ASTM D1238-23a

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

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...
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.

General Information

• Status: Published
• Publication Date: 14-Nov-2023
• ICS: 83.080.20 - Thermoplastic materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.30 - Thermal Properties

Relations

• Replaces: ASTM D1238-23 - Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer
• Effective Date: 15-Nov-2023
• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM E456-13a(2022) - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Referred By: ASTM D5205-16 - Standard Classification System and Basis for Specification for Polyetherimide (PEI) Materials
• Effective Date: 15-Nov-2023
• Referred By: ASTM D5577-19 - Standard Guide for Techniques to Separate and Identify Contaminants in Recycled Plastics
• Effective Date: 15-Nov-2023
• Referred By: ASTM D6388-18 - Standard Practice for Tests to Evaluate the Chemical Resistance of Geonets to Liquids
• Effective Date: 15-Nov-2023
• Referred By: ASTM D6389-23 - Standard Practice for Tests to Evaluate the Chemical Resistance of Geotextiles to Liquids
• Effective Date: 15-Nov-2023
• Referred By: ASTM F412-23 - Standard Terminology Relating to Plastic Piping Systems
• Effective Date: 15-Nov-2023
• Referred By: ASTM F3508-21a - Standard Guide for In-Situ Pipeline Renovation As Dual-Wall Composite Pipeline by Push/Pull Installation of Compressed-Fit Shape-Memory-Polymer Tubular (SMPT)
• Effective Date: 15-Nov-2023
• Referred By: ASTM D3485-22 - Standard Specification for Coilable High Density Polyethylene (HDPE) Cable in Conduit (CIC)
• Effective Date: 15-Nov-2023
• Referred By: ASTM D5138-23 - Standard Classification System and Basis for Specification for Liquid Crystal Polymers Molding and Extrusion Materials (LCP)
• Effective Date: 15-Nov-2023
• Referred By: ASTM F714-22 - Standard Specification for Polyethylene (PE) Plastic Pipe (DR-PR) Based on Outside Diameter
• Effective Date: 15-Nov-2023
• Referred By: ASTM D6434-12(2018) - Standard Guide for the Selection of Test Methods for Flexible Polypropylene Geomembranes
• Effective Date: 15-Nov-2023

Overview

ASTM D1238-23a - Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer - is a leading standard provided by ASTM International for determining the melt flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastic resins. By assessing the rate at which molten thermoplastics are extruded through a die under prescribed conditions, this method provides essential data for quality control, process monitoring, and material specification in plastics manufacturing.

This standardized test is particularly valuable for manufacturers, laboratories, and quality assurance teams who deal with plastic materials. While the results provide crucial insight into flow properties, it is important to note that the melt flow rate is an empirical parameter - it does not represent a fundamental polymer property but is significantly impacted by the polymer’s physical characteristics and test conditions.

Key Topics

• Quality Control in Thermoplastics: The method offers a straightforward way to monitor the consistency and uniformity of thermoplastic materials within or between production batches.
• Extrusion Plastometer Measurement: Uses a specialized device to measure the mass or volume of molten plastic extruded in a set time, under specified temperature and load conditions.
• Procedures and Conditions: Includes manual and automated measurement procedures - Procedure A (manual), B (automated with standard die), C (automated with “half” die for high-flow polyolefins), and D (multi-weight or Flow Rate Ratio FRR test).
• Empirical Nature of Results: The melt flow rate is influenced by the polymer’s molecular structure, temperature, load, and equipment, and may not directly correlate with large-scale processing behavior.
• Specification and Modifications: Some materials or specifications may require modifications to standard test conditions for applicability.

Applications

ASTM D1238-23a is widely used for:

• Material Quality Assurance: Verifying that thermoplastic pellets, powders, or compounded materials meet required specifications for extrusion, injection molding, or other processes.
• Process Consistency Monitoring: Ensuring that melt flow rates are consistent, which helps indicate uniform production and reduces variability in downstream processing.
• Comparative Material Assessment: Aiding purchasers and producers in comparing batches, lots, or different grades of thermoplastics based on their flow characteristics.
• Research and Development: Supporting polymer scientists in studying how molecular weight, branching, or additives affect processability.
• Specification Compliance: Many plastic material standards reference ASTM D1238 for determining melt flow as a requirement before processing.

Note: Always refer to material-specific guidelines and specifications before testing, as certain plastics (e.g., PVC) may require alternative methods (such as ASTM D3364) or specification-driven modifications.

Related Standards

Integrating ASTM D1238-23a into material testing may also involve related standards, such as:

• ISO 1133 - Internationally recognized method for measuring melt flow rates, similar in scope but differing in some technical details.
• ASTM D618 - Practice for Conditioning Plastics for Testing, essential for sample preparation.
• ASTM D883 - Terminology Relating to Plastics, helpful for definitions used in test reports.
• ASTM D3364 - Alternative method for PVC flow rate determination.
• ASTM D4000 - Classification System for Specifying Plastic Materials, which cross-references required test methods.
• ASTM E4 - Practices for Force Calibration; critical for verifying extrusion plastometer load accuracy.

Summary

Adoption of ASTM D1238-23a enables plastics manufacturers, converters, and laboratories to accurately measure and report the melt flow rate and melt volume-flow rate of thermoplastic materials. This supports robust quality control, improved product consistency, and compliance with international and industry standards for thermoplastics. For best results, ensure procedural compliance, equipment calibration, and alignment with any applicable material specifications.

Standards Content (Sample)

