Melt Flow Indexers

The Right Melt Flow Indexer for Every Testing Volume

Melt flow tests are a simple method of characterizing the flow properties of a plastic melted mass. This test method is widely used, especially in quality assurance and goods inwards testing. The demands placed on the extrusion plastometer vary according to which processing stage in the plastics industry is involved.

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Overview of Melt Flow Indexers

  • The Cflow is particularly suited for goods inward checks, when only a few tests must be performed. 
  • The Mflow is modular and features a weight pegging device and automatic field-dependent parameterization.
  • The Aflow, with its defined precompaction of polymers, automatic field-dependent parameterization, fast residual material purge with a force of up to 80 kg and cleaning at the push of a button helps you make your test sequence more reliable and efficient.

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A Simple Explanation of the Basic Principles of Melt Flow Testing

Determining the Melt Index of Thermoplastics to ISO 1133 and ASTM D1238

The essential elements of an extrusion plastometer, together with the accuracy requirements and test methodology, are specified in national and international standards. The standards involved are ISO 1133, JIS K 7210, ASTM D1238 as a general method and ASTM D3364 for tests on PVC, plus stipulations contained in specification standards.

Differentiation between test methods to standards:

  • Method A: Melt mass flow rate (MFR)
  • In this method, the extrudates are cut at uniform intervals of time. Then their mass is determined by an analytical scale. The test result is the extruded mass per unit of time. This is normally indicated in g/10 min.
  • The quality of the MFR result obtained is dependent on the accuracy of the cutting times and the weighed mass. When low MFR values are involved, manual cutting is only recommended if long cutting times are used. If you want to determine multiple extrudates from a single barrel filling, or if the MFR values are greater than 10 g/10 min, we recommend use of an automated extrudate cutter.
  • Method B: Melt volume flow rate (MVR)
  • To measure the MVR, the extrusion plastometer must be equipped with a piston displacement transducer. The MVR result is the extruded material volume per unit of time. It is specified in cm3/10 min and is calculated from the distance the piston travels per unit of time.
  • A significant advantage of this method is the elimination of mechanical cutting. With synchronized travel-time measured-values high accuracy can be achieved, even with short measuring times and short piston-travel. This enables up to 40 individual measurements from one barrel filling, depending on the material involved, accuracy requirements and MVR result.
  • Method C to ASTM D1238: Measurements with half-height/half-bore diameter of the die
  • Most commonly used are dies with a height of 8.00 mm and a bore-diameter of 2.095 mm. For measurement of MFR values greater than 75 g/10 min the standards recommend a half-height/half-bore-diameter die with dimensions 4.00/1.050 mm. This is designated as Method C in ASTM D1238.
  • Method D to ASTM D1238: Multi-stage tests
  • With many polyolefins it is common to state the MVR value for different load levels and determine the flow rate ratio (FRR).
  • This requires measurements from several fillings when simple extrusion plastometers are used. Extrusion plastometers equipped with an automatic load-change unit can measure multiple load-levels from a single filling.
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