Dr. Fixit Feviseal HY 300
A high-modulus hybrid sealant-adhesive that bonds and seals in one step — for facade, precast and roofing joints where plain silicone won’t hold structurally and plain PU won’t stay paintable.
What is it?
A one-part, moisture-curing hybrid sealant on Silyl Modified Polyurethane (SMP) chemistry, blending a polyurethane’s bonding strength with a silicone’s weatherability, curing to a tough, permanently flexible, paintable rubber.
Where is it used?
Facade and precast movement joints, metal-to-metal or metal-to-concrete bonding, roof tile fixing, door/window frame bonding, duct cover plates, and aluminium fabrication seams on new-build and large commercial work.
Why use it?
It pairs structural-grade adhesion (~1.8 MPa tensile) with ±25% movement accommodation and paintable, non-staining performance — a combination ordinary acetoxy silicones and most PU-only sealants can’t match together.
How is it applied?
Gun-applied from a 600 ml sausage into a cleaned, backer-rodded joint at 5-40°C, tooled within the ~30-minute tack-free window, curing at roughly 3.5 mm/24 hr.
About Dr. Fixit Feviseal HY 300
Feviseal HY 300 belongs to a sealant class most site engineers still call “silicone” out of habit, though it isn’t one. Its base is Silyl Modified Polyurethane (SMP) — also called hybrid or MS polymer technology — borrowing a polyurethane’s bonding strength and a silicone’s UV stability without either one’s drawbacks: no isocyanate fumes on cure, no acetic smell, and unlike acetoxy silicone, it takes paint once cured. Dr. Fixit sells it under Feviseal, Pidilite’s dedicated sealants brand, grading it “high modulus” — it builds strength fast and holds a joint firmly, which is why the datasheet lists it as sealant AND adhesive.
On site, this is the tube reached for when a joint has to hold something, not just keep water out — cladding trims, roof tile fixing, frame-to-masonry bonding, metal-to-concrete facade joints, duct cover plates. It’s rated for permanent elastic bonding across metals, rubber, wood, stone, glass, tile and most plastics, ships as a 600 ml sausage, cures at about 3.5 mm/day, and handles joints up to 30 mm wide at the right width-to-depth ratio. Space Arc typically specifies it for facade and precast joints across Delhi NCR, keeping softer Feviseal HY 100 or plain acetoxy silicone for cosmetic joints that don’t need structural bite.
The technical insight
The number worth reading twice is the ±25% Movement Accommodation Factor, backed by ISO 11600 Type F25HM, ASTM C920 Type S/NS/25T, and BS 5212-1:1990 — three classifications landing on the same figure. At 1.35±0.15 g/cm³ density, ~1.8 MPa tensile strength and Shore A 40±5, it sits in “high modulus” territory: stiffer than low-modulus sealants built purely for movement absorption. That’s the trade-off — it holds a bonded joint well, but a low-modulus product fatigues less under constant low-load movement. Tack-free time exceeds 30 minutes, and the -40°C to +100°C service range covers a Delhi winter to a sun-baked parapet unchanged.