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.
Designation: D1238 − 23a
Standard Test Method for
Melt Flow Rates of Thermoplastics by Extrusion
Plastometer
This standard is issued under the fixed designation D1238; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to
1.1 This test method covers the determination of the rate of
Determine the Precision of a Test Method
extrusion of molten thermoplastic resins using an extrusion
2.2 ANSI Standard:
plastometer.
B46.1 on Surface Texture
1.2 The values stated in SI units are to be regarded as
2.3 ISO Standard:
standard.
ISO 1133 Determination of the Melt-Mass Flow Rate (MFR)
1.3 This standard does not purport to address all of the
and the Melt Volume-Flow Rate (MVR) of Thermoplas-
safety concerns, if any, associated with its use. It is the
tics
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3. Terminology
mine the applicability of regulatory limitations prior to use.
3.1 Terms used in this standard are defined in accordance
NOTE 1—This standard and ISO 1133 address the same subject matter, with Terminology D883, unless otherwise specified. For terms
but differ in technical content.
relating to precision and bias and associated issues, the terms
used in this standard are defined in accordance with Terminol-
1.4 This international standard was developed in accor-
ogy E456.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
4. Summary of Test Method
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
4.1 After a specified preheating time, resin is extruded
Barriers to Trade (TBT) Committee.
through a die with a specified length and orifice diameter under
prescribed conditions of temperature, load, and piston position
2. Referenced Documents
in the barrel. Four procedures are described. Comparable
2.1 ASTM Standards:
results have been obtained by these procedures in interlabora-
D618 Practice for Conditioning Plastics for Testing
tory round-robin measurements of several materials and are
D883 Terminology Relating to Plastics
described in Section 16.
D3364 Test Method for Flow Rates for Poly(Vinyl Chloride)
4.2 Procedure A is used to determine the melt flow rate
with Molecular Structural Implications
(MFR) of a thermoplastic material. The units of measure are
D4000 Classification System for Specifying Plastic Materi-
grams of material/10 min (g/10 min). It is based on the
als
measurement of the mass of material that extrudes from the die
D5947 Test Methods for Physical Dimensions of Solid
over a given period of time. It is generally used for materials
Plastics Specimens
having melt flow rates that fall between 0.15 and 50 g/10 min
E4 Practices for Force Calibration and Verification of Test-
(see Note 2).
ing Machines
4.3 Procedure B is an automatically timed measurement
1 used to determine the melt flow rate (MFR) as well as the melt
This test method is under the jurisdiction of ASTM Committee D20 on Plastics
and is the direct responsibility of Subcommittee D20.30 on Thermal Properties.
volume rate (MVR) of thermoplastic materials. MFR measure-
Current edition approved Nov. 15, 2023. Published November 2023. Originally
ments made with Procedure B are reported in g/10 min. MVR
approved in 1965. Last previous edition approved in 2023 as D1238 - 23. DOI:
measurements are reported in cubic centimeters/10 min
10.1520/D1238-23A.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1238 − 23a
(cm /10 min). Procedure B measurements are based on the method. Table 1 in Classification D4000 lists the ASTM
determination of the volume of material extruded from the die materials standards that currently exist. An alternative test
over a given period of time. The volume is converted to a mass method for poly (vinyl chloride) (PVC) compounds is found in
measurement by multiplying the result by the melt density Test Method D3364.
value for the material (see Note 3). Procedure B is generally
5.5 Additional characterization of a material can be ob-
used with materials having melt flow rates from 0.50 to 1500
tained if more than one condition is used. In the case that two
g/10 min.
or more conditions are employed, a Flow Rate Ratio (FRR) is
obtained by dividing the flow rate at one condition by the flow
4.4 Procedure C is an automatically timed measurement
rate at another condition. Procedure D provides one method to
used to determine the melt flow rate (MFR) of polyolefin
measure more than one condition in a single charge.
materials. It is generally used as an alternative to Procedure B
on samples having melt flow rates greater than 75 g/10 min.
5.6 Frequently, variations in test technique, apparatus
Procedure C involves the use of a modified die, commonly
geometry, or test conditions, which defy all but the most
referred to as a “half-die,” which has half the height and half
careful scrutiny, exist, causing discrepancies in flow rate
the internal diameter of the standard die specified for use in
determinations. A troubleshooting guide is found in Appendix
Procedures A and B thus maintaining the same length to
X2 and it is a resource to be used to identify sources of test
diameter ratio. The test procedure is similar to Procedure B, but
error.
the results obtained with Procedure C shall not be assumed to
6. Apparatus
be half of those results produced with Procedure B.
6.1 Extrusion Plastometer (Alternative Names—Melt
4.5 Procedure D is a multi-weight test commonly referred to
Indexer, Melt Flow Indexer):
as a “Flow Rate Ratio” (FRR) test. Procedure D is designed to
allow MFR determinations to be made using two or three NOTE 4—Older plastometers that were manufactured in accordance
with “design specifications” detailed in previous revisions of this test
different test loads (either increasing or decreasing the load
method (pre D1238 - 04c) are deemed to be acceptable, as long as they
during the test) on one charge of material. The FRR is a
meet the dimensional and performance specifications stated in this section.
dimensionless number derived by dividing the MFR at the
NOTE 5—Relatively minor changes in the design and arrangement of
higher test load by the MFR at the lower test load. Results
the component parts have been shown to cause differences in results
generated from multi-weight tests shall not be directly com- among laboratories. For the best interlaboratory agreement, it is important
that the design adhere closely to the description herein; otherwise, it
pared with results derived from Procedure A or Procedure B.
should be determined that modifications do not influence the results. Refer
NOTE 2—Polymers having melt flow rates less than 0.15 or greater than
to Fig. 1.
900 g/10 min may be tested by the procedures in this test method;
however, precision data have not been developed.
6.1.1 The apparatus is a dead-weight piston plastometer
NOTE 3—Melt density is the density of the material in it molten state.
consisting of a thermostatically controlled heated steel cylinder
It is not to be confused with the standard density value of the material. See
with a bore that contains a die at the lower end, and a weighted
Table 4.
piston operating within the cylinder. The essential features of
the plastometer, illustrated in Figs. 1 and 2, are described in
5. Significance and Use
6.2-6.12. The bore of the extrusion plastometer shall be
5.1 This test method is particularly useful for quality control
properly aligned in the vertical direction (see Appendix X1).
tests on thermoplastics.
All dimensional measurements shall be made when the article
5.2 The data produced by this test method serves to indicate
being measured is at 23 6 5°C. As an acceptable alternative,
the uniformity of the flow rate of the polymer as made by an
the test force can be applied via a drive system working with
individual process. It is not to be used as an indication of
a load cell. In case of dispute between two cooperating
uniformity of other properties without valid correlation with
laboratories, the dead weight plastometer shall be considered
data from other tests.
correct.
5.3 The flow rate obtained with the extrusion plastometer is
6.2 Cylinder—The cylinder shall be 50 mm 6 10 mm in
not a fundamental polymer property. It is an empirically
diameter, 115 to 180 mm in length with a smooth, straight bore
defined parameter critically influenced by the physical proper-
9.5504 6 0.0076 mm in diameter. The cylinder bore shall be
ties and molecular structure of the polymer and the conditions
manufactured in a way that produces a finish approximately 12
of measurement. The rheological characteristics of polymer
rms or better in accordance with ANSI B46.1. Means shall be
melts depend on a number of variables. It is possible that the
provided to monitor the temperature inside the bore.
values of these variables occurring in this test will differ
6.3 Die (Orifice):
substantially from those in large-scale processes, which would
6.3.1 Standard Die—The outside diameter of the die shall
result in data that does not correlate directly with processing
be such that it will fall freely to the bottom of the hole in the
behavior.
cylinder. The orifice of the die shall have a smooth straight bore
5.4 Measure the flow rate of a material using any of the 2.095 6 0.005 mm in diameter and shall be 8.000 6 0.025 mm
conditions listed for the material in X4.1. For many materials, in length (see Fig. 2). The bore of the orifice and its finish are
there are specifications that require the use of this test method, critical. It shall have no visible drill or other tool marks and no
but with some procedural modifications that take precedence detectable eccentricity. The bore of the orifice shall be manu-
when adhering to the specification. Therefore, it is advisable to factured by techniques known to produce finishes approxi-
refer to that material specification before using this test mately 12 rms or better in accordance with ANSI B46.1.
D1238 − 23a
FIG. 1 General Arrangement of Extrusion Plastometer (See Sec-
tion 6.)
FIG. 2 Details of Extrusion Plastometer
tory are steel, synthetic sapphire, and cobalt-chromium-tungsten alloy.
6.3.2 “Half” Die—Used for Procedure C. When testing
When softer materials are used, it may be necessary to conduct critical
polyolefins with a MFR of 75 or greater (using the standard
dimensional checks and visual inspections on the die more often.
die), an alternate die has shown to improve the reproducibility
6.4 Piston:
of results by reducing the flow rate of these materials. The
6.4.1 The piston shall be made of steel. There shall be
outside diameter of the die shall be such that it will fall freely
insulation at the top as a barrier to heat transfer from the piston
to the bottom of the hole in the cylinder. The orifice shall have
to the weight. The piston shall be prevented from rubbing on
a smooth straight bore 1.048 6 0.005 mm in diameter and shall
the bore. Most commercially available instruments use a loose
be 4.000 6 0.025 mm in length (see Fig. 2A). The bore of the
fitting metal guide sleeve, but other methods are acceptable.
orifice and its finish are critical. It shall have no visible drill or
The weight of the sleeve shall not be considered as part of the
other tool marks and no detectable eccentricity. The bore of the
test load. The land (foot) of the piston shall be
orifice shall be manufactured by techniques known to produce
9.4742 6 0.0076 mm in diameter and 6.35 6 0.10 mm in
finishes approximately 12 rms or better in accordance with
length. Above the land, the piston shall be relieved to ≤ 9.0 mm
ANSI B46.1 (Note Note 6). No spacer shall be used with this
in diameter (see Fig. 2). The piston land shall be manufactured
die.
NOTE 6—Recommended die material is tungsten carbide. Also satisfac- by techniques known to produce finishes approximately 12 rms
D1238 − 23a
in accordance with ANSI B46.1. If corrosion is a problem, the “half” die, the temperature indicating device shall be calibrated
