What Is MFI?
The melt flow index test measures the mass of molten thermoplastic passing through a standard capillary die in ten minutes, under a specific temperature and load. The result is given in g/10 minutes and provides a practical indicator of the polymer's flowability; a high MFI means low viscosity and generally lower molecular weight.
Purpose of MFI
The purpose is to check batch-to-batch consistency of incoming raw material, predict processing behaviour, and detect degradation arising from recycling or processing.
Which Products Is MFI Applied To?
- Injection- and extrusion-grade raw materials (PP, PE, ABS, PA, PC)
- Recycled plastic pellets
- Masterbatches and additive compounds
- Automotive interior and exterior plastic parts (for degradation checking)
In Which Sectors Is MFI Used?
Standards Related to MFI
- ISO 1133-1
- ISO 1133-2
- ASTM D1238
MFI Conditions
- Temperature and load
- Determined according to the polymer; temperature-load combinations are defined per polymer in the standard
- Capillary dimensions
- Diameter and length defined in the standard
- Pre-heating
- The pre-heating time prescribed by the standard is observed after the specimen is loaded
Equipment for MFI
- Melt flow index tester (extrusion plastometer)
- Standard capillary and piston weights
- Analytical balance
- Drying oven and desiccator
- Cutting device and stopwatch
Sample Requirements for MFI
- Pellet or ground specimen
- Drying before testing is mandatory for hygroscopic polymers (PA, PC, PET)
- A few grams of specimen, depending on the number of measurements
- The polymer type must be stated — temperature and load are chosen accordingly
Duration of MFI
If drying is required, the duration extends accordingly; the measurement itself takes about half an hour per specimen.
MFI Procedure
- 1The specimen is dried under the conditions defined in the standard, if required.
- 2The machine is brought to the specified temperature and stabilised.
- 3The specimen is loaded into the barrel and compacted.
- 4The pre-heating time is observed.
- 5The specified load is applied.
- 6The extrudate emerging is cut at defined time intervals.
- 7The cut pieces are weighed and the result is calculated in g/10 minutes.
MFI Acceptance Criteria
The acceptance criterion is the declared value in the raw material's technical data sheet and the tolerance range in the specification. The MFI value itself carries no compliance limit; the reference is the supplier's declaration.
Evaluation of Results
The measured value is compared with the declared value. A higher-than-expected MFI can indicate chain scission and degradation, while a lower MFI can indicate cross-linking or contamination. Comparing MFI before and after processing shows process-induced degradation.
MFI Report
- Standard applied
- Polymer description and batch information
- Temperature and load condition
- Drying conditions (if applied)
- Individual measurements and the average MFI value
- Comparison with the declared value
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Raw-material technical specifications
- OEM plastic material specifications
Otomotiv Testleri — What Does This Testing Field Cover?
The section below describes the field that the MFI test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Automotive testing shows that a component keeps working under conditions representing the loads it will meet over the life of the vehicle. A vehicle is not a single product but an ENVIRONMENT: vibration, temperature cycling, salt water, stone impact, electrical transients and electromagnetic noise are all present at the same time and for years.
What distinguishes this family is that VEHICLE MANUFACTURER SPECIFICATIONS sit on top of the standards. ISO and SAE publications establish the common ground; but Volkswagen, BMW, Ford, Stellantis, Toyota and Renault define different severity levels, additional tests and different acceptance criteria in their own specifications. For a component, the phrase "complies with automotive standards" is not sufficient on its own; which manufacturer's specification, and which revision of it, must be answered.
The family carries three separate processes together and they are often confused. Homologation covers the type approvals a vehicle needs to enter traffic and runs under state authority. Supplier approval means passing the vehicle manufacturer's own quality and testing requirements and is a commercial relationship. The third is design verification: the engineering team demonstrating that its own design meets its targets.
At component level the test plan is built around the LOCATION OF USE. A module in the engine bay and a module in the boot do not go through the same temperature and vibration profile; a component inside a door and one in the roof console do not see the same water and dust exposure. The ISO 16750 series is the common framework for this location-based approach.
The shift to electric vehicles has reshaped the field. High-voltage safety, insulation coordination, battery safety, charging interface conformity and the electromagnetic behaviour of high-voltage components have been added to the classical automotive test set. In a quiet vehicle, acoustic and vibration expectations have changed too; sounds once masked by the combustion engine are now audible.
The quality system side cannot be separated from testing in this field. A manufacturer under IATF 16949 presents test results in the PPAP file; measurement system analysis, process capability study and the control plan stand around the test report. A single good result is not enough — the process must be shown to be able to repeat it.
Method groups in this field
Environmental and climatic
Temperature cycling, thermal shock, damp heat, salt spray, dust and water ingress (IP), solar radiation. Severity levels vary with the mounting location.
Mechanical
Sine and random vibration, shock, mechanical loads, fastener torque and durability cycles.
Electrical
Supply voltage variations, transients (ISO 7637), reverse polarity, overvoltage, short circuit and sleep current measurements.
EMC
Component emissions (CISPR 25), radiated and conducted immunity (ISO 11452 series), electrostatic discharge (ISO 10605).
Materials and emissions
Odour, fogging and VOC emissions from interior materials; flammability; UV ageing; coating durability and stone impact.
Functional safety and cyber security
Functional safety evidence under ISO 26262 and cyber security engineering under ISO/SAE 21434; these are tied to regulation through UNECE R155 and R156.
Commonly confused in this field
- An automotive report without a specification reference is not accepted in the supply chain; which OEM specification and revision was applied must be stated.
- Type approval and supplier approval are different processes. A component with E-Mark approval is not thereby considered to have passed the OEM's own acceptance tests.
- A result obtained on a prototype does not carry over to series production; PPAP is done with series production parts.
- On the EMC side, measuring emissions alone is incomplete; immunity is a separate body of work and is more critical in a vehicle.
- On electric vehicle components, high-voltage safety is a distinct competence; classical 12 V test infrastructure is not sufficient.
Which decisions these results support
- Supplier component approval and the PPAP file
- UNECE type approval and E-Mark marking
- Design verification and durability evidence
- Root cause analysis of field complaints and warranty returns
- Assessing the impact of a design or supplier change
Related Tests
Frequently Asked Questions About MFI
What is the difference between MFI and MVR?
MFI (MFR) gives the mass flow rate in g/10 min, while MVR gives the volumetric flow rate in cm³/10 min. Both can be obtained from the same measurement; melt density is needed for the conversion.
Why do I need to dry the specimen?
In hygroscopic polymers (PA, PC, PET), moisture in the water leads to hydrolytic degradation at high temperature and artificially raises the MFI. An undried specimen gives the value of the degraded state, not the true value.