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ASTM D1238 Polymer Melt Flow Rate Testing by Extrusion Plastometer

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ASTM D1238 Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer


ASTM D1238 test method test method covers the determination of the rate of extrusion of molten thermoplastic resins using an extrusion plastometer. it is particularly useful for quality control tests on thermoplastics. The data produced by ASTM D1238 test serves to indicate the uniformity of the flow rate of the polymer as made by an individual process. It is not to be used as an indication of uniformity of other properties without valid correlation with data from other tests.

The flow rate obtained with the extrusion plastometer is not a fundamental polymer property. It is an empirically defined parameter critically influenced by the physical properties and molecular structure of the polymer and the conditions of measurement. The rheological characteristics of polymer melts depend on a number of variables. It is possible that the values of these variables occurring in this test will differ substantially from those in large-scale processes, which would result in data that does not correlate directly with processing behavior.


Importance of Melt Flow Rate Test

The melt flow rate is a key parameter that reflects the viscosity of a polymer melt. It is an indication of how easily the material can flow when subjected to heat and pressure. A higher MFR suggests a lower viscosity, meaning the polymer flows more easily, while a lower MFR indicates higher viscosity, suggesting more resistance to flow. Understanding this behavior is essential for processes like extrusion, injection molding, and blow molding, where the flow characteristics of a polymer directly impact the efficiency and quality of the final product.


Materials Commonly Tested use ASTM D1238, ISO 1133

It is critical data for thermoplastics such as polyethylene,polypropylene, polystyrene, and polycarbonate that allow manufacturers to optimize their production parameters for injection molding and extrusion processes according to their behavior under heat and pressure.


Conducting the Melt Flow Rate Test

ASTM D1238 test method involves heating a polymer sample in a test chamber to a specified temperature. Once the polymer reaches the desired temperature, it is forced through a die of known diameter under a specified load using a piston. The mass of the polymer extruded through the die is collected over a defined period and weighed. The melt flow rate is then calculated by dividing the mass by the elapsed time, typically expressed in grams per 10 minutes.

There are two procedures in ASTM D1238: Procedure A (manual) and Procedure B (automated). 

Procedure A involves manually loading the sample and timing the test, while Procedure B uses automated equipment to perform these tasks. 

The choice of procedure usually depends on the available equipment and the level of precision required.


Similar standard: 

ISO 1133: Plastics — Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics — Part 1: Standard method
BS 2782-7.720A: METHODS OF TESTING PLASTICS - RHEOLOGICAL PROPERTIES - DETERMINATION OF THE MELT MASS-FLOW RATE (MFR) AND THE MELT VOLUME-FLOW RATE (MVR) OF THERMOPLASTICS
                       For the Rheological Properties Method 720A: Determination of the Melt Mass-Flow Rate (MVR) of Thermoplastics, while it does not specifically focus on melt flow index testing like ISO 1133 or ASTM D1238, BS 2782 includes procedures for testing other key properties of thermoplastics, such as tensile strength, impact resistance, and thermal properties. This standard provides a comprehensive framework for assessing plastic materials’ performance, which is valuable for quality assurance and product development in industries ranging from automotive to construction.
JSA - JIS K 7210-1 Plastics-Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics-Part 1: Standard method
                    JIS K7210 is a Japanese industrial standard established by the Japanese Industrial Standards Committee (JISC) for determining the melting rate of thermoplastic materials. This standard outlines the procedures for conducting MFR tests using a melt flow indexer apparatus, similar to ASTM D1238 and ISO 1133. JIS K7210 specifies the test conditions, equipment requirements, and calculation methods for determining thermoplastic MFR. The procedure outlined in JIS K 7210:2016 involves heating thermoplastic samples and extruding them through a mold under a specified load. Flow rate (MFR) is calculated by measuring the amount of material flowing through the mold within a given time. This test is crucial for understanding the processing characteristics of thermoplastic materials and ensuring manufacturing consistency.
GB/T 3682.1: Plastics—Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics—Part 1:Standard method


Related Standard

ISO 1133 Test Method of Determination melt mass-flow rate (MFR, MVR)

ISO 1133: Plastics -- Determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastics.

ISO 1133 standard specifies two procedures for the determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastic materials under specified conditions of temperature and load. One is a mass-measurement method. The other is a displacement-measurement method. Normally, the test conditions for measurement of melt flow rate are specified in the material standard with a reference to ISO 1133. The test conditions normally used for thermoplastics are listed in annexes. 

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