Frequently asked questions about granules and compounds

Short answers to the questions asked most often when choosing a granule or compound. Each answer is taken from the technical guides on this site; follow the link for more.

MFI and its test condition

What is MFI and why does the test condition matter?

MFI (melt flow index) says how freely a material flows when molten, in grams per 10 minutes. Without the test condition (temperature and load) it means nothing: the same material gives one number at 190 °C with 2.16 kg and a completely different one at 230 °C with 5 kg. Full guide: What is MFI?

Is a high or a low MFI better?

Neither. Pipe extrusion usually suits a lower MFI and injection of thin parts a higher one. Match the MFI to your own line, not to the price.

Why do two suppliers give two different MFI values for the same grade?

Usually because the test condition is not the same. Compare temperature and load first, then the number.

Fillers and ash percentage

What does ash percentage mean and how is it measured?

A sample of granule is burnt in a furnace so the polymer burns away; what remains is the mineral part (calcium carbonate, talc, glass fibre and the like), weighed and reported as weight percent. See ash and filler content.

Is talc better than calcium carbonate?

For stiffness and dimensional stability talc is usually more effective; calcium carbonate is cheaper and suits parts that do not need very high stiffness. See reinforced polypropylene.

Is more filler always better?

No. Stiffness rises with filler, but the part gets heavier and usually more brittle. The application of the part sets the right level.

When should I choose glass fibre?

When the part works under load or at high temperature and needs high mechanical strength; for most visible parts talc is enough and more economical.

Why does a cheaper grade often turn out dearer?

Price is quoted per kilogram but parts are made by volume. A filled grade is denser, so the same part uses more weight; compare price per kilogram multiplied by density, not price per kilogram alone.

Batch, datasheet and documents

What is a batch and what is the batch number for?

A batch is a quantity of granule made in one production run with one formulation. Two batches of the same grade share a name, but their MFI, filler dispersion, colour and moisture are not guaranteed to match. The batch number on the bag and on the datasheet means traceability: any production problem can be traced back to one batch. See batch consistency.

What documents should I ask a supplier for?

The datasheet of that batch with its batch number, MFI with its test condition, density, and ash or filler percentage with the test method and temperature; also ask what the filler is.

White electrical parts

For white electrical parts, is virgin or recycled base better?

In white, visible parts a virgin base gives a cleaner, more even colour; recycled is more economical for hidden or darker parts. Blends are possible provided the blend ratio is fixed and recorded. See white compound for electrical parts.

Ordering and price

What filler levels does Epic produce?

Epic produces compounds with filler content adjustable from 5 % to 80 %. Browse the families and grades under polymer types.

How do I get a datasheet and a price?

By WhatsApp or phone on +98 919 212 4919. Price: on request; the base price of raw materials is published every Sunday on the granule price page (Persian).