Polymeric surfactants offer many performance advantages over conventional monomerics. They are a unique class of high performance products that have been specially designed for stabilisation or co-stabilisation of aqueous and non-aqueous emulsions and dispersions. They are molecules featuring repeating hydrophilic and hydrophobic units. A wide variety of dispersed phase polarities can be formulated across the full range of formulation types. Polymeric surfactants are non-ionic molecules that tend to strongly adsorb at the oil-water interface and form a thick steric barrier around the dispersed phase producing formulations of high stability.
|Type of Surfactant||Application|
|PEG-alkyd||Emulsifier/ dispersant can be used in either oil or water|
|A-B-A Tri-block copolymer||Emulsifier/ dispersant for low polarity oils|
|Oligomeric||Emulsifier/ dispersant for low polarity oils|
|Comb graft copolymer||Dispersants for solid particles in water|
The required level of polymeric emulsifier depends on the type of oil, the ionic content of the aqueous phase and the desired droplet size of the final emulsion. Start with 1% surfactant on the dispersed stage, if failing then increase to 5%.
The surfactant is usually dissolved in the oil phase if possible, with gentle warming and agitation when appropriate. In most cases it will be necessary to produce the emulsion in a high-shear mixer/ emulsifier. The dispersed phase should be added slowly to the continuous phase under agitation on the mixer.
The emulsification behaviour can be modified by the addition of other non-ionic surfactants, hence initial experiments to evaluate the benefit of using polymeric surfactants should try to minimise the level of such components.
|Improved particle wetting||Efficient milling, saves energy, higher productivity, less wear|
|Increased solids loading||Low viscosity, higher productivity, better handling|
|Effective stearic barrier/ increased stability||Long shelf life, better handling, low storage loss|
|Viscosity reduction||Improved flow and rheology, energy savings|
|Compatibility with many resins/ solvents||Multi-purpose dispersions, reduced inventories|
|Hydrophobic agent at the solid/ liquid interface||Reduced water absorption, makes surface hydrophobic|
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