Where it is used
- Expansion, control and movement joints in facades and precast panels
- Metal-to-metal and metal-to-concrete structural bonding
- Roof tile fixing and lightweight construction bonding
- Door and window frame bonding to masonry, wood or metal
- Cover plates and gaskets over duct openings in walls or floors
- Bolted lap joints and aluminium fabrication seams
- Non-immersion joint sealing on ducts, tanks and silos
Key advantages
- High modulus with real adhesive-grade strength — sealant and structural bond in one
- ±25% Movement Accommodation Factor backed by ISO 11600, ASTM C920 and BS 5212-1
- Paintable with common industrial paints once cured, unlike acetoxy silicone
- Non-staining, including resistance to hydrophobic staining on natural stone
- Damp-tolerant with good low-temperature gun-ability
- Bonds an unusually wide substrate range — metal, rubber, wood, stone, glass, tile, plastic
- Low dirt pick-up keeps exposed joints cleaner over time
Limitations & considerations
- Capped at 30 mm joint width — not a substitute for dedicated wide expansion-joint systems
- Needs primer (Pidiprime A) for joints in constant water contact; not immersion-grade
- Won’t bond over bitumen residue, release agents or other surface contamination
- Ex-stock colours limited to grey and white; other shades made-to-order
- Apply only between 5-40°C, and use the opened sausage within 24 hours
Selection & best practice
Get joint geometry right first: 1:1 width-to-depth for 6-12 mm joints, 2:1 for 12-30 mm — wrong geometry is the most common cause of premature failure on Indian sites. Clean back to a sound, dry substrate (xylene degreases well), and always use a backer rod so the bead bonds only to the two opposite faces, not the base, or it tears on movement. Most substrates need no primer; joints in constant water contact need Pidiprime A. Tool the bead within the ~30-minute tack-free window and pull masking tape right after. In peak Delhi summer, avoid gunning in direct sun; in winter, condition sausages at ~20°C for 24 hours first.
Specifications
| Chemical base | Silyl Modified Polyurethane (SMP hybrid), one-part moisture curing |
| Standards compliance | ISO 11600 Type F25HM; ASTM C920 Type S, Grade NS, Class 25T, Type FB; BS 5212-1:1990 |
| Density | 1.35 ± 0.15 g/cm³ |
| Tensile strength | Approx. 1.8 MPa |
| Elongation at break | Minimum 400% |
| Movement Accommodation Factor | ± 25% |
| Shore A hardness | 40 ± 5 |
| Application / service temperature | 5°C-40°C application; -40°C to +100°C service |
| Pack size & coverage | 600 ml sausage; ~24 lm at 5×5 mm joint or ~6 lm at 10×10 mm joint |
Industry use cases
Commercial facade construction
Sealing precast panel and curtain-wall movement joints needing ±25% flex without losing adhesion to concrete or aluminium framing
Industrial roofing
Bonding and sealing metal roof tile laps exposed to Delhi’s summer heat and monsoon cycling
Door and window installation
Structural bonding of aluminium/UPVC frames to masonry openings on fit-outs
Utility and ducting work
Sealing gaskets and cover plates around service duct penetrations on large projects
Aluminium fabrication
Bolted lap joints needing a paintable, non-staining structural seal
Frequently asked questions
Is Feviseal HY 300 a silicone sealant?
Can I paint over it?
Does the joint need a primer first?
What’s the widest joint it can handle?
How long before it’s cured enough for rain or traffic?
What’s the shelf life of an opened sausage?
How we position Dr. Fixit Feviseal HY 300
Feviseal HY 300 is the structural end of Pidilite’s Feviseal range — pair it with softer Feviseal HY 100 for joints that move more than they bear load, or Feviseal GP Pro acetoxy silicone for cosmetic sanitary and glazing joints. Space Arc stocks and applies this family alongside Dr. Fixit’s waterproofing range, so a facade or roofing job can run as one system. Where a spec genuinely calls for water-immersion service — tanks, reservoirs, STPs — Fosroc’s Nitoseal MS600 is worth evaluating: same hybrid MS polymer chemistry, engineered for permanent immersion with WRAS potable-water approval, a claim HY 300’s own datasheet doesn’t make. For lower-modulus PU movement joints, Fosroc’s Nitoseal PU40 is another name specifiers sometimes shortlist.
Fosroc Nitoseal MS600 — For joints in permanent or intermittent water immersion — tanks, reservoirs, STPs — where WRAS potable-water approval is a specification requirement, Nitoseal MS600’s purpose-built immersion-grade MS polymer formulation is the more defensible choice, since Feviseal HY 300’s own datasheet calls for a primer on constantly wet joints rather than claiming immersion service.
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