Defoaming performance experiment -- measuring cylinder method, high speed stirring method, bubbling method, vibration method, circulation method

(1) Measuring cylinder method

This method is suitable for the preliminary test of low viscosity coatings and emulsions. Add 20-30ml sample into a 50ml cylinder with a grinding plug, and then add an appropriate amount of defoamer. Press the grinding plug tightly with your finger and shake it violently back and forth 20 times. Record the foam height immediately after stopping, and record the foam height once at a certain interval, and then compare the different defoamer. This method can be carried out even with few samples, which is simple and convenient, but the result is very coarse, which is only suitable for the preliminary screening of defoamer.

(2) High speed stirring method

The method is applicable widely, relatively simple and convenient, and the result is correct. It has foam level measurement method, i.e. dynamic test, suitable for low viscosity coatings and emulsions and specific gravity loop method, i.e. static, suitable for high viscosity coatings and emulsions.

(3) Cycle method

During roll coating or spray coating, the remaining paint after coating falls into the receiver for recycling. Imitating the antifoaming performance experiment method of the system, the falling height and flow rate of the circulating material are kept constant, and the height of the material in the receiver is recorded in each period of time.

(4) bubbling method

This method is to direct air into the system to produce foam, and other methods are different. It is suitable for low viscosity coatings or emulsions. Add 100ml of test material into a measuring cylinder with a diameter of 5cm. After adding defoamer, 500ml of air is introduced into the cylinder every minute with a quantitative pump. The temperature is controlled at 30℃, and the foam height is recorded at certain intervals.

(5) Vibration method

Red Devil vibration test press a certain height, repeated vibration. Add the test material to 1/2 volume of the experimental tank, and measure the density after vibration in accordance with the specified time. The time of the vibration can be determined by how easy the foam is to create. The smaller the air mixing rate, the better the defoaming effect.

(6) vacuum pumping method

After shaking the sample, put it into a container closed to observe the foam elimination rate. This method is suitable for the defoaming test of high viscosity system.

Coating experiment -- brush coating, roll coating, scraping coating, spray coating, should also include the full performance of the coating film

The samples were dispersed at high speed in a high-speed mixer for 1 minute (2000r/p), and immediately poured evenly on the PET film. After the surface was dried, the defoamization was observed and compared.

After measuring the defoaming performance of the coating, it is also necessary to carry out shrinkage, miscibility, gloss, color and other performance tests. The coating machine will paint on the glass plate, the thickness of up to 75un, observe the shrinkage of the paint film, with the wool felt roller coating on the cement board, the cement board is usually half of the surface of the first sealed, can be used to break the bubble speed and dry film residual bubbles to judge the size of the defoaming ability. Shrinkage cavity can also be observed.

Storage stability test - Observe defoaming performance and paint film appearance changes after natural storage and high temperature storage

The paint samples of the oiling antifoaming agent were placed in a 50℃ incubator for 1-2 weeks, and the properties were compared with the samples whose antifoaming ability was initially measured. This condition is generally equivalent to 6 months of storage at room temperature.