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Testing the MFR and MVR of Plastics

Term definition, characteristic values, test methods, test conditions and standards

The melt flow test (also referred to as melt index test or melt flow index test) is a test method used to determine the flow properties of thermoplastic materials. The test measures how much material flows through a standardized die while subjected to a specified load and temperature. The result is expressed as melt index (MI) or melt flow index (MFI), which by using various different test methods, delivers standard characteristic values such as MFR (melt mass-flow rate) and MVR (melt volume-flow rate).

The MFR and MVR tests are used to evaluate the processability of plastics and to ensure that the quality and properties of the produced plastic material meets the specified requirements. The test is commonly implemented by plastic manufacturers and processors who are tasked with guaranteeing that the plastic materials being tested are suitable for their intended application.

The melt flow test also plays an important role in the quality assurance of plastic products. Through regular melt index tests, deviations in the production chain can be detected and corrected at an early stage of the process.

Term definitions Standards Comparison of test methods Test conditions according to standard Downloads Request a consultation

Term definitions related to the MFR and MVR test

Melt flow test glossary
Normative term Characteristic value Unit Normative reference Synonyms Meaning

Melt mass-flow rate

MFR g/10min

ISO 1133-1

ASTM D1238

Melt Index

Melt flow index

Mass-flow rate

MFI value

Mass of a thermoplastic material passing through a die of specified dimensions and properties at a specified temperature and under a known load within a time period of 10 minutes.

Melt volume-flow rate

MVR cm3/10 min

ISO 1133-1

ASTM D1238

Volume-flow rate

MVI value

Volume of a thermoplastic material passing through a die of specified dimensions and properties at a specified temperature and under a known load within a time period of 10 minutes.

Flow rate ratio

FRR

ISO 1133-1

ASTM D1238

Quotient of two melt mass-flow rates measured under different standardized loads and thus representing different points on a viscosity curve.

Density of the plastic melt at test temperature

ρ g/cm3

ISO 1133-1

ASTM D1238

Melt density

MFR / MVR quotient. The value can be determined by simultaneously measuring the melt mass-flow rate and melt volume-flow rate in an extrusion plastometer.

Apparent shear rate

γ ̇ (gamma point)

1/s

ISO 11443

Apparent shear rate

Apparent shear rate

Shear rate resulting from the uncorrected calculation of the flow of a non-Newtonian fluid.

Apparent shear stress

τ (tau)

Pa

ISO 11443

Apparent shear stress

Shear stress calculated for a die with a small orifice ratio (L/D < 100) without applying a correction for a drop in pressure.

Apparent viscosity

η (eta) Pa s

ISO 11443

Apparent viscosity

Viscosity calculated from the quotient of the apparent shear stress and apparent shear rate.

Standards for MFR and MVR tests on plastics

  • ISO 1133-1 - Plastics – Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics – Part 1: Standard method
  • ISO 1133-2 - Plastics – Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics – Part 2: Method for materials sensitive to time-temperature history and/or moisture
  • ASTM D1238 - Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer
  • ASTM D3364 Standard Test Method for Flow Rates for Poly (Vinyl Chloride) with Molecular Structural Implications

In addition, the specification standards of the individual molding materials must be observed, in which the test temperatures, the nominal loads, and if necessary, other special material-specific conditions to be used for MFR and MVR tests are standardized. These may deviate from the ISO 1133 and ASTM D1238 standard specifications.

ISO vs. ASTM in MFR and MVR measurements

The procedures for MFR, MVR and FRR measurements on thermoplastics are equivalent but not identical according to ISO 1133 and ASTM D1238, since they differ in some respects, especially in the test procedure and test conditions:

  • For some polymers, the test temperatures and test weights are specified differently in ISO and ASTM.
  • The recommended volume of polymer to be used is slightly different.
  • The duration of the preheating phase is set to at least 5 minutes in ISO 1133-1, but can also be significantly longer. In ASTM D1238, the duration of the preheating phase is standardized at 7 minutes with a strict tolerance of ±0.5 minutes.
  • According to the ISO standard, the starting point of the test is at a piston position of 50 mm above the die, while ASTM sets this point at 46±2 mm.
  • Testing of sensitive polymer types with respect to time- or temperature-dependent history and/or moisture (e.g., PBT, PET, or PA) are described in the separate ISO 1133-2 standard, while ASTM D1238 specifies a narrowly tolerated time sequence of testing for all polymer types.
  • ISO 1133-1 leaves it largely up to the operator to determine suitable section or measurement intervals for the measurement procedure, while ASTM D1238 specifies very precisely over what piston travel distance or at which section interval measurements are to be made at which MFR or MVR value.

