The ISO 1409 outlines how to determine the surface tension of polymer dispersions and rubber latices. Two measurement methods with a force tensiometer are specified: the ring method and the plate method.

ISO 1409: Application and Use

In practical applications, determining the surface tension allows us to see how liquids wet a solid, how they mix with another liquid, and how they behave against a gas. The ISO 304 specifies how to determine the surface tension of polymer dispersions and rubber latices. It proposes two methods to do so: the ring and the plate method, conducted with a force tensiometer.

ISO 1409: Experimentation

Apparatus

To conduct measurements according to ISO 1409, the following apparatus is needed:

• tensiometer
• glass vessel (diameter of at least 45 mm)
• means to adjust the temperature of the sample liquid

As a sample body:

• a platinum or platinum-iridium ring (60 mm or 40 mm circumference) or
• a platinum or platinum-iridium plate

All Force Tensiometers of the DCAT series from DataPhysics Instruments comply with this standard.

Procedure

It is integral that the glass vessel and the sample bodies are properly cleaned before the measurements are conducted. The measurement should be repeated two to three times.

• Method A - ring method: This method is suitable, according to ISO 1409, for polymer dispersions and rubber latices, which have a viscosity of less than 200 mPa*s. The samples can be diluted with water to achieve this. Then, the ring is suspended from the balance. Afterwards, the sample container is first raised until the ring is submerged, then lowered. Before the ring detaches from the surface, the force is measured.
• Method B - plate method: The sample container is first raised until the plate is submerged, then lowered.. The force is measured to calculate the surface tension of the liquid.

The ISO 1409 is in use since 2020 and last reviewed in 2025. 

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