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ramé-hart instrument co. April 2014 Newsletter
|How Hydrophobic is your Swimsuit?
Competitive swimmers put a lot of energy and money into being the best and the fastest. One component to being fast is a good technical swimsuit which can cost upwards of $500. What makes these expensive suits so expensive? And are they really better than $50 swimsuits? Is there a correlation between price and water repellency properties? These are some of the questions that Jake, a high school student, attempted to answer in his recent Pennsylvania Junior Academy of Science Science Fair project. We're impressed with Jake's presentation: not just because he came in first place in regionals and is headed to Penn State College to compete at the state level -- but because of his excellent choice in contact angle measuring equipment: he used a ramé-hart Model 200 here at our New Jersey headquarters.
Jake identified three factors that make up a fast suit with minimal drag resistance: first, compression. The big-dollar technical racing suits all seem to have high compression. Second, seams. The high end suits are seamless while the practice suits are fabricated with seams. Seamless fabrication is more costly but offers superior results. Third, water repellency. This was the main focus of study: to discover if there is a correlation between contact angle and price.
Jake performed contact angle measurements on over a dozen different swimsuits from a spectrum of price points. If you are interested in seeing the detailed results of his study and some slides from his science project, go to: http://www.ramehart.com/pdf/swimsuit_study_2014.pdf.
The conclusion is that the suits on the lower end of the price spectrum, up to $260, exhibit a correlation between price and water repellency - as the price increases so too does the water contact angle. However, with the higher end suits, over $280, the correlation disappears. This is not to say they are bad suits; most of them exhibit a high water contact angle between 135° and 140°. But as the price increases, the contact angle does not.
Jake also discovered and mentions in
his presentation that while pure deionized water produces the highest
water contact angles, it's not representative of the real world because
people don't swim in pure water but in treated pool water. Some
additional testing resulted in the observation that the pure water
produced a contact angle about 30° higher than the contact angle of pool
water. Naturally, the chlorine and other chemicals in the pool water
lower its surface tension resulting in improved wetting behavior which
translates to degraded water repellency properties.
|Contact Angle Symposium
|The Ninth International Symposium on Contact Angle, Wettability and Adhesion is scheduled for 16 to 18-Jun-14 at Lehigh University in Pennsylvania. This is a great resource for researchers who are interested in learning about new developments in contact angle, wettability behavior, adhesion, surface treatments, and surface characterization. For more information, see http://www.mstconf.com/Contact9.htm.