Overview of the test methods according to ISO 1133 and ASTM D1238

ISO 1133 and ASTM D1238 describe the test methods for MFR and MVR determination in a similar manner and can therefore be categorized as technically equivalent standards, although there are significant differences in the application of the test requirements, which in some cases do not allow for reproducibility of the results between standards.

MFR, MVR and FRR tests to ISO 1133-1, ISO 1133-2 and ASTM D1238
Test methods Test results Typical measurement range Level of test sequence automation Applications Related extrusion plastometer

Method A - MFR
– time-controlled

Melt mass-flow rates, MFR in g/10 min Min: approx. 0.2 g/10 min
Max: approx. 75 g/10 min

Low level of automation

  • Manual start of the measurement
  • Time-controlled section intervals
  • Manual weighing of extrudate on analytical balance
Incoming goods inspection
Teaching and training
Tests on filled polymers with variable density distribution

Method A - MFR
– displacement-controlled

Melt mass-flow rates, MFR in g/10 min Min: approx. 0.2 g/10 min
Max: approx. 75 g/10 min

Improved level of automation

  • Automated start of the test when the start position is reached
  • Control of the section intervals according to displacement or time specifications
  • Manual weighing of extrudate on analytical balance
Incoming goods inspection
Teaching and training
Tests on filled polymers with variable density distribution
  • Mflow
  • Aflow

Method B - MVR

Melt volume-flow rates, MVR in cm³/10 min
Apparent shear rate
Apparent shear stress
Apparent viscosity

By simultaneously weighing the extrudate sections, the melt density at test temperature can be determined.

Min: approx. 0.1 g/10 min
Max: approx. 2000 g/10 min

High level of automation

  • Automated start of the test when the start position is reached
  • Control of the displacement measurement intervals according to displacement or time specifications
  • Continuous displacement and MVR measurement
  • Detection of bubble inclusions or errors
  • Instrument-supported purging of residual material
  • Automatic calculation of results
  • Graphical representation of measurement sequences, results and statistics
Incoming goods inspections
Teaching and training
Production control
Research and development

Method C - half-die
(Variation of method B)

Melt volume-flow rates, MVR in cm³/10 min
Apparent shear rate
Apparent shear stress
Apparent viscosity

By simultaneously weighing the extrudate sections, the melt density at test temperature can be determined.

Min: approx. 0.1 g/10 min
Max: approx. 2000 g/10 min

High level of automation

  • Automated start of the test when the start position is reached
  • Control of the displacement measurement intervals according to displacement or time specifications
  • Continuous displacement and MVR measurement
  • Detection of bubble inclusions or errors
  • Instrument-supported purging of residual material
  • Automatic calculation of results
  • Graphical representation of measurement sequences, results and statistics

For polyolefins with high flow rates

Incoming goods inspections
Teaching and training
Production control
Research and development

Method D - multi-weight test, FRR

Melt mass-flow rates, MFR
Melt volume-flow rates, MVR
Flow rate ratio, FRR

Apparent shear rate
Apparent shear stress
Apparent viscosity

Min: approx. 0.1 g/10 min
Max: approx. 900 g/10 min

High level of automation

  • Automated start of the test when the start position is reached
  • Control of the displacement measurement intervals according to displacement or time specifications
  • Optional testing in method A (MFR) or in method B (MVR)
  • Control of the test sequence via parameters specification
  • Weight sequence optionally increasing or decreasing
  • Stepless adjustability of the test loads
  • Free selection of the waiting time after changing the test load
  • Detection of bubble inclusions or errors
  • Instrument-supported purging of residual material
  • Automatic calculation of results
  • Graphical representation of measurement sequences, results and statistics
Incoming goods inspection
Teaching and training
Production control
Research and development
Shift work with changing operators

 

Brief description of test methods A through D for MFR and MVR tests

Method A - MFR test

In method A, the extrudate is cut off at constant time intervals and its mass is determined with an analytical balance. The test result is the extruded mass per unit of time (melt mass-flow rate MFR), which is indicated in g/10 min.

Method A can be used for all filled or unfilled thermoplastic polymers.

Method B - MVR test

In method B, instead of the mass of an extrudate cut in regular intervals, the extruded volume of the polymer melt is determined. For this, the extrusion plastometer must be equipped with a piston displacement transducer. The MVR (melt volume-flow rate) is the extruded material volume per unit of time and is indicated in cm3/10 min. It is calculated from the distance the piston travels per unit of time.

