Principle : A rheometer capillary is a device for measurement of the viscosity in shear and other rheological properties (= flow). the rhéomètres capillaries used for plastics are type systems piston-chain designed to measure the viscosity of the polymer dissolves as a function of temperature and strain rate.
the principle of operation is the following : a sample of thermoplastic (originally in the form of powder, granules or flakes) is liquefied by heating and forced to flow into a cylinder through a spinneret capillary.
two main methods can be used :
– one measure of the rate of flow by volume in the case of a test at constant pressure and fixed.
– is to measure the test pressure in the case of a test volume flow rate is constant and fixed.