Dispersant Dosage By Pigment Type

Why The Numbers Look So Different

Carbon black takes ten to thirty times more dispersant than titanium dioxide. That is not a quirk of one product, it is surface area. Carbon black carries an enormous specific surface area and a surface chemistry that is hard to anchor to, so it needs far more polymer to cover. Titanium dioxide is coarse and easy by comparison. Any dosage table that quotes one number for all pigments is hiding this.

The Comparison Table

The table below collects every dosage figure published on the eight dispersant data sheets. Blank cells mean the source does not publish a figure for that pigment class, and none has been estimated. Read every figure as a percentage on pigment weight.

Correct For Active Content

Before comparing two rows, multiply by active content. QK3740 at 10-30% on organic pigment is 100% active, so that is 10-30 parts of polymer per hundred parts of pigment. QK3770 at 30-70% on organic pigment is 40% active, so that is 12-28 parts of polymer. The two are much closer than the headline numbers suggest.

Where To Start In The Band

Start in the middle, not at the bottom. Under-dosing a dispersant does not simply give a smaller improvement, it can give flocculation, because there is enough polymer to bridge particles and not enough to cover them. Run three points and let the viscosity curve tell you where the plateau starts.

What To Measure At Each Point

Grind fineness on a Hegman gauge, mill base viscosity at a fixed shear rate, colour strength against a reference tint, and a rub-out on a mixed shade. Plot viscosity against dosage: the point where the curve flattens is the dosage that has covered the pigment surface. Adding more past that point only adds cost and water sensitivity.

Storage Is Part Of The Test

A mill base that passes on day one can flocculate in a month. Store samples at both ends of the published storage window and re-measure viscosity and colour at 7 and 28 days. Carbon black concentrates are where this matters most, which is exactly why QK3730 is written around anti-thickening behaviour.