Quick facts
- Catalogue code
- SPR 401 TL
- Chemistry
- Isophthalic NPG (neopentyl glycol)-based polyester — not terephthalic
- Role
- Composite mould production; tooling and die preparation
- Supply
- Non-accelerated · moderately thixotropic
A resin for making moulds
An FRP mould is itself a laminate, and every part taken from it copies its surface. SPR 401 TL is the grade the catalogue lists for composite mould production and tooling and die preparation. It is described as a highly reactive, high-molecular-weight isophthalic NPG (neopentyl glycol)-based polyester resin.
Why an isophthalic grade has an SPR 401 code
The catalogue states that SPR 401 TL is retained within the SPR 401 code range and is not a terephthalic grade. The code is a catalogue number; the chemistry is isophthalic. That is why this site lists it with the isophthalic family while keeping its code unchanged.
Reading the published values
The catalogue lists an opaque, cloudy to milky liquid with a viscosity of 400–650 cPs at 60 rpm and 1,500–2,500 cPs at 6 rpm, a thixotropic index of 2.5–3.8, a gel time of 15–30 minutes at 25 °C, a specific gravity of 1.12–1.16 and 35–42% styrene by weight. It is supplied non-accelerated and moderately thixotropic, with a reference cure of MEKP 1.5% and cobalt octoate 0.4%, each added separately.
Limitations and alternatives
Mould life, surface quality and dimensional stability depend on the pattern, the mould gelcoat, the laminate schedule, the cure and how the mould is used — no mould-life figure is published for the resin. For ordinary production laminates, a general laminating grade is the usual choice; the comparison guide on general laminating vs tooling grade resin explains the difference.
Source, roles and the Nepal enquiry path
The values on this page are the typical specification printed for SPR 401 TL in the supplier’s 2026 product catalogue. Samrat Poly Resins has since published a Technical Data Sheet for this grade, linked from the product page; its figures and the catalogue’s agree, and the catalogue is the source named beside every figure here.
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.
Key properties
| Property | Typical value |
|---|---|
| Appearance | Opaque, cloudy to milky liquid |
| Viscosity — 60 rpm | 400–650 cPs |
| Viscosity — 6 rpm | 1,500–2,500 cPs |
| Thixotropic index | 2.5–3.8 |
| Gel time | 15–30 minutes at 25 °C |
| Specific gravity | 1.12–1.16 |
| Styrene content | 35–42% by weight |
| Supply condition | Non-accelerated · moderately thixotropic |
| Reference cure system | MEKP 1.5% + Cobalt Octoate 0.4% — added separately during use |
Source: Samrat Poly Resins, India — product catalogue, 2026 edition (typical specification). Typical values describe the grade; they are not batch guarantees or acceptance limits.
Frequently asked questions
Is SPR 401 TL a terephthalic resin?
No. It is an isophthalic NPG-based polyester retained within the SPR 401 code range.
What does NPG mean?
Neopentyl glycol, the glycol on which this isophthalic polyester is based, as stated in the catalogue.
Can I use it for production parts?
The catalogue lists it for mould production and tooling. Production laminates normally use a general laminating grade; ask before using it outside its listed role.