Determination of Melt Mass Flow Rate (MFR) and Melt Volume Flow Rate (MVR)

The Cflow extrusion plastometer consists of an extrusion barrel which is heated exactly to a pre-set temperature, a die of standardized diameter and a piston with a weight applied to its upper end. The material to be tested is loaded into the extrusion barrel; after a specified pre-heating period it is extruded through the die by the force of the weight acting on the piston. The extrudate is cut off at constant time-intervals and weighed. The result is the melt mass flow rate (MFR), which is calculated from the extruded mass per 10 minutes.

This method is suitable for individual tests with lower specimen flow.

This method requires the extrusion plastometer to be equipped with a displacement transducer which measures piston travel during the test. The melt volume flow rate (MVR) is the extruded volume per 10 minutes.

 This method is often used in production checks as it is more suitable for automation and simpler in operation, mainly because no weight determination is necessary for the individual extrudate cuts. Provided the density of the melt is known, the MFR value can be calculated; melt density can be determined by connecting a balance to the device. 

In some cases it can be of interest to know the ratio between flow rates determined under different piston loadings. This value is known as ‘Flow Rate Ratio’ (FRR). 

Aflow plastometers are equipped with a load-change function. This allows tests from one barrel-loading at different weight steps, saving time compared with individual measurements.

The weight steps can be programmed in an ascending, descending or mixed sequence. The test sequence can be time-controlled or displacement-controlled for each measurement step, giving the operator maximum freedom in the arrangement and optimization of test methods.