Halogen-Free Fire-Retardant Resin data sheet (PDF)Ask for a quote
Two ways to make a polyester fire-retardant
A standard polyester laminate burns. Fire-retardant resins change that behaviour, broadly in one of two ways. Halogenated systems use chlorine- or bromine-containing chemistry, which interferes with the flame reactions in the gas phase. Halogen-free systems avoid those elements and rely on other mechanisms, commonly mineral fillers that release water when heated and dilute the fuel.
SPR 201 FR (HF) is the halogen-free grade of Samrat Poly Resins’ orthophthalic SPR 201 series. The catalogue lists it for halogen-free fire-retardant FRP laminates, marine composite components and applications specifying halogen-free fire retardancy.
Why specifications ask for halogen-free
When halogenated materials burn, their smoke can contain acidic and corrosive gases. For enclosed spaces people have to escape from — rail carriages, metro cars, ships, some buildings — specifications may limit smoke toxicity and therefore restrict halogenated flame retardants. That is why the catalogue lists a halogen-free grade alongside the halogenated SPR 201 FR.
The point for a buyer is to follow the specification. Halogen-free is the route where it is required, not an automatic improvement where it is not.
What the typical values show
SPR 201 FR (HF) is opaque, white to light yellow, with a typical viscosity of 1,500–3,500 cPs at 25 °C and specific gravity of 1.25–1.45. Those figures describe a filled resin, heavier and thicker than a clear laminating grade, which affects how it wets reinforcement and how laminates are built.
Its gel time is 15–30 minutes at 25 °C typical and styrene content 30–40%, at the reference cure of MEKP 1.5% with cobalt octoate 0.4%, each added separately.
Why no fire rating is quoted for the resin
Fire tests are run on a specimen of a defined construction: gelcoat, laminate, thickness and sometimes core. The classification that results belongs to that build. The same resin in a thinner laminate, with a different gelcoat or a different glass content, can classify differently.
For that reason the catalogue calls SPR 201 FR (HF) fire-retardant and publishes no classification for it. A project that names a standard — rail, marine or building — should share it, so the grade can be discussed against the test the finished part must pass.