MMaterialsgateNEWS 2017/04/06

A self-healing, water-repellant coating that's ultra durable

A self-healing, water-repellent, spray-on coating developed at the University of Michigan is hundreds of times more durable than its counterparts.

It could enable waterproofing of vehicles, clothing, rooftops and countless other surfaces for which current waterproofing treatments are too fragile. It could also lower the resistance of ship hulls, a step that would reduce the fuel consumption of the massive vessels that transport 90 percent of the world's cargo.

The developers say the new concoction is a breakthrough in a field where decades of research have failed to produce a durable coating. While water-repellent finishes are available at present, they're typically not strong enough for applications like clothing or ship hulls. This discovery changes that.

"Thousands of superhydrophobic surfaces have been looked at over the past 20 or 30 years, but nobody has been able to figure out how to systematically design one that's durable," said Anish Tuteja, U-M associate professor of materials science and engineering. "I think that's what we've really accomplished here, and it's going to open the door for other researchers to create cheaper, perhaps even better superhydrophobic coatings."

The coating is made of a mix of a material called "fluorinated polyurethane elastomer" and a specialized water-repellent molecule known as "F-POSS." It can be easily sprayed onto virtually any surface and has a slightly rubbery texture that makes it more resilient than its predecessors.

If it is damaged, the coating can heal itself hundreds of times. It can bounce back "even after being abraded, scratched, burned, plasma-cleaned, flattened, sonicated and chemically attacked," the researchers wrote in a paper recently published in ACS Applied Materials & Interfaces.

In addition to recovering physically, the coating can heal itself chemically. If water-repellent F-POSS molecules are scraped from the surface, new molecules will naturally migrate there to replace them. That's how the coating can renew itself hundreds of times. Its healing ability is limited only by its thickness.

The discovery is being commercialized by HygraTek, a company founded by Tuteja with assistance from U-M Tech Transfer.

Beyond the coatings detailed in the paper, the project produced what amounts to a recipe that researchers can use to optimize future coatings to a specific application's requirements for cost, durability and other factors.

As lead author and U-M doctoral student Kevin Golovin explains, the team used a process that was radically different from previous research in the field.

"Most materials science researchers have focused on identifying one specific chemical system that's as durable and water-repellent as possible," he said. "We approached the problem differently, by measuring and mapping out the basic chemical properties that make a water-repellent coating durable. And some of the results surprised us."

For example, most hydrophobic coatings are made of two main ingredients: an active molecule that provides the water-repellency and a binder. Generally, researchers have assumed that using more durable ingredients would make a more durable coating. But Tuteja's team found that that's not necessarily the case.

They discovered that even more important than durability is a property called "partial miscibility," or the ability of two substances to partially mix together. The other key variable the team discovered is the stability of the water-repellent surface.

Most water-repellent coatings work because their surface has a very specific geometry, often microscopic pillars. Water droplets perch on the tips of these pillars, creating air pockets underneath that deny the water a solid place to rest and cause it to roll off easily. But such surfaces tend to be fragile -- slight abrasion or even the pressure of the water itself can damage them.

The team's research found that a surface that's slightly pliable can escape this pitfall -- even though it seems less durable, its pliable properties enable it to bounce back from damage.

Tuteja estimates that the coatings will be available for use before the end of 2017 for applications including water-repellent fabrics and spray-on coatings that can be purchased directly by consumers.

Source: University of Michigan – 04.04.2017.

Investigated and edited by:

Dr.-Ing. Christoph Konetschny, Inhaber und Gründer von Materialsgate
Büro für Material- und Technologieberatung
The investigation and editing of this document was performed with best care and attention.
For the accuracy, validity, availability and applicability of the given information, we take no liability.
Please discuss the suitability concerning your specific application with the experts of the named company or organization.

You want additional material or technology investigations concerning this subject?

Materialsgate is leading in material consulting and material investigation.
Feel free to use our established consulting services

MMore on this topic

Molybdenum disulfide (MoS2), which is ubiquitously used as a solid lubricant, has recently been shown to have a two-dimensional (2D) form that is similar to graphene.

But, when thinned down to less than a nanometer thick, MoS2 demonstrates properties with great promise as a functional material for electronic devices and surface coatings. Researchers at the University of Illinois at Urbana-Champaign have developed a new approach to dynamically tune the micro- and nano-scale roughness of atomically thin MoS2, and consequently the appropriate degree of hydrophobicity for various potential MoS2-based applications. "The knowledge of how new materials interact with water is a fundamental," explained SungWoo Nam, an assistant professor of mechanical science and engineering at Illinois. "Whereas the wettability of its more famous cousin, graphene... more read more

Colorado State University researchers have invented an ice-repellent coating that out-performs today's best de-icing products.

Anyone who's ever chipped ice off a windshield or nervously watched a plane get de-iced, take note: Colorado State University researchers have invented an ice-repellent coating that out-performs today's best de-icing products. Researchers led by Arun Kota, assistant professor of mechanical engineering and biomedical engineering, have created an environmentally friendly, inexpensive, long-lasting coating that could keep everything from cars and ships to planes and power lines ice-free. Their innovation, described in the Journal of Materials Chemistry, is a gel-based, soft coating made out of PDMS (polydimethylsiloxane), a silicone polymer gel with already widespread industrial... more read more

Superhydrophobic surfaces have attracted global attention due to their water-repellant characteristics and myriad number and variety of applications.

A team of researchers with the Department of Mechanical Engineering at Pohang University of Science and Technology (POSTECH), led by Professor Dong Sung Kim and comprised of Research Professor Donghwi Choi and 4th year undergraduate student Jaewon Yoo, has found an elegant, cost-effective, and environmentally friendly method of applying a superhydrophobic layer to objects by using commercially available salt particles, polydimethylsiloxane (PDMS), and water. In nature, one can observe such ultrahydrophobicity on a Lotus leaf. The leaf has microscopic protrusions on its surface which minimizes adhesion. As a result, water droplets along with any dirt particles on the surface simply roll right... more read more

MaterialsgateNEWSLETTER

Partner of the Week

Search in MaterialsgateNEWS

MaterialsgateFAIR:
LET YOURSELF BE INSPIRED