Viscosity is one of the main physical and chemical properties of liquid or colloidal systems. There are many methods for testing the viscosity of liquid coatings, which are suitable for different coatings. For clear varnishes and low-viscosity paints, the flow-out method is mainly used. For high-viscosity coatings, the viscosity should be measured by stress method at different shear rates.
ISO 2431-1993 (E): 1 set of 4 Flow Cups with discharge holes of 3mm, 4mm, 5mm and 6mm. It is suitable for Newtonian or near-Newtonian liquids, and the kinematic viscosity range of the tested sample is 7 ~ 685 mm2/s.
The outflow viscometer suitable for the construction site is mainly recommended to use the Zahn cup, which is a cup type with a light viscosity, the bottom is cylindrical and spherical, the handle is long, and the volume is 44cm3. According to the size of the small hole at the bottom, it is divided into 5 models to form a set, which is used to measure products with different viscosities, and the measuring range is 20~1200mm2/s.
For high-viscosity liquids with non-Newtonian fluid properties and viscous paints and emulsion paints, Rotational Viscometers are generally used . In addition to measuring the viscosity change of non-Newtonian liquids at different rotational speeds (shear rates), it can also be used to study the rheological properties of non-Newtonian liquids, that is, the properties of flow and deformation, including viscosity, thixotropy, yield value and flow curve . The Stormer Rotational Viscometer measures the viscosity by measuring the force (g) required to produce a speed of 200 r/min when the blade is immersed in the sample. Test results are expressed in KU (Krebsunit).
GB/T 1723-93 stipulates the method of measuring coating viscosity with Tu-1 viscometer, Tu-4 viscometer and falling ball viscometer. Tu-1 viscometer is suitable for the measurement of coating products with a flow time of not less than 20 seconds; Tu-4 viscometer is suitable for the measurement of coating products with a flow time of less than 150 seconds; falling ball viscometer is suitable for measuring high-viscosity transparent coating products.
