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.
Interest/Objective:
the rhéomètres capillaries allow the trials in conditions truly representative of the conditions of manufacture, particularly to the technology of high-pressure and high-speed such as injection moulding. they are therefore particularly useful for the optimization of the manufacturing process. they allow you to test the polymers, the polymers compounds, composites for strengthening weak and other similar materials.
other rheological properties can be measured or estimated using the rheometer capillary viscosity at elongation, swelling in the output of industry, thermal stability, slip at the wall. other related measures can also be carried out for the thermal conductivity, the dependence of the density as a function of pressure and temperature (pvt), the resistance of the melted.