Two continuous-fibre processes
Filament winding and pultrusion both use continuous roving, which gives strong, efficient laminates, and both impregnate it from a resin bath. There the similarity ends. Winding lays fibre onto a rotating mandrel to build a hollow shape and cures it, usually at ambient temperature, after the wind. Pultrusion pulls fibre through a heated die and cures a constant profile continuously in seconds.
Why each needs its own resin
A winding resin must wet roving fast and stay workable for the whole wind: SPR 301 FW is non-thixotropic, 200–400 cPs at 25 °C typical, with a gel time of 20–60+ minutes at 25 °C at its MEKP and cobalt reference cure.
A pultrusion resin must stay stable in the bath and then cure within seconds in the die: SPR 401 PT is specified by a hot-die gel time of 40–80 seconds at 130–140 °C, cured by a heat-activated peroxide blend with 0% production MEKP and 0% production cobalt.
Published typical values
| Property | Filament Winding Grade Resin (SPR 301 FW) | Pultrusion Grade Resin (SPR 401 PT) |
|---|---|---|
| Chemistry | Isophthalic unsaturated polyester | Terephthalic unsaturated polyester |
| Viscosity (typical) | 200–400 cPs at 25 °C | 300–600 cPs at 25 °C |
| Gel time / pot life (typical) | 20–60+ minutes at 25 °C | 40–80 seconds at 130–140 °C (Hot-Die); 15–25 minutes at 25 °C (Ambient QC) |
| Specific gravity / density (typical) | 1.04–1.14 | 1.10–1.14 |
| Styrene content (typical) | 35–45% by weight | 36–42% by weight |
| Reference cure | MEKP 1.5% + Cobalt Octoate approximately 0.4% — added separately during use | Heat-activated peroxide blend, total dosage 1.0–2.0% — added separately during processing |
| Source of values | 2026 catalogue; grade TDS | 2026 catalogue; grade TDS |
Typical values, reproduced from each product’s own published data. They describe the liquid resin at its reference condition, not a finished part, and are not guaranteed limits.
Choosing
The product shape usually decides the process, and the process decides the resin. Where the service is corrosive, vinyl ester is used in both processes; see the vinyl ester routes for filament winding and pultrusion.