MC-Bauchemie MC-Nafuplan GP
A single-component, moisture-curing polyurethane sealant that stays flexible in movement, perimeter and facade joints through years of Indian weather.
What is it?
A one-part, gun-grade polyurethane joint sealant from MC-Bauchemie that cures on contact with atmospheric moisture to form a tough, elastic rubber seal.
Where is it used?
Window and door perimeters, wall-to-floor junctions in wet areas, precast and facade panel joints, and general construction movement joints.
Why use it?
It absorbs joint movement without splitting or peeling, resists UV, weather and ozone, and can be overpainted to match the finish.
How is it applied?
Clean and prime the joint faces, fit a backer rod, gun the sealant off a cartridge, tool it smooth, and let ambient humidity cure it.
About MC-Bauchemie MC-Nafuplan GP
MC-Nafuplan GP is MC-Bauchemie’s single-component polyurethane joint sealant, built for the everyday sealing work that keeps a building watertight and quiet. It arrives ready to use in a cartridge, needs no mixing, and cures simply by drawing on the moisture already present in the air and on the joint surface. Once cured it behaves like a firm elastic rubber rather than a rigid filler, so it can stretch and compress as the structure breathes with temperature swings, wind load and normal settlement without losing its grip on either joint face.
For engineers and applicators working across Delhi NCR and the rest of India, the appeal is practical. It bonds to the substrates found on nearly every jobsite, from concrete and masonry to aluminium framing, galvanised steel, UPVC and glass, provided the correct primer is used first. It holds up to sun, rain and ozone on exposed facades, and it can be painted over once fully cured so the seal disappears into the finished elevation. Space Arc Engineering supplies it as an authorised MC-Bauchemie distributor, with technical support on primer selection, joint design and application on hand for site teams.
The technical insight
The chemistry behind MC-Nafuplan GP is a moisture-curing polyurethane prepolymer. While the cartridge is sealed, the reactive isocyanate groups on the polymer chains sit dormant. The moment the sealant is gunned into an open joint, those groups begin reacting with water vapour in the air and with the trace moisture on the primed joint faces. That reaction stitches the chains together into a three-dimensional cross-linked network, converting the soft paste into a cohesive elastomer with a Shore A hardness in the region of 20 to 30. Because cure works inward from the exposed surface, deeper sections take longer to develop full strength, which is why bead depth and joint design matter as much as the product itself. The cured rubber carries load through elastic recovery: as a joint opens and closes, the sealant stretches and rebounds rather than tearing, typically accommodating movement in the ±15 to 25 percent range of the designed joint width. Good adhesion, backed by the right primer, is what lets it transfer that movement without peeling at the bond line, the most common failure point in any sealed joint.
Where it is used
- Perimeter sealing around window and door frames on external elevations
- Wall-to-floor and skirting junctions in bathrooms, kitchens and other wet areas
- Vertical and horizontal joints between precast concrete facade panels
- Movement and expansion joints in walls, floors and general building construction
- Sealing gaps around aluminium, UPVC and galvanised steel framing members
- Weather-sealing of building envelope and cladding interfaces
- Junctions between dissimilar materials such as concrete to metal or glass
- General construction and repair joints requiring a flexible, paintable seal
Key advantages
- Single-component and ready to gun straight from the cartridge, with no on-site mixing or ratio errors
- Cures with ambient and surface moisture, so it works in normal site conditions without heat or catalysts
- Stays elastic after cure, flexing with the joint instead of cracking like a rigid filler
- Bonds to a wide range of substrates including concrete, masonry, aluminium, galvanised steel, UPVC and glass when correctly primed
- Resistant to UV, weather and ozone, suiting exposed facades in Indian climates
- Overpaintable with water-based and solvent-based paints once fully cured, for a seamless finish
- Available in grey, white, black and brown, with other shades for larger projects
- Backed by Space Arc technical support on primer choice and joint detailing
Limitations & considerations
