ASTM D8540-23

• Abstract:

  SIGNIFICANCE AND USE; 5.1 This test is particularly suited to control and development work. Data obtained by this test method shall not be used to predict the behavior of plastic materials at elevated temperatures except in applications in which the factors of time, temperature, method of loading, and fiber stress are similar to those specified in this test method. The data are not intended for use in design or predicting endurance at elevated temperatures. ; 5.2 For many materials, it is possible there will be a specification that requires 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. Refer to Table 1 in Classification D4000, which lists the ASTM material standards that currently exist.; SCOPE; 1.1 This test method covers the determination of the temperature at which an arbitrary deformation occurs when specimens are subjected to an arbitrary set of testing conditions. ; 1.2 This test method applies to molded and sheet materials available in thicknesses of 3 mm (1/8 in.) or greater and which are rigid or semirigid at normal temperature. ; Note 1: Sheet stock less than 3 mm (0.125 in.) but more than 1 mm (0.040 in.) in thickness may be tested by use of a composite sample having a minimum thickness of 3 mm. The laminae must be of uniform stress distribution. One type of composite specimen has been prepared by cementing the ends of the laminae together and then smoothing the edges with sandpaper. The direction of loading shall be perpendicular to the edges of the individual laminae. ; 1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only. ; 1.4 This standard and ASTM D648 address the same subject matter and are essentially the same test. However, due to known differences in results caused by the differences in heat transfer media, the results from this standard and ASTM D648 must not be compared or considered equivalent. ; 1.5 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 2: The text of this standard references notes and footnotes that provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard. ; Note 3: This standard and ISO 75-1 and ISO 75-2 address the same subject matter, but differ in technical content, and results shall not be compared between the two test methods. ; 1.6 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.

• Status: Published
• Publication Date: 31-Oct-2023
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.30 - Thermal Properties

• 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

Overview

ASTM D8540-23, Standard Test Method for Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position Using a Dry Bath, is published by ASTM International. This standard outlines procedures for determining the temperature at which plastics deform under a specified flexural load using a dry bath as the heat transfer medium. It is widely used in product development, quality control, and materials research, specifically focusing on rigid and semirigid plastics with a minimum thickness of 3 mm, or composite specimens when thinner sheets are necessary.

This method is not intended for predicting end-use performance at elevated temperatures unless the exact combination of time, temperature, loading method, and fiber stress matches those specified in the standard. It is crucial for comparative analysis, material grading, and specification compliance within the plastics industry.

Key Topics

• Test Scope and Applicability: Covers molded and sheet plastics at least 3 mm thick or composite specimens. Applicable to rigid and semirigid plastics.
• Testing Procedure:
  • Specimens are loaded in the edgewise position as simple beams.
  • A specified stress is applied using metal supports and weights.
  • The specimen is heated in a fluidized dry bath at a controlled rate (2 ± 0.2°C/min).
  • Deflection is measured, and the temperature at a standard deflection (0.25 mm) is recorded.
• Heat Transfer Medium: Utilizes a dry bath, often a fluidized powder such as aluminum oxide, ensuring efficient and uniform heat transfer without affecting the specimen.
• Reporting Requirements: Specimen dimensions, test conditions, deflection temperature, stress applied, heating rate, and any non-typical characteristics are documented for traceability and quality purposes.
• Significance of Results: Useful primarily for process and material quality control, research, and meeting certain specification requirements. Not suitable for design or predicting long-term thermal performance.

Applications

• Quality Control: Manufacturers use ASTM D8540-23 to monitor consistency in polymer formulations and production processes, ensuring materials meet performance standards before market release.
• Material Research & Development: R&D teams assess new polymers, additives, and blends for temperature resistance under load, enabling rapid screening and comparison.
• Specification Compliance: Many specification sheets and procurement contracts require proof of deflection temperature under flexural load to ASTM D8540-23, supporting buyer confidence and regulatory adherence.
• Comparative Material Selection: Engineers and designers compare materials for applications where elevated temperature performance under short-term load is critical, such as automotive, electrical, or building products.
• Control of Manufacturing Processes: By identifying the impact of molding conditions and material modifications, companies can optimize processing parameters for improved product performance.

