The cloud point temperature is a characteristic value in the quality control of synthetic resins for printing inks. Deviations in cloud point can lead to sedimentation in the varnish, differences in drying speed, loss of gloss and tack stability.
Definition of Cloud Point
The cloud point is the temperature at which a resin begins to precipitate in the liquid phase. The automatic cloud point test method introduced here, has been approved by the leading resin manufacturers worldwide as a standard method for production setting and quality control of printing ink resins.
Standardization test procedure for cloud point determination (ASTM D6038)
This test procedure requires minimal resin and test oil and is providing excellent repeatability and reproducibility. Each test run is using only 20g of sample material consisting of a 10 % solution of resin in a test oil with defined solvency.
Under precisely controlled conditions, the sample is heated up to 250 °C and remains at this temperature for two minutes during which the resin is completely dissolved. After this time a controlled cooling phase begins and the cloud point is accurately measured by a calibrated turbidity detection system in a temperature range of 40-200 °C. The test result is printed on an integrated impact printer. The total duration of the test is less than 15 minutes for cloud point >50 °C.