Quick facts
- Grades compared
- SPR 201 CTG (orthophthalic) · SPR 301 CT (isophthalic)
- Shared role
- Sag-resistant lay-up for cooling-tower and wind-energy FRP
- Deciding factor
- Water quality, chemical treatment and heat the tower sees
What differs
Both grades exist for the same job: resin that stays where it is laid on the vertical and large surfaces of cooling-tower and wind-energy parts. The difference is the chemistry. SPR 201 CTG is orthophthalic and shares GP Clear’s published viscosity, gel time and styrene values. SPR 301 CT is isophthalic, and the catalogue lists it with heat, chemical and corrosion resistance and high strength.
The processing windows also differ: SPR 201 CTG gels in under 8 minutes, SPR 301 CT in 15–35 minutes at 25 °C, which changes how much area a crew can wet out before the resin gels.
How to decide
Describe the tower before choosing. If the circulating water is clean, untreated and at moderate temperature, and the part mainly needs sag-resistant lay-up, the orthophthalic SPR 201 CTG is the grade listed for that role. If the water is chemically treated, hard or contaminated, the tower runs hot for long periods, or the owner’s specification calls for isophthalic, choose SPR 301 CT.
Plan the lay-up to the gel time as well: large panels laid by a small crew may suit the longer window of SPR 301 CT; shorter cycles may suit SPR 201 CTG. Confirm either choice with a trial on your own mould and conditions.
What the data does not tell you
SPR 201 CTG publishes one viscosity figure without a shear condition; SPR 301 CT publishes two readings at stated spindle speeds plus a thixotropic index. The numbers therefore cannot be set against each other to say which grade sags less — only a trial on a vertical surface shows that. SPR 201 CTG has no published specific gravity.
Neither record publishes a service-temperature limit, a water-chemistry limit or mechanical figures for a finished tower part. “Heat, chemical and corrosion resistance” is catalogue wording for SPR 301 CT, not a rating.
Sources, roles and the Nepal enquiry path
Both grades are described by the typical specification printed in the supplier’s 2026 product catalogue. Samrat Poly Resins has since published a Technical Data Sheet for each grade; both are linked from their product pages and agree with the catalogue figures.
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.
Two cooling-tower grades side by side
| Criterion | SPR 201 CTG | SPR 301 CT |
|---|---|---|
| Chemistry | Orthophthalic polyester | Isophthalic polyester |
| Thixotropy and supply | Described as a thixotropic grade; supplied non-accelerated | Non-accelerated, thixotropic; thixotropic index 2.0–3.5 |
| Viscosity | 350–450 cPs (single published figure) | 400–650 cPs at 60 rpm; 1,500–2,000 cPs at 6–12 rpm |
| Gel time | Under 8 minutes | 15–35 minutes at 25 °C |
| Styrene · specific gravity | 33–40% · not published | 37–45% by weight · 1.10–1.15 |
| Reference cure | MEKP 1.5% + cobalt octoate 0.4%, added separately | MEKP 1.5% + cobalt octoate 0.4%, added separately |
| Listed uses and properties | Cooling-tower and wind-turbine FRP components; sag-resistant lay-up on vertical surfaces | Cooling-tower and wind-energy composite components; heat, chemical and corrosion resistance, high strength |
| Choose when… | The part needs sag-resistant lay-up and the tower’s water and chemical conditions are mild | The tower sees treated or aggressive water, chemicals or sustained heat, or the owner specifies isophthalic |
Source: Samrat Poly Resins, India product catalogue, 2026 edition (typical specification) for both grades. The two viscosity entries are measured differently and are not directly comparable. Typical values describe each grade; they are not batch guarantees or acceptance limits.
Frequently asked questions
Which grade sags less on a vertical surface?
The published data cannot answer that: the two viscosity figures are measured differently. Run a trial on a vertical panel with your own reinforcement, film build and temperature.
Is SPR 201 CTG just GP Clear with an additive?
The catalogue lists it as its own thixotropic grade that shares GP Clear’s published viscosity, gel time and styrene values. No formulation is published, so treat it as a separate grade.
Does the isophthalic grade suit every cooling tower?
It is listed with heat, chemical and corrosion resistance, but suitability depends on the water chemistry, treatment chemicals and temperature of the specific tower. State those when you enquire.
Can the two grades be used in the same tower?
That is a design decision for the tower maker, based on which parts face water and chemicals. Any combination should be confirmed by trial and by the owner’s specification.