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Reinforced polypropylene compound (talc, calcium carbonate, glass fibre): what to ask your supplier
Plain polypropylene is light, cheap and chemically resistant, but for many automotive, appliance and electrical parts it is not stiff enough or stable enough under heat. The answer is a reinforced compound: polypropylene combined with talc, calcium carbonate or glass fibre. This guide shows what each does and what to ask a supplier for.
Filler or reinforcement? Talc, calcium carbonate and glass fibre
| Additive | What it improves | What it costs | Common naming |
|---|---|---|---|
| Talc | Stiffness (flexural modulus), dimensional stability, lower shrinkage, better heat stability | Higher density; lower impact strength at high levels | PP-T20 · PP-T30 · PP-T40 |
| Calcium carbonate | Stiffness and a cheaper compound, even surface | Higher density; less reinforcing than talc | PP-CaCO3 20 · 30 · 40 |
| Glass fibre | High tensile and flexural strength, more heat resistance under load | Dearer; fibre orientation in the mould matters | PP-GF20 · PP-GF30 |
The number beside the name is the weight percent of additive: PP-T20 means polypropylene with about 20 % talc. With glass fibre, how well the fibre bonds to the polymer (through a coupling agent, usually maleic-anhydride polypropylene) matters as much as the percentage.
What to ask your supplier for
- The real filler percentage, by ash test: the simplest verification. A sample is burnt in a furnace and what remains is roughly the mineral filler (ISO 3451 or ASTM D5630). If you bought “T30” and the ash is 22 %, the part will be less stiff than expected.
- MFI with its test condition: for polypropylene usually 230 °C with 2.16 kg.
- Density: rises with filler and directly affects part weight and cost.
- Flexural modulus and tensile strength (ISO 178 and ISO 527): the reason you buy a reinforced compound.
- Impact strength (Charpy or Izod, ISO 179/180): especially for bumpers, wheel covers and parts that take knocks.
- Batch number on the datasheet and the bag, for traceability.
Where each is used
- Automotive parts: bumpers, dashboards, wheel covers and fan shrouds need a balance of stiffness and impact, usually a talc-filled copolymer.
- Home appliances: housings and parts that must hold their shape in heat and humidity.
- Electrical and lighting parts: boxes and bases needing dimensional and thermal stability.
- Price-sensitive general parts: calcium carbonate is the more economical option.
Questions
Talc or 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.
Is a higher filler level always better?
No. Stiffness rises, but the part gets heavier and usually more brittle. The application sets the right level.
How do I know the stated percentage is real?
Ask for the ash test, or run it on a sample; it is simple, cheap and telling.
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.
To choose the right reinforced compound for your part and mould, contact the Epic Polymer specialists: +98 919 212 4919 · WhatsApp.