What is the melt flow index (MFI)?
The thermal properties of materials are directly related to their production processes and product usage.
Common indicators for the thermal properties of polymer materials include heat deflection temperature, melt flow index, melting point, coefficient of linear expansion, and more.
Today, we will focus on discussing the measurement of the melt flow index of plastics.
What is the melt flow index?
Melt flow rate or melt flow index, commonly referred to as MFI, is the mass or volume of molten plastic that passes through a standardized capillary in 10 minutes under a certain temperature and load.
It is used to describe the flowability of plastic materials during the injection molding process and plays a role in confirming and adjusting the manufacturing process.
Melt flow index is commonly used as a parameter for quality control and processing conditions of thermoplastic resins.
The importance of testing the melt flow index of plastics
1. The melt flow index affects the properties of plastics. Generally, plastics with higher melt flow index have better flowability and easier processing and exhibit good stiffness and barrier characteristics. However, they may have poor impact resistance, environmental stress cracking resistance, outdoor performance, and resistance to chemical media. On the other hand, as the melt flow index decreases, properties such as fracture strength, hardness, toughness, and aging resistance improve.
2. Processing methods like spinning and injection molding of polyesters are performed in a molten state, and the viscosity of the melt is one of the most important parameters in rheological properties and ensures product quality.
3. The melt flow index is a parameter that characterizes the flow rate of materials inside the screw of an extruder. It measures the flowability of polymers under a given shear force and temperature.
4. Materials with a higher melt flow index typically have a lower friction coefficient with the screw in the extruder, resulting in lower output. Moreover, materials with high melt flow index often contain more impurities, leading to increased pressure on the die head and potential blockages.
5. Testing the flowability of materials ensures whether they meet production requirements. If the test results do not meet the specifications, they cannot be used as raw materials for production.
Understanding and controlling the melt flow index of plastics is vital in ensuring optimal processing, product quality, and performance characteristics.
Categories
injection molding