piston or piston land, if removable, shall be made of corrosion as stated in Table 1 except temperatures are measured at
resistant material. 79 6 1 mm and 14 6 1 mm above the upper surface of the die.
6.4.2 For procedure A, the piston shall be scribed with two 6.5.4 An alternative method is to insert the temperature
reference marks 4 mm apart in such fashion that when the
sensor without a brass tip into the melt from the top of the
lower mark coincides with the top of the cylinder, guide sleeve cylinder so that it is 10 and 75 6 1 mm above the upper face
or other suitable reference point, the bottom of the piston is 48
of the die.
mm above the top of the die (see Fig. 1) and the timed test run
6.5.5 The temperature sensor and readout equipment used
shall start within these two reference marks. The targeted
for calibration of the extrusion plastometer shall be traceable to
starting point shall be 46 6 2 mm above the upper face of the
a national standard (for example, NIST).
die. (see Fig. 1).
6.6 Timing Device/System—For Procedure A, a timing de-
6.4.3 The combined weight of piston and load shall be
vice with an accuracy of 0.1 s shall be used. For Procedures B,
within a tolerance of 60.5 % of the selected load.
C, and D, an automatic timing system shall measure and time
6.4.4 The load corresponding to a test weight may also be
piston movement within the specified travel range. The re-
applied by a drive system working with a load cell. A
quirements of the automatic timing system shall be as follows:
calibration of the load cell in combination with the piston shall
6.6.1 Sense and indicate the piston travel time within
be performed, and performance shown to be equivalent or
60.01 s.
better than the requirements listed in 6.4.3. Information on
6.6.2 Measure piston travel within 60.4 % of the nominal
calibration of the load cell can be found in 6.14.
selected value (see 11.7) for use in the flow rate calculations.
6.4.5 If the instrument is equipped with such a drive system,
This requires that the measurement be 6.35 6 0.025 mm or
its design shall ensure that no effect of temperature is present
25.4 6 0.102 mm.
which is bigger than the given tolerances as defined for the test
6.6.3 Operate within a fixed portion of the cylinder. This is
weights. A typical design of a well-protected load measurement
defined as the portion of the cylinder between 48 mm and
system includes a closed housing around the load sensor to
18.35 mm above the top of the die.
prevent it from short-term warming, an adapted insulation to
6.6.4 Any effects on the applied load caused by the Timing
prevent excessive heat transfer from the hot piston to the load
Device/System must be included in the allowable tolerance
sensor, and the use of a temperature compensated load cell.
given in 6.4.3.
6.5 Temperature Control System:
6.6.5 The equipment used to calibrate the Timing Device/
6.5.1 The equipment shall have the capability of heating and
System shall be traceable to a national standard (for example,
maintaining the temperature inside the bore of the cylinder in
NIST).
accordance with the requirements specified in Table 1 through-
6.7 Operating Tools:
out the duration of the test.
6.7.1 Level—Used to verify the vertical alignment of the
6.5.2 The preferred method for calibrating the temperature
bore of the extrusion plastometer. This is necessary to mini-
is to use a temperature sensor assembly having a sensor with at
mize subtractive loads resulting from rubbing or friction
least an accuracy of 60.08°C at 200°C and a 20 6 0.5-mm
between the piston tip and sidewall. Means of alignment are
long brass tip press fit on the end of the sensor. The diameter
discussed in Appendix X1.
of the brass tip shall closely match the diameter of the die and
6.7.2 Go/No-Go Gauge:
the length of the active measuring length of the temperature
sensor (see Appendix X3).
6.7.2.1 For the standard die, a go/no-go gauge suitable to
6.5.3 Temperatures shall be verified with the bottom of the inspect the inner diameter of the hole in the die. The go
temperature sensor at 10 and 75 6 1 mm above the upper face
member of the gauge shall be no smaller than 2.090 mm. The
of the die and at each test temperature, without touching the no-go member shall be no larger than 2.100 mm. (See Note 7.)
die. Allow at least four minutes for equilibrium of temperature
6.7.2.2 For the “half” die, a go/no-go gauge suitable to
to be reached for each position. Temperature variation shall be
inspect the hole in the die. The go member of the gauge shall
determined over a minimum of 15 minutes. When using the
be no smaller than 1.043 mm. The no-go member shall be no
larger than 1.053 mm. (See Note 7.)
NOTE 7—Frequent use of Go/No-Go Gauges subject them to wear. They
TABLE 1 Maximum Allowable Variation in Temperature with
should be verified routinely.
Distance and Time Throughout the Test
6.7.3 Funnel—For charging samples to the cylinder
Test temperature Temperature tolerance, °C
set point
6.7.4 Packing Tool—For charging samples to the cylinder
T °C At 75 ± 1 mm At 10 ± 1 mm
(see Appendix X5)
above the die above the die
A A
6.7.5 Spatula—Or similar device used to cut extrudate
surface (°C) surface (°C)
125 # T < 250 ±2.0 ±0.2
6.7.6 Balance—Capable of weighing to 0.001 g
250 # T < 300 ±2.5 ±0.5
300 # T ±3.0 ±1.0
6.8 Cleaning Equipment:
A
When using the “half” die, the temperature indicating device shall be calibrated as
6.8.1 Cylinder bore cleaning tool
stated in this table except temperatures are measured at nominal 79 ± 1 mm and
6.8.2 Die cleaning tool
14 ± 1 mm above the upper surface of the die.
6.8.3 Cotton patches
D1238 − 23a
6.9 Weight Support—Used with high Melt Flow Rate mate- 9. Procedural Conditions
rial to prevent material from flowing out during the preheat
9.1 A list of possible test conditions for various materials is
period.
shown in Table X4.1 found in Appendix X4. Test conditions
6.10 Die Plug—Used with high melt flow rate material to shall be shown as: Condition _ _ _ / _ _ _, where the
plug the die when weight support measures are not enough to temperature in degrees Celsius is shown first, followed by the
prevent material from flowing out during the preheat period. weight in kilograms. For example: Condition 190/2.16.
6.11 Automatic Weight Lowering and Lifting Device—
NOTE 10—Some materials may require special materials of construction
or handling for performing this test. Please refer to the material specifi-
Optional for Procedures A, B, and C, but required for Proce-
cation for appropriate recommendations.
dure D. Device for automatically applying test loads to the
piston. This device is often useful as a weight support.
10. Procedure A—Manual Operation
6.12 Multi-Weight (Flow Rate Ratio) Accessory—For test-
10.1 Select conditions of temperature and load from X4.1 or
ing in accordance with Procedure D, it is necessary to have an
in accordance with material specifications. Where multiple test
accessory that permits Melt Flow Rate determinations to be
conditions exist, test conditions shall be agreed upon by the
made using two or three different test loads on one charge of
cooperating laboratories. If test conditions are not known,
material by loading or unloading test loads, or both, at pre-set
select conditions that result in flow rates between 0.15 to 50
heights.
g/10 min.
NOTE 8—Different manufacturers of equipment may offer options that
help to automate the test and/or data collection. These are acceptable for
10.2 Inspect the extrusion plastometer for cleanliness (see
use provided they operate in a manner that does not conflict with
Note 11). All surfaces of the cylinder bore, die and piston shall
descriptions in Section 6 and the procedures listed in Sections 10, 11, 12,
be free of any residue from previous tests.
and 13.
NOTE 11—The degree of cleanliness can significantly influence the flow
6.13 Micrometer—Apparatus for measuring the dimensions
rate results, therefore a thorough method of cleaning should be estab-
of the piston foot shall comply with the requirements of Test
lished. It has been found that swabbing the barrel with a clean cotton patch
Method D5947.
several times is satisfactory for most materials and that the die, barrel, and
piston are more easily cleaned while hot. For materials that are difficult to
6.14 If an extrusion plastometer utilizes a drive system
clean from the metal surfaces, use of a brass brush has been found to be
instead of dead weights, the applied force shall comply with
satisfactory.
Practices E4, except the load measurement requirements shall
10.3 Check the die bore diameter at frequent intervals with
fulfill the same accuracy requirements as the dead weight
appropriately sized go/no-go gauge (checked with die at
requirements in 6.4.3 (60.5 % accuracy and repeatability).
23 6 5°C) to verify that the die is within the tolerances given
6.14.1 Apparatus:
in 6.3.1. Visually examine the die bore to verify that it is not
6.14.1.1 Calibration should mimic the use of the machine
scratched or damaged. Also visually inspect the land of the
and include the combined weight of the piston and applied
piston foot to verify that it is not scratched or damaged and use
force of the load cell. The calibration set-up should resemble
a micrometer to verify that the dimensions are within the
Fig. 3.
tolerances given in 6.4.1 (see Note 12).
6.14.2 Procedure:
6.14.2.1 A calibration of the load cell shall be performed in NOTE 12—Cleaning and usage will eventually cause damage or wear to
the, bore, die and the land of the piston. Data has shown that erroneous
accordance with Practices E4 with permissible maximum error
results will be obtained if these components are not within the appropriate
of 0.50 % and repeatable within 0.50 % of each other.
tolerances.
10.4 Set the temperature in accordance with the manufac-
7. Test Specimen
turer’s instructions.
7.1 The test specimen is permitted to be in any form that
10.5 Insert the die and the piston into the bore. Allow the
allows it to be introduced into the bore of the cylinder, for
temperature of the cylinder, with the piston and die in place, to
example, powder, granules, strips of film, or molded slugs.
stabilize within 60.2°C of the selected test temperature for at
NOTE 9—It may be desirable to pre-form or pelletize a powder. Trapped
air causes the piston to fall faster, hence measurements are affected. least 15 minutes before starting a test. When equipment is used
continuously, it is not necessary to heat the piston and die for
8. Conditioning 15 minutes when runs of the same or similar material at the
same test temperature are being measured over a continuous
8.1 Many thermoplastic materials do not require condition-
time frame, provided the piston and die are cleaned and
ing prior to testing. Some materials that contain volatile
re-inserted into the bore within five minutes after removal from
components, are chemically reactive, or have other special
the extrusion plastometer at the end of each test. If the piston,
characteristics will require appropriate conditioning proce-
or die, or both, are removed from the bore for longer than five
dures. Moisture not only affects reproducibility of flow rate
minutes, they shall be considered “cold” and the full 15
measurement but, in some types of materials, degradation is
minutes heating stabilization time shall be required.
accelerated by moisture at the high temperatures used in
testing. Check the applicable material specification for any 10.6 Remove the piston from the bore (see Note 13). Within
conditioning requirements before using this test. See Practice 60 seconds, charge the cylinder with a weighed portion of the
D618 for appropriate conditioning practices. sample in accordance with the expected flow rate (as given in
D1238 − 23a
FIG. 3 Calibration Set-Up
