The viscosity of a coating, also known as the consistency of a coating, refers to a property in which the fluid itself has an adhesive force that causes the interior of the fluid to impede its relative flow.
This indicator mainly controls the consistency of the paint, which meets the requirements of use, which directly affects the construction performance, the leveling property of the paint film, and the sag. By measuring the viscosity, the degree of polymerization of the coating after storage for a period of time can be observed. According to different construction requirements, the viscosity is adjusted with a suitable diluent to achieve different viscosity indexes required for brushing, gas, and airless spraying. The national standard GB/T1723-93 specifies three methods for measuring viscosity, including the coating-1, the coating-4 viscosity cup and the Stormer viscometer to determine the viscosity of the coating. The most commonly used method is the Stormer viscosity. Measurement method. This method is simple and easy, and the viscosity of the paint sample is measured by the rotation of the rotor.
Stommer type viscometer should be noted when measuring:
(1) The specified temperature should be between 21 and 25 °C. Because the temperature is too high, the viscosity is relatively thin, the temperature is too low, and the viscosity is thick, which is not a standard value.
(2) The rotor should be cleaned after each measurement.
(3) Wait until the display reading is stable, which is the viscosity value of the sample.
An empirical test for the viscosity of a coating product is to use a stick to pick up the coating for observation after stirring. Normal paint should fall freely and continuously, if it is interrupted and retracted, indicating that the paint is thicker. Generally, the paint on the stick and the paint in the barrel will be connected to the flowing stream in a short time, and the connection distance is 30 to 50 cm, which is close to the degree of brushing. Less than 30cm, indicating that the viscosity of the coating is too small, that is, the coating is too thin; greater than 50cm, indicating that the viscosity is too large, that is, the coating is too thick. This viscosity, which is subject to the construction requirements and at the same time through multiple practical applications, is not measured by a viscometer, and is called the working viscosity.
The method of measuring the viscosity of the -4 cup is most commonly used. Generally, the viscosity of the coating is between 40 and 150 s. However, the viscosity of the thixotropic coating measured by this method is too large, and a rotary viscometer is required. Rotary paddle viscometer, coaxial drum rotary viscometer, cone flat viscometer, etc., such as the viscosity of the architectural coating is measured by the Strome viscometer (a type of rotary viscometer), the viscosity measured at this time It is the load required to produce a 200r/min speed, expressed in g or KU. When adjusting the viscosity of the coating, appropriate diluent should be added as appropriate, and mechanical agitation should be used to make the coating uniform. The amount of diluent generally does not exceed 5% of the total mass of the coating, while coatings that are applied by high pressure airless spraying are generally free of diluent.
(provided by Shenyang Building Materials Network) <
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