Explanation

It is also called shear viscosity. The flow of fluids includes laminar flow (or sheet flow) and turbulence. When the flow speed is not high, the flow of viscous liquids is laminar, and when the flow speed is high or when encountering obstacles, it will form vortices. The flow changes from laminar flow to turbulent flow. Laminar flow can be seen as liquid flowing in a thin layer under shear stress, with velocity gradients between layers. To maintain the velocity gradient between layers, a certain amount of shear force needs to be applied. Accordingly, the white part of liquid resists the white friction force of thin layer flow under the action of shear stress, which is called shear viscosity. It can be used as a measure of friction resistance of macromolecule melt during processing. The shear viscosity is equal to the ratio of shear stress to shear strain coefficient. The higher the shear viscosity, the worse the flow ability of the melt under shear. There are mainly three practical methods for measuring the shear viscosity of polymer melts. They are falling ball viscometer, rotational viscometer and capillary tube extrusion rheometer.

Classification