Use and Testing of Additives

Additives are generally used in very small amounts ( 1 % of total formulation) and correct dosage is extremely important for optimum effectiveness and also to avoid undesirable side effects. The dosage has to be determined in test series. 

Many additives can be incorporated relatively easily into the paint system during or after the last phase of production (let down). In some cases, however (e.g., with many rheological additives), certain incorporation conditions have to be observed. Wetting and dispersing additives, for example, always have to be present in the mill-base to achieve the desired results. 

Ideally, the effectiveness of an additive should be checked in the complete formulation and under conditions as close as possible to those prevailing in practice. Checking a defoamer just in the binder system, for example, can only be regarded as a preliminary test, because the behavior in the complete formulation may differ substantially. 

Many defects that are to be eliminated by the use of additives are also influenced by the substrate to be coated and the application method. Differences between additives can be established in simple laboratory tests. However the final composition of a specific formulation must take into account as many application parameters as possible (e.g., the state of substrate, application method, and drying conditions). 

In most cases additives influence not just one property of the coating. They may also have undesirable or beneficial side effects. Additives are not magical products but need to be used rationally and carefully to provide the desired satisfactory results. As detailed and complete a knowledge as possible of the mechanism of action of the products, their possible effects and side effects, their limitations, and the underlying causes of paint defects are certainly helpful, but due to the complexity of paints and coatings empirical knowledge is indispensible. 

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