🔩 Melt flow rate MFR and MVR of thermoplastics — extrusion plastometer
In short
The molten plastic is extruded from the plastometer barrel through a die under a specified load and at a specified temperature. The test is performed according to PN-EN ISO 1133-1:2022-12; Procedures: Procedure A — mass measurement, MFR result in g/10 min; procedure B — measurement of piston displacement, MVR result in cm³/10 min. The procedure comprises 8 steps; it is used for: Quality control and batch identification of thermoplastic raw materials, Comparison of plastics with different filler contents (MVR), Assessment of material degradation after recycling or repeated processing.
At a glance
- Standard: PN-EN ISO 1133-1:2022-12
- Category: Materials and NDT
- Procedure steps: 8
- Procedures: Procedure A — mass measurement, MFR result in g/10 min; procedure B — measurement of piston displacement, MVR result in cm³/10 min
- Units: MFR: the correct SI unit is dg/min, g/10 min customarily accepted. MVR: dm³/min, customarily cm³/10 min
- Typical temperatures: Polyethylene 190 °C, polypropylene 230 °C, polystyrene 190 °C, polyoxymethylene 190 °C, ethylene–vinyl acetate copolymer 190 °C
Overview
The standard specifies two procedures for determining the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastics under specified conditions of temperature and load. Procedure A is a mass-measurement method, procedure B a displacement-measurement method. The test conditions are usually given in the material standard with a reference to this standard; typical conditions for thermoplastics are collected in the annexes. The description of the apparatus and the principle quoted below comes from the edition ISO 1133:2005, on which the current first part of the series is based.
The melt volume-flow rate MVR is particularly useful when comparing materials with different filler contents and when comparing filled with unfilled plastics. MFR can be determined from the MVR measurement if the melt density at the test temperature and pressure is known. The methods are in principle also applicable to plastics whose rheological behaviour changes during the measurement as a result of phenomena such as hydrolysis, condensation or crosslinking, but only when the effect is limited and the repeatability and reproducibility are within an acceptable range; for materials with strongly altered rheological behaviour these methods are not suitable, and the viscosity number in dilute solution according to the relevant part of ISO 1628 is recommended for characterization.
The standard notes that the shear rates in these methods are much lower than under normal processing conditions, so the data for different plastics need not always correspond to their behaviour during processing; both methods serve primarily for quality control. Typical conditions are 190 °C for polyethylene and 230 °C for polypropylene, with a standard nominal load of 2.16 kg.
Method principle
The melt mass-flow rate and the melt volume-flow rate are determined by extruding molten material from the barrel of a plastometer under specified conditions of temperature and load. For the mass-flow rate, extrudate segments cut off at measured time intervals are weighed and the extrusion rate is calculated in g/10 min. For the volume-flow rate, the distance the piston travels in a specified time, or the time needed to travel a specified distance, is measured and the result is expressed in cm³/10 min. The volume-flow rate can be converted into the mass-flow rate and vice versa if the density of the material under the test conditions is known. The plastic placed in a vertical barrel is extruded through a die by a piston loaded with a known weight; the load is the combined mass of the piston and the added weight.
Applications
- Quality control and batch identification of thermoplastic raw materials
- Comparison of plastics with different filler contents (MVR)
- Assessment of material degradation after recycling or repeated processing
- Selection of processing parameters for injection moulding and extrusion
- Acceptance testing of polyethylene, polypropylene, polystyrene, polyacetal and ethylene–vinyl acetate copolymers
Key parameters
| Parameter | Value |
|---|---|
| Procedures | Procedure A — mass measurement, MFR result in g/10 min; procedure B — measurement of piston displacement, MVR result in cm³/10 min |
| Units | MFR: the correct SI unit is dg/min, g/10 min customarily accepted. MVR: dm³/min, customarily cm³/10 min |
| Typical temperatures | Polyethylene 190 °C, polypropylene 230 °C, polystyrene 190 °C, polyoxymethylene 190 °C, ethylene–vinyl acetate copolymer 190 °C |
| Standard load | Test piston with a standard nominal load of 2.16 kg; the load is the combined mass of the piston and the weight |
| Barrel | Length 115–180 mm, internal diameter 9.550 mm ± 0.025 mm; for some materials measurements up to 450 °C |
| Die | Of tungsten carbide or hardened steel, length 8.000 mm ± 0.025 mm, bore with a nominal diameter of 2.095 mm with a tolerance of ±0.005 mm |
| Piston | Head 6.35 mm ± 0.10 mm long, with a diameter smaller than the internal diameter of the barrel by 0.075 mm ± 0.010 mm; two ring marks as reference points |
| Temperature stability | Temperature differences measured between 10 mm and 75 mm above the upper surface of the die must not exceed the values in Table 1 of the standard throughout the test |
Standard
- Standard number
- PN-EN ISO 1133-1:2022-12
- Title (PL)
- Tworzywa sztuczne — Oznaczanie masowego wskaźnika szybkości płynięcia (MFR) i objętościowego wskaźnika szybkości płynięcia (MVR) tworzyw termoplastycznych — Część 1: Metoda standardowa
- Title (EN)
- Plastics — Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics — Part 1: Standard method
Step-by-step procedure
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Selection of test conditions
Adopt the temperature and load from the material standard for the plastic tested; typical conditions are given in the annexes of the standard (e.g. polyethylene 190 °C, polypropylene 230 °C, nominal load 2.16 kg).
