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Technical Information
It is of great importance to use the right amount of dispersion control additive in order to achieve an optimum pigment dispersion. The dispersion control additive (commonly called dispersant) main function is to prevent pigment re-agglomeration by forming a barrier-like layer around the pigment surface. It is therefore necessary to calculate the amount of dispersant needed according to the surface area of the pigment.
From past experience, a handy calculation method has been developed that will minimize initial testing trials. The method is based on the oil absorption, BET and DBP values. These values are usually provided by the pigment suppliers.
Definitions:
Oil absorption-value ( expressed in g/100g): The oil absorption (OA) of a pigment is defined as the number of grams of linseed oil absorbed by 100 gms of the pigment.
BET-value (expressed in m2/g): The BET-value is defined as being the surface area of a pigment per its weight; and is determined by N2-adsorption method according to Brunauer, Emmet and Teller.
DBP-value (expressed in cm3/100g): The Dibutylphtalate (DBP)-value is defined as being the volume of Dibutylphtalate absorbed by 100 grams of black pigment.
The link below will take you to a list containing more than a thousand of different commercially known pigments. In case a pigment is not listed in, please contact your pigment supplier to get the required value (OA, BET or DBP) for your calculation of dispersant dosage. If this is not possible, please send us a sample of your pigment and our technical service technicians will be pleased to establish a tailored formulation for you.
The general guideline for calculating the amount of dispersant required to stabilize a certain type and quantity of pigment will be correct in most cases. However, organic pigments might require amounts of dispersants beyond or below the calculated ones. Such unexpected required amounts are dependant on the way the pigment is pre-treated. Many pigments are pre-treated nowadays, in such a way that they can be dispersed easier than the untreated ones.