Quick facts
- Grades compared
- SPR 201 FR (halogenated) · SPR 201 FR (HF) · SPR 301 FR
- Halogen-free options
- One orthophthalic (SPR 201 FR (HF)), one isophthalic ATH-filled (SPR 301 FR)
- Fire ratings
- None published; the finished part is tested to the project’s standard
- Deciding factor
- What the project specification requires
What differs
The three grades reach fire retardancy by different formulations. Fire Retardant Resin (SPR 201 FR) uses a halogenated fire-retardant formulation. SPR 201 FR (HF) is a halogen-free fire-retardant grade in the orthophthalic family. ISO Fire Retardant Resin (SPR 301 FR) is halogen-free and ATH-filled on an isophthalic-based backbone; “ISO” means isophthalic, not an ISO certification.
Their published processing values also differ. The two TDS grades list 400 cPs and a 5.5-minute gel time; SPR 201 FR (HF) lists 1,500–3,500 cPs and 15–30 minutes at 25 °C, with a higher specific gravity of 1.25–1.45. That affects wet-out, working time and how the laminate is laid.
How to decide
The project specification decides, not the resin label. First establish whether the specification requires halogen-free materials. If it does not, and it calls for fire retardancy, the halogenated Fire Retardant Resin is a listed route. If it requires halogen-free, choose between SPR 201 FR (HF) and SPR 301 FR by the laminate’s other needs: an isophthalic base where the part also faces water or chemical exposure, or where the specification names it; the orthophthalic halogen-free grade where it does not.
Then plan to test. Whichever resin is chosen, the finished laminate — with its reinforcement, thickness, gelcoat and any filler — is what has to meet the fire standard the project names.
What the data does not tell you
No fire rating, flame-spread class, smoke or toxicity figure, or standard is published for any of the three. “Fire retardant” and “halogen-free” describe the formulation, not the performance of a finished part, and none of these resins makes a part fireproof.
The viscosity figures are not a like-for-like comparison: the two TDS grades publish 400 cPs without a stated temperature, while SPR 201 FR (HF) states 25 °C, and the sources differ. Confirm current documents and run a processing trial before relying on the difference.
Sources, roles and the Nepal enquiry path
SPR 201 FR (HF) values are the typical specification printed in the supplier’s 2026 product catalogue; no Technical Data Sheet for it has been published on this site. Fire Retardant Resin and ISO Fire Retardant Resin values are from their Technical Data Sheets as shown on their product pages.
Samrat Poly Resins, India manufactures the grade and issues its technical information. Samrat FRP Traders is the Nepal supplier and importer and handles enquiries; price, packaging, lead time and stock in Nepal are confirmed on enquiry.
Three fire-retardant resins side by side
| Criterion | SPR 201 FR | SPR 201 FR (HF) | SPR 301 FR |
|---|---|---|---|
| Fire-retardant route | Halogenated formulation | Halogen-free | Halogen-free, ATH-filled |
| Base chemistry | Unsaturated polyester | Orthophthalic polyester | Isophthalic-based polyester |
| Appearance | White liquid | White to light-yellow opaque liquid | White liquid |
| Viscosity | 400 cPs | 1,500–3,500 cPs at 25 °C | 400 cPs |
| Gel time | 5.5 minutes | 15–30 minutes at 25 °C | 5.5 minutes |
| Styrene · specific gravity | 35% · not published | 30–40% · 1.25–1.45 | 35% · 1.18 |
| Cure | Room-temperature cure with MEKP catalyst | Non-accelerated; MEKP 1.5% + cobalt octoate 0.4%, added separately | Room-temperature cure with MEKP catalyst |
| Listed uses | Automotive and railway components, marine and electrical uses, FRP panels, building components | Halogen-free fire-retardant laminates, marine composite components, uses specifying halogen-free fire retardancy | Railway and marine uses, automotive fire-performance parts, FRP panels, electrical enclosures, tunnels, construction |
| Choose when… | The project specifies fire retardancy and does not exclude halogens | The project specifies halogen-free and an orthophthalic laminate meets its other requirements | The project specifies halogen-free and the laminate also needs an isophthalic base |
Sources: SPR 201 FR (HF) — Samrat Poly Resins, India product catalogue, 2026 edition (typical specification); Fire Retardant Resin and ISO Fire Retardant Resin — each product’s supplier Technical Data Sheet as published on this site. None of these values is a fire rating. Typical values describe each grade; they are not batch guarantees or acceptance limits.
Frequently asked questions
Is a halogen-free resin more fire resistant than a halogenated one?
Not necessarily. Halogen-free describes how fire retardancy is achieved, not how well a part performs. The finished laminate’s test against the project’s standard decides.
What is the difference between SPR 201 FR (HF) and SPR 301 FR?
Both are halogen-free. SPR 201 FR (HF) is orthophthalic; SPR 301 FR (ISO Fire Retardant Resin) is isophthalic-based and ATH-filled, with different published processing values.
Can you tell me which grade passes my fire standard?
No resin record here carries a fire rating. Send the standard and the part build-up with your enquiry; the finished part has to be tested to that standard.
Do I also need a fire-retardant gelcoat?
Often the surface layer is part of what is tested. The range carries fire-retardant gelcoats, and the catalogue pairs a fire-retardant gelcoat with the fire-retardant laminating resin of the same project.