Suspoemulsion (SE) formulations are used to combine two active ingredients with very different physical properties into one formulation. They are a combination of suspension concentrate (SC) and concentrated aqueous emulsion (EW) technologies.
The advantages are that it is possible to formulate multiple active ingredients together, broadening the spectrum of activity and eliminating the disadvantage of tank-mix incompatibility.
- Incorporates multiple active ingredients with different solubilities or melting points
- A mixture of active ingredients is often used to provide a broader spectrum of pest control
- Formulating active ingredients together eliminates the need for tank mixing which can lead to incompatibility in the spray tank
- The surfactant system needs to support both an insoluble organic solid and a liquid
- Partial solubility of the active ingredients in water or oil phases causes stability problems
- Generally they are highly loaded so can have long term stability issues if the correct surfactants are not used
The Formulator's Toolbox (Full Version)
How to formulate an SE
SEs can be difficult to formulate. However, to avoid breakdown processes such as flocculation, crystal growth and coalescence, we advise using polymeric surfactants. Improved anchoring and colloidal stabilisation are key to meeting the required performance criteria.
We recommend developing stable EW and SC formulations separately. After you achieve stable formulations we recommend combining them. In order to reduce instability in the final SE formulation we advise the use of the same surfactant system where possible.
Recommended products for SE
Many of the common instability factors in SEs can be overcome through the use of polymeric surfactants, which adsorb strongly onto the relevant particle or droplet surfaces preventing them from achieving close interactions. The chosen polymeric systems for the SC and EW components should be as closely related chemically to each other as possible. Atlas G-5002L is therefore often critical to the development success of a SE. This is because Atlas G-5002L acts as both an emulsifier and a co-dispersant, thereby stabilising both systems without the risk of transfer between relevant partitions.
Atlox 4916 is a high molecular weight polymeric emulsifier and dispersant with a low HLB. With its unique ‘star structure’, it has superior anchorage at the oil/water/particle interface providing matchless stability even in the most challenging formulation conditions. This unique star shaped structure is what gives Atlox 4916 its superior stability which even in the harsh conditions of an SE formulation.
High performance emulsifiers/co-dispersants available from Croda are the range of phosphate esters. These surfactants come with the added benefit of maintaining this high performance in strong electrolyte solutions. A good initial candidate for developments is Crodafos C10/5A.