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Rathy Cato
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Other than molecular weight, what are the factors which affect the melt flow rate of thermoplastic?
Melt flow index (MFI) is a measure of the flowability of a polymer under specific conditions. It is defined as the mass of polymer that can be extruded through a standard die in a given period of time and at a specific temperature and load.
Several factors can influence the melt flow index of a polymer, including molecular weight, molecular weight distribution, temperature, pressure, and additives. Higher molecular weight and broader molecular weight distribution tend to decrease MFI, while higher temperature and pressure tend to increase it.
Melt flow index is typically measured using a melt flow rate (MFR) tester, also known as a melt indexer. This instrument measures the weight of the polymer extruded through a die in a given time period at a specified temperature and load. The MFI value is then calculated by dividing the weight by the time and converting to a standard unit.
Melt flow index is an important factor in the processing of polymers as it can affect the properties of the final product. A high MFI can result in a weaker and more brittle product, while a low MFI can lead to difficulties in processing. It is also used as a quality control measure to ensure consistency in production.
Melt flow index can be used as a general guideline for comparing the flow properties of different polymers, but it is important to consider other factors such as molecular weight and additives. Additionally, different polymers may have different MFI testing conditions, so it is not always a direct comparison. It is best to consult the manufacturer's data sheet for a more accurate comparison.