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Automatic cloudpoint measurements
As most physical phenomena, turbidity is depending on temperature. Therefore, the cloudpoint temperature of a liquid is a characteristic property, which is defined as the temperature at which a liquid begins to become cloudy. Some liquids become cloudy at rising and other at falling temperatures. To determine the cloudpoint accurately and reproducibly, the temperature of the test
liquid must be heated up or cooled down under controlled conditions. The test liquid must be stirred continuously in order to avoid inhomogenities and the temperature in the liquid must be measured accurately by a precision resistance thermometer.
Degree of compatibility
In many applications, the test liquid is a solution of a solid material and a solvent, so that the cloudpoint is depending on the compatibility of these two components. Variances in the solvency properties of the solvent are leading to different results in cloudpoint measurements. Therefore, test solvents of consistent composition and analytical quality must be used for accurate
cloudpoint measurements.
Standard test method
The standard test procedure to test the cloudpoint of natural or synthetic resins for the production of printing inks is as follows: Two grams (0.07 oz) of resin and 18 grams (0.63 oz) of test oil are weighted into a glass test tube in which a magnetic stirrer rod has been inserted. Under controlled heating and stirring conditions the sample is heated up to 230 °C (450 °F) and
remains at this temperature level for 2 minutes during which the resin is completely dissolved in the test oil. This clear and homogeneous solution is then cooled down until the cloudpoint temperature is reached. At the end of the test the measured value is printed on paper with a test report by an integrated data printer.
Novel turbidity detection system
The turbidity detection system of the CHEMOTRONIC is based on the principle of light absorption due to suspended particles in the liquid. Errors due to colour changes are eliminated by the use of a narrow band infrared light source. The user can adjust which turbidity is recognised as cloudpoint by executing a calibration procedure and choosing one of the 10 turbidity levels.
Recommended by EUROCOMMIT
The CHEMOTRONIC is recommended by the European working group for standardisation of ink test methods EUROCOMMIT as a preferred method for cloudpoint measurements in research and industry. Extensive round-robin tests have proven the reliability of this test method.
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