ASTM D1238 - 20

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

    Active Standard ASTM D1238 | Developed by Subcommittee: D20.30

    Book of Standards Volume: 08.01


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    Significance and Use

    5.1 This test method is particularly useful for quality control tests on thermoplastics.

    5.2 The data produced by this test method 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.

    5.3 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.

    5.4 Measure the flow rate of a material using any of the conditions listed for the material in X4.1. For many materials, there are specifications that require the use of this test method, but with some procedural modifications that take precedence when adhering to the specification. Therefore, it is advisable to refer to that material specification before using this test method. Table 1 in Classification D4000 lists the ASTM materials standards that currently exist. An alternative test method for poly (vinyl chloride) (PVC) compounds is found in Test Method D3364.

    5.5 Additional characterization of a material can be obtained if more than one condition is used. In the case that two or more conditions are employed, a Flow Rate Ratio (FRR) is obtained by dividing the flow rate at one condition by the flow rate at another condition. Procedure D provides one method to measure more than one condition in a single charge.

    5.6 Frequently, variations in test technique, apparatus geometry, or test conditions, which defy all but the most careful scrutiny, exist, causing discrepancies in flow rate determinations. A troubleshooting guide is found in Appendix X2 and it is a resource to be used to identify sources of test error.

    1. Scope

    1.1 This test method covers the determination of the rate of extrusion of molten thermoplastic resins using an extrusion plastometer.

    1.2 The values stated in SI units are to be regarded as standard.

    1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

    Note 1: This standard and ISO 1133 address the same subject matter, but differ in technical content.

    1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    D618 Practice for Conditioning Plastics for Testing

    D883 Terminology Relating to Plastics

    D3364 Test Method for Flow Rates for Poly(Vinyl Chloride) with Molecular Structural Implications

    D4000 Classification System for Specifying Plastic Materials

    D5947 Test Methods for Physical Dimensions of Solid Plastics Specimens

    E456 Terminology Relating to Quality and Statistics

    E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method


    ICS Code

    ICS Number Code 83.080.20 (Thermoplastic materials)

    UNSPSC Code

    UNSPSC Code 13102000(Thermoplastic plastics)


    Referencing This Standard
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    DOI: 10.1520/D1238-20

    Citation Format

    ASTM D1238-20, Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer, ASTM International, West Conshohocken, PA, 2020, www.astm.org

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