Determination of paint viscosity

涂料的粘度又叫涂料的稠度，是指流体本身存在粘着力而产生流体内部阻碍其相对流动的一种特性。这项指标主要控制涂料的稠度，合乎使用要求，其直接影响施工性能、漆膜的流平性、流挂性。通过测定粘度，可以观察涂料贮存一段时间后的聚合度，按照不同施工要求，用适合的稀释剂调整粘度，以达到刷涂、有气、无气喷涂所需的不同粘度指标。

国家标准CB/T 1723- 93规定了3种测定粘度的方法，包括涂-1、涂-4粘度杯及落球粘度计测定涂料粘度的方法，其中常用的测定方法是涂-4粘度杯测定法。此种方法简便易行，即以100mL的漆液，在规定温度下，从直径为4mm的孔径中流出，记录时间，以s表示，此为测定漆样的粘度。

测量时需注意

(1)测定的规定温度应在21~25C之间。因为温度过高测定的粘度比较稀，温度过低，粘度比较稠，不是标准值。

(2)每次测完要清洁涂-4杯，选用所测涂料相应的溶剂，防止测定小孔被堵。

(3)先用手指或器具堵严小孔漏嘴，倒满100mL漆液，用玻璃棒将气泡和多余试样挑入凹槽，防止测样不到或超过标准。

(4)迅速移开手指时，同时启动秒表，待试样流束刚中断时立即停止秒表，计时。

The empirical test method for the viscosity of paint products is to stir up the paint with a stick for observation . Normal paint should fall freely and continuously, if there is interruption and retraction, it means that the paint is thick . Generally, the paint on the stick and the paint in the barrel will flow continuously in a short period of time, and the connection distance is 30~50cm, which is close to the level of brushing. If it is less than 30cm, it means that the viscosity of the paint is too small, that is, the paint is too thin; if it is greater than 50cm, it means that the viscosity is too high, that is, the paint is too thick. This kind of viscosity, which is subject to the construction requirements and has been applied many times without using a viscometer, is called the working viscosity.

The method of measuring viscosity by coating -4 cups is the most commonly used method. Generally, the viscosity value of paint is between 40 and 150s. However, the viscosity of thixotropic paint measured by this method is too large, and a Rotational Viscometer is required. There are rotating paddle viscometers, coaxial Drum rotary viscometer, cone-shaped plate viscometer, etc., such as the measurement of the viscosity of architectural coatings using the Stormer viscometer (a type of rotary viscometer), the measured viscosity at this time is the result of the 200r/min rotation speed The required load is expressed in g or KU.

When adjusting the viscosity of the paint, appropriate diluent should be added as appropriate, and mechanical stirring should be used to make the paint uniform from top to bottom . The amount of diluent generally does not exceed 5% of the total mass of the paint, and the paint applied by high-pressure airless spraying generally does not add diluent.