Table 2), reinsert the piston and add the appropriate weight. testing conditions shall be completed at least 2 minutes prior to
The charging weights given in Table 2 are merely suggestions, making the initial cut-off (see Note 14).
and the actual charging weight for a specific sample, if not
NOTE 13—Placing the piston on an insulated surface after removing it
known, will need to be determined by trial and error. Adjust the
from the bore will reduce heat loss.
charge weight so that the piston is in the proper position at the
NOTE 14—Material is purged by forcing the piston to a position that
end of the pre-heat period. If necessary, it is acceptable to
will ensure that subsequent travel of the piston during the remainder of the
purge excess material from the cylinder bore so that the piston
pre-heat period will position the piston at the correct start position. The
is in the proper position at the end of the pre-heat period. material should be allowed to soften and melt before manually purging.
Purging of material done at conditions with greater force than NOTE 15—Additional care may be necessary to prevent thermal
D1238 − 23a
A
TABLE 2 Standard Test Conditions, Sample Mass, and Testing
specimen contains visible bubbles, discard it and begin the test
B
Time
again. If the initial cut-off was initiated outside of the toler-
Suggested Mass
Factor for ances of the pre-heat period or the piston position
Flow Range, of Time Inter-
Obtaining Flow
g/10 min Sample in val, min requirements, discard the specimen and repeat the test with
Rate in g/10 min
Cylinder, g
readjusted piston position after the initial purge, or change the
0.15 to 1.0 2.5 to 3.0 6.00 1.67
weight.
>1.0 to 3.5 3.0 to 5.0 3.00 3.33
>3.5 to 10 4.0 to 8.0 1.00 10.00
10.10 Once the extrudate is cool, weigh to the nearest 1 mg.
>10 to 25 4.0 to 8.0 0.50 20.00
>25 4.0 to 8.0 0.25 40.00
10.11 Multiply the weight of the extrudate by the appropri-
A 3
This is a suggested mass for materials with melt densities of about 0.7 g/cm . ate factor shown in Table 2 to obtain the flow rate in grams per
Correspondingly, greater quantities are suggested for materials of greater melt
10 min.
densities. Density of the molten resin (without filler) may be obtained using the
procedure described by Terry, B. W., and Yang, K., “A New Method for Determining
NOTE 17—Some labs have found it helpful to take interim cuts of the
Melt Density as a Function of Pressure and Temperature,” SPE Journal , SPEJA,
extrudate at uniform time intervals during the specified extrusion time
Vol. 20, No. 6, June 1964, p. 540 or the procedure described by Zoller, Paul, “The
period. The individual cuts may give an indication of the presence of
Pressure-Volume-Temperature Properties of Polyolefins,” Journal of Applied Poly-
bubbles which may be masked due to their size or to opacity of the sample
mer Science, Vol 23, 1979, p. 1051. It may also be obtained from the weight of an
which will result in test error. This technique is particularly helpful in the
extruded known volume of resin at the desired temperature. For example, 25.4 mm
(1 in.) of piston movement extrudes 1.804 cm of resin. An estimate of the density case of highly pigmented materials.
of the material can be calculated from the following equation:
10.12 Purge the remainder of the sample from the bore and
resin density at test temperature 5 M/1.804
follow the extrusion plastometer manufacturer’s instructions
where:
for removing the die from the bore. Swab out the cylinder with
M = mass of extruded resin.
cotton patches and the cylinder bore cleaning tool. Thoroughly
B
See 10.13.
clean the die and the piston to remove all residues (Note Note
18).
NOTE 18—The die may be cleaned by dissolving the residue in a
solvent. A better method is pyrolytic decomposition of the residue in a
degradation in the extrusion plastometer. This is sometimes done by the
nitrogen atmosphere. Place the die in a tubular combustion furnace or
addition of an appropriate antioxidant. For highly unstable materials, it
other device for heating to 550 6 10°C and clean with a small nitrogen
may be necessary to use alternative techniques as an indication of flow
purge through the die. This method is preferable to flame or solvent
characteristics.
cleaning, being faster than solvent cleaning and less detrimental to the die
10.7 Start the test by initiating the timing device that
than an open flame. In certain cases where materials of a given class
having similar flow characteristics are being tested consecutively, interim
monitors the pre-heat period, which is a period of time that
die cleaning may be unnecessary. In such cases, however, if the effect of
allows the material to soften and begin to melt. The pre-heat
cleaning upon flow rate determination is negligible, this step may be
period shall last for 7.0 6 0.5 min from the completion of the
avoided.
charge unless otherwise stated in the materials specification.
10.13 In case a specimen has a flow rate at the borderline of
10.8 For materials with flow rates greater than 10 g/10 min,
the ranges in Table 2 and slightly different values are obtained
a weight (and if needed, a piston) support must be used to
at different time intervals, the referee value shall be obtained at
prevent the piston from travelling during the pre-heat period in
the longer time interval.
order to ensure that there is enough material in the bore to
correctly test the material. The support is to be installed in a
11. Procedure B—Automatically Timed Flow Rate
manner that holds the lower scribe mark of the piston approxi-
Measurement
mately 25 mm above the top of the guide bushing or other
11.1 Install/enable the automatic timing device on the ex-
suitable reference mark. Alternatively, it is acceptable for the
trusion plastometer.
operator to delay applying the weight to the piston. The support
shall be removed or the weight applied to the piston at such a
11.2 Select conditions of temperature and load from Table
time as to allow the operator to make the initial cut-off within
X4.1 or in accordance with material specifications. Where
7 6 0.5 min of the completion of the charge.
multiple test conditions exist, test conditions shall be agreed
upon by the cooperating laboratories. A melt density value (see
NOTE 16—It has been found that the effect of supporting the weight is
significant to the flow rate results. The choice of piston support was made Table 2 and Table 3) for the material is required if MFR is to
to cover all conditions and flow rates 10 to 50 g/10 min. Piston/weight
be calculated from the results.
supports will vary between extrusion plastometer manufacturers.
11.3 Inspect the extrusion plastometer for cleanliness (see
10.9 At the end of the pre-heat period and when the top
Note 18). All surfaces of the cylinder bore, die and piston shall
scribe mark on the piston is visible above the cylinder (or top
be free of any residue from previous tests.
of the guide sleeve) and the lower scribe mark is in the cylinder
(or below the top of the guide sleeve) indicating that the piston 11.4 Check the die bore diameter at frequent intervals with
land is 46 6 2 mm from the top of the die, reset the timer to appropriately sized go/no-go gauge (checked with die at
zero then simultaneously make the initial cut-off. Discard the 23 6 5°C) to verify that the die is within the tolerances given
extrudate from the pre-heat period. Make the final cut-off in 6.3. Visually examine the die bore to verify that it is not
exactly when the time interval selected (see Table 2) is reached. scratched or damaged. Also visually inspect the land of the
Collect and weigh the extrudate specimen. If the extrudate piston foot to verify that it is not scratched or damaged and use
D1238 − 23a
TABLE 3 Factors for Calculation of Flow Rate
11.9 Start the test by initiating the timing device that
Factor for monitors the pre-heat period, which is a period of time that
Material Tempera- Piston Travel, Calculation of
allows the material to soften and begin to melt. The pre-heat
(Unpigmented) ture, °C L, cm (in.) Flow
A period shall last for 7.0 6 0.5 min from the completion of the
Rate, F
charge unless otherwise stated in the materials specification.
Polyethylene 190 2.54 (1) 826
Polyethylene 190 0.635 (0.25) 207
11.10 For materials with flow rates greater than 10 g/10
Polypropylene 230 2.54 (1) 799
min, a weight (and if needed, a piston) support must be used to
Polypropylene 230 0.635 (0.25) 200
A 3
prevent the piston from travelling during the pre-heat period in
Factors calculated using melt-density values of 0.7636 g/cm for polyethylene
and 0.7386 g/cm for polypropylene, as expressed in article by Zoller, Paul, “The order to ensure that there is enough material in the bore to
Pressure-Volume-Temperature Properties of Polyolefins,” Journal of Applied Poly-
correctly test the material. The support is to be installed in a
mer Science, Vol 23, 1979, P. 1051. The base densities at 23°C for which the melt
manner that holds the lower scribe mark of the piston approxi-
densities are reported were 0.917 g/cm for annealed low-density polyethylene
and polypropylene homopolymer.
mately 25 mm above the top of the guide bushing or other
suitable reference mark. Alternatively, it is acceptable for the
operator to delay applying the weight to the piston. The support
shall be removed, or the weight applied to the piston at such a
time as to allow the measurement to start within 7 6 0.5 min of
a micrometer to verify that the dimensions are within the
the completion of the charge. (For automated weight lowering
tolerances given in 6.4.1 (see Note 12).
systems, the bottom of the piston foot is held at approximately
11.5 Set the temperature in accordance with the manufac-
71 mm above the top of the die.)
turer’s instructions.
11.11 For materials greater than 50 g/10 min, use of a die
11.6 Insert the die and the piston into the bore. Allow the
plug is an option in addition to the piston/weight support. The
temperature of the cylinder with the piston and die in place to
die plug is inserted before charge and is removed prior to
stabilize within 60.2°C of the selected test temperature for at
removing the piston/weight support. (Warning—Rapid expul-
least 15 minutes before starting a test. When equipment is used
sion of material when die plug is removed is hazardous.)
continuously, it is not necessary to heat the piston and die for
11.12 At the end of the pre-heat period and when automatic
15 minutes when runs of the same or similar material at the
timing system senses that the piston has reached the pre-
same test temperature are being measured over a continuous
selected starting point (indicating that the piston land is 46 6 2
time frame, provided the piston and die are cleaned and
mm from the top of the die), the automatic timing system shall
re-inserted into the bore within five minutes after removal from
begin measuring the time it takes for the piston to travel the
the extrusion plastometer at the end of each test. If the piston,
pre-selected distance (see 11.7). If the extrudate specimen
or die, or both, are removed from the bore for longer than five
contains visible bubbles, discard the results and begin the test
minutes, they shall be considered “cold” and the full 15
again (see Note 14). If the initial timed measurement was
minutes heating stabilization time shall be required.
initiated outside of the tolerances of the pre-heat period or the
11.7 Adjust the automatic timing system to operate within
piston position requirements, discard the results and repeat the
the 6.35 6 0.25 mm measuring range for materials with
test after readjusting the piston position after the initial purge
expected melt flow rates of less than 10 g/10 min, or
or changing the charge weight.
25.40 6 0.25 mm measuring range for materials with expected
