How to choose CaCO3 filler masterbatch: mesh size, filler content, carrier resin
Four parameters decide whether a calcium carbonate filler masterbatch saves you money or ruins your film: filler content, mesh size, carrier resin and surface coating. Everything else is secondary.
1. Filler content: 70–85% is the working range
Filler content is the percentage of calcium carbonate by weight inside the granule. Standard export grades sit between 70% and 85%. The trade-off is direct:
| Filler content | Effect on cost | Effect on mechanical properties | Typical use |
|---|---|---|---|
| 70–75% | Lower saving per kg | Tensile and tear strength retained best | Thin film below 30 µm, high-strength packaging |
| 75–80% | Balanced | Moderate loss in elongation | General blown film, woven sacks, injection parts |
| 80–85% | Highest saving per kg | Noticeable drop in impact and elongation | Thick sections, non-critical parts, cost-first runs |
Two buyers asking for "80% filler" can end up with very different products, because the number says nothing about particle size, coating or moisture. Always ask for the filler content and the parameters below before comparing price per ton.
2. Mesh size: 1250 vs 2500 is a dispersion decision
Mesh is a screen classification, not an average particle size, but the practical conversion is useful:
| Mesh | Approximate top cut | Effect |
|---|---|---|
| 800–1000 mesh | ~15 µm | Cheapest; visible agglomerates in thin film; screen pack pressure rises |
| 1250 mesh | ~10 µm | Workhorse grade for film 30–80 µm |
| 2000–2500 mesh | ~5–6 µm | Best dispersion and surface finish; higher cost; needed below 25 µm film |
Finer mesh buys you dispersion and surface quality, not strength. If your problem is gels, die lines or specks, going from 1250 to 2500 mesh usually helps more than changing filler content.
3. Carrier resin must match your virgin resin
The carrier is the plastic that holds the calcium carbonate. If it does not match the resin you run, you get incompatibility defects that no amount of filler tuning will fix.
- LDPE / LLDPE carrier — for PE blown film, cast film and PE injection. The default for film producers.
- PP carrier — for PP injection, raffia, woven sacks and PP sheet. Using a PE-carrier grade in PP shows up as gels and weak weld lines.
- Mixed or recycled carrier — acceptable in thick, non-critical parts, but expect lot-to-lot variation in MFI.
4. Coating: stearic acid coated vs uncoated
Coated grades carry a stearic acid layer on the particle surface. This lowers viscosity, improves dispersion, and reduces the tendency to absorb moisture. Uncoated grades are cheaper and work in high-load, thick-section applications. For film below 50 µm, coated is normally the right choice.
5. The four numbers to request from every supplier
Before you compare quotations, ask for these on the TDS — not in an email, on the document:
- Filler content in %, with the test method
- Mesh or top cut in µm, not just a mesh number
- MFI in g/10 min with the test condition (190 °C / 2.16 kg for PE)
- Moisture in %, specification ≤ 0.15% for film grades
Common questions
Is higher filler content always cheaper per finished part?
No. Cost per kilogram of masterbatch falls, but above roughly 80% you often need a higher addition rate to keep the same output, and you lose elongation and impact strength. Compare cost per finished part, not per ton of masterbatch.
Can I use one grade for both PE film and PP injection?
Not reliably. The carrier resin differs. A PE-carrier grade in PP tends to produce gels and weak knit lines, while a PP-carrier grade in PE film reduces bubble stability.
What mesh do I need for 20 µm blown film?
Use 2000–2500 mesh with a coated surface and a moisture specification of 0.15% or lower. At that thickness, agglomerates above about 10 µm become visible specks.
Does filler masterbatch work in recycled resin?
Yes, and it is common practice. Expect to reduce the addition rate by 10–20% relative to virgin resin, because recycled material already carries ash and its MFI varies batch to batch.
Related: addition rate by process · how to read a masterbatch TDS · CaCO3 filler masterbatch specifications