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Checking the apparatus
Check the condition of the barrel, the piston head and the piston — excessive wear indicates misalignment; regularly inspect for wear and changes in surface appearance. Check the die bore diameter with a gauge; withdraw a die out of tolerance and inspect the end faces of the die for chipping around the bore.
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Heating and stabilization
Heat the barrel to the test temperature and stabilize it; check that the temperature differences between 10 mm and 75 mm above the die are within the values in Table 1 of the standard throughout the test.
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Charging the barrel
Select the mass of the test portion according to the expected flow rate and charge the barrel with the material, compressing it so as to remove air; keep the charging time short (in laboratory practice not longer than one minute), then insert the piston.
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Preheating
Wait for the preheating time until the material reaches the test temperature and the flow condition stabilizes; during this time the die outlet may be blocked with a plug to prevent leakage.
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Loading and measurement
Apply the required load to the piston and start the measurement when the lower reference mark on the piston reaches the measuring position. Procedure A: cut off successive extrudate segments at measured time intervals. Procedure B: measure the piston travel in a specified time or the time to travel a specified distance.
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Discarding the first segment
Cut off and discard the first extrudate segment; use the subsequent segments for the calculations. Discard segments containing air bubbles.
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Calculations and report
Procedure A: weigh the segments and calculate MFR in g/10 min. Procedure B: calculate MVR in cm³/10 min from the volume corresponding to the piston displacement. Where necessary, convert MVR to MFR if the melt density under the test conditions is known. In the report give the material, the temperature, the load, the procedure, the results of the individual determinations and the mean value.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Extrusion plastometer | Vertical heated barrel, piston with interchangeable weight, die, die retaining plate, insulation and temperature sensor | — |
| Barrel | Mounted vertically, length 115–180 mm, internal diameter 9.550 mm ± 0.025 mm, with a surface finish of 0.25 µm roughness | — |
| Piston with weights | Head 6.35 mm ± 0.10 mm; solid or hollow piston — hollow with very low loads, solid or hollow with guides with higher loads; piston thermally insulated from the weight | — |
| Interchangeable die | Tungsten carbide or hardened steel; bore diameter checked regularly with a go/no-go gauge, a die out of tolerance is withdrawn | — |
| Temperature control system | Thermocouples, platinum resistance sensors or mercury thermometers built into the wall; the system may be calibrated to indicate the melt temperature | — |
| Analytical balance | For weighing the cut-off extrudate segments in procedure A | — |
| Die plug | Blocks the die outlet and prevents the material from flowing out before the measurement begins | — |
| Extrudate cutting tool | For cutting off segments at measured time intervals | — |
Health and safety (OHS)
- Barrel and die heated to 190–230 °C, and for some materials up to 450 °C — thermal gloves, tools for removing the die, caution when cleaning hot
- Hot extrudate sticks to the skin — cut with a tool, never with fingers
- Weights of several kilograms above the open barrel — risk of crushing the hands, apply and remove carefully
- Thermal decomposition products of plastics (fumes) — extraction above the workstation, especially at high temperatures
- Cleaning the barrel with solvents — ventilation, no open flame
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 1133-1:2022-12 — “Plastics — Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics — Part 1: Standard method”.
How does this method work?
The melt mass-flow rate and the melt volume-flow rate are determined by extruding molten material from the barrel of a plastometer under specified conditions of temperature and load. For the mass-flow rate, extrudate segments cut off at measured time intervals are weighed and the extrusion rate is calculated in g/10 min.
What is the measuring range and accuracy?
Procedures: Procedure A — mass measurement, MFR result in g/10 min; procedure B — measurement of piston displacement, MVR result in cm³/10 min; Units: MFR: the correct SI unit is dg/min, g/10 min customarily accepted. MVR: dm³/min, customarily cm³/10 min; Typical temperatures: Polyethylene 190 °C, polypropylene 230 °C, polystyrene 190 °C, polyoxymethylene 190 °C, ethylene–vinyl acetate copolymer 190 °C; Standard load: Test piston with a standard nominal load of 2.16 kg; the load is the combined mass of the piston and the weight.
How long does the test take?
The procedure comprises 8 steps. The standard does not give a duration for every stage — the laboratory's own procedure decides.
What equipment is required?
Extrusion plastometer, Barrel, Piston with weights, Interchangeable die, Temperature control system, Analytical balance, Die plug, Extrudate cutting tool.
Where is this test used?
Quality control and batch identification of thermoplastic raw materials; Comparison of plastics with different filler contents (MVR); Assessment of material degradation after recycling or repeated processing; Selection of processing parameters for injection moulding and extrusion; Acceptance testing of polyethylene, polypropylene, polystyrene, polyacetal and ethylene–vinyl acetate copolymers.
What safety precautions apply?
Barrel and die heated to 190–230 °C, and for some materials up to 450 °C — thermal gloves, tools for removing the die, caution when cleaning hot; Hot extrudate sticks to the skin — cut with a tool, never with fingers; Weights of several kilograms above the open barrel — risk of crushing the hands, apply and remove carefully; Thermal decomposition products of plastics (fumes) — extraction above the workstation, especially at high temperatures; Cleaning the barrel with solvents — ventilation, no open flame.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 1133-1.