How do you test ASTM melt flow rate?

 

1. Sample Preparation: A representative sample of the thermoplastic material is prepared. The sample is usually in the form of pellets, granules, or powder. It may need to be dried prior to testing to remove any moisture content that could affect the test results.

 

2. Test Apparatus: The ASTM D1238 test apparatus consists of a heated barrel, a piston with a specified diameter and length, and a die with a specific diameter and length.

 

3. Test Temperature and Load: Select the appropriate test temperature and load based on the specific material being tested. The ASTM D1238 standard provides a range of test conditions based on the type of material. Common test temperatures range from 190°C to 230°C, and loads can vary from 2.16 kg to 21.6 kg.

 

4. Test Procedure:

 

   a. Preheat the barrel and die to the specified test temperature.

   b. Load the sample into the barrel and cover it with a weight to prevent any premature flow.

   c. Insert the piston into the barrel and allow it to reach thermal equilibrium with the sample.

   d. After the specified preheating time, release the piston, allowing the molten material to flow through the die.

   e. Measure the mass of the extruded material within a specified time interval, usually 10 minutes.

 

5. Calculation: The ASTM D1238 test method typically yields two parameters, the Melt Flow Rate (MFR) and the Melt Volume Rate (MVR). The MFR is expressed in grams per 10 minutes (g/10 min), while the MVR is expressed in cubic centimeters per 10 minutes (cc/10 min). These values indicate the flow rate and viscosity of the material under the specified test conditions.

 

6. Reporting Results: Test results are reported as the MFR or MVR value along with the corresponding test conditions, including temperature, load, and any other relevant parameters. This information allows for comparison between different materials or monitoring the consistency of a material during production.

 

It's important to note that the ASTM D1238 standard provides different test methods, such as Procedure A and Procedure B, based on the nature of the material (e.g., low-density polyethylene, high-density polyethylene). These procedures may have slight variations in the testing conditions, so it's crucial to refer to the specific ASTM standard relevant to the material being tested.