11.13 Record the time to the nearest 0.01 s for the piston to
melt flow rates greater than or equal to 10 g/10 min and set to
complete the selected distance of travel.
begin timing when the bottom of the piston foot is 46 6 2 mm
above the top of the die. 11.14 Purge the remainder of the sample from the bore and
follow the extrusion plastometer manufacturer’s instructions
NOTE 19—It has been found that for some materials the melt flow rates
for removing the die from the bore. Swab out the cylinder with
obtained on a material will be different depending on which travel length
is chosen; therefore, it is important to use the same measurement range to cotton patches and the cylinder bore cleaning tool. Thoroughly
compare interlaboratory and intralaboratory results.
clean the die and the piston to remove all residues (see Note
11).
11.8 Remove the piston from the bore (see Note 13). Within
60 seconds, charge the cylinder with a weighed portion of the
12. Procedure C—Automatically Timed Flow Rate
sample in accordance with the expected flow rate (as given in
Measurement for High Flow Rate Polyolefins Using
Table 2), reinsert the piston and add the appropriate weight.
“Half” Die
The charging weights given in Table 2 are merely suggestions,
and the actual charging weight for a specific sample, if not 12.1 Procedure:
known, will need to be determined by trial and error. Adjust the 12.1.1 Install/enable the automatic timing device on the
charge weight so that the piston is in the proper position at the extrusion plastometer.
end of the pre-heat period. If necessary, it is acceptable to 12.1.2 Select conditions of temperature and load from X4.1
purge excess material from the cylinder bore so that the piston or in accordance with material specifications. Where multiple
is in the proper position at the end of the pre-heat period. test conditions exist, test conditions shall be agreed upon by the
Purging of material done at conditions with greater force than cooperating laboratories. A melt density value (not bulk den-
testing conditions shall be completed at least 2 minutes prior to sity) for the material is required if MFR is to be calculated from
the expiration of the preheat period (see Note 14). the results.
D1238 − 23a
12.1.3 Use the procedure described in 11.3 – 11.14 with the and/or die are removed from the bore for longer than five
following exceptions: minutes, they shall be considered “cold” and the full 15
12.1.3.1 Use the “half” die as described in 6.3.2. minutes heating stabilization time shall be required.
12.1.3.2 Adjust the timing device to operate within the 13.1.9 Remove the piston from the bore (see Note 13).
25.40 6 0.25 mm measuring range and set to begin timing Within 60 seconds, charge the cylinder with a weighed portion
when the bottom of the piston foot is 50 6 2 mm above the top of the sample in accordance with the expected melt flow rate
of the die. (as given in Table 2), reinsert the piston and use the weight
lifting and lowering device to add the test load to the piston.
13. Procedure D—Multi-Weight Using Automatically
13.1.10 Some materials, particularly those with expected
Timed Flow Rate Measurement
melt flow rates less than 10g/10 min during the first measure-
ment period require the operator to purge some material to a
13.1 Procedure:
position that insures subsequent travel of the piston will
13.1.1 Install/enable the automatic timing device, automatic
activate the timing device at the desired starting point for the
weight lifting/lowering device and multi-weight (FRR) acces-
first measurement within 7.0 6 0.5 min after the completion of
sory on the extrusion plastometer. The multi-weight test shall
the charge. The lower scribe mark of the piston shall be at least
be made in either increasing weight or decreasing weight
25 mm above the top of the cylinder after purging. Any purging
conditions. Follow the equipment manufacturer’s instructions
must be completed at least 2 minutes prior to start of the test
for installation and operation.
Melt Flow Rates.
13.1.2 Configure the multi-weight (FRR) accessory to take
13.1.11 Materials with higher expected flow rates will
at least two MFR determinations at each load condition used
require that the weight and piston support be used after
before changing to the next test load. After switching load
charging the material. For Procedure D, this can be accom-
conditions, achieve stable flow by allowing sufficient piston
plished with the automatic weight lifting/lowering device. The
travel or time to elapse before beginning measurements (see
support shall be removed at such a time as to allow the
Note 20). Piston travel distances shall be chosen so that at least
automatic timing device to activate at the starting point for the
2 seconds elapse during the measurement and that the distances
first measurement within 7.0 6 0.5 min after the completion of
are determined within 60.4 %.
the charge. Only use the piston support if there is excessive
NOTE 20—Normally, 5 mm of piston travel or 2 minutes is sufficient to
material flow (see Note 16).
obtain stable flow after changing test loads.
13.1.12 If a die plug is used to prevent excessive leakage
13.1.3 Adjust the automatic timing device to make multiple
before the test, for materials with a melt flow rate greater than
test measurements as required and set to begin timing the first
50 g/10 min, then the die plug is to be inserted before the
measurement when the bottom of the piston foot is 46 6 2 mm
charge and removed prior to removing the piston/weight
above the top of the die. Do not take readings below 18.35 mm
support. The initial charge shall be adjusted to ensure appro-
above the top of the die.
priate measurement loads based on suggestions in Table 2. If
13.1.4 Inspect the extrusion plastometer for cleanliness (see
the timer is not activated within 7 6 0.5 min after the
Note 11). All surfaces of the cylinder bore, die and piston shall
completion of the charge the test must be repeated with
be free of any residue from previous tests.
readjusted charge weights.
13.1.5 Check the die bore diameter at frequent intervals
13.1.13 Record the time, to the nearest 0.01 s, for the
with appropriately sized go/no-go gauge (checked with die at
individual piston travel determinations measured for each test
23 6 5°C) to verify that the die is within the tolerances given
load.
in 6.3.1. Visually examine the die bore to verify that it is not
13.1.14 Repeat the above for any additional test loads.
scratched or damaged. Also visually inspect the land of the
13.1.15 Purge the remainder of the sample from the bore
piston foot to verify that it is not scratched or damaged and use
and follow the extrusion plastometer manufacturer’s instruc-
a micrometer to verify that the dimensions are within the
tions for removing the die from the bore. Swab out the cylinder
tolerances given in 6.4.1 (see Note 12).
with cotton patches and the cylinder bore cleaning tool.
13.1.6 Set the temperature in accordance with the manufac-
Thoroughly clean the die and the piston to remove all residues
turer’s instructions.
(see Note 11).
13.1.7 A melt density value (see Table 2) for the material is
required in order to calculate MFR for the individual determi-
14. Calculation of Flow Rate
nations.
13.1.8 Insert the die and the piston into the bore. Allow the
14.1 Calculation for Procedures B and C:
temperature of the cylinder with the piston and die in place to
14.1.1 Calculate the flow rate in grams per 10 min or
stabilize within 60.2°C of the selected test tempe
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D1238 − 23 D1238 − 23a
Standard Test Method for
Melt Flow Rates of Thermoplastics by Extrusion
Plastometer
This standard is issued under the fixed designation D1238; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
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
2.1 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
E4 Practices for Force Calibration and Verification of Testing Machines
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2 ANSI Standard:
B46.1 on Surface Texture
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.30 on Thermal Properties (Section
D20.30.08). .
Current edition approved Feb. 1, 2023Nov. 15, 2023. Published February 2023November 2023. Originally approved in 1965. Last previous edition approved in 20202023
as D1238 - 20.D1238 - 23. DOI: 10.1520/D1238-23.10.1520/D1238-23A.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1238 − 23a
2.3 ISO Standard:
ISO 1133 Determination of the Melt-Mass Flow Rate (MFR) and the Melt Volume-Flow Rate (MVR) of Thermoplastics
3. Terminology
3.1 Terms used in this standard are defined in accordance with Terminology D883, unless otherwise specified. For terms relating
to precision and bias and associated issues, the terms used in this standard are defined in accordance with Terminology E456.
4. Summary of Test Method
4.1 After a specified preheating time, resin is extruded through a die with a specified length and orifice diameter under prescribed
conditions of temperature, load, and piston position in the barrel. Four procedures are described. Comparable results have been
obtained by these procedures in interlaboratory round-robin measurements of several materials and are described in Section 16.
4.2 Procedure A is used to determine the melt flow rate (MFR) of a thermoplastic material. The units of measure are grams of
material/10 min (g/10 min). It is based on the measurement of the mass of material that extrudes from the die over a given period
of time. It is generally used for materials having melt flow rates that fall between 0.15 and 50 g/10 min (see Note 2).
4.3 Procedure B is an automatically timed measurement used to determine the melt flow rate (MFR) as well as the melt volume
rate (MVR) of thermoplastic materials. MFR measurements made with Procedure B are reported in g/10 min. MVR measurements
are reported in cubic centimeters/10 min (cm /10 min). Procedure B measurements are based on the determination of the volume
of material extruded from the die over a given period of time. The volume is converted to a mass measurement by multiplying
the result by the melt density value for the material (see Note 3). Procedure B is generally used with materials having melt flow
rates from 0.50 to 1500 g/10 min.
4.4 Procedure C is an automatically timed measurement used to determine the melt flow rate (MFR) of polyolefin materials. It
is generally used as an alternative to Procedure B on samples having melt flow rates greater than 75 g/10 min. Procedure C involves
the use of a modified die, commonly referred to as a “half-die,” which has half the height and half the internal diameter of the
standard die specified for use in Procedures A and B thus maintaining the same length to diameter ratio. The test procedure is
similar to Procedure B, but the results obtained with Procedure C shall not be assumed to be half of those results produced with
Procedure B.
4.5 Procedure D is a multi-weight test commonly referred to as a “Flow Rate Ratio” (FRR) test. Procedure D is designed to allow
MFR determinations to be made using two or three different test loads (either increasing or decreasing the load during the test)
on one charge of material. The FRR is a dimensionless number derived by dividing the MFR at the higher test load by the MFR
at the lower test load. Results generated from multi-weight tests shall not be directly compared with results derived from Procedure
A or Procedure B.
NOTE 2—Polymers having melt flow rates less than 0.15 or greater than 900 g/10 min may be tested by the procedures in this test method; however,
precision data have not been developed.
NOTE 3—Melt density is the density of the material in it molten state. It is not to be confused with the standard density value of the material. See Table
4.
