How Does the Surface Tension of a Solvent Affect My Cleaning Results?
MicroCare precision cleaners are the best choice in the industry for cleaning difficult shapes and awkward pieces. The reason for this success is the very low surface tension these products exhibit.
Surface tension is the cohesive behavior of a liquid in which the molecules of the liquid are more attracted to each other than to the surfaces around it. This is an “attractive force” and is exerted upon the surface molecules of a liquid by the molecules beneath the surface. The behavior we all see and know is when the liquid forms itself into a shape having the smallest surface area.
High surface tension liquids, like water, form three-dimensional balls or bubbles, as in the photo on the right. Low surface tension materials spread out, flowing across a surface and exhibit very little three-dimensional height.
We experience surface tension is a thousand ways, every day. Every time we wash the dishes or take a shower, we add soap to the water to lower the surface tension of the water so that it more readily soaks into pores and soiled areas. The water strider is an insect which can walk on the surface of water because their weight is not enough to penetrate the surface. Many camping tents are somewhat rainproof in that the surface tension of water will bridge the pores in the finely woven material. But if you touch the tent material with your finger, you break the surface tension and the rain will drip through. And, interestingly, cold water has more surface tension than hot water, which is why hot water cleans better than cold water.
Surface Tension Affects Precision Cleaning
When it comes to precision cleaning, especially in a vapor degreaser, solvents with lower surface tension will out-perform high-surface tension fluids. Lower surface tension means the solvent can get into tight spaces easily. It directly affects the ability of the solvent to wet a surface, and obviously you can’t clean if you can’t wet.
Here’s how the numbers rack up:
|Product Generation||Brand Name or Description||Base Chemistry||Surface Tension (dyne/cm)|
|First Generation Solvents||TCE||Chlorine||29|
|PCE or Perc||Chlorine||35|
|Second Generation||Genesolv™ 2004†||HCFC-141b||19|
|Third Generation||Novec 71DA||HFE-7100||16|
|Fourth Generation||Opteon Sion/SF79||MPHE||21|
|Tergo™ Generation||Tergo™ Metal Cleaning Fluid||HFO-110||21|
|Tergo™ CFCF Rinse||HFO-110||14|
|Tergo™ High Perf. Flux Remover||HFO-110||19|
* Indicates a flammable solvent; this usually is an ingredient in an azeotropic blend.
† Indicates a Class 1 or Class 2 ozone-depleting solvent; no longer used by environmentally responsible companies and countries; included here merely for completeness.
A higher wetting index means the product will deliver better cleaning. As you can see, the best cleaners include the new Vertrel™ and Opteon™ solvents from Chemours and the new Tergo™ cleaners from MicroCare.
So here’s the short answer you were probably looking for: when it comes to tough cleaning problems, modern, nonflammable solvents are a far perfect choice than old-style aqueous cleaners. The new products don’t have any of the environmental baggage of the old-style solvents and are great replacements for ozone-depleting solvents such as HCFC-225, toxic solvents such as TCE and the high-global-warming solvents such as perfluorocarbons (PFCs).