The rotary viscometer is used to measure the shear force of liquid between concentric circles, conical plates and andante plates, and is an effective tool to determine the dynamic viscosity. It is suitable for the determination of liquid viscosity of Newtonian fluid or similar Newtonian fluid characteristics, and the test range is 10~109 mPa•s. This paper will introduce the preparation of instruments and reagents, elaborate the test methods, and point out the precautions and results.

Instruments and reagents

When performing rotary viscosity tests, it is necessary to use rotary viscometers, beakers, super thermostats, thermometers and thermostats ovens. For liquid samples, the temperature needs to be precisely controlled in a 500mL beaker. For solid objects, they should be preheated and melted in the oven and then put into the super constant temperature tank for temperature adjustment.

Measurement and application of viscosity of rotary viscometer

Procedure of use

Install the protection frame, screw the selected rotor into the connecting screw, and adjust the instrument level so that the liquid level mark of the rotor is parallel to the liquid level.

Start the motor, make the rotor rotate in the liquid, and wait for the pointer to stabilize or read at the specified time. Use the pointer lever for reading and adjust the rotor or speed for a better reading.

If the extension cable is used, it can be carried without a protection frame. If it is installed on the support, it needs to be installed in 180° reverse, and then the end of the extension cable is screwed into the connection screw for testing.

Select the appropriate rotor and speed according to the estimation of the liquid viscosity range. If it is impossible to estimate, first use a small rotor and slow speed test, gradually adjust.

Repeat the operation for three times, the difference between the test values shall not exceed 3% of the average value, and the arithmetic average value is used to represent the test result.

Measurement and application of viscosity of rotary viscometer

Matters needing attention

When testing with a rotary viscometer, ensure that the instrument is clean and well-tuned and that the rotor is fully immersed in the liquid. The temperature of the test liquid should be accurate to avoid the influence of too high or too low temperature on the test result. According to the test requirements, use the appropriate rotor and speed to correctly read the value displayed by the instrument. Clean and maintain instruments and reagents before and after testing. Make sure the test environment is relatively constant, especially temperature and humidity. Environmental changes may affect the test results, so the interference of environmental changes on the test results should be avoided as far as possible during the viscosity test. Some samples may require a certain amount of pretreatment or stabilization time before testing, such as dissolving solid samples, stabilizing temperatures, etc. Ensuring the stability of the sample helps to obtain accurate test results. In actual testing, compliance with the above supplementary points will help ensure the accuracy and repeatability of the rotary viscometer test.

Reference standard

This test method conforms to the national standard GB/T 20035-2008 “Determination of Liquid viscosity” and GB/T 2794-1995 “Determination of adhesive viscosity” of the People’s Republic of China.