Coating viscosity determination

Instruments and reagents

Coated - 4 cups; glass rod; stopwatch (division 0. 2s); Rotational Viscometer; Stormer viscometer. The experimental setup is shown in Figure 5-13 and Figure 5-14.

Paint: Nitro wood paint, interior latex paint.

Method and principle

Viscosity is a characteristic that hinders the relative flow inside the fluid. It is the flow resistance , also known as viscosity (stiction) or internal friction, that is, the degree of viscosity or thinness of the liquid coating. Different coating methods require different paint viscosities. The viscosity of the paint used for manual brushing, flow coating, stick coating and high-pressure airless spraying can be higher, and the air spraying method requires a lower viscosity of the paint. Viscosity is greatly affected by temperature. The viscosity of the paint is related to the ambient air temperature and the temperature of the paint itself. When the paint is heated, the viscosity will naturally decrease. During the construction process, as the solvent evaporates, the viscosity of the paint will increase. Pay attention to measure the viscosity of the paint at any time.

The viscosity of coatings is divided into original viscosity (factory viscosity) and construction viscosity (working viscosity). The original viscosity refers to the viscosity of the paint purchased by the paint unit. The working viscosity is to prepare the paint with a diluent, which is suitable for a certain finishing method and can ensure the viscosity of a normal coating.

The relevant standards for the determination of paint viscosity mainly include GB/T 1723-93, GB/T 9 7 5 1. 1-2008 "Determination of Viscosity by Rotary Viscometer for Paints and Varnishes Part One", GB/T 9269 -2009 "Paint Viscosity Determination of Stormer Viscometer Method " GB/T 17 23-93 method is commonly used to measure the viscosity of Tu-4 cup, Tu-1 cup and falling ball viscometer . The working principle of the Rotational Viscometer (Figure 5-15) is to use a cylinder, disc or paddle to rotate to make it generate a rotary flow, and measure the stress required to make it reach a fixed shear rate . Converted to viscosity.

Measurement steps

1. GB/T 17 23 — 93 (Method for determination of paint viscosity)

Tu-1 cup is suitable for measuring products whose outflow time is not less than 20s; Tu-4 cups is suitable for measuring products whose outflow time is less than 150s; falling ball viscometer is suitable for measuring products with higher viscosity. The specified sample temperature is determined to be 23°C ± ± 0.2°F. Adjust the paint at this temperature for a period of time, plug the small hole leak with fingers or utensils, and fill it with 100ml. Use a glass rod to pour air bubbles and excess samples into the sample. Groove to prevent the test sample from falling below or exceeding the standard. Put a 200ml iron can or Jieci cup on the leak nozzle; when you quickly remove your finger, start the stopwatch at the same time, and stop the stopwatch immediately when the sample stream is just interrupted; Repeat the test, The difference between the two measured values ​​shall not be greater than 3% of the average value, and the average value of the two measured values ​​shall be taken as the test result.

2. GB/T 97 51. 1 — 2008 (Determination of viscosity with Rotational Viscometer)

试样温度控制在 23±0.2℃注意保护新轴与游丝）， 检查仪器、 调节水平， 去除试样中的气泡。

在连接转子时要注意保护黏度计的连接头， 并用手指轻轻将其提起， 这样可以避免承重系统中的钢针和宝石轴承座的强烈碰撞与摩擦。 转子的螺帽和黏度计的螺纹连接头要保持光滑及清洁， 以避免转子转动不正常。 黏度测最的标准容器是 600mL 的烧杯， 为保持测量条件的 一 致性， 不同样品的测最应使用固定容积的容器。

进行测量前， 选择转子和转速组合；转速或转子的改变会导致黏度读数的变化。 黏度大的样品， 使用面积小的转子和较低的转速；对于低黏度的样品， 情况相反。

转动升降旋钮， 将转子浸入样品中至转子杆上的凹槽刻痕处。如果是圆盘式转子， 注意要以 一 个角度倾斜地浸入样品中（先将转子以 一 个角度倾斜插入样品中， 然后再安装到黏度计机头上）， 以避免因产生气泡而影响测试结果。

Before reading, it should be kept for a period of time to allow the reading to stabilize. The length of time depends on speed used and the nature of the fluid; in order to obtain high-accuracy test results, the torque reading should be within the range of 30~90. After the measurement, remove the rotor, clean it put it back into the box in which the rotor is installed. NDJ-1 type reading: Indication reading X factor = result. For example, if the core rotor is used and the speed is 12r/min, then the coefficient is 500, if the indicator is 60, then the result is 60X500 = 30000 (mPa• s). NDJ-1 Rotational Viscometer coefficients are shown in Table 5-5.

3. GB/T 9269 — 2009 "Determination of Coating Viscosity Stormer Viscometer Method)

GB/T 9269-2009 is applied to the determination of the viscosity of architectural coatings. During the measurement, the temperature of the sample is controlled at 23. o·c ± o. 2·c. Clean, select, install the rotor (pay attention to protecting the new shaft and hairspring), check Instrument, adjust the level, remove air bubbles in the sample, immerse the paddle in the sample to be tested , measure the mass required to make the rotating speed reach 200r/min, and the result is expressed in KU.

Precautions

① The sample should be stirred evenly at regular intervals, and special attention should be paid to keeping .

② After the first measurement, clean and apply -4 cups, and choose the corresponding solvent to prevent the small holes from being blocked.

result report

See Table 5-6 for the result report.