5. 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.
D1238 − 23a
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.
6. Apparatus
6.1 Extrusion Plastometer (Alternative Names—Melt Indexer, Melt Flow Indexer):
NOTE 4—Older plastometers that were manufactured in accordance with “design specifications” detailed in previous revisions of this test method (pre
D1238 - 04c) are deemed to be acceptable, as long as they meet the dimensional and performance specifications stated in this section.
NOTE 5—Relatively minor changes in the design and arrangement of the component parts have been shown to cause differences in results among
laboratories. For the best interlaboratory agreement, it is important that the design adhere closely to the description herein; otherwise, it should be
determined that modifications do not influence the results. Refer to Fig. 1.
6.1.1 The apparatus is a dead-weight piston plastometer consisting of a thermostatically controlled heated steel cylinder with a
bore that contains a die at the lower end, and a weighted piston operating within the cylinder. The essential features of the
plastometer, illustrated in Figs. 1 and 2, are described in 6.2-6.12. The bore of the extrusion plastometer shall be properly aligned
in the vertical direction (see Appendix X1). All dimensional measurements shall be made when the article being measured is at
FIG. 1 General Arrangement of Extrusion Plastometer (See Sec-
tion 6.)
D1238 − 23a
FIG. 2 Details of Extrusion Plastometer
23 6 5°C. As an acceptable alternative, the test force can be applied via a drive system working with a load cell. In case of dispute
between two cooperating laboratories, the dead weight plastometer shall be considered correct.
6.2 Cylinder—The cylinder shall be 50 mm 6 10 mm in diameter, 115 to 180 mm in length with a smooth, straight bore
9.5504 6 0.0076 mm in diameter. The cylinder bore shall be manufactured in a way that produces a finish approximately 12 rms
or better in accordance with ANSI B46.1. Means shall be provided to monitor the temperature inside the bore.
6.3 Die (Orifice):
6.3.1 Standard Die—The outside diameter of the die shall be such that it will fall freely to the bottom of the hole in the cylinder.
The orifice of the die shall have a smooth straight bore 2.095 6 0.005 mm in diameter and shall be 8.000 6 0.025 mm in length
(see Fig. 2). The bore of the orifice and its finish are critical. It shall have no visible drill or other tool marks and no detectable
eccentricity. The bore of the orifice shall be manufactured by techniques known to produce finishes approximately 12 rms or better
in accordance with ANSI B46.1.
6.3.2 “Half” Die—Used for Procedure C. When testing polyolefins with a MFR of 75 or greater (using the standard die), an
alternate die has shown to improve the reproducibility of results by reducing the flow rate of these materials. The outside diameter
of the die shall be such that it will fall freely to the bottom of the hole in the cylinder. The orifice shall have a smooth straight
bore 1.048 6 0.005 mm in diameter and shall be 4.000 6 0.025 mm in length (see Fig. 2A). The bore of the orifice and its finish
are critical. It shall have no visible drill or other tool marks and no detectable eccentricity. The bore of the orifice shall be
manufactured by techniques known to produce finishes approximately 12 rms or better in accordance with ANSI B46.1 (Note Note
6). No spacer shall be used with this die.
NOTE 6—Recommended die material is tungsten carbide. Also satisfactory are steel, synthetic sapphire, and cobalt-chromium-tungsten alloy. When softer
materials are used, it willmay be necessary to conduct critical dimensional checks and visual inspections on the die more often.
6.4 Piston:
6.4.1 The piston shall be made of steel. There shall be insulation at the top as a barrier to heat transfer from the piston to the
weight. The piston shall be prevented from rubbing on the bore. Most commercially available instruments use a loose fitting metal
guide sleeve, but other methods are acceptable. The weight of the sleeve shall not be considered as part of the test load. The land
(foot) of the piston shall be 9.4742 6 0.0076 mm in diameter and 6.35 6 0.10 mm in length. Above the land, the piston shall be
relieved to ≤ 9.0 mm in diameter (see Fig. 2). The piston land shall be manufactured by techniques known to produce finishes
approximately 12 rms in accordance with ANSI B46.1. If corrosion is a problem, the piston or piston land, if removable, shall be
made of corrosion resistant material.
6.4.2 For procedure A, the piston shall be scribed with two reference marks 4 mm apart in such fashion that when the lower mark
coincides with the top of the cylinder, guide sleeve or other suitable reference point, the bottom of the piston is 48 mm above the
top of the die (see Fig. 1) and the timed test run shall start within these two reference marks. The targeted starting point shall be
46 6 2 mm above the upper face of the die. (see Fig. 1).
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6.4.3 The combined weight of piston and load shall be within a tolerance of 60.5 % of the selected load.
6.4.4 The load corresponding to a test weight may also be applied by a drive system working with a load cell. A calibration of
the load cell in combination with the piston shall be performed, and performance shown to be equivalent or better than the
requirements listed in 6.4.3. Information on calibration of the load cell can be found in 6.14.
6.4.5 If the instrument is equipped with such a drive system, its design shall ensure that no effect of temperature is present which
is bigger than the given tolerances as defined for the test weights. A typical design of a well-protected load measurement system
includes a closed housing around the load sensor to prevent it from short-term warming, an adapted insulation to prevent excessive
heat transfer from the hot piston to the load sensor, and the use of a temperature compensated load cell.
6.5 Temperature Control System:
6.5.1 The equipment shall have the capability of heating and maintaining the temperature inside the bore of the cylinder in
accordance with the requirements specified in Table 1 throughout the duration of the test.
6.5.2 The preferred method for calibrating the temperature is to use a temperature sensor assembly having a sensor with at least
an accuracy of 60.08°C at 200°C and a 20 6 0.5-mm long brass tip press fit on the end of the sensor. The diameter of the brass
tip shall closely match the diameter of the die and the length of the active measuring length of the temperature sensor (see
Appendix X3).
6.5.3 Temperatures shall be verified with the bottom of the temperature sensor at 10 and 75 6 1 mm above the upper face of the
die and at each test temperature, without touching the die. Allow at least four minutes for equilibrium of temperature to be reached
for each position. Temperature variation shall be determined over a minimum of 15 minutes. When using the “half” die, the
temperature indicating device shall be calibrated as stated in Table 1 except temperatures are measured at 79 6 1 mm and 14 6 1
mm above the upper surface of the die.
6.5.4 An alternative method is to insert the temperature sensor without a brass tip into the melt from the top of the cylinder so
that it is 10 and 75 6 1 mm above the upper face of the die.
6.5.5 The temperature sensor and readout equipment used for calibration of the extrusion plastometer shall be traceable to a
national standard (for example, NIST).
6.6 Timing Device/System—For Procedure A, a timing device with an accuracy of 0.1 s shall be used. For Procedures B, C, and
D, an automatic timing system shall measure and time piston movement within the specified travel range. The requirements of the
automatic timing system shall be as follows:
6.6.1 Sense and indicate the piston travel time within 60.01 s.
6.6.2 Measure piston travel within 60.4 % of the nominal selected value (see 11.7) for use in the flow rate calculations. This
requires that the measurement be 6.35 6 0.025 mm or 25.4 6 0.102 mm.
6.6.3 Operate within a fixed portion of the cylinder. This is defined as the portion of the cylinder between 48 mm and 18.35 mm
above the top of the die.
TABLE 1 Maximum Allowable Variation in Temperature with
Distance and Time Throughout the Test
Test temperature Temperature tolerance, °C
set point
T °C At 75 ± 1 mm At 10 ± 1 mm
above the die above the die
A A
surface (°C) surface (°C)
125 # T < 250 ±2.0 ±0.2
250 # T < 300 ±2.5 ±0.5
300 # T ±3.0 ±1.0
A
When using the “half” die, the temperature indicating device shall be calibrated as
stated in this table except temperatures are measured at nominal 79 ± 1 mm and
14 ± 1 mm above the upper surface of the die.
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6.6.4 Any effects on the applied load caused by the Timing Device/System must be included in the allowable tolerance given in
6.4.3.
6.6.5 The equipment used to calibrate the Timing Device/System shall be traceable to a national standard (for example, NIST).
6.7 Operating Tools:
6.7.1 Level—Used to verify the vertical alignment of the bore of the extrusion plastometer. This is necessary to minimize
subtractive loads resulting from rubbing or friction between the piston tip and sidewall. Means of alignment are discussed in
Appendix X1.
6.7.2 Go/No-Go Gauge:
6.7.2.1 For the standard die, a go/no-go gauge suitable to inspect the inner diameter of the hole in the die. The go member of the
gauge shall be no smaller than 2.090 mm. The no-go member shall be no larger than 2.100 mm. (See Note 7.)
6.7.2.2 For the “half” die, a go/no-go gauge suitable to inspect the hole in the die. The go member of the gauge shall be no smaller
than 1.043 mm. The no-go member shall be no larger than 1.053 mm. (See Note 7.)
NOTE 7—Frequent use of Go/No-Go Gauges subject them to wear. They should be verified routinely.
6.7.3 Funnel—For charging samples to the cylinder
6.7.4 Packing Tool—For charging samples to the cylinder (see Appendix X5)
6.7.5 Spatula—Or similar device used to cut extrudate
6.7.6 Balance—Capable of weighing to 0.001 g
6.8 Cleaning Equipment:
6.8.1 Cylinder bore cleaning tool
6.8.2 Die cleaning tool
6.8.3 Cotton patches
6.9 Weight Support—Used with high Melt Flow Rate material to prevent material from flowing out during the preheat period.
6.10 Die Plug—Used with high melt flow rate material to plug the die when weight support measures are not enough to prevent
material from flowing out during the preheat period.
6.11 Automatic Weight Lowering and Lifting Device—Optional for Procedures A, B, and C, but required for Procedure D. Device
for automatically applying test loads to the piston. This device is often useful as a weight support.
6.12 Multi-Weight (Flow Rate Ratio) Accessory—For testing in accordance with Procedure D, it is necessary to have an accessory
that permits Melt Flow Rate determinations to be made using two or three different test loads on one charge of material by loading
or unloading test loads, or both, at pre-set heights.
NOTE 8—Different manufacturers of equipment may offer options that help to automate the test and/or data collection. These are acceptable for use
provided they operate in a manner that does not conflict with descriptions in Section 6 and the procedures listed in Sections 10, 11, 12, and 13.
6.13 Micrometer—Apparatus for measuring the dimensions of the piston foot shall comply with the requirements of Test Method
D5947.
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6.14 If an extrusion plastometer utilizes a drive system instead of dead weights, the applied force shall comply with Practices E4,
except the load measurement requirements shall fulfill the same accuracy requirements as the dead weight requirements in 6.4.3
(60.5 % accuracy and repeatability).
