Viscosity

The term viscosity relates back to the typically viscous juice from berries in the botanical systematics of mistletoes (viscum spp.) from which birdlime was gained. Viscosity is a physical value and gives information about the siziness of a liquid. Its reciprocal value is fluidity, measuring the flowability of a liquid. The larger the viscosity, the more viscous or the less fluid the medium is. We differentiate between dynamic and kinematic viscosity. Dynamic or absolute viscosity is measured in Pa.s or mPa.s and is usually determined with the aid of a rotation viscometer. The dynamic viscosity of most liquids reduces as the temperature increases. The kinematic viscosity is specified in m2/sec. It is the measurement for the internal friction of a liquid and describes the resistance of liquids against shear stress. Here, the term shear viscosity is used as opposed to bulk viscosity which results for instance from a consistent pressure to liquids. Kinematic viscosity can be calculated by dividing the dynamic viscosity by the density of a liquid. STRIKO process technology requires specifications on viscosity from its customers if for instance it is about choosing the right type of mixer in the static mixer product range for a special application. The more precisely the existing process parameters are known the more effectively a static mixer can be designed and produced.