2, Class A |
| Service temperature range | -30 deg C to +80 deg C |
| Minimum substrate / application temperature | 5 deg C (and rising) |
| Hardness (7 days, 25 deg C) | 15-25 Shore A |
| Application (pot) life | 1-2 hours at 20 deg C; 30-60 minutes at 35 deg C |
| Tack-free time | approx. 24-48 hours at 20 deg C; 16-24 hours at 35 deg C |
| Max vertical joint width without slump | 25 mm (wider joints in multiple applications) |
| Typical coverage | approx. 100 m of 10 mm-deep joint per litre (varies with joint profile and substrate porosity) |
| Recommended primer | Nitoprime 25 (adheres to damp or dry concrete) |
| Backer / bond-breaker | Expancell closed-cell backer cord or debonding tape |
| Pack size | 4 litre packs (base + hardener) |
| Shelf life | 12 months in unopened original containers (cool, dry storage) |
| Chemical resistance | Common mineral acids, alkalis, petroleum fuels and oils; bio-degradation in sewage |
Industry use cases
Water & Wastewater Infrastructure
Sealing expansion and construction joints in reservoirs, water treatment tanks, sewage treatment plants and effluent channels, where a watertight, effluent- and bio-degradation-resistant joint is essential and concrete is rarely fully dry.
Metro, Tunnels & Transport
Movement joints in subways, underpasses, cut-and-cover tunnels and station boxes that combine water ingress risk with structural movement, common on Delhi NCR metro and highway projects.
Basements & Below-Ground Structures
Construction and contraction joints in deep basements and retaining walls subject to water-table pressure, where bond-breaker tape and a flexible, watertight seal are required.
Industrial & Process Floors
Floor and bund joints in plant rooms, fuel depots, chemical handling and process areas exposed to oil, fuel and chemical spillage, where the pitch-modified PU resists hydrocarbons.
Marine & Coastal Works
Joints in sea walls, docks and tidal structures, where the accelerated grade allows placement in tidal windows and the seal resists continuous salt-water exposure.
Frequently asked questions
What type of sealant is Fosroc Nitoseal PU220?
How much joint movement can Nitoseal PU220 accommodate?
Does Nitoseal PU220 need a primer?
Where is Nitoseal PU220 typically used in India?
What is the working time and cure time after mixing?
How does PU220 differ from other Fosroc sealants like Nitoseal MS or Thioflex 600?
How we position Fosroc Nitoseal PU220
Within the Fosroc joint-sealant range, Nitoseal PU220 is the heavy-duty, pitch-modified polyurethane chosen for water-retaining, below-ground and chemically aggressive joints rather than for visible architectural work. It complements rather than replaces the wider Nitoseal family: building and facade joints are usually better served by colour-matched gun-grade options such as Nitoseal MS-polymer or the Nitoseal 220/building grades, while polysulphide sealants like Thioflex 600 remain a common alternative for general chemical-resistant movement joints. For trafficked floor and pavement joints carrying heavy wheel loads, Fosroc’s Colpor 200PF or similar pavement-grade sealants are the more appropriate specification, since PU220 is optimised for watertightness and flexibility rather than indentation resistance. Among comparable products from other manufacturers, credible equivalents include Sika’s Sikaflex polyurethane joint sealants and PRO-range fuel-resistant grades, MBCC/Master Builders Solutions MasterSeal joint sealants, and STP (Pidilite) polyurethane and polysulphide sealants, all of which address overlapping water and movement-joint applications. As an authorised Fosroc distributor and applicator serving Delhi NCR and Pan-India, Space Arc Engineering supplies Nitoseal PU220 with the matching Nitoprime primers and Expancell backer materials, and can advise on joint design, primer selection and the correct grade where a project sits at the boundary between sealing, waterproofing and pavement-joint requirements.
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