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ramé-hart Newsletter

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January 2017

  Contact Angle and Adhesion
  Among the dozens of applications for which our ramé-hart contact angle goniometers and tensiometers are used, one common purpose is to ensure that surfaces are properly cleaned prior to bonding and coating processes. Since a surface that is contaminated with oils or other foreign matter will exhibit poor wetting, it's standard protocol for many processes to clean the surface prior to bonding or coating.

Our contact angle tools are used to check the cleaning step to ensure that it successfully lowers the surface energy of the solid surface to an acceptable range. However, surface energy alone is not always enough. Since many surfaces also require a roughness in order to achieve optimal bonding, the advancing and receding contact angles are also often measured in order to characterize the impact roughness has on the wetting behavior of the surface. Generally, as the contact angle hysteresis (i.e., the difference between the advancing and receding contact angles) increases so too does the surface roughness. A small hysteresis is an indication of not only of surface smoothness (i.e., lack of roughness) but also chemical homogeneity.

Since surfactants are commonly used in cleaning processes, the efficiency of the surfactants can be quantified by measuring the surface tension using a ramé-hart tensiometer.

And since many bonding processes involve hot melt and other adhesives applied at higher temperatures, one of our Environmental Chambers and our Elevated Temperature Syringe can be used to capture contact angle and surface tension at working temperatures.

Bonding to surfaces that exhibit high surface energy such as metals present fewer challenges compared to low surface energy surfaces such as polymers. Plastics are often treated using chemical, plasma and corona treatments prior to bonding or coating in order to increase the surface energy.

Successful bonding requires an intimate familiarity with the properties of the bonding agent as well as the wetting properties and surface energy of the surface. These properties can be captured and analyzed using ramé-hart instrument products.

  Our Five Most Popular Videos
  For a number of years, our video series has been a big hit with potential and existing customers who wish to learn more about how our tools work. We are constantly adding new videos. You can watch them here:  https://www.youtube.com/user/ramehart/ Currently we have over 100,000 views and dozens of subscribers. Here are our top five most popular videos:

1. Interfacial Tension, 9.5k views. In this tutorial, we dispense an oil to form an inverted pendant drop. We create an experiment to measure the interfacial tension between the oil and the external phase which is water.

2. Advancing and Receding Contact Angles with the Automated Dispensing System, 9k views. In this tutorial, we show how to use the step command to add volume to a drop while taking measurements in order to capture the advancing contact angle. We then step in and measure in order to capture the receding contact angle. Note that the right line option is used to filter out the dispensing needle.

3. Contact Angle on Superhydrophobic Surface, 7.4k views. In this video, we demonstrate how the contact angle is measured on superhydrophobic surface. In this example, we capture a contact angle of 171°.

4. Advancing and Receding Contact Angles using the Tilting Plate Method, 7.2k views. In this tutorial, we create a new experiment using the Automated Tilting Base to add a 1° tilt prior to each measurement. As the tilt angle increases, the advancing contact angle increase while the receding contact angle decreases. In this case, the drop stays on the surface all the way to 90° tilt.

5. Surface Tension, 7.2k views. This video shows the steps involved in creating and running a surface tension experiment using a pendant drop and DROPimage Advanced. 

Please explore our videos here https://www.youtube.com/user/ramehart/videos. If you don't see what you're looking for, please let us know and we will add your request to our 2017 video wish list.

  Happy New Year
  Wishing you and your team a Happy and Prosperous New Year. If we can be of any assistance to you and your surface analysis needs in 2017, please reach out to us. Thank you for your continued business.

Carl Clegg
Director of Sales
Phone 973-448-0305
Contact us



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