Related Standards

When implementing ASTM D8540-23, users should be aware of related and companion standards, particularly:

• ASTM D648: Standard Test Method for Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position (uses a different heat transfer medium; results are not directly comparable to D8540).
• ASTM D618: Practice for Conditioning Plastics for Testing.
• ASTM D883: Terminology Relating to Plastics.
• ASTM D4000: Classification System for Specifying Plastic Materials.
• ASTM D5947: Test Methods for Physical Dimensions of Solid Plastics Specimens.
• ISO 75-1 and ISO 75-2: International standards for deflection temperature of plastics under load, with notable technical differences from ASTM D8540-23.
• IEC 60751 and IEC 60584-1: Standards for thermocouples and temperature measurement equipment used in test setups.

Understanding these connections ensures effective application, consistency in reporting, and international alignment where required.

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Keywords: ASTM D8540-23, deflection temperature of plastics, flexural load, dry bath, plastics testing, material performance, thermal deflection, quality control, polymer standards, ASTM standards.

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: D8540 − 23
Standard Test Method for
Deflection Temperature of Plastics Under Flexural Load in
the Edgewise Position Using a Dry Bath
This standard is issued under the fixed designation D8540; 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.
1. Scope Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.1 This test method covers the determination of the tem-
Barriers to Trade (TBT) Committee.
perature at which an arbitrary deformation occurs when speci-
mens are subjected to an arbitrary set of testing conditions.
2. Referenced Documents
1.2 This test method applies to molded and sheet materials
2.1 ASTM Standards:
available in thicknesses of 3 mm ( ⁄8 in.) or greater and which
D618 Practice for Conditioning Plastics for Testing
are rigid or semirigid at normal temperature.
D648 Test Method for Deflection Temperature of Plastics
NOTE 1—Sheet stock less than 3 mm (0.125 in.) but more than 1 mm
Under Flexural Load in the Edgewise Position
(0.040 in.) in thickness may be tested by use of a composite sample having
D883 Terminology Relating to Plastics
a minimum thickness of 3 mm. The laminae must be of uniform stress
distribution. One type of composite specimen has been prepared by D4000 Classification System for Specifying Plastic Materi-
cementing the ends of the laminae together and then smoothing the edges
als
with sandpaper. The direction of loading shall be perpendicular to the
D5947 Test Methods for Physical Dimensions of Solid
edges of the individual laminae.
Plastics Specimens
1.3 The values stated in SI units are to be regarded as
E1 Specification for ASTM Liquid-in-Glass Thermometers
standard. The values given in parentheses are for information
E77 Test Method for Inspection and Verification of Ther-
only.
mometers
1.4 This standard and ASTM D648 address the same subject
E608/E608M Specification for Mineral-Insulated, Metal-
matter and are essentially the same test. However, due to
Sheathed Base Metal Thermocouples
known differences in results caused by the differences in heat
E691 Practice for Conducting an Interlaboratory Study to
transfer media, the results from this standard and ASTM D648
Determine the Precision of a Test Method
must not be compared or considered equivalent.
E1137/E1137M Specification for Industrial Platinum Resis-
1.5 This standard does not purport to address all of the
tance Thermometers
safety concerns, if any, associated with its use. It is the
E2251 Specification for Liquid-in-Glass ASTM Thermom-
responsibility of the user of this standard to establish appro-
eters with Low-Hazard Precision Liquids
priate safety, health, and environmental practices and deter-
2.2 ISO Standards:
mine the applicability of regulatory limitations prior to use.
ISO 75-1 Plastics—Determination of Temperature of De-
NOTE 2—The text of this standard references notes and footnotes that
flection Under Load—Part 1: General Test Method
provide explanatory material. These notes and footnotes (excluding those
ISO 75-2 Plastics—Determination of Temperature of De-
in tables and figures) shall not be considered as requirements of the
flection Under Load—Part 2: Plastics and Ebonite
standard.
IEC 60751 Industrial Platinum Resistance thermometers and
NOTE 3—This standard and ISO 75-1 and ISO 75-2 address the same
subject matter, but differ in technical content, and results shall not be
platinum temperature sensors.
compared between the two test methods.
IEC 60584-1 Thermocouples—Part 1 EMF specifications
1.6 This international standard was developed in accor-
and tolerances
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
This test method is under the jurisdiction of ASTM Committee D20 on Plastics Standards volume information, refer to the standard’s Document Summary page on
