The melt flow index, or MFI, is an important parameter that helps determine the flow rate of the polymer sample at the melting point. The mass flow rate of the polymer is recorded for a definite period. The MFI value is an indicator of the flowability of the thermoplastic sample. MFI can be calculated by conducting tests under various conditions and constant load. The melt flow index tester is the best tool to measure melt viscosity. It is commonly used to grade polymers based on quality and molecular weight.

What Is Melt Flow Index Tester?

The melt flow index tester measures the flowability of a polymer. The equipment helps determine the rate at which a polymer melts and flows through a small-diameter capillary under standard conditions of temperature and pressure. The MFI tester is widely used in the plastics industry for quality control and to predict the behavior of a polymer during processing and fabrication. MFI is simply the quality of polymer pushed through the die of a specified dimension at the melting point or set temperature recovered over a specific period.

How To Measure Melt Flow Index

Step 1: The polymer granules are packed into a clear cylindrical barrel. The temperature conditions are set. The melt flow index tester uses a specific size orifice in a heated barrel. It has a piston and weight towards the top inserted into the barrel to apply force towards the polymer sample and expel them through the orifice.
Step 2: After applying heat for a specified period to soften or melt the resin sample, the machine is left for some time to achieve the pre-defined temperature. Weights are placed on the sample to force the molten polymer outside the equipment. The sample forced through the nozzle is cut into smaller pieces by the sample cutter.
Step 3: The sample cuttings collected for 10 minutes are measured and subjected to a digital weighing machine wherein it is measured in grams. A higher index flow rate implies lower viscosity of the polymer sample. As the polymer viscosity decreases, the flow per unit time increases. Fewer grams passing through the nozzle or a lower melt flow index rate implies higher viscosity.

Benefits Of Calculating The MFI Of A Polymer Sample

• MFI is used as a quality control parameter to ensure that the polymer material is consistent regarding its flow characteristics. This is vital to ensure that the final product has the preferred properties and performance.
• It can be used to optimize the processing conditions of a polymer. By adjusting the temperature and pressure during processing, the MFI can be controlled to achieve the desired flow properties of the polymer.
• MFI value can be used to characterize the rheological properties of a polymer, such as its viscosity, molecular weight distribution, and melt strength. This information helps design and develop new polymer formulations and optimize processing conditions.
• MFI results are used in selecting a polymer for a specific application. For example, a high MFI polymer may be preferred for injection molding applications where fast flow rates are needed. However, a low MFI polymer may be selected for blow molding applications where slower flow rates are desired.
• It is a standard parameter used in many international standards and regulations to characterize polymers. Compliance with these standards is necessary for product approval and commercialization in many industries.

Final Thoughts

Melt flow index results play a significant role in deciding the physical properties of polymers. Hence manufacturers must invest in quality testing equipment. The melt flow index tester equipment by Pacorr is designed per globally acclaimed standards like ISO 1133 and ASTM D 1238 for accurate results. It can help evaluate the consistency and quality of polymer sample that helps deliver quality end products. It has a digital microprocessor-based display to monitor and measure various parameters during the test.