Rheological tests
Rheological testing plays a key role in the polymer industry, as the flow, shear, and deformation properties of materials directly influence processability, production stability, and the quality of the final product.
Melt flow index (MFI), MFR, MVR
Melt flow index test (MFI, MFR, MVR)
The melt flow index test is one of the most important rheological characteristics of thermoplastics, providing direct information on the processability, viscosity and molecular weight of the material. The test allows for quick and reliable comparisons of different raw materials, detection of manufacturing variations and identification of problems such as flow defects, structural irregularities or aging of the raw material.
MÜKI LABOR performs melt flow index measurements using modern equipment in accordance with two methods defined by industrial standards:
• MFR (Mass Flow Rate):
During the test, the mass of the material flowing out within a specified period of time is measured. This method is particularly suitable for monitoring changes in filler content, viscosity, and processability.
• MVR (Volume Flow Rate):
In this case, the volume of the extruded polymer is determined. The method is highly sensitive to changes in molecular weight distribution and structural variations.
The combined use of the two methods provides an accurate picture of the rheological behavior of the polymer, making the test particularly useful:
– in quality control of automotive raw materials,
– in the detection of injection molding and extrusion problems,
– in material identification,
– in the approval of new raw materials,
– in the testing of production stability.
Applied standards
MSZ EN ISO 1133-1
MSZ EN ISO 1133-2
Viscosity Number (VN)
Determination of viscosity number (VN)
The viscosity number (VN) is one of the most important characteristics of polymers, providing direct information about the molecular weight, polymer chain length and processability of the material. During the test, the flow properties of a diluted polymer solution are analyzed under specific conditions. The method is sensitive to structural changes, aging, degradation or possible contamination of the raw material.
Determining the viscosity number is particularly important in industries where the molecular weight of the polymer decisively influences the mechanical and functional properties of the final product. Based on the determined VN value, it can be concluded:
– the length and distribution of the polymer chain,
– the stability of the production process,
– possible thermal or shear damage to the material,
– the comparability of different production batches,
– the suitability of new or recycled raw materials.
The test is of great importance in injection molding, extrusion and film production processes, where viscosity has a direct impact on product quality, thickness, tensile strength and optical properties. VN measurement can also identify subtle structural differences that are more difficult to detect with other testing methods.
Applied standard
ISO 307
ISO 1628-5
Type of tests
Rheological tests – Analysis of the flow and deformation behavior of materials
What do we examine during rheological measurements?
The melt flow index (MFI or Melt Flow Rate – MFR) is a rheological (material flow) characteristic that shows how easily a thermoplastic melt flows at a specified temperature and pressure.
The aim of rheological tests is to provide a detailed picture of the internal structure of the material and how it reacts under different manufacturing and loading conditions. The most important test parameters are:
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When a manufacturing problem, material quality discrepancy or development issue arises, rheology and DSC testing together provide the most accurate diagnosis. Our experts will help you compile and interpret the appropriate test protocol.
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Shear strength, shear thinning or thickening rate – determines the behavior of the material at varying speeds.
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Melt Flow Index (MFI/MFR) – a characteristic ideal for rapid, industrial quality control.
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Elastic and tensile properties – critical for films, tubes and thin-walled products.
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Thermal stability from a rheological perspective – indicates degradation, aging or additive deficiency.
Based on these, conclusions can be drawn about the material's processability, stability, possible defects or causes of manufacturing problems.
The role of DSC tests in rheological evaluation
Closely related to rheological tests are DSC (Differential Scanning Calorimetry) measurements, which evaluate the response of a material to thermal effects.
During DSC tests, we determine the melting, crystallization and glass transition temperatures (as well as their enthalpies) of amorphous and partially crystalline plastics.
The method is particularly suitable for:
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identification of plastics,
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to identify the causes of manufacturing or quality problems,
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to test for aging, degradation or mixing.
The device can also measure oxidation induction time (OIT) and oxidation induction temperature (OITe), which are important indicators of the thermal and oxidative stability of polymers.
DSC and rheological measurements together provide a complete picture of the polymer's structure, processability, and long-term behavior.
Why are rheological tests essential?
Rheology is one of the most important diagnostic tools for optimizing production and identifying the causes of problems. It can be used to determine:
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why the extrusion pressure or injection molding cycle time changes,
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why flow lines, sinking, distortion or surface deterioration occur,
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how additives affect the behavior of the material,
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why the processing of two raw materials that are thought to be the same differs,
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what recipe or parameter modification is required.
Rheological tests therefore not only provide measurement results, but also guidelines for stable, efficient and cost-optimized production.
What does Müki Labor help with?
In addition to measurements, our laboratory also provides professional interpretation, comparative analysis, and, if necessary, solution suggestions.
Our collaboration supports:
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the introduction of new raw materials,
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supplier quality control
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identifying the causes of defective products,
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improving production stability,
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laying the foundation for development projects.
Where is it most commonly used?
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automotive industry, electronics industry
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injection molded and extruded technical products
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packaging films, coatings
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construction plastic systems
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special polymer blends and composites
Rheological tests are essential in all areas where manufacturing and material behavior are related.
Contact our experts
When a manufacturing problem, material quality discrepancy or development issue arises, rheology and DSC testing together provide the most accurate diagnosis. Our experts will help you compile and interpret the appropriate test protocol.
Contact
Phone
Headquarters
1119 Budapest, Than Károly Street 17.
Location
1117 Budapest, Budafoki Street 187-189.
Müki Labor Ltd.
If you have any questions about our tests, services or your request for a quote, our expert colleagues are ready to assist you. Whether it is a standard test, custom method development, defect or failure detection or quality assurance issue, we handle all inquiries in detail and with a short deadline.
It is important to us that our clients receive accurate information as quickly as possible, which is why we respond to all incoming inquiries within a short time. If you need a personal consultation, professional consultation or an inspection offer, please contact us for further information.
We look forward to hearing from you at the contact details provided, where we will be happy to help you choose the right direction of investigation and start the process.
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