The coatings are a mix of fluorinated polyurethane and fluid-repellent fluorinated polyhedral oligomeric silsesquioxanes, or F-POSS.
Such coatings have to be optically clear and also sufficiently smooth to repel oils and alcohols. Researchers managed to achieve this by carefully tweaking the repellent ingredient and binder.
‘In the past, researchers might have taken a very durable substance and a very repellent substance and mixed them together,’ lead researcher Anish Tuteja said. ‘But this doesn’t necessarily yield a durable, repellent coating.’
Combining a polyurethane binder and F-POSS makes it possible to produce a mixture that can be sprayed, brushed, dipped or spin-coated. The researchers said that once applied it binds tightly onto a wide variety of surfaces. The team claims that although the surface can be scratched with a sharp object, it is durable in everyday use.
‘The repellent and binder mix together well enough to make a clear coating, but there’s a very small amount of phase separation between them,’ said graduate researcher Mathew Boban. ‘That separation allows the F-POSS to float to the surface and create a nice repellent layer.’
Tuteja believes that it can be cost-effective to make coatings from this combination of materials. Fluorinated polyurethane is inexpensive and readily available. Although F-POSS is not so easy to source, attempt to scale up the process scale-up are under way. If this is successful, it should greatly reduce production cost. He claims it might reach the market in the next couple of years.
Obvious applications include health and social care setting such as daycare centres. Other potential uses include refrigeration, power generation and oil refining.
Researchers suggest that in the refining industry it could allow condensed water and chemicals to slough off more quickly, increasing process efficiency.