Role of Surfactants in Biological Enhancement

Standing of the role of the adjuvants in the application of agrochemicals. This should lead to optimization of the efficacy of the chemical as vell as reduction of hazards to the operators, the crops and the environment. 

Both approaches must be considered when selecting an adjuvant for a given agrochemical and the type of formulation that is being used. The most important adjuvants are (1) surface active agents and (2) polymers. In some cases these are used in combination with crop oils (e.g. methyl oleate). Several complex recipes may be used and in many cases the exact composition of an adjuvant is unknown. 

Adjuvants are applied in two ways (1) by incorporation in the formulation -mostly the case with flowables (SCs and EWs). (2) In tank mixtures during application. Such adjuvants can be complex mixtures of several surfactants, oils, polymers, etc. 

The choice of an adjuvant depends on the (1) nature of the agrochemical, water soluble or insoluble (lipophilic), whereby its solubility and log P values are important. (2) Mode of action of the agrochemical, i.e. systemic or non-systemic, selective or non-selective. (3) Type of formulation that is used, i.e. flowable, EC, grain, granule, capsule, etc. 

Other shapes may be produced, e.g. rod-shaped and lameDar micelles. Since micelles play a vital role when considering adjuvants, their properties must be understood in some detail. As mentioned in Chapter 2, micelle formation is a dynamic process, i.e. a dynamic equilibrium is set up whereby surface active agent molecules are constantly leaving the micelles while others enter the micelles (the same apphes to the counter-ions). The dynamic process of micellization is described by two relaxation processes (1) A short relaxation time ti (of the order of s), which is the lifetime for a surfactant molecule in a micelle. (2) 

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In this chapter, I will concentrate on the application of surfactants in the various agrochemical formulations. The role of surfactants in enhancing biological efficacy will be dealt with in some detail. 

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