The thermal performance of the material is directly related to its production process and product use. The thermal performance indicators of common polymer materials include heat distortion temperature, melt index, glass transition temperature, melting point, linear expansion coefficient, etc. Today we will focus on the measurement of plastic melt index!
Firstly what is melt index?
Melt flow rate or melt flow index, referred to as melt index. It refers to the mass or volume of the melt through the capillary tube of the standard die every 10 minutes under a certain temperature and load. MI is commonly used to express it, and it is now uniformly called the melt flow rate internationally, expressed in MFR.
It is used to describe the fluidity of plastic materials in the injection molding process, and has a certain effect on the confirmation and adjustment of the process in the injection molding production process. Melt index is usually used as a parameter of thermoplastic resin quality control and molding process conditions.
Importance of testing plastic melt index
1. The level of melt index affects the performance of the plastic. Plastic raw materials generally have high melt index, high fluidity, convenient molding and processing, good stiffness and barrier properties; poor impact resistance, environmental stress cracking resistance, outdoor properties, and chemical resistance properties; the smaller the melt index, the fracture Strength, hardness, toughness, aging resistance and stability have been improved.
2. Processing such as spinning and injection molding of polyester is carried out in the 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 ensuring product quality.
3. The melt index is a parameter that characterizes the flow rate of the raw material in the screw. The flow rate of the polymer is measured under the given shear force, which is related to the shear force and temperature.
4. The friction coefficient between the material with high melt index and the screw in the extruder is relatively small, so the output is relatively small. The material with high melting index generally has more impurities, which puts a lot of pressure on the machine head, which is easy to cause network blockage.
5. Whether the fluidity of the test material can meet the production requirements, if the test result is unqualified, it cannot be used as a production material.