What is ASTM test method for MFI?

 

Here is a summary of the key steps involved in the ASTM D1238 test method for MFI:

 

1. Specimen preparation: The test specimen is typically prepared in the form of pellets, granules, or powder. It should be representative of the material being tested and free of any contamination.

 

2. Equipment setup: Set up an extrusion plastometer, also known as a melt flow indexer, which consists of a heated barrel, a piston, and a die. The equipment is designed to measure the flow of molten thermoplastic material through the die.

 

3. Calibration: Calibrate the equipment in accordance with the manufacturer's instructions to ensure accurate measurements. This typically involves verifying the temperature accuracy and checking the piston displacement.

 

4. Test conditions: Establish the testing conditions, which include the test temperature and the load (weight) applied to the piston during the test. The specific conditions are determined based on the material being tested and may be specified in the relevant product standard or specification.

 

5. Preheating: Preheat the equipment to the specified test temperature to ensure the thermoplastic material is in a molten state.

 

6. Test procedure: Load a specified mass of the specimen into the heated barrel of the equipment and place the piston on top. Allow the material to melt and flow through the die under the weight of the piston. The extrudate is collected and weighed over a specified time period.

 

7. Data recording: Measure the mass of the extrudate collected during the test period and record the time taken to collect the specified mass.

 

8. Data analysis: Calculate the melt flow rate (MFR) or melt flow index (MFI) based on the mass of the extrudate and the test time. The MFI is typically reported in units such as grams per 10 minutes (g/10 min) or grams per minute (g/min).

 

It is important to note that ASTM D1238 provides a standardized test method for MFI measurement, but it does not account for all aspects of material behavior or processability. Other factors, such as molecular weight, shear rate, and shear stress, may also influence the flow properties of thermoplastics. Therefore, it is crucial to consider the limitations of the MFI test and supplement it with additional tests or evaluations when necessary.