Volume-17 (07/2007)

Optimising Automotive Coatings - the Balancing Act between Adhesion Energies, Interfacial Tensions, and Spreading Coefficients

The optimisation of any coating process involves controlling the bulk rheology of the coating, the surface chemistry aspects of the coating, and the surface energetics of the solid. Here we share some recent work on the surface chemistry aspects of solvent based coatings used to colour the plastisol materials which make up much of the interior of most automobiles – dashboards, door interiors, arm rests, and the like. Without surface treatment (corona, flame, plasma, or other) plastisol is a fairly hydrophobic (low surface polarity) and moderately low overall surface energy material, onto which the coating needs to properly spread (wet) and then adhere. The goodness of adhesion needs to be considered in the both the short and long term.

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Practical Contact Angle Measurement (2):
Measurement with nicely deposited drops

In the second part of our practical series on contact angle measurement we are concentrating on drop deposition. What is the difference between static and dynamic contact angles? What influence does the drop volume have? How can the drops be deposited on the sample? The clarification of such questions helps to exactly match the deposition conditions to the particular problem and the functional range of the sample, and how to deal with some of the problems that occur in practice.

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