Extensional rheometer is designed to measure directly the extensional viscosity of viscoelastic materials in the molten state
The MXR2 extensional rheometer from Magna Projects and Instruments is designed to measure directly the extensional viscosity of viscoelastic materials in the molten state.
For example, many polymer melts have significant extensional properties which can have a profound effect on processing behaviour (eg, by extrusion, calendaring, rolling, blow moulding, injection moulding).
The extensional viscosity behaviour of two materials can be much different to that predicted from the conventionally-measured shear viscosity, so failure to take extensional behaviour into account can lead to processing problems.
Extensional viscosity is thus an important facet of materials flow behaviour.
The MXR2 rheometer addresses the practical problems of clamping a molten polymer and supporting it before and during the test.
A bath of silicone oil is use to provide support to the molten sample and to control the temperature.
A precision, programmable servo-drive system allows the sample to be extended at strain rates of up to 100s-1: at this speed, the test duration is only about 0.1 second! The instantaneous tensile force on the sample is measured via a specially-developed, low-force load beam, and the data recorded via a computer system equipped with high-speed data acquisition. As well as measuring extensional viscosity at controlled strain rates and temperatures, the MXR2 may also be used to perform other tests such as stress relaxation upon molten polymers and other materials.
