Technical data sheet: properties and parameters of plasic resin
https://baobikhangloi.com.vn/bang-du-lieu-ky-thuat-cac-dac-tinh-va-thong-so-cua-hat-nhua 1. Melt Flow Index (MFI) Melt Flow Index (MFI) or also known as flow rate - Melt Flow Rate (MFR) is a measure of the ability of molten plastic to move under a specific pressure. This is an important, regularly tested metric as they tell us and control the flow of molten plastic from the tank through the screw to the blow mold, die, injection molding head or any other parts that have any other shaping function. MFI is inversely proportional to the viscosity of the resin. Low MFI means high viscosity materials, they flow with greater resistance and hence slower than low viscosity materials. The MFI can be the only indicator on the technical data sheet that has no specific value that can vary significantly from batch to batch with the same resin code. This is because polymer copolymerization is unlikely to take place precisely at the molecular level. The length of the polymer chains affects the average molecular weight and viscosity of the finished product, and changes the MFI. In many cases, MFI index is the criterion to evaluate the quality of a batch produced on the same type of plastic resin and manufacturer. The MFI index tells us which materials are suitable for which type and treatment method in the manufacturing industry. Injection molding machines, blow extruders tend to be suitable for materials with high flow rates (low viscosity). The extruder is compatible with low flow rate (high viscosity) materials. Strict control of the MFI value of input materials is important to the productivity and quality of the product. The MFI number exceeds the normal level, causing the plastic to be pushed out too quickly, and if it is too low, will cause the plastic to flow out too slowly. In all cases, other parameters on the mechanical system are affected. There are two methods of measuring plastic flow, automatic or manual, based on ASTM D1238 or ISO 1133 test standards. The manual measurement process, temporarily called process A, is useful for organizations whom do occasional testing, using a variety of materials in order to find a better and more suitable material for their production of plastic products job. Process B, on the other hand, is an automated process, ideal for organizations that repeatedly test the same material under different conditions, to find the correct value for scientific purposes. Theoretically, both methods, if properly implemented, should give identical test results. The range of factors that can affect MFI flow index test results is very wide. For accurate results, it is necessary to be aware of each problem, strictly follow the equipment inspection and maintenance procedures. The plastometer machine used in the test is constructed of a temperature-controlled cylindrical material tank. The resin introduced into this tube, after being melted, is forced to flow through a capillary tube with a diameter of 2,095 mm at the bottom of the barrel, under the pressure of a piston actuated by a standard weight. The mass of molten plastic in grams that flows through the capillary in 10 minutes is the MFI of the material. There is also a slight difference between standards ASTM D1238 and ISO 1133. But they perform essentially the same function, and the manufacturers consider them to be technically equivalent. ASTM D1238 is the test method for measuring MFI flow rates for thermoplastics expressed in units of grams/10 minutes. And ISO 1133 standard defines volumetric melt rate (MVR) in cm3/ 10 minutes The melt volume (MVR) obtained in the ISO 1133 test, multiplied by the melt density gives the MFI. However, it should be noted that the density when melted plastic is not the same as the density of the material under normal conditions. For example, Polypropylene has a specific density of 0.91 grams/cm3 but their melting density is only 0.70 grams/cm3. Applying the density or density value under normal conditions to calculate the MFI with the MVR value gives misleading results.
