Flow rate index of thermoplastics

Mass (MFR) or volume flow rate (MVR)

The quantity that characterizes the flow rate of thermoplastics in the processing process is the mass flow rate (MFR) or volume flow rate (MVR). MFR and MVR are determined using a load plastometer. The essence of determining the flow index is to measure the average flow speed of the material at established values ​​of the basic parameters of the processing process (temperature and pressure).

Determination of the flow coefficient

Determination of the flow rate using Method A: mass flow rate (MFR)

In this method, the extrudate is cut at regular intervals and the weight is then determined using a scale. The result is the extruded mass per unit of time, usually expressed in g/10 min.

Determination of the flow coefficient using Method B: volumetric flow rate (MVR)

This method requires the plastometer to be equipped with a piston motion sensor. The MVR result is the volume of extruded material per unit of time and is expressed in cm³/10 min. The weight coefficient is determined from the distance the piston travels per unit time.
The photo shows the ZwickRoell Mflow Plastometer device


  • PN-EN ISO 1133
  • ASTM D1238
  • ASTM D3364
Document No. Title/Description
ASTM D3364 Standard Test Method for Flow Rates for Poly(Vinyl Chloride) with Molecular Structural Implications
ASTM D1238 Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer
PN-EN ISO 1133 Plastics — Determination of the melt mass-flow rate (MFR) and melt volumeflow rate (MVR) of thermoplastics