STP ShaliPrime 2PU
Two-component solvent-based polyurethane primer that locks PU floor toppings, deck coats and liquid-applied membranes onto concrete and steel — overcoatable in 6-12 hours and supplied in 10 kg kits with pan-India applicator support from Space Arc.
What is it?
A two-component, solvent-based polyurethane primer from STP Limited, mixed 87:13 by weight. The colourless, low-viscosity liquid penetrates concrete pores and keys onto blast-cleaned steel before resin systems go down.
Where is it used?
Under PU floor toppings and deck coatings in car parks, ramps, warehouses, cold stores, food plants, hospitals and hangars — and as the first coat on mild-steel substrates before epoxy or PU protective coatings.
Why use it?
It develops 1.6 MPa pull-off adhesion to concrete in 7 days and seals the pores that would otherwise outgas and pinhole the finish coat, so the topping bonds cleanly and stays bonded.
How is it applied?
Mix the full kit for 3 minutes with a slow-speed stirrer, then lay by brush, roller, spray or squeegee at 0.15-0.60 kg/m2 depending on the surface. Overcoat within 6-12 hours.
About STP ShaliPrime 2PU
ShaliPrime 2PU sits at the base of STP Limited’s polyurethane flooring and coating build-ups. It is a two-pack system — a polyurethane resin (Part A, 8.7 kg) and an isocyanate hardener (Part B, 1.3 kg) — supplied as a factory-proportioned 10 kg kit so there is no site weighing to get wrong. Mixed material is colourless, carries 75 ± 3% solids by volume, and is designed to soak into mechanically prepared concrete or grip freshly blast-cleaned steel, leaving an 80-120 micron film that the next resin coat bonds to chemically.
For contractors, its value is programme speed on live sites. The primer is touch dry in 1-2 hours at 28°C, takes light foot traffic in a day, and accepts the topping after just 6-12 hours — effectively prime in the evening, coat the next morning. Because one product handles both horizontal decks and vertical concrete as well as metal inserts, kerbs and upstands, a car-park or plant-room job runs on a single primer stock. Space Arc Engineering supplies ShaliPrime 2PU across Delhi NCR and pan-India, backed by trained application crews for complete ShaliFloor system installations.
The technical insight
The main enemy of any resin floor on concrete is outgassing: air trapped in capillary pores expands as slab temperature rises and pushes up through the wet topping, leaving pinholes and blisters. ShaliPrime 2PU counters this physically and chemically. Its solvent carrier thins the polyurethane enough to be drawn deep into the pore structure; as the solvent flashes off, the isocyanate component cross-links with the polyol resin and with hydroxyl groups and residual moisture at the substrate interface, plugging the capillaries with cured polymer. The result is a sealed, uniform surface that stops air release and gives the topping a chemically active layer to bond to — which is why overcoating inside the 6-12 hour window matters, while unreacted groups remain available. On steel, priming immediately after Sa 2½ blasting locks onto the bare profile before flash rusting can re-form.
Where it is used
- Priming concrete before STP PU floor toppings such as ShaliFloor 2PU FC, ShaliFloor SL TC 3 PU and ShaliFloor Deck Coat 2PU
- Car park decks, ramps, parking bays, pedestrian walkways and roof decks
- Industrial floors in warehouses, cold stores, factories and aircraft hangars
- Hygienic flooring bases in food and beverage plants, dairies and commercial kitchens
- Hospitals, laboratories and high-tech manufacturing facilities
- First coat on blast-cleaned mild steel before epoxy or polyurethane protective coatings
- Primer beneath PU liquid-applied waterproofing membranes, including vertical concrete faces
- Broadcast primer layer (0.50-0.60 kg/m2) where a sand-seeded key is specified
Key advantages
- Verified 1.6 MPa adhesion to concrete at 7 days — above the pull-off strength typically specified for resin flooring substrates
- Seals porous concrete against outgassing, cutting pinholes and bubbles in the finish coat
- Fast programme: touch dry in 1-2 hours, overcoatable in 6-12 hours, light foot traffic within a day
- One primer for concrete and steel simplifies decks with metal inserts, drains and kerb angles
- High solids for a solvent-borne primer at 75 ± 3% by volume, giving a genuine 80-120 micron film per coat
- Applies by brush, roller, spray or squeegee with a workable 1-hour pot life at 28°C
