How Does Surface Tension Affect Cleaning Performance?

One of the biggest barriers to cleaning a surface is a chemical phenomenon known as “surface tension.” Many cleaning fluids from MicroCare have an extremely low surface tension which may enable them to out-perform other cleaning choices.

Surface Tension Examined:

In liquids, molecules cling to each other with an “intermolecular cohesive force.” This force is balanced and equal in all three dimensions because each molecule is attached to neighboring molecules in every direction. But at the perimeter of the liquid some molecules are in contact with a dissimilar material (such as glass, plastic or air) to which they cannot bond. In response, they bind to each other even more strongly.

This enthusiastic bonding creates surface tension. Surface tension makes raindrops spherical because water has a surface tension of 73 dynes/cm. With a surface tension of 484 dynes/cm, mercury forms playful droplets when spilled on a smooth surface. But surface tension causes problems as well. High surface tension makes it hard to clean small parts, PCBs with tight stand-offs or inside very small apertures.

Now, it’s important to realize that surface tension is not the only characteristic that affects cleaning results. Other features can be equally or even more important, such as density, materials compatibility, price, handling, aroma and packaging. But all things being equal, a cleaner with a lower surface tension will out-perform a cleaner with a higher surface tension. Let’s look at the details.

Better Choices:

Lower surface tension indicates a produces better cleaning. One of the lowest surface tensions of all is the MicroCare CMS. With a surface tension of only 19.2 dynes/cm, this fluid delivers the ultimate in surface wetting and the best possible cleaning result.

When combined with other chemical characteristics, it is possible to use surface tension to create an index that predicts the effectiveness of a cleaning fluid. This is called “the wetting index” and is a highly useful predictor of cleaning performance. As this table shows, the Universal Flux Remover has a lower surface tension than many other cleaning fluids. This should enable users to get their parts cleaner, faster, at lower cost, than any other technology.

Surface Tension and Wetting Indices for Selected Cleaning Fluids

Fluid Density Surface Tension Viscosity Wetting Index
Water 0.997 72.8 1.00 14
IPA Alcohol 0.79 21.7 2.40 15
n-Propyl Bromide 1.32 25.9 0.49 104
MicroCare™ Tergo MCF 1.28 21.0 0.42 145
Chemours Vertrel® Sion™ 1.28 21.0 0.42 145
MicroCare™ CMS 1.34 19.2 0.58 120

It is important to remember that surface tension is not the only predictor of good cleaning. In some instances, the benefits of low surface tension may not even be noticeable with an aerosol cleaner. But it’s an interesting innovation with much promise, and as such it is worth testing in many demanding applications.