Determination of Coating Density

Instruments and reagents

Pycnometer (Figure 5-8) (capacity is about l00mL); analytical balance (accurate to 1 mg); thermometer (accurate to 0.2 °C); thermostatic chamber; dust cover. Deionized water; latex paint (interior paint).

Method and principle

Use deionized water to calibrate the volume of the pycnometer: first fill the pycnometer with water, use the subtraction method to weigh the mass of the water in the bottle, test the water temperature at this time, check the density of the water at this temperature, divide the mass of the water by this When the density of water is obtained, the volume of the pycnometer can be obtained. After the pycnometer is filled with the product to be tested, use the subtraction method to weigh the mass of the coating in the bottle, and divide the mass of the coating by the volume of the pycnometer to obtain the density of the coating.

Measurement steps

① Calibrate the volume of the pycnometer according to the standard GB/T 6682-1992, and it needs to be calibrated at regular intervals .

② Weigh the mass of the pycnometer and record it as m ₁ .

③ Fill the pycnometer with the sample, wipe off the spilled sample with an absorbent material, weigh it again and record it as m ₂ .

④ Use the difference between m ₂ and m ₁ to calculate the mass of the paint sample, and divide the mass of the paint sample by the volume of the pycnometer to obtain the density of the paint sample.

⑤ Repeat the measurement twice according to the above method.

Precautions

① It is necessary to keep the temperature of the paint and the room at 23 °C ± 2 °C.

②The pycnometer needs to be calibrated at regular intervals, or when the volume of the pycnometer changes, it needs to be calibrated.

③ The paint sample needs to emerge from the small hole on the top of the pycnometer to ensure that the pycnometer is completely filled with liquid and prevent the generation of air bubbles.