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December 2009

 
ASTM D 7334
Recently ASTM International released a new standard for characterizing surface wettability: "Practice for Surface Wettability of Coatings, Substrates and Pigments by Advancing Contact Angle Measurement."1 The primary motive for this new standard has been to develop a highly quantifiable method for predicting adhesion, printability and paintability. Surfaces that produce contact angles lower than 45° are said to have good wetting while even more hydrophilic surfaces with contact angles in the 10° to 20° range are said to have excellent wetting. As contact angle decreases, wetting increases and so too does adhesion and the likelihood that coatings will stick to the surface and look good over time.

Water is used to measure the advancing (or maximum) contact angle (as opposed to the static or receding contact angle). In addition to characterizing the surface properties, contact angle can also be used to detect cleanliness and determine the efficacy of processes such as rinsing, etching, and solvent wiping (for example, on plastics).


Coating Defect Caused by Surface with Poor Wetting Characteristics

Coatings can suffer from myriad defects - pinholing, skinning, cratering, and crawling to name a few.1 Contact angle is used to predict the success of applying a particular coating to a treated or untreated surface. Moreover, the relative success of the various surface treatments can also be predicted by understanding how the treatments affect wettability.

This is the first standard published by ASTM that uses contact angle to address coatings and will be of interest to anyone involved in the manufacture of paint or its application. Interestingly, the standard "is intended to supplement the manufacturer's instructions for the device being used to make the measurements, but is not intended to replace them."2

1 http://tinyurl.com/yfcjmys for a complete glossary
2 http://www.astm.org/Standards/D7334.htm
 

Switchable Wetting Properties
In an effort to control wetting, researchers in Sweden have developed a novel approach that reverses the contact angle and spreading of a water droplet by electrochemically reducing or oxidizing a polymer surface.1 These same researchers are applying this method to induce wettability in order to control the flow of water on a polyaniline surface.2 This technique can aid researchers involved in micro- and nano-fluidics - a somewhat new discipline focused on precisely controlling the movement of fluids on a surface at the microscopic and nanoscopic levels. A commercial example of nanofluidics can be found in an inkjet printhead.

By altering the electrochemical state of a polymer, these Swedish researchers claim to have invented a reversible wettability switch which can toggle between lyophobic and lyophilic molecules to switch wetting properties of a surface.3

The ability to control wetting plays a key roll in the development of such diverse and emerging technologies as fuel cells and biotechnical devices. Since nanofluidics is so new, expect to see in the future many new applications that operate by controlling wetting properties.

1 doi:10.1002/adma.200306131
2 doi:10.1016/j.tsf.2006.04.001
3 US Patent Application 20080223717
 

Windows 7

We're pleased to announce that with the recent release of Microsoft Windows 7, we have upgraded all (3) editions of our DROPimage software to run on Windows 7. In our bench tests the new version of Windows is more stable and faster than both Vista and XP. Additionally, there are a number of new features in Windows 7 that make it compelling. The Snipping Tool, for example, makes it super easy to capture a picture from your screen to save, email, or print out. This little tool will be a great benefit to our customers who like to send us pictures of their contact angle and surface tension measurements for comment and evaluation. Then there's Windows 7's Pin, Jump Lists, Snap, Peek, and Shake. Sounds like a new dance. Beginning in 2010 all new ramé-hart systems will ship with Windows 7.
 

Call for Papers

On behalf of our friends at MST Conferences, we'd like announce a call for papers for the upcoming Seventh International Symposium on Contact Angle, Wettability, and Adhesion which will be held in Danbury, CT, June 23-25, 2010. If you or a colleague are interested in presenting a paper, please email a 200-word abstract to Dr. Lacombe at rhl@mstconf.com by December 15th. For more details, go to: http://tinyurl.com/yecf55e If you are planning on attending, then we look forward to seeing you there. ramé-hart instrument co. has been a symposium sponsor for many years.
 

Happy Holidays

On behalf of everyone at ramé-hart instrument co., we'd like to wish everyone a Happy Holiday and a Prosperous New Year. Thank you to all of our customers for helping to make 2009 a good year for us despite the many economic challenges that are shared by all.

 

Regards,

Carl Clegg
Director of Sales
Phone 973-448-0305
www.ramehart.com
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