Why Oil Absorption Matters When You Use CaCO3 in Masterbatch

What "oil absorption" actually means

When suppliers talk about oil absorption of calcium carbonate, they mean how much plasticizer or oil the powder can soak up. The standard test uses DOP (dioctyl phthalate): it measures the grams of oil needed to turn 100 grams of CaCO3 into a smooth paste. The result is written as, for example, 60 g/100g.

Think of CaCO3 particles like a sponge. The finer the powder and the rougher its surface, the more oil it traps in pores and around the particles. This single number quietly decides how your masterbatch behaves.

Why masterbatch makers should care

Masterbatch is a concentrated mix of filler, carrier resin, and a few additives. The CaCO3 does not just sit there — its surface has high energy and many tiny pores, so it "drinks" oil from the carrier. If oil absorption is high, a lot of your expensive carrier resin gets soaked up and loses its job of wetting and dispersing the particles.

The visible symptoms are familiar: the compound turns dry and crumbly, dispersion gets worse, screw torque rises, and you need more resin to keep the mix workable. That means higher cost and lower output per run.

Low oil absorption means more filler, less cost

With a low oil absorption grade, you can load more calcium carbonate into the same amount of carrier without the mix falling apart. More filler per kilogram directly lowers your material cost, while flow and pellet quality stay stable. For high-filler masterbatch, this difference is where margin is won or lost.

Surface treatment is the game changer

This is the part many buyers miss. Untreated precipitated calcium carbonate such as our HB-101 sits around 60 g/100g. Coat the same particles with stearic acid and the number drops sharply — our SFA-PCC-99 surface-modified grade reaches about 35 g/100g, with activation degree 99%.

Why? The hydrophobic coating lowers surface energy and seals the pores, so the powder no longer competes with the resin for oil. For masterbatch producers pushing high loadings, the modified grade is usually the smarter buy even at a small premium.

A practical buying tip

Always ask for the oil absorption value (DOP method) on the COA, and compare grades at the same particle size. Finer powder normally shows higher oil absorption, so match the mesh before judging. An honest supplier will give you the number without hesitation.

How SHAOFEI can help

SHAOFEI TRADING supplies both standard PCC (HB-101, 1250 mesh, CaCO3 98%, whiteness 94) and surface-modified PCC (SFA-PCC-99, activation 99%, oil absorption about 35 g/100g). Full COA, MSDS, and TDS are available, and samples can be sent for your own lab test.