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About melt flow index

Oct 12, 2018

What is  melt flow index?

Melt flow rate or melt flow index, referred to as melt index. Refers to the mass or volume of the standard die capillary passed through the melt every 10 minutes under a certain temperature and load. Expressed in MFR.

It describes the fluidity of the plastic material in the injection molding process and has a certain effect on the confirmation and adjustment of the process in the injection molding process. The melt index is usually used as a parameter for quality control of thermoplastic resins and molding process conditions.

The importance of testing the plastic melt flow index

1. The height of the melt refers to the performance of the plastic. The plastic raw material generally has a high melt index, and the fluidity is large, the molding process is convenient, the stiffness and the barrier property are good; the impact resistance property, the environmental stress cracking resistance characteristic, the outdoor property, and the chemical medium resistance property are poor; the smaller the melt index, the fracture Strength, hardness, toughness, and aging stability are all improved.

2. Polyester spinning and injection molding are processed in a molten state. The viscosity of the melt is one of the most important parameters in its rheological properties, and it is also the key to ensure product quality.

3. The melt index is a parameter that characterizes the flow rate of the feedstock within the screw. The fluidity of the polymer is determined for a given shear force and is related to shear and temperature.

4. The material with high melt index has a relatively small coefficient of friction with the screw in the extruder, and thus the output is relatively small. High-melting materials generally have more impurities, and the pressure on the machine head is large, which is likely to cause network blockage.

5. Whether the flow properties of the test materials can meet the production requirements, if the test results are not qualified, they cannot be used as raw materials for production.

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