6.14.1 Apparatus:
6.14.1.1 Calibration should mimic the use of the machine and include the combined weight of the piston and applied force of the
load cell. The calibration set-up should resemble Fig. 3.
FIG. 3 Calibration Set-Up
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6.14.2 Procedure:
6.14.2.1 A calibration of the load cell shall be performed in accordance with Practices E4 with permissible maximum error of
0.50 % and repeatable within 0.50 % of each other.
7. Test Specimen
7.1 The test specimen is permitted to be in any form that allows it to be introduced into the bore of the cylinder, for example,
powder, granules, strips of film, or molded slugs.
NOTE 9—It may be desirable to pre-form or pelletize a powder. Trapped air causes the piston to fall faster, hence measurements are affected.
8. Conditioning
8.1 Many thermoplastic materials do not require conditioning prior to testing. Some materials that contain volatile components,
are chemically reactive, or have other special characteristics will require appropriate conditioning procedures. Moisture not only
affects reproducibility of flow rate measurement but, in some types of materials, degradation is accelerated by moisture at the high
temperatures used in testing. Check the applicable material specification for any conditioning requirements before using this test.
See Practice D618 for appropriate conditioning practices.
9. Procedural Conditions
9.1 A list of possible test conditions for various materials is shown in Table X4.1 found in Appendix X4. Test conditions shall be
shown as: Condition _ _ _ / _ _ _, where the temperature in degrees Celsius is shown first, followed by the weight in kilograms.
For example: Condition 190/2.16.
NOTE 10—Some materials may require special materials of construction or handling for performing this test. Please refer to the material specification for
appropriate recommendations.
10. Procedure A—Manual Operation
10.1 Select conditions of temperature and load from X4.1 or in accordance with material specifications. Where multiple test
conditions exist, test conditions shall be agreed upon by the cooperating laboratories. If test conditions are not known, select
conditions that result in flow rates between 0.15 to 50 g/10 min.
10.2 Inspect the extrusion plastometer for cleanliness (see Note 11). All surfaces of the cylinder bore, die and piston shall be free
of any residue from previous tests.
NOTE 11—The degree of cleanliness can significantly influence the flow rate results, therefore a thorough method of cleaning should be established. It
has been found that swabbing the barrel with a clean cotton patch several times is satisfactory for most materials and that the die, barrel, and piston are
more easily cleaned while hot. For materials that are difficult to clean from the metal surfaces, use of a brass brush has been found to be satisfactory.
10.3 Check the die bore diameter at frequent intervals with appropriately sized go/no-go gauge (checked with die at 23 6 5°C)
to verify that the die is within the tolerances given in 6.3.1. Visually examine the die bore to verify that it is not scratched or
damaged. Also visually inspect the land of the piston foot to verify that it is not scratched or damaged and use a micrometer to
verify that the dimensions are within the tolerances given in 6.4.1 (see Note 12).
NOTE 12—Cleaning and usage will eventually cause damage or wear to the, bore, die and the land of the piston. Data has shown that erroneous results
will be obtained if these components are not within the appropriate tolerances.
10.4 Set the temperature in accordance with the manufacturer’s instructions.
10.5 Insert the die and the piston into the bore. Allow the temperature of the cylinder, with the piston and die in place, to stabilize
within 60.2°C of the selected test temperature for at least 15 minutes before starting a test. When equipment is used continuously,
it is not necessary to heat the piston and die for 15 minutes when runs of the same or similar material at the same test temperature
are being measured over a continuous time frame, provided the piston and die are cleaned and re-inserted into the bore within five
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minutes after removal from the extrusion plastometer at the end of each test. If the piston, or die, or both, are removed from the
bore for longer than five minutes, they shall be considered “cold” and the full 15 minutes heating stabilization time shall be
required.
10.6 Remove the piston from the bore (see Note 13). Within 60 seconds, charge the cylinder with a weighed portion of the sample
in accordance with the expected flow rate (as given in Table 2), reinsert the piston and add the appropriate weight. The charging
weights given in Table 2 are merely suggestions, and the actual charging weight for a specific sample, if not known, will need to
be determined by trial and error. Adjust the charge weight so that the piston is in the proper position at the end of the pre-heat
period. If necessary, it is acceptable to purge excess material from the cylinder bore so that the piston is in the proper position at
the end of the pre-heat period. Purging of material done at conditions with greater force than testing conditions shall be completed
at least 2 minutes prior to making the initial cut-off (see Note 14).
NOTE 13—Placing the piston on an insulated surface after removing it from the bore will reduce heat loss.
NOTE 14—Material is purged by forcing the piston to a position that will ensure that subsequent travel of the piston during the remainder of the pre-heat
period will position the piston at the correct start position. The material should be allowed to soften and melt before manually purging.
NOTE 15—Additional care may be necessary to prevent thermal degradation in the extrusion plastometer. This is sometimes done by the addition of an
appropriate antioxidant. For highly unstable materials, it may be necessary to use alternative techniques as an indication of flow characteristics.
10.7 Start the test by initiating the timing device that monitors the pre-heat period, which is a period of time that allows the
material to soften and begin to melt. The pre-heat period shall last for 7.0 6 0.5 min from the completion of the charge unless
otherwise stated in the materials specification.
10.8 For materials with flow rates greater than 10 g/10 min, a weight (and if needed, a piston) support must be used to prevent
the piston from travelling during the pre-heat period in order to ensure that there is enough material in the bore to correctly test
the material. The support is to be installed in a manner that holds the lower scribe mark of the piston approximately 25 mm above
the top of the guide bushing or other suitable reference mark. Alternatively, it is acceptable for the operator to delay applying the
weight to the piston. The support shall be removed or the weight applied to the piston at such a time as to allow the operator to
make the initial cut-off within 7 6 0.5 min of the completion of the charge.
NOTE 16—It has been found that the effect of supporting the weight is significant to the flow rate results. The choice of piston support was made to cover
all conditions and flow rates 10 to 50 g/10 min. Piston/weight supports will vary between extrusion plastometer manufacturers.
A
TABLE 2 Standard Test Conditions, Sample Mass, and Testing
B
Time
Suggested Mass
Factor for
Flow Range, of Time Inter-
Obtaining Flow
g/10 min Sample in val, min
Rate in g/10 min
Cylinder, g
0.15 to 1.0 2.5 to 3.0 6.00 1.67
>1.0 to 3.5 3.0 to 5.0 3.00 3.33
>3.5 to 10 4.0 to 8.0 1.00 10.00
>10 to 25 4.0 to 8.0 0.50 20.00
>25 4.0 to 8.0 0.25 40.00
A 3
This is a suggested mass for materials with melt densities of about 0.7 g/cm .
Correspondingly, greater quantities are suggested for materials of greater melt
densities. Density of the molten resin (without filler) may be obtained using the
procedure described by Terry, B. W., and Yang, K., “A New Method for Determining
Melt Density as a Function of Pressure and Temperature,” SPE Journal , SPEJA,
Vol. 20, No. 6, June 1964, p. 540 or the procedure described by Zoller, Paul, “The
Pressure-Volume-Temperature Properties of Polyolefins,”Journal of Applied Poly-
mer Science, Vol 23, 1979, p. 1051. It may also be obtained from the weight of an
extruded known volume of resin at the desired temperature. For example, 25.4 mm
(1 in.) of piston movement extrudes 1.804 cm of resin. An estimate of the density
of the material can be calculated from the following equation:
resin density at test temperature 5M/1.804
where:
M = mass of extruded resin.
B
See 10.13.
D1238 − 23a
10.9 At the end of the pre-heat period and when the top scribe mark on the piston is visible above the cylinder (or top of the guide
sleeve) and the lower scribe mark is in the cylinder (or below the top of the guide sleeve) indicating that the piston land is 46 6 2
mm from the top of the die, reset the timer to zero then simultaneously make the initial cut-off. Discard the extrudate from the
pre-heat period. Make the final cut-off exactly when the time interval selected (see Table 2) is reached. Collect and weigh the
extrudate specimen. If the extrudate specimen contains visible bubbles, discard it and begin the test again. If the initial cut-off was
initiated outside of the tolerances of the pre-heat period or the piston position requirements, discard the specimen and repeat the
test with readjusted piston position after the initial purge, or change the weight.
10.10 Once the extrudate is cool, weigh to the nearest 1 mg.
10.11 Multiply the weight of the extrudate by the appropriate factor shown in Table 2 to obtain the flow rate in grams per 10 min.
NOTE 17—Some labs have found it helpful to take interim cuts of the extrudate at uniform time intervals during the specified extrusion time period. The
individual cuts may give an indication of the presence of bubbles which may be masked due to their size or to opacity of the sample which will result
in test error. This technique is particularly helpful in the case of highly pigmented materials.
10.12 Purge the remainder of the sample from the bore and follow the extrusion plastometer manufacturer’s instructions for
removing the die from the bore. Swab out the cylinder with cotton patches and the cylinder bore cleaning tool. Thoroughly clean
the die and the piston to remove all residues (Note Note 18).
NOTE 18—The die may be cleaned by dissolving the residue in a solvent. A better method is pyrolytic decomposition of the residue in a nitrogen
atmosphere. Place the die in a tubular combustion furnace or other device for heating to 550 6 10°C and clean with a small nitrogen purge through the
die. This method is preferable to flame or solvent cleaning, being faster than solvent cleaning and less detrimental to the die than an open flame. In certain
cases where materials of a given class having similar flow characteristics are being tested consecutively, interim die cleaning may be unnecessary. In such
cases, however, if the effect of cleaning upon flow rate determination must be shown to be negligible if this step is is negligible, this step may be avoided.
10.13 In case a specimen has a flow rate at the borderline of the ranges in Table 2 and slightly different values are obtained at
different time intervals, the referee value shall be obtained at the longer time interval.
11. Procedure B—Automatically Timed Flow Rate Measurement
11.1 Install/enable the automatic timing device on the extrusion plastometer.
11.2 Select conditions of temperature and load from Table X4.1 or in accordance with material specifications. Where multiple test
conditions exist, test conditions shall be agreed upon by the cooperating laboratories. A melt density value (see Table 2 and Table