and is the direct responsibility of Subcommittee D20.30 on Thermal Properties. the ASTM website.
Current edition approved Nov. 1, 2023. Published November 2023. DOI: Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/D8540-23 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8540 − 23
2.3 NIST Document: results if the pressure is sufficient to restrict the downward
NBS Special Publication 250-22 motion of the specimen at its center.
3. Terminology 7. Apparatus
7.1 The apparatus shall be constructed essentially as shown
3.1 General—The definitions of plastics used in this test
method are in accordance with Terminology D883 unless in Fig. 1 and shall consist of the following:
7.1.1 Specimen Supports, metal supports, allowing the load
otherwise indicated.
to be applied on top of the specimen vertically and midway
4. Summary of Test Method
between the supports, which shall be separated by a distance,
defined in 7.1.1.1. The contact edges of the supports and of the
4.1 A bar of rectangular cross section is tested in the
piece by which load is applied shall be rounded to a radius of
edgewise position as a simple beam with the load applied at its
3 6 0.2 mm (0.118 6 0.008 in.).
center to give maximum fiber stresses of 0.455 MPa (66 psi),
7.1.1.1 Span—100.0 6 0.5 mm (3.937 6 0.020 in.).
1.82 MPa (264 psi) or 8.0 MPa (1160 psi). The specimen is
7.1.2 Immersion Bath—An immersion bath containing the
immersed under load in a heat-transfer medium provided with
heat-transfer medium shall be equipped with an agitation
a means of raising the temperature at 2 6 0.2°C ⁄min. The
system, temperature-measuring device, and heater. The heater
temperature of the medium is measured when the test bar has
shall have automatic control of the selected bath temperature
deflected 0.25 mm (0.010 in.). This temperature is recorded as
rise rate. The bath shall be constructed to allow the specimens
the deflection temperature under flexural load of the test
to be submerged at least 35 mm below the surface of the
specimen.
heat-transfer medium.
5. Significance and Use
7.1.3 Heat-Transfer Medium—Shall be a fluidized powder
in which the specimen shall be immersed, which will not affect
5.1 This test is particularly suited to control and develop-
the specimen. It shall be well-agitated during the test and shall
ment work. Data obtained by this test method shall not be used
be provided with a means of raising the temperature at a
to predict the behavior of plastic materials at elevated tempera-
uniform rate of 2 6 0.2°C ⁄min. This heating rate shall be
tures except in applications in which the factors of time,
considered to be met if, over every 5-min interval during the
temperature, method of loading, and fiber stress are similar to
test, the temperature of the bath shall rise 10 6 1°C at each
those specified in this test method. The data are not intended
specimen location.
for use in design or predicting endurance at elevated tempera-
tures.
NOTE 4—Aluminum Oxide has been found satisfactory and safe for
short-term heat cycles up to 500°C.
5.2 For many materials, it is possible there will be a
specification that requires the use of this test method, but with 7.1.4 Deflection Measurement Device, suitable for measur-
some procedural modifications that take precedence when ing specimen deflection of at least 0.25 mm (0.010 in.). It shall
adhering to the specification. Therefore, it is advisable to refer be readable to 0.01 mm (0.0005 in.) or better. Electronic
to that material specification before using this test method. displacement sensing devices shall be used.
7.1.5 Weights—A set of weights of suitable sizes so that the
Refer to Table 1 in Classification D4000, which lists the ASTM
material standards that currently exist. specimen are loaded to a fiber stress of 0.455 MPa (66 psi) 6
2.5 % ,1.82 MPa (264 psi) 6 2.5 % or 8.00 MPa (1160 psi) 6
6. Interferences
2.5%. The mass of the rod that applies the testing force shall be
determined and included as part of the total load. Calculate the
6.1 The results of the test are dependent on the rate of heat
testing force and the mass that must be added to achieve the
transfer between the heat transfer medium and the specimen
desired stress as follows:
and the thermal conductivity of the heat transfer media.
F 5 2Sbd ⁄3L (1)
6.2 The results of this test are dependent on the measured
width and depth of the specimen and the final deflection at
F 5 F⁄9.80665
which the deflection temperature is determined.
6.3 The type of mold and the molding process used to M 5 F⁄9.80665 2 m
w r
produce test specimens affects the results obtained in this test.
where:
Molding conditions shall be in accordance with the standard
F = load, N,
for that material or shall be agreed upon by the cooperating
F = load, kgf,
laboratories.
S = fiber stress in the specimen (0.455 MPa, 1.82 MPa or
6.4 Results of testing are affected by the design of the test
8.0 MPa),
equipment. The test span (100 mm) will influence the resultant
b = width of specimen, mm,
measurement. Instrumentation equipped with metal clips or
d = depth of specimen, mm,
