What points must be considered in choosing a surface active dispersing agent ?
The purpose of surface sctive dispersing agents is to stabilise pigments/binder/solvent systems and thereby improve their compatibility. The substances used are usually quaternary ammonium salts or anionic compounds, the letter generally in the form of fatty acid salts, alkyl sulphonates and similiar substances. Their effectiveness is especially evident if the polar molecule group resembles the pigment and the non-polar one the binder.
This concept would have to be modified if the binder itself contains an appreciable number of polar groups. In that case an amphoteric dispersing agent containing cationic as well as anionic portions (e.g. amino-fatty acid based) would be more suitable.
One could also use nonionic compounds such as polyalkyl esthers. Generally speaking it is always advisable to refer the extensive compatibility tables supplied by additive manufacturers.
