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ASTM D1238 For Melt Flow Rates Of Thermoplastics Used In Melt Flow Index Tester

The ASTM D1238 standard test method is used for testing the quality of thermoplastics. The testing procedure is performed to check the uniformity of the polymer’s flow rate. It is also important to note that the flow rate cannot be considered the fundamental polymer property. The physical property and molecular structure of the polymer affect the parameters of the thermoplastics.

Prior to using the standard test method, it is important to determine the material specifications. The additional character of material can be determined if the testing procedure is performed in more than one condition. Using more than one condition, the flow rate at one condition is divided by the flow rate at another condition.

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The test method includes determining the rate of extrusion of molten thermoplastic resins with the help of an extrusion plastomer. Once preheated at a specified, resin is extruded through a die with a specified length and orifice diameter under prescribed conditions of temperature, load, and piston position of the barrel. There are several procedures used in ASTM D1238 standard test method:

  • Procedure A determines the melt flow rate (MFR) of a thermoplastic material, measure in grams of material/10 minutes (g/10 min). The method is based on the measurement of the mass of material extruding from the die over a given period of time. The procedure is applicable for materials with melt flow rates between 0.15 and 50 g/10 min.
  • Procedure B determines the MFT and melt flow volume rate of thermoplastic materials and is used for materials that have flow rate from 0.50 to 1500 g/10 min.
  • Procedure C determines the MFT of polyolefin materials and is also used an alternative to procedure B that has melt flow rate more than 75 g/10 min. This method uses modified die (referred to as a half-die).
  • Procedure D is referred as “Flow Rate Ratio” (FRR) test that determines MFR using two or three different test loads (either increasing or decreasing the load during the test) on one charge of material.

Melt Flow Index Tester Complied with ASTM D1238 Standard Test Method

Presto’s Melt Flow Index Tester evaluated the flow properties of the molten plastics or resins and defined as the rate of flow (in grams per 10 minutes) of extrudates of molten resins through a jet of a specific length and diameter.  The test is performed under suggested conditions of load, temperature and piston position in a cylindrical cavity inside a heated metallic tube barrel.


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