other types of auxiliary supports designed to maintain speci- L = distance between supports, 100 mm), see 7.1.1.1,
m = added mass, kg, and
mens perpendicular to the applied load will affect the test
w
m = mass of the rod that applies the testing force to the
r
specimen, kg.
Available from National Institute of Standards and Technology (NIST), 100
Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov. 7.1.6 Temperature Measurement System:
D8540 − 23
FIG. 1 Apparatus for Deflection Temperature Test
7.1.6.1 Digital Indicating System—Consisting of a be 12.7 mm 6 0.5 mm (0.500 6 0.020 in.). The width of the
thermocouple, resistance thermometer (RTD), and so forth, as specimen shall be any width from 3 mm to 13 mm (0.118 in.
the sensor, together with associated conditioning, conversion, to 0.512 in.).
and readout instrumentation adequate to cover the range being
9.1.1 For tests performed at 8.0 MPa stresses, specimens
tested. The sensor and related electronics shall be accurate to at
shall be 6.35 mm or less in width due to the safety concerns of
least 60.5°C. Thermocouples shall comply with the require-
raising and lowering the weights required and the load limita-
ments of Specification E608/E608M or IEC 60584-1. Resis-
tions for common instruments.
tance thermometers shall comply with the requirements of
NOTE 5—Tolerances on the depth and width dimensions should be of
Specification E1137/E1137M or IEC 60751.
the order of 60.13 mm (0.005 in.) along the length of the specimen to
7.2 Micrometers shall meet the requirements of Test Meth- minimize variations.
NOTE 6—The test results obtained on specimens approaching 13 mm in
ods D5947 and be calibrated in accordance with that test
width may be 2 to 4°C above those obtained from 4 mm or narrower test
method.
specimens because of poor heat transfer through the specimen.
8. Sampling
9.2 The specimens shall have smooth flat surfaces free from
saw cuts, excessive sink marks, or flash.
8.1 Sample in a statistically acceptable manner. When
samples are taken from a production lot or process, the process
9.3 Molding conditions shall be in accordance with the
shall be in a state of statistical control.
specification for that material or shall be agreed upon by the
cooperating laboratories. Discrepancies in test results due to
9. Test Specimen
variations in molding conditions are often minimized by
9.1 At least two test specimens of the same nominal width annealing the test specimens before the test. Since different
shall be used to test each sample at each fiber stress. The length materials require different annealing conditions, annealing
of the specimen shall at a minimum be the distance between procedures shall be employed only if required by the material
supports +12.7 mm (0.500 in.). The depth of the specimen must standard or if agreed upon by the cooperating laboratories.
D8540 − 23
10. Preparation of Apparatus placed at the same level as the specimen and within 10 mm of
the point at which the specimen is loaded.
10.1 The apparatus shall be arranged so that the deflection
of the specimen at midspan is measured by the deflection 12.4 Ascertain that the temperature of the bath is suitable.
measurement device described in 7.1.3. It is acceptable if the The bath temperature shall be at ambient temperature at the
apparatus is designed to shut off the heat automatically and start of the test unless previous tests have shown that, for the
sound an alarm or record the temperature when the specific particular material under test, no error is introduced by starting
deflection has been reached. Sufficient heat transfer medium at a higher temperature.
shall be used to cover the sensing end of the temperature
12.5 Carefully apply the loaded rod to the specimen and
measuring device to the point specified in their calibration.
lower the assembly into the bath.
NOTE 7—It is desirable to have a means to cool the bath in order to
12.6 Adjust the load so that the desired stress of 0.455 MPa
reduce the time required to lower the temperature of the bath after the test
(66 psi), 1.82 MPa (264 psi), or 8.00 MPa (1160 psi) is
has been completed. This may be accomplished by using a cooling coil
obtained.
installed in the bath. If the rate of temperature rise of the heat transfer
medium is adversely affected by the presence of residual coolant in the
NOTE 10—Verification of the load should be made on all new
coils, the coolant should be purged prior to starting the next test.
equipment or following any other change that could affect the loading.
Verification of the load should also be performed periodically to ensure
11. Conditioning
that the equipment is within calibration (see Annex A1 and Appendix X1).
Depending on the type of deflection measurement device used, it may be
11.1 Conditioning—Condition the test specimens in accor-
necessary to adjust the device such that it records the deflection in the
dance with Procedure A of Practice D618 unless otherwise
displacement range of the device where the test is to be made.
specified b
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