Where FRP appears in wind energy
A wind turbine carries a good deal of composite beyond its blades. Nacelle covers, spinner or hub covers, access hatches, cable-management parts, internal platforms and enclosures are commonly moulded in glass-reinforced plastic, and many are large open-mould parts laid up by hand or spray.
The 2026 catalogue lists two polyester grades for this area: the orthophthalic SPR 201 CTG for wind-turbine FRP components and the isophthalic SPR 301 CT for wind-energy composite components. Both are thixotropic, because the parts are large and much of their surface is laid up at steep angles.
What is outside the scope
Primary blade structures are not a listed application for either grade. Blades are normally built to the turbine maker’s own qualified resin system and laminate specification, and they are commonly epoxy-based. A buyer making a blade-related part should confirm with the turbine maker what system is specified before approaching any resin supplier.
For epoxy work outside the blade structure, Samrat’s Fiberglass Epoxy Resin lists wind-turbine components among its published application contexts. That listing is not a blade qualification; the turbine maker’s specification still decides.
Questions to settle first
Component and service questions
- Which component is it, and does the turbine maker specify a resin family or qualification?
- Is the part inside the nacelle or exposed outside at height?
- Will it see coastal, offshore or industrial atmosphere?
- What is the lay-up angle and the laminate thickness per stage?
- Is a gelcoat specified for the outer surface, and which one?
Choosing between CTG and CT
SPR 201 CTG is the orthophthalic choice where sag-resistant lay-up is the main requirement. Its gel time, under 8 minutes typical at the reference cure, is short, which suits smaller stages and quick turnarounds.
SPR 301 CT adds isophthalic chemistry, which the catalogue specifies for heat, chemical and corrosion resistance, and a longer typical gel time of 15–35 minutes at 25 °C that suits large panels built in stages. Exposed exterior parts in harsh atmospheres, or a specification that names isophthalic resin, point towards CT.
Published typical values
| Property | Orthophthalic Cooling Tower Grade Resin (SPR 201 CTG) | Isophthalic Cooling Tower Grade Resin (SPR 301 CT) |
|---|---|---|
| Chemistry | Orthophthalic unsaturated polyester | Isophthalic unsaturated polyester |
| Viscosity (typical) | 350–450 cPs | 400–650 cPs (60 rpm); 1,500–2,000 cPs (6–12 rpm) |
| Thixotropy | Not published | 2.0–3.5 |
| Gel time / pot life (typical) | Under 8 minutes | 15–35 minutes at 25 °C |
| Styrene content (typical) | 33–40% | 37–45% by weight |
| 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.
Limits and trials
The catalogue publishes liquid-resin typical values for both grades, not laminate mechanical, fatigue or weathering data. Wind components are often subject to their customer’s own material qualification, so the resin choice may need to pass that process regardless of what the datasheet shows.
Trial on the real mould: check sag at the full stage thickness on the steepest face, wet-out of the reinforcement used, and the surface under the chosen gelcoat. Record temperature and working time, because a nacelle mould in a cold shop and one in summer behave differently.