Application guide

Resin for Dough Moulding Compound (DMC) Production

How DMC dough is mixed and how a compounder chooses between the orthophthalic, isophthalic and terephthalic DMC resins in the range.

A dedicated DMC grade in each of three chemistries.

Dough moulding compound (DMC) is a bulk dough of resin, filler, chopped glass and additives, mixed rather than spread, then weighed into charges and moulded under heat and pressure. This guide covers making the dough and choosing its resin; pressing the parts is covered in DMC and SMC compression moulding. The range offers three DMC resin routes: the orthophthalic DMC/SMC Resin, the isophthalic Isophthalic DMC Resin (SPR 301 DMC) and the terephthalic Terephthalic DMC Resin (SPR 401 DMC).

What manufacturers build

DMC producers make dough compound that they mould themselves or sell to moulders. The catalogue lists dough moulding compound production and compression-moulded composite components for SPR 301 DMC, and adds complex moulded FRP parts for SPR 401 DMC. The orthophthalic DMC/SMC Resin’s Technical Data Sheet lists moulding compounds, electrical housings, manhole covers, automotive panels, transport components, water tanks and sanitaryware. The two newer grades are explained in What Is Isophthalic DMC Resin? and What Is Terephthalic DMC Resin?.

Why this material suits the work

As with SMC, the family is chosen by the chemistry the compound requires: orthophthalic, isophthalic or terephthalic. The orthophthalic DMC/SMC Resin is published at 600 cPs at 25 °C with a 12–18 minute gel time and 35% styrene. SPR 301 DMC is an isophthalic resin for hot-mould DMC processing, at 800–1,400 cPs at 25 °C, a 12–18 minute gel time and 31–36% styrene; it shares one published specification with SPR 301 SMC but is a separate product. SPR 401 DMC is a terephthalic resin with its own specification: a clear to light-yellow liquid of 1,200–2,200 cPs at 25 °C, a 14–22 minute ambient QC gel time, a specific gravity of 1.11–1.15 and 31–36% styrene. The decision rules are set out in Orthophthalic vs isophthalic vs terephthalic DMC resin.

Required resin characteristics

A resin chemistry matched to what the compound requires: orthophthalic, isophthalic or terephthalic
A viscosity the dough formulation and filler loading are built around
Non-accelerated supply, so the compounder sets the cure package for hot moulding
Compatibility with the compounder’s filler, glass and additive package, confirmed by trial
A dedicated DMC grade, since the SMC and DMC resins are separate products

Process context

In general practice the resin, cure package, fillers and additives are blended in a kneading mixer, and chopped glass is usually added towards the end so the fibre is worked in without being over-mixed. The dough is stored until use, weighed into charges and moulded in heated tools. The catalogue reference cures are MEKP 1.5% with cobalt octoate 0.4% for SPR 301 DMC, and MEKP 1.5% with cobalt octoate 0.5% for SPR 401 DMC; in each case the peroxide and cobalt are added separately and never mixed directly. The cure package used in a hot-moulded dough, filler and glass loading, storage and moulding conditions are the compounder’s and moulder’s decisions, set by their own trials.

Advantages

Three chemistries in the range let a compounder match the resin to what the compound requires
SPR 401 DMC has its own published specification, separate from SPR 401 SMC
The catalogue lists complex moulded FRP parts among the uses of SPR 401 DMC
Non-accelerated supply across the DMC grades leaves cure control with the compounder

Common products

Dough moulding compound for sale to moulders
Compression-moulded composite components
Complex moulded FRP parts
Electrical housings and switchgear components
Manhole covers and utility products

Common questions

Can I use SPR 301 SMC for dough compound, since the published specification is shared?

Order the DMC grade. The catalogue publishes one shared typical specification for SPR 301 SMC and SPR 301 DMC, but they are separately manufactured products with their own applications.

How does SPR 401 DMC differ from SPR 401 SMC?

It has its own specification: 1,200–2,200 cPs against 800–1,500 cPs at 25 °C, an ambient QC gel time of 14–22 against 12–18 minutes, and a reference cobalt level of 0.5% against 0.4%.

Which DMC resin chemistry should I choose?

The one the compound requires. If the part specification names a chemistry, follow it; otherwise compare the three routes against the part’s service and confirm the choice by trial on your own compound.

Will the resin meet an electrical or fire requirement?

A resin grade alone does not answer that. Electrical and fire performance belong to the moulded part and the full formulation, and need the standard named and test evidence for the part.

Producing DMC?

Tell us the compound you make, the chemistry it requires, the parts it feeds and the quantity you expect to take. Nepal price, packaging and lead time are confirmed on enquiry.

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