Quick facts
- Grades compared
- DMC/SMC Resin (SPR 201) · SPR 301 DMC · SPR 401 DMC
- Chemistries
- Orthophthalic · isophthalic · terephthalic
- Grade with its own DMC specification
- SPR 401 DMC: 1,200–2,200 cPs, 14–22 min, cobalt 0.5%
- Deciding factor
- Part geometry and the heat, chemical and electrical demands of its service
What differs
DMC is a bulk, dough-form compound pressed into compression-moulded parts. Each of the three polyester families offers a resin for it, and the way the specification is published differs. The orthophthalic DMC/SMC Resin is one TDS grade for both DMC and SMC. SPR 301 DMC shares one typical specification with SPR 301 SMC, although the two are separate products. SPR 401 DMC has its own specification: higher viscosity (1,200–2,200 cPs at 25 °C), a longer ambient gel time (14–22 minutes) and a reference cobalt dosage of 0.5% rather than 0.4%.
The terephthalic DMC grade is also the only one of the three that lists complex moulded FRP parts among its uses.
How to decide
Start from the moulded part and its service. For general-purpose DMC parts — housings, covers and similar — where the compound is already formulated around an orthophthalic resin, DMC/SMC Resin is the documented route. If the part’s specification or service calls for an isophthalic resin, review SPR 301 DMC. If the specification is terephthalic, or complex part geometry needs the longer ambient gel window, review SPR 401 DMC.
Do not carry SMC settings over to DMC, or one family’s settings to another: viscosity and reference cure differ, so compound mixing and press conditions should be confirmed with a trial.
What the data does not tell you
The gel times are ambient 25 °C figures; heated-mould cure behaviour is not published for any of the three. No mechanical, electrical or heat-deflection figures are published for a finished DMC part, so claims such as suitability for electrical housings belong to the compound and part testing, not to the resin data alone.
The orthophthalic values come from a TDS and the other two from the 2026 catalogue. Confirm current documents before ordering.
Sources, roles and the Nepal enquiry path
SPR 301 DMC and SPR 401 DMC values are the typical specification printed in the supplier’s 2026 product catalogue; no Technical Data Sheet for either has been published on this site. DMC/SMC Resin values are from its Technical Data Sheet as shown on its product page.
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.
Three DMC resins side by side
| Criterion | DMC/SMC Resin (SPR 201) | SPR 301 DMC | SPR 401 DMC |
|---|---|---|---|
| Chemistry | Orthophthalic polyester | Isophthalic polyester | Terephthalic polyester |
| How the specification is published | One TDS grade covering DMC and SMC contexts | Shares one typical specification with SPR 301 SMC; still a separate product | Its own specification, different from SPR 401 SMC |
| Viscosity | 600 cPs at 25 °C | 800–1,400 cPs at 25 °C | 1,200–2,200 cPs at 25 °C |
| Gel time | 12–18 minutes at 25 °C | 12–18 minutes at 25 °C | 14–22 minutes at 25 °C (ambient QC) |
| Styrene · specific gravity | 35% · 1.12 | 31–36% · 1.10–1.14 | 31–36% · 1.11–1.15 |
| Supply and reference cure | Non-accelerated; cure as stated in the supplier TDS | Non-accelerated; MEKP 1.5% + cobalt octoate 0.4%, added separately | Non-accelerated; MEKP 1.5% + cobalt octoate 0.5%, added separately |
| Listed uses | DMC/SMC compounds; electrical housings, manhole covers, automotive panels, water tanks, sanitaryware | DMC production; compression-moulded composite components | DMC production; compression-moulded components; complex moulded FRP parts |
| Choose when… | A general-purpose DMC part and a compound built around orthophthalic resin | The DMC part needs an isophthalic resin by its service or specification | The part is terephthalic by specification, or complex moulding needs its longer ambient gel window |
Sources: SPR 301 DMC and SPR 401 DMC — Samrat Poly Resins, India product catalogue, 2026 edition (typical specification); DMC/SMC Resin — its supplier Technical Data Sheet as published on this site. Typical values describe each grade; they are not batch guarantees or acceptance limits.
Frequently asked questions
Are SPR 301 DMC and SPR 301 SMC the same resin?
The catalogue publishes one shared typical specification for them, but they are separately manufactured products. Order the one that matches your compound.
Why does SPR 401 DMC use 0.5% cobalt?
That is the reference cure printed in the catalogue for this grade. It is a reference for quality control; the initiator and accelerator are always added separately.
Is higher viscosity a problem for DMC?
Not in itself. Viscosity affects filler loading and mixing, so the compound formulation has to be balanced for the resin chosen and confirmed by trial.
Can the orthophthalic resin make electrical housings?
The DMC/SMC Resin documentation lists electrical housings among its uses. Whether a particular housing meets its requirement is decided by testing the finished part.