Mineral Powder or Filler Masterbatch — Which Form Should You Actually Buy?

Direct answer

Buy neat mineral powder if you run a compounding line: a twin-screw extruder, gravimetric powder dosing, dust extraction and someone who owns the formulation. Buy a filler masterbatch if you feed an extruder or moulding machine directly: the mineral is already dispersed in a carrier resin at a fixed loading, so you add pellets to pellets and change nothing else on the line. The two forms of the same mineral are not interchangeable at the same dosage. A 75 % concentrate dosed as though it were neat powder puts roughly three quarters of that weight of mineral into the part, and the formulation collapses.

What the two forms really cost

Powder is cheaper per kilogram of mineral, and it is the only route if you need an unusual loading, a specific coating level or your own additive package around the filler. The price of that freedom is equipment and labour: powder needs dosing accuracy, feeding that will not bridge, dust control, and a screw configuration that disperses agglomerates. Poorly dispersed calcium carbonate does not act as a filler, it acts as a defect population, and the first symptom is usually film gels or reduced impact rather than an obvious dosing error.

A masterbatch moves that dispersion work upstream to a compounder who already has the equipment. You pay for the carrier resin and the compounding step, and you accept the loading and coating the supplier has fixed. In exchange you get a free-flowing pellet, no dust, predictable let-down and a specification you can reproduce on any machine in the plant.

The mesh number is not the delivery form

A frequent confusion in RFQs: a product called "1250 mesh" or "5000 mesh" calcium carbonate may still be delivered as a pellet. The mesh figure describes the fineness of the mineral inside — how far the ground calcium carbonate was milled before it was compounded — not the state in which it arrives on your dock. Always confirm two separate lines on the data sheet: product form (powder or pellet) and mineral content (a percentage). A pellet quoting 75 % or 80 % mineral content is a masterbatch, whatever the name suggests.

How the dosage translates

If a formulation calls for 20 % calcium carbonate in the finished part and you buy a 75 % masterbatch, the let-down is roughly 20 / 0.75 ≈ 27 % masterbatch. That is the whole arithmetic, and it is where most first orders go wrong. Two checks before you place the order:

• The finished-part mineral target, not the concentrate percentage, is what the mechanical properties depend on.
• The carrier resin has to be compatible with the host resin. A PE-carrier concentrate in a PP part is common and usually acceptable at low let-down; the same concentrate at 30 % let-down changes the matrix.

What to send us at RFQ

The host polymer and grade, the process (blown film, woven tape, injection, pipe), the mineral loading target in the finished part, whether you can feed powder, and the property you are protecting — stiffness, cost, whiteness or dimensional stability. With those five lines we can tell you which form is cheaper for your plant rather than which is cheaper per tonne.