Rheometer standardisation

A rheometer with multiple discrete dies, or die orifices in individual or shared die bodies, set within a common conditioning environment, configured for conducting different tests in parallel, through respective dies, with test conditions, including temperature and pressure, appropriate for each test and with multi-test ‘parallel’ or harmonised outcomes for a more complete assessment than any individual test, even a prime measure such as MFI, taken in isolation;

• with MFI remaining an invaluable part of a wider test spectrum since the other tests can be related to an MFI determination, albeit at each MFI test condition;
• the rheometer having refinements of which two involve capillary die geometry, and reflecting
• a simple and direct means of more accurate replication of important elements, factors or influences of Melt Flow Index flow conditions;
• standardisation, harmonisation or conformity of a so-called ‘multi-shear’ rheometer measurement or test with a Melt Flow Index measurement or test, in a common conditioning environment, to allow test inter-relationship;
• precise pressure measurement in a polymer melt, using appropriate sensors such as conventional liquid-filled sensors;
• reflecting rheometer reliance upon difficult measurement of polymer melt pressure;
• gear pump volumetric efficiency improvement at low flow rates for driving a sample through the dies;
• improved polymer temperature conditioning.

A rheometer configured for rheometric measurement for a range of materials using a range of different die profiles and dimensions, along with different test chamber through flow rates, and a range of gear pump speeds or capacities to drive material through the dies;

• with a so-called ‘replicate’ die profile, configuration, context and environment, together with environmental conditioning, of temperature and/or pressure, and a set of dies covering a measurement range or spectrum as a replicate group or cluster including an MFI die;
• whereby overall, the rheometer, or an isolated rheometer portion or test stream, is standardised to a prescribed rheological measurement reference standard, of which MFI is a prime example, variously with one or more of the following features:
• a so-called ‘Cluster Die’, with one or more die orifices ‘matched’ to a standard Melt Flow Index Die, for equivalent or replicate rheological effect;
• an orifice matched to a standard Melt Flow Index Die, to produce both a ‘multiplier’ pressure drop and equivalent overall rheological effect;
• individual regional adjustment(s), or combined regional adjustment(s);
• a slow, ‘matching’ taper to conjoin two flow regions, with minimal interference of flow pattern or pressure drop;
• thermometer placement in the body surrounds of a heated die, to measure die melt temperature;
• calibration or cross-referral of a thermometer for die melt temperature by temporary and/or permanent placement of other thermometers in the die melt, in the die and at the heating element(s) of the die;
• a temperature stabilisation device for melt pressure transducers of rigid or flexible stem construction, of any type of pressure transducer;
• the dies being disposed in a common and complementary measurement chamber, internal die disposition, transition pathway, entry and exit profiles, within temperature-conditioned confines and with embedded thermometer and pressure sensor.