Fire-Retardant Gelcoat for Rail, Transport and Automotive FRP Surfaces

The catalogue lists SPR 201 FR-GC for rail and metro composite components, automotive FRP components and surface gelcoat for fire-retardant FRP laminates, and SPR 401 FRGC for fire-retardant gelcoat surfaces on rail and transport composite components, automotive composite components and fire-retardant moulded FRP parts. Typical makers are fabricators of interior and exterior panels, covers and moulded parts for vehicles and transport, and of other moulded parts where a fire-retardant construction is specified. For the laminate side of such panels, see the fire-retardant FRP panels and cladding guide.

Both grades are thixotropic, so they hold on the mould face without running. SPR 201 FR-GC is listed as a milky white to grey opaque liquid (custom-tinted variants where supplied), 5,000–11,000 cPs at high shear and 30,000–45,000 cPs at low shear at 25 °C, gel time 9–16 minutes, specific gravity 1.35–1.55 and 17–25% styrene by weight. SPR 401 FRGC is an opaque, thick pigmented liquid in white, grey or custom colour, 12,000–18,000 cPs at 2 rpm and 2,000–3,500 cPs at 20 rpm, thixotropic index 4.5–6.0, gel time 12–22 minutes, density 1.25–1.45 g/cm³ and 28–35% styrene, with strong mechanical properties listed. Their cure references differ, as described below. Neither gelcoat gives a part a fire rating: the finished construction is tested to the standard the project names. Choose by the project’s laminate chemistry, colour and test requirement; the ortho vs terephthalic FR gelcoat comparison and the hubs for SPR 201 FR-GC and SPR 401 FRGC explain each.

The mould is cleaned and released, the gelcoat is catalysed and applied to the mould face in an even film, and it is left to gel before the fire-retardant laminate is laid up behind it. The application method and film thickness are not published for these grades; confirm them on enquiry. The cure references differ. For SPR 201 FR-GC the catalogue lists MEKP 1.5–2.0% added during use, and no accelerator is listed in its reference cure — confirm the full cure system for your process on enquiry rather than assuming one. For SPR 401 FRGC the reference cure is MEKP 1.5% with cobalt octoate 0.4%. The peroxide and the cobalt accelerator are added to the resin separately, one after the other with mixing in between; a concentrated peroxide is never mixed directly with cobalt. The figures are typical catalogue values that describe the grade, not batch guarantees, and dosage for your workshop temperature is settled by trial.