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Spotlight on Contact Angle Measurement

Today we’re going to shine our spotlight on surface energy measurement, and more importantly, Contact Angle measurement. Contact Angle meters are also known as optical Tensiometer’s or Goniometer’s, and are a popular method of Surface Energy measurement. Although this differs slightly from our usual Plasma focused articles, Contact Angle measurement is an integral step in the Plasma Treatment process.

Increasing Wettability - Petri DishesMany engineers find, when attempting to print, coat or adhere to “non-stick” plastics, the liquid doesn’t wet the materials surface well and will often form into small beads.  Why is this? Generally, as a rule, to achieve good adhesion, the surface energy of the material must be higher than the relative surface tension of the liquid (ink, adhesive, coating, etc.)

Due to this, measuring and understanding the relationship between the surface energy of the material and the surface tension of the ink, adhesive or coating is critical to ensure the correct levels of surface activation are achieved.

Why Contact Angle Measurement?

ThetaLITE Contact Angle MeasurementContact Angle meters allow direct measurements of surface tension, interfacial tension and contact angles. The versatility of the Contact Angle meter, being suitable for characterisation of both liquids and solids, make this a popular measurement technique in both industrial and academic settings.

Combining both high technology test instrumentation, and a non-destructive testing method, obtaining accurate, objective and repeatable analysis is made simple.

A Contact Angle meter, such as the ThetaLite, can compare the effects of a range of surface treatments and gather data that correlates to various surface conditions, e.g. wettability, surface energy, etc.

What is Contact Angle Measurement?

Contact Angle, θ, is a quantitative measure of the wetting of a solid by a liquid. It is defined geometrically as the angle formed by a liquid at the three-phase boundary where a liquid, gas and solid intersect. The well-known Young equation describes the balance at the three-phase contact of solid-liquid and gas.

γsv = γsl + γlv cos θY

The interfacial tensions, γsv, γsl and γlv, form the equilibrium contact angle of wetting, many times referred as Young Contact Angle, θY.

What do your values indicate?

Non-Wetting Contact Angle
Non-Wetting Contact Angle

Simply put, a low contact angle values indicate that the liquid spreads on the surface while high contact angle values show poor spreading of the liquid, coating or adhesive.

Wetting Contact Angle
Wetting Contact Angle

When the contact angle is 0 degrees, complete wetting (spreading) occurs, between 0-90 degrees, the solid is wettable and above 90 degrees indicates that the surface is non-wetting with the liquid being tested.

Often, printing inks and adhesives are of a fixed surface tension and altering the surface energy is often the only option engineers are left with to improve adhesion. Plasma Treatment is an excellent method of improving adhesion properties due to altering the surface molecules to improve adhesion; our process doesn’t alter the bulk properties of the material and more importantly is a clean, dry and environmentally friendly process.

Speak to an expert…

If you’re having problems with adhesion and would like to speak to the experts, give the Dyne Technology engineers a call on +44(0) 1543 411 460 or email support@dynetechnology.co.uk.

Contact Plasma Treatment expertsIf you’re interested in finding out more about surface measurement solutions, we recommend getting in touch with the surface measurement experts, Dyne Testing.