Isophthalic Cooling Tower Grade Resin data sheet (PDF)Ask for a quote
Two demands on one cooling-tower part
A cooling-tower moulding has to survive two things. During manufacture it is laid up on large, often vertical mould faces, where the resin must not drain. In service it lives in warm, humid air and is splashed or wetted by circulating water that is usually dosed with treatment chemicals.
SPR 301 CT is the isophthalic grade the 2026 catalogue lists for that combination: thixotropic for the lay-up, isophthalic for the service. It is also listed for wind-energy composite components.
Reading the viscosity and thixotropic index
The catalogue gives SPR 301 CT two viscosity figures: 400–650 cPs measured at 60 rpm and 1,500–2,000 cPs at 6–12 rpm. A rotational viscometer spinning fast shears the resin, as a roller does; spinning slowly, it approximates the resin resting on the mould. The gap between the two readings is the thixotropy.
The thixotropic index, 2.0–3.5 for this grade, expresses that gap as a ratio of the low-speed to high-speed readings. A higher index means a stronger recovery at rest. It is a comparative laboratory figure; the proof of sag resistance is still the real mould.
Why isophthalic chemistry
Isophthalic polyesters are built on isophthalic acid rather than the phthalic anhydride of orthophthalic grades. The catalogue specifies its SPR 301 family where a laminate faces water immersion, chemical service or sustained outdoor conditions, which describes a cooling tower’s working life.
That is positioning, not a promise for every water. The catalogue does not publish a maximum water temperature or a chemical-resistance chart for SPR 301 CT, so the circulating-water temperature and treatment programme belong in the enquiry.
A longer working window
At the reference cure — MEKP 1.5% with cobalt octoate 0.4%, each added separately — the typical gel time is 15–35 minutes at 25 °C. That is considerably longer than the under-8-minute figure of the orthophthalic SPR 201 CTG, which suits large panels laid up in stages but needs to be planned into production timing.
Information that helps a recommendation
Describe the part and its lay-up angle, the reinforcement and stage thickness, the water temperature and treatment chemicals, and any design specification. With those, the technical team can say whether SPR 301 CT, the orthophthalic CTG or a vinyl ester is the right starting point for a trial.