Structure formation in paints and coatings

Résumé :

Paints and coatings are typically a mix of small particles, like pigments, along with a polymer glue or binder. Similar products include inks, varnishes, cosmetics, ceramics and even the lithium-ion battery electrodes that power modern electric vehicles. These materials are prepared as a liquid, spread over a surface, and dried.  As anyone who has painted a wall will know, however, this process can easily go wrong. Even a well-prepared paint can develop an undesirable skin and wrinkle, crack, or peel, and these coatings can also visibly degrade over time.

In this talk I will go through the key stages of film formation, or how a colloidal dispersion dries.  I will show how small angle scattering experiments (SANS/SAXS) helped to elucidate how the structure of the film changes during drying, evolving from a dilute gas of particles, into a transient gel where capillary pressures balance electrostatic repulsion, to a final aggregated solid. I will then turn to look at how the insight gained has led to a better understanding of mechanical instabilities like fracture, shear banding, birefringence, and peeling, as well as revealing an unexpected route to colloidal crystallisation.

Finally, I will summarise our recent work using neutron scattering techniques to investigate blanching, a degradation process that can cause a visible whitening in the traditional varnishes that are used as a protective outer coating on many historically and artistically important paintings.

Speaker’s website: https://www.ntu.ac.uk/staff-profiles/science-technology/lucas-goehring

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Orsolya Czakkel (College 9 Secretary)

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