Choosing a DMC resin
DMC parts range from simple electrical boxes to intricate switchgear components and fittings. The catalogue offers DMC resins in the three polyester families and chooses among them by what the compound and part require.
How the three differ
The orthophthalic option is the DMC/SMC Resin, with a published TDS. SPR 301 DMC is isophthalic and shares the catalogue’s combined SMC / DMC specification with SPR 301 SMC. SPR 401 DMC is terephthalic, with its own specification: more viscous, with a slightly longer ambient gel time, and listed for complex moulded FRP parts.
Published typical values
| Property | DMC/SMC Resin (SPR 201 SMC · DMC) | Isophthalic DMC Resin (SPR 301 DMC) | Terephthalic DMC Resin (SPR 401 DMC) |
|---|---|---|---|
| Chemistry | Orthophthalic unsaturated polyester resin | Isophthalic unsaturated polyester | Terephthalic unsaturated polyester |
| Viscosity (typical) | 600 cPs (at 25°C) | 800–1,400 cPs at 25 °C | 1,200–2,200 cPs at 25 °C |
| Gel time / pot life (typical) | 12–18 minutes (at 25°C; review current TDS for test context) | 12–18 minutes at 25 °C | 14–22 minutes at 25 °C (ambient QC) |
| Styrene content (typical) | 35% | 31–36% by weight | 31–36% by weight |
| Reference cure | Not published | MEKP 1.5% + Cobalt Octoate 0.4% — added separately during use | MEKP 1.5% + Cobalt Octoate 0.5% — added separately during use |
| Source of values | DMC/SMC Resin TDS | 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.
Viscosity and the dough
In a dough compound, resin viscosity is one of the levers that sets body and flow at a given filler loading. A more viscous base resin such as SPR 401 DMC changes how the dough mixes and fills the tool. That can suit a particular formulation; it is not an improvement in itself.
Confirm on moulded parts
Electrical, mechanical, heat and flammability performance belong to the formulated, moulded compound. When the family choice is not obvious, compound and mould specimens with the candidate resins and test them against the part’s requirement.