3) for the material is required if MFR is to be calculated from the results.
11.3 Inspect the extrusion plastometer for cleanliness (see Note 18). All surfaces of the cylinder bore, die and piston shall be free
of any residue from previous tests.
11.4 Check the die bore diameter at frequent intervals with appropriately sized go/no-go gauge (checked with die at 23 6 5°C)
TABLE 3 Factors for Calculation of Flow Rate
Factor for
Material Tempera- Piston Travel, Calculation of
(Unpigmented) ture, °C L, cm (in.) Flow
A
Rate, F
Polyethylene 190 2.54 (1) 826
Polyethylene 190 0.635 (0.25) 207
Polypropylene 230 2.54 (1) 799
Polypropylene 230 0.635 (0.25) 200
A 3
Factors calculated using melt-density values of 0.7636 g/cm for polyethylene
and 0.7386 g/cm for polypropylene, as expressed in article by Zoller, Paul, “The
Pressure-Volume-Temperature Properties of Polyolefins,” Journal of Applied Poly-
mer Science, Vol 23, 1979, P. 1051. The base densities at 23°C for which the melt
densities are reported were 0.917 g/cm for annealed low-density polyethylene
and polypropylene homopolymer.
D1238 − 23a
to verify that the die is within the tolerances given in 6.3. Visually examine the die bore to verify that it is not scratched or damaged.
Also visually inspect the land of the piston foot to verify that it is not scratched or damaged and use a micrometer to verify that
the dimensions are within the tolerances given in 6.4.1 (see Note 12).
11.5 Set the temperature in accordance with the manufacturer’s instructions.
11.6 Insert the die and the piston into the bore. Allow the temperature of the cylinder with the piston and die in place to stabilize
within 60.2°C of the selected test temperature for at least 15 minutes before starting a test. When equipment is used continuously,
it is not necessary to heat the piston and die for 15 minutes when runs of the same or similar material at the same test temperature
are being measured over a continuous time frame, provided the piston and die are cleaned and re-inserted into the bore within five
minutes after removal from the extrusion plastometer at the end of each test. If the piston, or die, or both, are removed from the
bore for longer than five minutes, they shall be considered “cold” and the full 15 minutes heating stabilization time shall be
required.
11.7 Adjust the automatic timing system to operate within the 6.35 6 0.25 mm measuring range for materials with expected melt
flow rates of less than 10 g/10 min, or 25.40 6 0.25 mm measuring range for materials with expected melt flow rates greater than
or equal to 10 g/10 min and set to begin timing when the bottom of the piston foot is 46 6 2 mm above the top of the die.
NOTE 19—It has been found that for some materials the melt flow rates obtained on a material will be different depending on which travel length is chosen;
therefore, it is important to use the same measurement range to compare interlaboratory and intralaboratory results.
11.8 Remove the piston from the bore (see Note 13). Within 60 seconds, charge the cylinder with a weighed portion of the sample
in accordance with the expected flow rate (as given in Table 2), reinsert the piston and add the appropriate weight. The charging
weights given in Table 2 are merely suggestions, and the actual charging weight for a specific sample, if not known, will need to
be determined by trial and error. Adjust the charge weight so that the piston is in the proper position at the end of the pre-heat
period. If necessary, it is acceptable to purge excess material from the cylinder bore so that the piston is in the proper position at
the end of the pre-heat period. Purging of material done at conditions with greater force than testing conditions shall be completed
at least 2 minutes prior to the expiration of the preheat period (see Note 14).
11.9 Start the test by initiating the timing device that monitors the pre-heat period, which is a period of time that allows the
material to soften and begin to melt. The pre-heat period shall last for 7.0 6 0.5 min from the completion of the charge unless
otherwise stated in the materials specification.
11.10 For materials with flow rates greater than 10 g/10 min, a weight (and if needed, a piston) support must be used to prevent
the piston from travelling during the pre-heat period in order to ensure that there is enough material in the bore to correctly test
the material. The support is to be installed in a manner that holds the lower scribe mark of the piston approximately 25 mm above
the top of the guide bushing or other suitable reference mark. Alternatively, it is acceptable for the operator to delay applying the
weight to the piston. The support shall be removed, or the weight applied to the piston at such a time as to allow the measurement
to start within 7 6 0.5 min of the completion of the charge. (For automated weight lowering systems, the bottom of the piston foot
is held at approximately 71 mm above the top of the die.)
11.11 For materials greater than 50 g/10 min, use of a die plug is an option in addition to the piston/weight support. The die plug
is inserted before charge and is removed prior to removing the piston/weight support. (Warning—Rapid expulsion of material
when die plug is removed is hazardous.)
11.12 At the end of the pre-heat period and when automatic timing system senses that the piston has reached the pre-selected
starting point (indicating that the piston land is 46 6 2 mm from the top of the die), the automatic timing system shall begin
measuring the time it takes for the piston to travel the pre-selected distance (see 11.7). If the extrudate specimen contains visible
bubbles, discard the results and begin the test again (see Note 14). If the initial timed measurement was initiated outside of the
tolerances of the pre-heat period or the piston position requirements, discard the results and repeat the test after readjusting the
piston position after the initial purge or changing the charge weight.
11.13 Record the time to the nearest 0.01 s for the piston to complete the selected distance of travel.
11.14 Purge the remainder of the sample from the bore and follow the extrusion plastometer manufacturer’s instructions for
D1238 − 23a
removing the die from the bore. Swab out the cylinder with cotton patches and the cylinder bore cleaning tool. Thoroughly clean
the die and the piston to remove all residues (see Note 11).
12. Procedure C—Automatically Timed Flow Rate Measurement for High Flow Rate Polyolefins Using “Half” Die
12.1 Procedure:
12.1.1 Install/enable the automatic timing device on the extrusion plastometer.
12.1.2 Select conditions of temperature and load from X4.1 or in accordance with material specifications. Where multiple test
conditions exist, test conditions shall be agreed upon by the cooperating laboratories. A melt density value (not bulk density) for
the material is required if MFR is to be calculated from the results.
12.1.3 Use the procedure described in 11.3 – 11.14 with the following exceptions:
12.1.3.1 Use the “half” die as described in 6.3.2.
12.1.3.2 Adjust the timing device to operate within the 25.40 6 0.25 mm measuring range and set to begin timing when the bottom
of the piston foot is 50 6 2 mm above the top of the die.
13. Procedure D—Multi-Weight Using Automatically Timed Flow Rate Measurement
13.1 Procedure:
13.1.1 Install/enable the automatic timing device, automatic weight lifting/lowering device and multi-weight (FRR) accessory on
the extrusion plastometer. The multi-weight test shall be made in either increasing weight or decreasing weight conditions. Follow
the equipment manufacturer’s instructions for installation and operation.
13.1.2 Configure the multi-weight (FRR) accessory to take at least two MFR determinations at each load condition used before
changing to the next test load. After switching load conditions, achieve stable flow by allowing sufficient piston travel or time to
elapse before beginning measurements (see Note 20). Piston travel distances shall be chosen so that at least 2 seconds elapse during
the measurement and that the distances are determined within 60.4 %.
NOTE 20—Normally, 5 mm of piston travel or 2 minutes is sufficient to obtain stable flow after changing test loads.
13.1.3 Adjust the automatic timing device to make multiple test measurements as required and set to begin timing the first
measurement when the bottom of the piston foot is 46 6 2 mm above the top of the die. Do not take readings below 18.35 mm
above the top of the die.
13.1.4 Inspect the extrusion plastometer for cleanliness (see Note 11). All surfaces of the cylinder bore, die and piston shall be
free of any residue from previous tests.
13.1.5 Check the die bore diameter at frequent intervals with appropriately sized go/no-go gauge (checked with die at 23 6 5°C)
to verify that the die is within the tolerances given in 6.3.1. Visually examine the die bore to verify that it is not scratched or
damaged. Also visually inspect the land of the piston foot to verify that it is not scratched or damaged and use a micrometer to
verify that the dimensions are within the tolerances given in 6.4.1 (see Note 12).
13.1.6 Set the temperature in accordance with the manufacturer’s instructions.
13.1.7 A melt density value (see Table 2) for the material is required in order to calculate MFR for the individual determinations.
13.1.8 Insert the die and the piston into the bore. Allow the temperature of the cylinder with the piston and die in place to stabilize
within 60.2°C of the selected test temperature for at least 15 minutes before starting a test. When equipment is used continuously,
it is not necessary to heat the piston and die for 15 minutes when runs of the same or similar material at the same test temperature
are being measured over a continuous time frame, provided the piston and die are cleaned and re-inserted into the bore within five
minutes after removal from the extrusion plastometer at the end of each test. If the piston and/or die are removed from the bore
for longer than five minutes, they shall be considered “cold” and the full 15 minutes heating stabilization time shall be required.
D1238 − 23a
13.1.9 Remove the piston from the bore (see Note 13). Within 60 seconds, charge the cylinder with a weighed portion of the
sample in accordance with the expected melt flow rate (as given in Table 2), reinsert the piston and use the weight lifting and
lowering device to add the test load to the piston.
13.1.10 Some materials, particularly those with expected melt flow rates less than 10g/10 min during the first measurement period
require the operator to purge some material to a position that insures subsequent travel of the piston will activate the timing device
at the desired starting point for the first measurement within 7.0 6 0.5 min after the completion of the charge. The lower scribe
mark of the piston shall be at least 25 mm above the top of the cylinder after purging. Any purging must be completed at least
2 minutes prior to start of the test Melt Flow Rates.
13.1.11 Materials with higher expected flow rates will require that the weight and piston support be used after charging the
material. For Procedure D, this can be accomplished with the automatic weight lifting/lowering device. The support shall be
removed at such a time as to allow the automatic timing device to activate at the starting point for the first measurement within
7.0 6 0.5 min after the completion of the charge. Only use the piston support if there is excessive material flow (see Note 16).
13.1.12 If a die plug is used to prevent excessive leakage before the test, for materials with a melt flow rate greater than 50 g/10
min, then the die plug is to be inserted before the charge and removed prio
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