Method for Determination of Coating Viscosity by SWIRL/spin Viscometer

1. Scope and description
   This method is mainly used for the quality control of anti-corrosion coatings, the measurement of absolute viscosity, and the viscosity determination of the main agent (component A) in two-component coatings. Test results are expressed in Pa • s (Pascal • seconds).
   2.Instruments and Materials

(1) Rotational viscometer: domestic NDJ-1 type (or American Brookfield DV-II+ type), measuring range 10~100000mPa • s, the instrument is shown in Figure 1; (2) Container: a beaker or paint can with a diameter of not less than 70mm; (3) Thermometer: The maximum range is 0~50°C, and the division is 0.1°C; (4) Stopwatch: The division value is 0.1s.

3.test methods

(1) Select the corresponding rotor and screw it into the connecting shaft of the instrument, then lower the instrument slowly, and gradually immerse the rotor into the sample to be tested, so that the liquid level of the sample just reaches the mark of the rotor shaft.

(2) Put a thermometer in the sample and let it stand for a period of time to keep the temperature of the sample and the rotor of the viscometer at (23±
0.2)°C (generally carried out in a constant temperature room).

(3) Press the pointer control lever on the upper part of the instrument, turn on the power switch, start the motor, and turn the variable speed knob at the same time to adjust the required speed, and finally loosen the pointer control lever to make the rotor rotate stably in the sample.

(4) Start the stopwatch for timing, choose different rotation times (usually 60s or 120s) according to different paint samples, and read after the pointer stabilizes.

(5) The reading of the pointer on the dial needs to be multiplied by the coefficient of the rotor to finally get the actual measured viscosity value.

η = Ka

In the formula, η——absolute viscosity, mPa • s;

K - coefficient;

α——The reading pointed by the pointer (deflection angle).

The coefficients of each rotor are shown in Table 1.

4. Result representation

The test results are expressed in Pa • s or mPa • s.

5. Instrument Description

(1) The domestic NDJ-1 or NDJ-1A rotary viscometer has 4 types of rotor specifications, that is, 1, 2, 3, and 4 rotors (No. 1 is the largest and No. 4 is the smallest), and there are also 4 types of rotor speeds. Namely 6r/min, 12r/min, 30r/min, 60r/min. For high-viscosity samples, use a small rotor and a slower speed; for low-viscosity samples, use a larger rotor and a faster speed. Refer to Table 2 for the relationship between rotor, speed and range.

Table 2 Relationship between rotor, speed and range