How to evaluate the defoaming performance of defoamer by high-speed stirring test method?

How to use the high-speed stirring test method to evaluate the defoaming performance of the defoamer?

According to the viscosity of the applicable object, two methods were designed respectively. One is the foam level measurement method, that is, a dynamic test, which is suitable for low-viscosity paints and emulsions; the other is the density cup method, that is, a static test, which is suitable for high-viscosity paints and emulsions. The operation method is as follows.

(1) Foam level measurement method Put 100ml of paint sample into a 200ml tall cup with a scale of 1ml, add a specified amount of defoamer, start high-speed stirring (3 000~4 000r/min), and keep the speed constant , the time is 120~180s. Measure the foam height when the stirring time is 30s, 60s, 120s and 180s, or observe the time (s) required for the foam to reach a certain height.

(2) specific gravity cup method

In a 200ml container, weigh 150~200g of paint sample, add a specified amount of defoamer, start high-speed stirring (2 000~6 000r/min), and keep stirring at a constant speed for 120s. Measure the density with a pycnometer immediately after stopping stirring.

Measure again after 15 minutes - - secondary density. and compared with the original sample.

The advantage of the high-speed stirring method is that it is relatively simple and convenient, the result is more accurate, and the applicable objects are also wider.