Hot melt index

The melt flow index (MFI) is a key measurement for evaluating the viscosity and flowability of a molten polymer 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 plastics , verify their thermal stability and their suitability for transformation processes such as injection, extrusion or blow molding.

Principle of measurement

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

A high MFI indicates good fluidity (materials that are easier to mold), while a low MFI reveals higher viscosity (materials that are more rigid or have a higher molecular weight).
This parameter also helps detect potential thermal degradation , formulation changes , or batch incompatibility issues .

For further analysis, also see:

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

Industrial applications

The hot 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 processing : evaluation of the processing properties of food-grade plastics according to food contact regulations.
• Plants and biopolymers : characterization of bio-based and biodegradable materials derived from biomass.

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

Analytical interest and complementarity

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

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

These additional analyses allow for a complete characterization of the material , from its formulation to its performance under real-world conditions of use.

YesWeLab Services

YesWeLab provides you with a network of ISO 17025 and/or COFRAC specializing in rheology, thermal testing, and polymer analysis .
Our experts will assist you in selecting the appropriate 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 view 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 request or quote, contact our scientific team today.