1. This method is suitable for determining the dynamic viscosity of non-Newtonian fluids (polymer solutions, suspensions, emulsion dispersion liquids or surfactant solutions, etc.).

2. Instruments and utensils

2.1 Rotational viscometers (NDJ-1 and NDJ-4 are prescribed by the Chinese Pharmacopoeia) Viscometers (such as NDJ-1 and NDJ-4) that use frequency stabilization measures must be spared. Accuracy 1% Accurately weigh 8.0g hydroxypropyl methylcellulose sample, put into dry, tared 400mL tall beaker, add about 100idL of 80-90 degrees Celsius hot water, stir 10min to make dispersion uniform, Under stirring, add cold water to a total of 400 mLo and keep stirring for about 30 minutes to make a 2% (w/w) solution, put it in the refrigerator and cool it in an ice bath until the surface becomes thin ice. 20±0.1 degrees to detect viscosity.

3.1 The installation and operation of the instrument shall be carried out according to the instruction manual of the instrument, and the appropriate rotor and rotating speed shall be selected according to the viscosity range of the test product and the provisions of the pharmacopoeia under the main text of the product.

3.2 Adjust the temperature of the constant temperature water according to the measurement under each drug item.

3.3 Take the test sample and place it in the container specified by the instrument, and after constant temperature for 30 minutes, measure the deflection angle (Q ) according to law. Turn off the motor, restart the machine and measure again, the difference between each measured value and the average value should not exceed ±3% of the average value, otherwise a third measurement should be made.

3.4 Calculate the average value of 2 measurements according to the formula to obtain the dynamic viscosity of the test product.

4. Record and calculate

4.1 Record the model of the rotational viscometer, the rotor number and rotational speed used, the viscometer constant (K value), the measurement temperature, and the a value measured each time.

4.2 Calculation formula

Dynamic viscosity (MPa-s) two Ka

where K? is the viscometer constant measured with a standard liquid of known viscosity, a is the deflection angle