A microemulsion (ME) is defined as a system of oil, water and surfactants that forms a single, optically clear and thermodynamically stable emulsion.
MEs are water based formulations with a very small emulsified droplet size; this makes the formulation transparent.
They are thermodynamically stable over a wide temperature range due to this very fine droplet size, usually between 0.01 and 0.05 μm. Therefore in contrast to other emulsion systems, where the oil droplets can slowly coalesce causing phase separation, in ME formulations this does not occur.
Anionic surfactants are required in an ME formulation to form a spontaneous emulsion. Due to the overall charge on an anionic emulsifier it provides additional electrostatic stabilisation.
The combination of a low and high HLB non-ionic surfactant is recommended to provide steric stabilisation at the emulsion interface.
Our extensive range of phosphate esters gives the formulator a high degree of flexibility in their formulation design of microemulsions. When combined with other surfactants such as sarcosinates, they can provide stable microemulsion systems in very challenging conditions. As with the combination of non-ionic surfactants, it is important to consider pairing a phosphate ester with high solubility in your target aqueous system, along with a phosphate ester with high solubility in your target oil system.
Atplus 310 is a single product, emulsifier package. Its novel blend makes formulating an ME relatively easy and simple as blending ratios of the emulsifiers have already been predetermined. Microemulsions do not normally form in high electrolyte conditions. This is due to the disruption that electrolytes cause to steric stabilisation and the shielding effect to electrostatic repulsion between droplets. Atplus 310 however, is designed to overcome this problem and allows the formation of high electrolyte microemulsions.
In an ME formulation the active ingredient must be fully soluble in the carrier solvent. If the active ingredient is solid, it will need to be dissolved in a solvent. Croda’s Seatons Natural Oil range are 100% natural and renewable, which make them a great choice for use in crop care formulations.
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