Requirement of equipment for testing the Melt flow rate of plastics stated in ASTM D 1238

The Melt flow volume or melt flow rate of plastic is the amount of molten plastic that can flow through an orifice of specific diameter in ten minutes. In order to determine the exact value of the MFR of a sample, there is a requirement of a special testing equipment called Melt Flow Index Tester. The instrument is very helpful in providing exact analysis of the MFR of the sample. In order to obtain the best results, it is essential that the instrument used for testing the Melt Flow Rate fulfills all the requirements stated in the quality testing standard ASTM D 1238 which is used for governing the testing instrument for MFR.

Here are the requirements for the MFI Tester used for testing the MFR of a sample as per ASTM D 1238.

1. For this test, an extrusion plastometer should be used which should be a dead weight piston plastometer that consists a heating cylinder which is thermostatically controlled.
2. The heating cylinder must contain a bore in which a die is present at its lower end.
3. Along with that, a weighted piston should be used to exert weight on the specimen.
4. The diameter of the cylinder must be 50 mm with a tolerance of ±10 mm. The length of the cylinder should be 115 to 180 mm. The bore in the cylinder should have a diameter of 9.5504 mm ± 0.0076 mm.
5. The standard die that will be placed in the cylinder will have a bore of 2.095 ± 0.005 mm diameter and a length of 8.000 ±0.25 mm. The bore of the orifice must not have any drill or finishing marks for smooth travel of the molten plastic.
6. Along with that, there must be a piston made of steel along with dead weight should be provided with the instrument to exert weight on the sample. The piston should be insulated to prevent heat transfer from the heating barrel to the piston.
7. The diameter of the piston must be 9.4742 ± 0.0076 mm in diameter.
8. The equipment must have a system for temperature control. The temperature sensor must have a sensitivity of ±0.8⁰ C at 200⁰
9. There must be an arrangement to supervise automatic and manual cutting of the samples with the help of a knife at desired intervals.

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