- Not a structural adhesive or a substitute for a load-bearing bond; it seals joints, it does not hold members together
- Needs the correct MC-Bauchemie primer on most substrates to reach reliable adhesion; skipping the primer risks bond-line failure
- Requires ambient humidity above roughly 30 percent to cure, and cure slows in very dry or cold conditions
- Full cure before overpainting takes around 24 to 72 hours, so painting cannot immediately follow application
- Bead depth must be controlled with a backer rod or bond breaker; over-deep beads cure slowly and can fail in three-sided adhesion
- Colour range is limited off the shelf, with wider shades only viable at project volumes
Selection & best practice
Start with joint design: size the width and depth for the expected movement and set the correct width-to-depth ratio using a closed-cell backer rod, which also prevents three-sided adhesion. Cut back all joint faces to sound, clean substrate, then remove dust, laitance, oil and old sealant. Apply the MC-Bauchemie primer recommended for the specific substrate and let it flash off before sealing. Gun the sealant in a continuous bead, pushing it ahead of the nozzle to fill the joint without trapping air, then tool the surface firmly within the skinning time to compact it against both faces and shape a neat profile. Work within the 5 to 35 degrees Celsius application window and confirm ambient humidity is high enough for cure. Protect the fresh bead from water, traffic and contamination, and allow full cure, roughly 24 to 72 hours depending on conditions, before overpainting or exposing it to service movement. Store cartridges sealed at 5 to 25 degrees Celsius, out of direct sunlight, and use within the 12-month shelf life.
Specifications
| Product type | Single-component, moisture-curing polyurethane joint sealant |
| Cure mechanism | Reaction of isocyanate groups with atmospheric and surface moisture |
| Shore A hardness (cured) | Approximately 20 to 30 |
| Movement accommodation | Approximately +/-15 to 25% of joint width |
| Application temperature | 5 to 35 degrees Celsius |
| Cure condition | Ambient humidity above approximately 30% |
| Overpaintable | Yes, after full cure with water- and solvent-based paints |
| Colours | Grey, white, black, brown (other shades for large projects) |
| Shelf life / storage | 12 months sealed; store 5 to 25 degrees Celsius, out of direct sunlight |
Industry use cases
Residential & Commercial Facades
Sealing window and door perimeters and precast panel joints so elevations stay watertight and free of draughts through monsoon and summer cycles.
Wet Areas & Sanitary
Flexible wall-to-floor and skirting joints in bathrooms, kitchens and utility areas that resist water while accommodating slab and wall movement.
Precast & Cladding
Elastic seals between precast concrete units and cladding interfaces where panels expand, contract and shift under wind and thermal load.
General Building Construction
Everyday movement and construction joints across concrete, masonry and metal framing where a paintable, weather-durable seal is needed.
Repair & Refurbishment
Resealing failed or aged perimeter and movement joints during maintenance, restoring watertightness without heavy reconstruction.
Frequently asked questions
Is MC-Nafuplan GP a waterproofing product or a joint sealant?
Do I need a primer before applying it?
How much joint movement can it handle?
Can it be painted over?
What surfaces does it bond to?
How should it be stored and how long does it last?
How we position MC-Bauchemie MC-Nafuplan GP
MC-Nafuplan GP is the workhorse single-component PU sealant in the MC-Bauchemie joints-and-sealants range, best suited to perimeter, wet-area and general movement joints. Where a job needs a companion product from the same brand family, pair it with the matching MC-Bauchemie substrate primer for reliable adhesion, and step up to MC-Bauchemie’s higher-movement or self-levelling PU sealants for wide expansion joints or horizontal traffic-bearing joints. For projects standardised on other brands we distribute, Fosroc’s Nitoseal PU line and Sika’s Sikaflex PU sealants are close equivalents, while heavy-duty trafficked expansion joints may call for a dedicated expansion-joint system rather than a gun-grade sealant.
Fosroc Nitoseal PU — Specifiers standardised on Fosroc, or needing a documented ISO 11600 Type F 25LM movement class, may prefer Nitoseal PU as a directly equivalent single-component gun-grade polyurethane sealant.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.