Melt flow index

The Melt Flow Index (MFI) is a key measurement for assessing the viscosity and flowability of a polymer melt under a given load and temperature.
Performed according to ISO 1133 , this analysis determines the mass of material extruded in 10 minutes through a calibrated orifice, providing a direct indicator of the material's processability

MFI is used to control the quality of plastic materials , verify their thermal stability and their suitability for transformation processes such as injection, extrusion or blowing.

Principle of measurement

The test involves placing a polymer sample in a cylinder heated to a specific temperature (usually between 190°C and 300°C depending on the polymer type).
Under a standard load, the molten polymer flows through a calibrated nozzle, and the extruded mass is weighed to calculate the mass melt flow rate (MFR) expressed in g/10 min.

A high MFI indicates good flowability (easier to mold materials), while a low MFI reveals higher viscosity (more rigid or higher molecular weight materials).
This parameter also allows the detection of possible thermal degradation , formulation changes or compatibility problems between batches .

For additional analyses, also discover:

• DSC thermal analysis to study melting and crystallization transitions,
• analysis TGA to assess thermal stability,
• or tensile testing to measure mechanical properties associated with the rheology of the material.

Industrial applications

The melt flow index test applies to all thermoplastic polymers used in the following industries:

• Packaging : validation of the quality of polyethylenes (PE, PP) used for films, bottles and trays.
• Technical materials and polymers : control of polyamides, polycarbonates, ABS or PBT intended for injection or extrusion.
• Cosmetics and nutraceuticals : verification of the quality of primary and secondary packaging in contact with formulations.
• Food industry : evaluation of the processing properties of food plastics according to food contact regulations.
• Plants and biopolymers : characterization of bio-sourced and biodegradable materials from biomass.

This analysis is an essential quality control to ensure consistent performance, process reproducibility and compliance with industry standards.

Analytical interest and complementarity

The melt flow index can be supplemented by other tests for a more in-depth understanding of rheological and thermal behavior:

• Intrinsic viscosity analysis to correlate MFI to polymer molecular weight;
• Bending test to assess stiffness after transformation;
• FTIR infrared spectroscopy to check the chemical composition of the polymer;
• Accelerated aging test to study the evolution of MFI over time.

These additional analyses make it possible to obtain a complete characterization of the material , from its formulation to its performance in real conditions of use.

YesWeLab Services

YesWeLab provides you with a network of ISO 17025 and/or COFRAC , specialized in rheology, thermal testing and polymer analysis .
Our experts will assist you in choosing the test conditions (load, temperature, duration) and in interpreting the results according to your production or research objectives.

Thanks to the YesWeLab digital platform , you can centralize your analysis requests, track your samples and consult your reports online. Since 2020, YesWeLab has been supporting manufacturers in the materials, packaging and polymer with their quality control, development and compliance needs.

For any specific requests or quotes, contact our scientific team today.