Melt mass flow rate (MFR), often also referred to as melt index, describes the ease of flow of plastics at a defined temperature. This property is measured by extruding a thermoplastic polymer melt at a specified temperature, under a pressure generated by a specific weight, through a capillary tube of known dimensions. The result is the extruded mass per unit of time, expressed in g/10 min. With a known melt density it is possible to determine MFR from the melt volume flow rate (MVR). In this test method the weighing of polymer extrudates is replaced by continuous measurement of the extrusion volume. The result for the MVR value is shown in cm³/10 min. The advantage of this test is the significantly greater level of test sequence automation, requiring no operator intervention. The test method employs a specimen size of approximately 4 to 8g. A test lasts approximately 10 to 25 minutes and requires only limited technical expenditure. Moisture-sensitive polymers such as Polyamide 6 or Polyamide 66 must first be dried at temperatures below 80°C to a moisture content of less than 0.08%. Variations in molecular distribution can be identified quickly and reliably in this simple way, particularly in the polyolefins often used for manufacturing pipes, as well as in other polymers. This test method is usually employed in goods inwards checks by pipe manufacturers and allows them to ensure that continuous production can be maintained, even when changing batches.
The fully automatic Aflow
Speed, operator-independence and high test-result reproducibility – all these things count in R&D and in 24-hour operations such as production control.