A significant advantage of method B is the elimination of mechanical cutting. With good synchronization of the displacement/time measurement value, this method can achieve a high level of accuracy within short measurement times and piston displacements. Thus, depending on the material, accuracy requirement and MVR result, it is possible to carry out more than 30 individual measurements with a single extrusion barrel filling.

The MVR value can be used for material specification purposes according to ISO 10350-1. However, In the case of filled molding materials, the simple conversion to an MFR value is usually not possible because of fluctuations in the density of the plastic melt.

Method C - MVR test with half-die

Method C refers to an MVR test variation of method B.

For thermoplastics with an MFR value greater than 75 g/10 min, in addition to being able to reduce the nominal load, both ISO 1133 and ASTM D1238 support the use of a die with half the height and half the diameter of the orifice. However, direct reproducibility of results that are determined using the standard die is not possible.

Method D, multi-weight test – FRR

With some polyolefins it is common to state the MVR value for different load levels and determine the flow rate ratio (FRR). When using simple extrusion plastometers, this requires measurements from several fillings. Extrusion plastometers, such as the Aflow extrusion plastometer from ZwickRoell, which is equipped with an automatic load changing device can measure multiple load levels from a single filling.

Test conditions for melt flow rate measurements

PolymerISOASTM D1238
IUPAC codesStandardDryingTemp. [°C]Weight [kg]Temp. [°C]Weight [kg]
PolyolefinsPEISO 17855-1
ISO 4427-1
ISO 4437-1
ISO 15494
ISO 22391
(no)190
190
190
2.16
21.6
5
125
125
190
190
190
190
190
250
310
0.325
2.16
0.325
2.16
5
10
21.6
1.2
12.5
UHMW-PEISO 21304-2190
230
21.6
21.6
PPISO 19069-2
ISO 15494
ISO 15874-2
(no)190
230
5
2.16
2302.16
PE & PPISO 18263-22302.16
StyrenePSISO 24022-2(no)2005190
200
230
230
5
5
1.2
3.8
PS-IISO 19063-2(no)2005
SANISO 19064-2(no)22010220
230
230
10
3.8
10
ABSISO 19062-2(no)220
240
265
10
10
10
200
220
230
5
10
3.8
ABS/PC blends(no)230
250
265
265
3.8
1.2
3.8
5
MABSISO 19066-2(no)220
240
265
10
10
10
ASA, ACS, AEDPSISO 19065-2(no)22010230
230
1.2
3.8
ASA, ACS, AEDPS
(high-heat grades)
ISO 19065-2(no)240
265
10
10
AcrylicPMMAISO 24026-2(no)2303.8230
230
1.2
3.8
PolyesterPC homopolymer
PC copolymer
ISO 21305-2< 0.02 %300
330
1.2
2.16
3001.2
PBT, PBTPISO 20028-2<0.02% (PBT)2301
2501

2651
1.2
2.16
5
10
21.6
PETISO 20028-2< 0.02 %27011.2
2.16
5
10
250
285
2.16
2.16
High viscosity PETISO 20028-2
ISO 12418-2
28011.2
2.16
5
10
PET and PBTISO 20029-21901
2301

2501
2.16
5
10
Cellulose esterCA,CH, CN, CP, CAB(no)190
190
190
210
0.325
2.16
21.6
2.16
VinylPVC-P
PVC-U
ISO 24023-2
ISO 21306-2
(no)1752
20.0
PVC19021.6
PVAC(no)15021.6
EVACISO 21301-1(no)1902.16
PVDF230
230
5
21.6
Other polymersPB-1ISO 21302-1
ISO 15876-3
ISO 15494
(no)190
190
2.16
5
POMISO 29988-2(no)1902.16190
190
1.05
2.16
PAISO 16396-2< 0.02 %2251
2501

