Adjuvants for agrochemcials can have more than one function. A substantial number of adjuvant products are mixes of compounds differing in chemistry and function and this results in multiple functionallity. An example of a multiple functional adjuvant is A mix of ammonium sulphate and a polymer. Secondly, one chemical compound or type of compound may interact with different stages in the targeting of a pesticide. A polyoxyethylene tallow amine surfactant improves both the wetting of the leaf surface and the foliar uptake of glyphosate. One can discriminate between adjuvant-functions that have a direct influence on the availability of the active ingredient and adjuvant-functions that have an indirect influence on the availability.
Table: Potential functions of adjuvants for agrochemicals
|Direct influence on availability of the active ingredient
|Indirect influence on availability of the active ingredient|
|Reduction of drift
|Reduction of volatilization
|Influence on pH|
|Improved retention of spray solution
|Improved compatibility with other ai's |
|Increased foliar uptake of ai
|Hindering antagonistic effects by inorganic cations|
|Prevents wash-off during rain
|Marker for deposition of spray solution|
With a few hundred products adjuvants are a real market in the USA. In Europe and elsewhere the number of products is increasing. Adjuvant producers generally provide limited information regarding the structure and concentration of compounds in an adjuvant product. In spite of this, a number of different classes can be distinguished (see table below).
Alkoxylation (with ethylene and/or propylene oxide) and esterification are frequently used methods to change the hydrophilic lipophilic balance, the molecular weight and the three-dimensional structure of the surfactant. Further, the degree of branching (alcohols), presence of unsaturated C-C bounds and the presence of functional groups like sulphate, phosphate and sulpho-succinate, are used to modify the physical-chemical properties.
The physical-chemical properties of an adjuvant determine its usefulness in a certain application. Different chemical structures may have similar physical-chemical properties required for a certain adjuvant function. That's why so many different structures are sometimes recommended for the same function.
Table: Adjuvant classes
Seed oil (triglycerides)
|Fatty acids from vegetable origin
Alkoxylated and esterified
||Based on: alcohols, fatty acids, alkylphenols, alkylamines, sorbitol, sorbitan, trisiloxane, and alkylpolyglycosides|
||Ammonium sulphate, ureum, ammonium nitrate, calcium nitrate|
||Acid wax, ester wax, ethoxylated acid wax|
||Polyacrylamides, polyethylene oxide, polyvinils|