Definition of viscosity (viscosity)
Viscosity represents the internal resistance of the liquid to flow. It reflects the degree of viscosity and thinness of the Coating. Coatings with excessive viscosity have large internal movement resistance, difficult flow, inconvenient finishing, and wet coatings are not easy to levelling, and are prone to defects such as coating marks and wrinkling, which affect construction; on the contrary, if the Coating viscosity is too low, it will cause defects such as sagging, too thin coating, and too many coating times.
There are many ways to measure viscosity, and at present, T-4 cups are mostly used
Viscometer measures Coating viscosity. When Coating is used, it can be divided into original viscosity (factory viscosity), the original viscosity is the viscosity of the original paint; construction viscosity is also called working viscosity, that is, the viscosity suitable for a certain finishing method.
The construction viscosity is the most suitable viscosity determined by experiments according to the specific conditions in production (such as Coating varieties and finishing methods, etc.), and expressed by specific numbers (such as the number of seconds of coating-4 cup viscosity). It is one of the important parameters for formulating finishing process regulations.
There are many kinds of liquid Coating viscosity detection methods, which are used for different varieties. Generally, the viscosity detection of transparent varnishes and low-viscosity Paints is mainly based on the outflow method, and the detection of transparent varnishes is also the bubble method and the falling ball method. For high-viscosity varnishes or Paints, the viscosity is determined by measuring the stress at different rates, generally using Rotational Viscometer.
Coating viscosity can be adjusted by solvent. Therefore, Coating viscosity is related to the solvent content in the Coating composition. When the solvent content in Coating is high, its viscosity is low. Coating viscosity is also related to the environment temperature and the temperature of Coating itself. When the temperature is high or the Coating is heated, the viscosity will decrease. During construction, if a large amount of solvent evaporates, the Coating will naturally thicken.
The outflow method is to measure the time for the liquid Coating to flow out in a container with a certain solution and pore size to indicate the viscosity of the Coating. Various Viscosity Cups (meters) are commonly used to measure. Such as Viscometer, Iwata Cup, Rotational Viscometer, etc