- Cured film resists acid and alkali spot exposure and occasional steam cleaning up to 120°C
- Pre-weighed 10 kg kits (8.7 kg + 1.3 kg) eliminate site batching errors
Limitations & considerations
- Solvent-based and isocyanate-containing — needs forced ventilation, no hot work nearby, and full PPE; not ideal for occupied or poorly ventilated interiors
- Concrete must be at least 28 days old with moisture below 4% and ambient RH not above 75%; rising damp or osmosis-prone slabs are excluded
- Not suitable over asphalt, weak or friable concrete, unmodified sand-cement screeds, PVC tiles or substrates that flex, such as steel walkways
- Not recommended for exterior slabs on grade in freeze-thaw exposure
- Pot life of 1 hour at 28°C shortens further in Indian summer conditions — mix only what the crew can lay
- If the 6-12 hour overcoat window is missed, the surface may need abrading before the topping goes down
Selection & best practice
Preparation decides the result. Grit-blast or scarify concrete to strip laitance and open the texture, cut out weak patches, expose blowholes, then vacuum thoroughly; blast steel to ISO Sa 2½ and prime it straight away, before flash rust forms. Stir Part A, add all of Part B, and mix for 3 minutes at 300-400 rpm; let the mix stand 5 minutes to release entrapped air, then transfer to a fresh container and re-mix briefly — avoid whipping air in. Keep substrate and ambient temperature between +10°C and +40°C. On absorbent concrete the primer disappears fast, leaving pale dry patches: re-prime those areas rather than flooding the first coat, since ponded primer cures glossy and weak. Apply the topping within 6-12 hours, and keep the primed surface clear of oil, chemicals and traffic until then. Clean tools immediately with STP Thinner — cured material only comes off mechanically.
Specifications
| Mixing ratio (Part A : Part B, by weight) | 87 : 13 |
| Theoretical coverage, horizontal concrete | 0.35-0.45 kg/m2 (broadcast primer: 0.50-0.60 kg/m2) |
| Theoretical coverage, vertical concrete / vertical metal | 0.25-0.35 kg/m2 / 0.15-0.25 kg/m2 |
| Solids content | 75 ± 3% by volume |
| Mixed density | 1.52 ± 0.02 g/cc |
| Pot life at 28°C | 1 hour |
| Touch dry / overcoating time (28°C, 60% RH) | 1-2 hours / 6-12 hours |
| Adhesion to concrete, 7 days | 1.6 MPa |
| Pack size / shelf life | 10 kg kit (8.7 + 1.3 kg); 12 months at 5-38°C |
Industry use cases
Car Parks & Basements
Primes ramps, parking bays and drive aisles ahead of ShaliFloor Deck Coat 2PU systems, bonding to both the deck slab and steel expansion-joint nosings in one operation.
Warehousing & Cold Chain
Fast overcoat times keep racking-aisle recoating inside weekend shutdowns; the cured film tolerates cold-store service beneath PU screeds and toppings.
Food, Beverage & Pharma
The sealing coat under hygienic PU floors in dairies, kitchens and processing halls, where a pinhole-free finish is an audit requirement, not a preference.
Manufacturing & Heavy Industry
Doubles as a blast-primer on MS structures, tank bases and machine plinths before epoxy or PU protective coatings in factories and hangars.
Healthcare & Laboratories
Base coat for seamless resin floors in hospitals and labs, applied during phased handovers thanks to next-day light-traffic readiness.
Frequently asked questions
How much area does one 10 kg kit cover?
How soon can the floor topping go over it?
Can it be applied on new or damp concrete?
Is one coat enough?
Does it work under epoxy systems too?
What safety measures are needed on site?
How we position STP ShaliPrime 2PU
ShaliPrime 2PU is the standard first coat under STP’s ShaliFloor 2PU FC, ShaliFloor SL TC 3 PU and ShaliFloor Deck Coat 2PU systems, so specifying it with the matching topping keeps the whole build-up under one manufacturer. Where solvent odour or confined spaces rule out a solvent-borne product, STP’s ShaliPrime 2E SF solvent-free epoxy primer is the in-family alternative. Projects written around Fosroc’s Nitoflor flooring range are typically primed with Fosroc Nitoprime 31 instead — Space Arc stocks and applies both families, so the primer can follow the topping specification rather than force a substitution.
Fosroc Nitoprime 31 — Specifiers building a Fosroc Nitoflor epoxy or PU floor system generally prime with Nitoprime 31 so the entire build-up carries a single manufacturer’s system warranty.
Related Protective Coatings products
Source STP ShaliPrime 2PU for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.