Pigments are widely used in a variety of applications, such as paint, plastics, rubber, printing inks and so on. In order to ensure the stability of the pigment, the application and the quality of the end product, the determination of various physical and chemical properties of the pigment is very important. This paper mainly introduces the method of measuring the conductivity of pigment water suspension and its significance in practical application.
1. The importance of measurement

The conductivity of a pigment can reveal its solubility in water and the concentration of ions in it. This method is not suitable for pigments that are obviously soluble in water. However, for most pigments, this determination can provide us with valuable data on pigment stability, applicability, and properties of coatings or other composites.

Measurement and application of electrical conductivity of pigment water suspension FIG. 1

Determination and application of electrical conductivity of pigment water suspension

2. Determination method

(1) Water wettability test:

First, it is necessary to determine the water wettability of the pigment. Mix the pigment with boiled distilled water and observe its wetting. The pigment is hydrophilic if it is easily wetted by water, and hydrophobic if it is not easily wetted by water.

(2) Determination of hydrophilic pigments:

Weigh 20g of paint into a beaker and add 180g of boiling pure water.

After boiling the mixture for 5 minutes with continuous stirring, cool to about 60°C and add 200g of pure water.

Strain the mixture and discard the first 10mL of filtrate.

The conductivity of the filtrate was measured using a conductivity meter and a conductivity electrode. During this process, it is necessary to ensure that the temperature of the filtrate is 23°C and the position of the electrode is accurate.

(3) Determination of hydrophobic pigments:

20g of pigment is mixed with 4-16g of methanol to form a uniform paste.

Add boiling pure water and dilute to 200g.

After cooling to 60°C, filter and discard the first 10mL filtrate as well.

The electrical conductivity is also determined according to the above method.

3. Interpretation of results

The results should be averaged over two measurements and be accurate to 1%. The results of electrical conductivity measurement can provide an important basis for the selection and application of pigments. For example, high electrical conductivity can mean the presence of more soluble salts in the pigment, which can adversely affect properties such as the stability of the pigment, color saturation, and corrosion resistance of the coating.

Determination and application of electrical conductivity of pigment water suspension

4. Precautions in the experiment

The instruments and materials used are subject to rigorous inspection and calibration. For example, filter paper needs to be cleaned with pure water first to ensure that its conductivity does not exceed 5.0μS/cm.

In the measurement process, ensure that the experimental conditions, such as temperature, the exact weight of the substance, etc. are carried out in strict accordance with the standard.

According to the nature of the pigment, choose the appropriate determination method. This is essential to obtain accurate measurement results.

5. Reference standards

The determination method is carried out according to the national standard GB5211.12-86 “Determination of resistivity of pigment water extract”.

6. Conclusion

The measurement of electrical conductivity of pigment water suspension has important guiding significance for the selection and application of pigment. Through this determination method, the physical and chemical properties of pigments can be better understood, thus ensuring the high quality of the final product. The measurement of the conductivity of pigment water suspension plays a key role in the development, production and application of pigment. In order to ensure the performance of coatings or other pigment applications, this determination of pigments is essential.