Posted in Contact Angle, D L Williams, Hansen Solubility Parameters, Physical Chemistry

Contact Angle Standards and Measurement System Evaluation

As my research group began to enter into the world of precision cleaning, we needed to come up to speed on contact angle measurement.  In doing so, we met Anselm Kuhn who was a great help and mentor.  Together, we produced an inexpensive way to standardize contact angle measurements using spherical ruby lenses.  We also evaluated the many freely-available contact angle measurement programs that act as plugins for ImageJ.  This work was published in the German metal finishing journal Galvanotechnik.

Williams, D. L.; Kuhn, A. T.; Amann, M. A.; Hausinger, M. B.; Konarik, M. M.; Nesselrode, E. I. Computerized Measurement of Contact Angles, Galvanotechnik, 101, 2502-2512, (2010)

Abstract

Measurement of contact angles often provides valuable information as to the cleanliness of a surface as well as the ease of wetting of a surface with a coating such as paint or other organic species. Previous methods based on use of a sessile drop were subject to considerable operator error. In order to minimise such errors, the computer-based analysis of drop shape has been developed. The use of such software which is Windows-compatible and easy to learn, is described, giving results where operator-error is minimised. The method has considerable potential for Quality Control in surface finishing.

 

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Posted in Contact Angle, D L Williams, Hansen Solubility Parameters, Solvent Blending

Chemically-Resistant Glove Selection

Background

As a college chemistry student I was eager to read the labels on every product I could find to bask in my newfound knowledge of organic nomenclature.  Imagine my frustration when I found more useful information on a bottle of shampoo than I found on a can of Lacquer Thinner.  Fortunately, labelling has improved, and most major components can be found on the sides of the can.

Still, I suffered with the lingering question of “Why did they mix toluene and MEK to make product X?”.  It was an exciting day in 2006, when a student came into the office and asked me why I wasn’t using the Hansen Solubility Parameters to pick solvents.  I had sent her on a literature search for solubility models, and she found the Hansen Solubility Parameters Handbook 1st Edition.  (Don’t be too hard on me.  I was raised as a vibrational spectroscopist and had little experience in solubility studies.)  A quick view of the book gave me a “Eureka” moment, as I found ways to blend solvents, and “stick non-stick surfaces to a surface”. 

I have been modelling solvent blends for recrystallization, precision cleaning, and polymer swelling for about 3 years.  Much of my initial work was in an Excel spreadsheet using the equations in the CRC Handbook on the Hansen Solubility Parameters.  But I eventually “graduated” to using the HSPiP software and eBook1 available at http://www.hansen-solubility.com/

Glove Selection

Perhaps your lab is typical in selecting nitrile gloves for everything.  Changes are made when one loses a finger (of a glove) in a beaker of solvent.  This is not the best practice, but many will not believe me when I say that there is an “easy alternative” to the “lost-finger” selection scheme.  Continue reading “Chemically-Resistant Glove Selection”