Orthophthalic Cooling Tower Grade Resin data sheet (PDF)Ask for a quote
The lay-up problem this grade solves
FRP cooling towers are made of large mouldings — casing panels, fan stacks, basins and louvre frames — and much of that surface is laid up vertically or at a steep angle. A resin that flows freely will drain down such a face before it gels. The upper laminate is left short of resin and the lower laminate is left with runs and excess.
SPR 201 CTG is the orthophthalic answer to that problem in Samrat Poly Resins’ 2026 catalogue: a thixotropic grade listed for cooling-tower FRP components, wind-turbine FRP components and sag-resistant lay-up on vertical surfaces.
Thixotropy, explained plainly
A thixotropic resin changes its apparent thickness with handling. When it is brushed, rolled or sprayed, it thins and wets the glass. Left alone on the mould, it recovers its body and resists flowing downhill. That behaviour is engineered into the resin; it is not the same as simply using a thicker resin, which would wet glass poorly.
For a laminator the practical test is simple: does the resin stay where it was rolled, at the thickness of each stage, until it gels? The answer depends on the mould angle, the reinforcement, the stage thickness and the workshop temperature, which is why the catalogue asks for confirmation on the real mould.
Orthophthalic chemistry and what it implies
Orthophthalic polyester is the general-purpose family, built on phthalic anhydride. It is economical and widely used for tanks, sheets and moulded parts that do not face hot or aggressive service. The catalogue’s selection guide notes that CTG shares its typical liquid values with the general laminating grade SPR 201 GPC; its thixotropy is what sets it apart.
A cooling tower is not only a lay-up problem, though. Circulating water can be warm and chemically treated. Where that service is part of the specification, the catalogue points to the isophthalic SPR 301 CT, which combines thixotropy with the chemistry it lists for heat, chemical and corrosion resistance.
Wind-energy components, and what is not included
The catalogue also lists wind-turbine FRP components for CTG. Covers, housings and similar non-primary parts are made by open-mould lay-up in the same way as cooling-tower panels. Blades are a different matter: primary blade structures are normally built to the turbine maker’s qualified resin system, and they are not a listed application for this grade.
Questions to settle before choosing CTG
Which part is being made, and at what angle is it laid up? What reinforcement and stage thickness will be used? What water will the part see in service, and at what temperature? Is there a customer or design specification naming a resin family? Those four answers decide whether CTG, the isophthalic CT or another grade is the right starting point.