If you're having trouble viewing this email, you may see it online.
ramé-hart instrument co.
August 2013 Newsletter
|How to Make Your Puma Clyde Suede Sneakers Superhydrophobic for Less than Twenty (US) Dollars|
When I was in high school, there was
nothing in the world I wanted more than a pair of Puma Clyde suede
leather sneakers and a
Ford Mustang (each preferably in red). I wore white canvas Converse All-Stars back then and my first
car was a green Ford Pinto. While I fell short of my dreams, one of the
benefits of becoming an adult with a job is you can buy things that as a
kid you could only dream about. So, I finally got around to buying
myself a red Ford Mustang and a pair of red Puma Clyde suede sneakers. By the
way, neither has disappointed.
The Puma Clydes are super comfortable and stylish in that nerdy old-school kind of way. Perhaps the only way to truly improve them is to make them superhydrophobic. When Marcy, our administrative assistant, saw NeverWet in the news and then when I, the very next day, saw a banner ad on some website for Rustoleum NeverWet at Home Depot, I clicked on buy-it and ordered a kit which cost $19.97 (plus shipping and handling).
NeverWet is a trademark of Ross Nanotechnology. We contacted Ross a couple of years ago and requested a sample of NeverWet while doing some research on superhydrophobic surface treatments. Apparently it wasn't quite ready for prime time and our request was declined. Since then Ross has improved the technology and has entered into a licensing agreement with Rustoleum who is packaging and selling the product through Home Depot for consumer use. Full disclosure: we do not represent Ross, NeverWet, Rustoleum, or Home Depot. And none of these parties have paid us to endorse their product. Nor do we own their stock. We simply make the world's best tools for measuring contact angle which comes in handy for measuring things like superhydrophobicity.
The kit arrived a few days later and consists of two 9-ounce aerosol cans. The first can is called Step 1, Base Coat, and, from the MSDS which I downloaded from Rustoleum's website, appears to consist mostly of naphtha and ester solvents. The instructions call for two or more base coats applied several minutes apart. Then a minimum of 30 minutes is required before Step 2, the Top Coat, can be applied. Another 30 minutes is required for drying after the top coat is applied but 12 hours is recommended for maximum performance. The top coat, from the MSDS, appears to consist mostly of acetone. The package claims that the kit is capable of covering 10 square feet.
We were so giddy with excitement when our kit arrived that we decided to test a half dozen different materials. In addition to the Puma Clydes, we also measured contact angle before and after treatment on anodized aluminum, ceramic tile, wood, umbrella fabric, and polycarbonate. The table below shows the results from our testing.
Table 1: Contact angle (CA) before and after NeverWet Treatment
The Pumas won the contest for becoming the most hydrophobic after treatment but they had the unfair advantage of being the most hydrophobic to start with. The NeverWet treatment improved the contact angle by nearly 25° pushing the suede leather surface into the superhydrophobic range. (Generally superhydrophobicity requires a water contact angle in excess of 150°.) See the video below. In addition to a higher contact angle, the roll off angle decreased although we did not precisely measure this since doing so would require us to cut a sample from the shoe, a sacrifice I couldn't make to a pair of shoes I've waited years to own. Overall, the shoes are more water repellant than when we started. There was no visible discoloration on this particular sample and the only possible downside to treating the surface is a loss of breathability. One of the Rustoleum FAQS indicates that the breathability is a function of how heavy the base coat is applied: a light base coat helps retain breathability but with diminished water repelling properties. Time will tell how long the treatment will remain effective. We may report back in a few months.
We also chose to test a piece of brushed anodized aluminum like the surface of a grill cover or patio furniture. The contact angle improved by just over 31° but this and all of the other samples failed to reach the superhydrophobic range. The treatment also left the surface rougher on this sample. In the case of the grill cover, it's not clear how the treatment would react to high temperatures.
The ceramic tile showed the greatest improvement in contact angle increasing over 100°. However, it was quite hydrophilic to start with. Before you rush out to make your kitchen or bathroom self-cleaning, however, note that soaps, detergent, and high water pressure reduce the hydrophobicity of the treated surface. Moreover, the treatment is not designed for or effective on submerged surfaces.
The wood sample was a piece of unfinished poplar. In addition to increasing the contact angle by 45°, the surface also lost its absorptive properties. The surface is also noticeably rougher but any discoloration is not noticeable. If you are making outdoor furniture, it may be preferred if the wood is first stained and sealed before the NeverWet treatment is applied. Decks and picnic tables could benefit from being treated with NeverWet but the added benefits may not justify the cost of application.
The umbrella turned out to be the biggest disappointment and was the one surface that we thought could benefit the most from becoming more water repellant. However, the NeverWet treatment increased the contact angle by only 13°. In addition, the black nylon material became tinted with a milky white haze rendering it less new looking and became tacky with a gritty sticky texture.
The polycarbonate sample exhibited an improvement in contact angle of just over 50°. However, the once clear surface is now hazy. Light passes but you cannot see through it. This means that motorcycle face guards, sunglasses, windows, windshields, and other clear plastic and glass surfaces are not candidates for NeverWet treatment.
There are some limited applications that could benefit from the NeverWet treatment. No doubt it is fun to play with. But the cons keep it from being a full-scale blockbuster.
Still not sure? Why not get
your own kit and try it out. See
Let us know how it works out for you.
|Ninth Annual Contact Angle Symposium on Contact Angle, Wettability, and Adhesion|
We are pleased to announce the upcoming
Symposium on Contact Angle which will be held at Lehigh University in
Bethlehem, Pennsylvania, 16 to 18-Jun-2014. For more details on the
symposium including the call for papers, visit
http://www.mstconf.com/Contact9.htm. In years past, we have
attended, exhibited at, and sponsored this event. It is an excellent
resource for the surface science researcher and highly recommended.