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What is surface tension ?

To understand it easy, letís take, as an example, water which is always the reference because it is simple to use with a very high molecular energy (the highest after mercury).
Molecules of water are attracted together because molecular energy and external molecules of a drop are only under attraction of the centre of the drop of water (the spheric drop is the smallest surface you can get).

tension de surface

Surface tension : exemple of water

If you put this round drop on a flat material which has a weak surface energy, the internal attracted forces of the drop will be preponderant and the drop will have a minimum surface contact with the material (e.g., plastic film).

On the reverse, if the material (e.g. glass) is developing a molecular surface energy close to the energy of water, the energy of the material will balance the forces inside the drop which will increase its contact surface with this material, drop gets flat, wettability.

water and surface tension

If instead of using water, we use a liquid much weaker in energy (e.g., alcohol, hydrocarbon) on a plastic film of low surface energy but strong enough regarding alcohol, this film will be preponderant on the internal molecules alcohol energy. So alcohol drops will get flat, the material will be preponderant on the internal forces of the alcohol drop, of course this alcohol drop will be much more flat on glass which is even wettable with water with its energy higher than alcohol.

surface tension

Unit length of surface tension

Surface tension is measured in forces per unit length. Its unit is newton per metre and we measures it also in dyne per cm. In our surface tension pens, we uses these two units. One dyn/cm corresponds to one mN/m.

In practice: why this strength is so important ?

This surface tension is essential in printing, sticking and plastic industry. Higher is the surface tension of a material, stronger will be the adhesion of a substance (stick, ink) applicated on itself.

Why do we measures the surface tension ?

+ To know if a material is able to be printed or sticked.
+ To know the cleanness of a metallic material.
+ To know if a material was been treated corona, plasma ...

We advises our surface tension test ink range to measure the surface tension ...

Why do we treats the surface tension ?

+ To can print or stick plastic materials which is usually difficult.

Equipment for corona treatment and for plasma treatment...

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