2751

3001
1.2
2.16
5
10
21.6
235
235
235
275
275
1
2.16
5
0.325
5
PCL(no)80
125
2.16
2.16
EVOHISO 21309-22102.16
PolyphenylsPPE + PS, unfilled
PPE + PP
PPE + PS, filled
PPE + PA
PPE + PPS
ISO 20557-2250
250
300
280
300
10
10
5
5
10
PPSISO 20558-2315
315
315
1.2
2.16
5
3155
FluoropolymerFEP (PFEP)ISO 20568-2(no)372
372
2.16
5
3722.16
PFAISO 20568-2(no)37253725
ETFEISO 20568-2(no)29752975
EFEPISO 20568-22655
PVDFISO 20568-2(no)230
230
5
21.6
120
120
230
230
5
21.6
2.16
5
VDF/CTFEISO 20568-2230
230
2.16
5
VDF/HFPISO 20568-2230
230
2.16
5
VDF/TFEISO 20568-22975
VDF/TFE/HFPISO 20568-22655
PCTFEISO 20568-2(no)265
265
21.6
31.6
265
265
265
12.5
21.6
31.6
CPTISO 20568-22975
ECTFEISO 20568-2(no)271.52.16271.5
271.5
2.16
5
PVDF230
230
5
21.6
PolysulfonePPSUISO 24025-2(no)3655365
380
5
2.16
PSUISO 24025-2(no)3432.16343
360
2.16
10
PESUISO 24025-23502.16360
380
10
2.16
AlternativelyISO 24025-236010
Thermoplastic elastomerTPUISO 16365-2(< 0.03%)Tmelt + 10°C2.16
5
10
21.6
TPE190
200
220
230
240
250
2.16
5
2.16
2.16
2.16
2.16
TEO2302.16
KetonesPEEKISO 23153-2400
400
2.16
10
4002.16
PKISO 21970-12402.16

Values in brackets [ ... ] are used in practice, however no standard-based reason is known.

  1. Any weight and temperature combination is acceptable
  2. To ASTM D3364

If you have any questions or would like to know more about these test method or products for melt flow testing, please contact us.

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Related products for MFR and MVR test

Frequently asked questions related to the MFR measurement and MVR measurement

Polyolefins, such as PE or PP, are generally quite easy to test and place only minor demands on the conditioning of the test specimen. The framework requirements for temperature and test weight are defined in ISO 17855-1, ISO 22391 and in ISO 19069-2. The test standard used is ISO 1133-1 or ASTM D1238. The MFR and MVR measurement is normally performed under method A (plastic MFR) or method B (plastic MVR). When the flow rate ratio FRR is to be determined, method D is used.

Polyesters are among the moisture-sensitive polymers and must be dried to a very low residual moisture level before testing. This is expediently achieved by means of a vacuum furnace with nitrogen purging and subsequently checked by moisture determination using Karl Fischer titration. The polymer is transported to the testing instrument under exclusion of air and measured in method A (MFR) or B (MVR) directly after it has been quickly filled into the extrusion plastometer. The temperature and test weight parameters for PET and PBT are specified in ISO 20028-2. For PET it is also common to provide the intrinsic viscosity, which is determined using a Ubbelohde viscometer according to IS 1628-1. In addition to this relatively complex procedure, it is common in the production sector to determine the IV value via a correlation calculation from the MFR value, which is much faster to measure.

Since testing instruments according to ISO and ASTM standards are very similar in design and the metrologically relevant components such as the die, piston and extrusion barrel are identical, you can assume an almost identical value level of MFR and MVR values, provided that the same test load and same test temperature are used for the respective polymer.

The main difference in the methods for MVR and MFR determination on thermoplastics according to ISO 1133 and ASTM D1238 lies in the test procedure and the test conditions:

  • Test temperatures and test weights are different for some polymers.
  • The recommended volume of polymer to be used is slightly different.
  • Preaheating phase: ISO 1133-1: more than 5 minutes; ASTM D1238: 7±0.5 minutes.
  • Starting point of the test: ISO standards at a piston position of 50 mm above the die; ASTM standard piston position 46±2 mm.
  • Testing of moisture-sensitive and rapidly thermally degrading plastics: separate ISO standard 1133-2; ASTM D1238 for all polymer types
  • Section or measurement intervals: in ISO, this is largely left up to the operator; ASTM D1238 specifies very precisely over what piston travel distance or at what section interval measurements are to be made at which MFR value or MVR value.

More information on melt flow testing

MFR/ MVR plastics
ASTM D1238, ASTM D3364
Determination of melt mass-flow rate (MFR), melt volume-flow rate (MVR), flow rate ratio (FRR)
to MFR/ MVR plastics
Melt flow index test plastics
ISO 1133-1, ISO 1133-2
Determination of melt mass-flow rate (MFR or MFI), melt volume-flow rate (MVR)
to Melt flow index test plastics
Extrusion Plastometers / Melt Flow Index Testers
The right extrusion plastometer for every testing volume.
Use an extrusion plastometer (also called melt flow index tester) for characterizing flow properties of a plastic melted mass. ✓Detailed information ✓Applications
to Extrusion Plastometers / Melt Flow Index Testers

Downloads

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  • Industry Brochure: Plastics & Rubber PDF 9 MB
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  • Product Information: Mflow Extrusion Plastometer PDF 127 KB
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