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AR296

Predicting coatability

Contact angle and surface tension results as a basis for targeted development of coating formulations

An effective and reliable method for assessing and predicting coating performance is of critical importance in new material development/quality control. Particularly in the case of multi-layer systems, careful fine-tuning of individual components is essential to achieving good wetting and therefore coatability. With suitable measurement methods, it is possible to predict the behavior of multi-layer systems in regards to coatability. Such methodology is an indispensable tool for guiding additive selection, and significantly reduces the time and cost associated with (re)formulation.

 

In this study, contact angle and surface tension measurements of an automotive primer (cured) and basecoat (liquid), respectively, were used to form a complete description of the coating/substrate system. The presented analysis includes values calculated from the aforementioned measurements, i.e. surface free energy, (with polar and disperse fractions), work of adhesion, spreading coefficient, interfacial tension, and "wetting envelope". The results show how a polyether macromer-modified polyacrylate additive was used to optimize substrate coatability.

Background

Interest in producing higher-value, ‘smart’ materials has grown intensely over the last decade [1-3]. During production of such materials, functional coatings are often used to selectively enhance certain properties, or even allow for situational responses. Due to this, a wide range of coatings have been developed for many applications including self-cleaning, anti-corrosion, anti-microbial, anti-friction, environmentally friendly, super-hydrophobic/hydrophilic and oleophobic/oleophilic to name just a few. In recent times every-day items that incorporate multiple functional coatings into their design have become increasingly common [4]. As the complexity of these multi-layer composites increases, so does the challenge in ensuring compatibility between each coating. As all layers are interconnected (either directly or indirectly) it is often helpful to consider the so-called “chain of compatibility” in the final product.

 

In industry, different coatings are usually obtained from different suppliers and are often designed on different bases, i.e. water-based vs solvent-based. Therefore, additives are frequently used to optimize properties and maintain the chain of compatibility.

 

The structure of multi-layer coatings

Determining the most appropriate additives to use, in the correct amounts, can be tricky and usually involves a time-consuming trial and error process. Utilizing suitable measurement methods makes it easier to predict wetting behavior and coatability, thereby significantly reducing cost and time required to reformulate.

 

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