ASTM D3941-20

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: D3941 − 14 D3941 − 20
Standard Test Method for
Flash Point by the Equilibrium Method With a Closed-Cup
Apparatus
This standard is issued under the fixed designation D3941; 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.
INTRODUCTION
Test Methods D56 and D93 describe procedures using the Tag Closed Tester and the Pensky-
Martens Tester, respectively. Both test methods depend on a definite rate of temperature increase to
control the precision of the test method. The rate of heating may not in all cases give the accuracy
expected because of low thermal conductivity of certain materials. To reduce this effect, ISO/TC 35,
Paints and Varnishes, and ISO/TC 28, Petroleum Products and Lubricants, have issued ISO 1523 in
which the heating rate is considerably slower. This test method is similar to ISO 1523, but uses
standard ASTM cups, style, and format. Due to the slower heating rate, the time required to make a
determination of a flash point is considerably longer than for Test Methods D56 and D93 but the
accuracy is improved.
1. Scope*Scope
1.1 This test method covers the determination of the flash point of liquids in which the specimen and the air/vapor mixture above
it are approximately in temperature equilibrium.
1.2 This test method is limited to a temperature range from 0 to 110°C (32 to 230°F).
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.4 Warning—Mercury has been designated by many regulatory agencies as a hazardous substance that can cause serious
medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Use caution
when handling mercury and mercury-containing products. See the applicable product Safety Data Sheet (SDS) for additional
information. The potential exists that selling mercury or mercury-containing products, or both, is prohibited by local or national
law. Users must determine legality of sales in their location.Warning—Mercury has been designated by many regulatory agencies
as a hazardous material that can cause central nervous system, kidney and liver damage. Mercury, or its vapor, may be hazardous
to health and corrosive to materials. Caution should be taken when handling mercury and mercury containing products. See the
applicable product Safety Data Sheet (SDS) for details and EPA’s website, http://www.epa.gov/mercury/faq.htm, for additional
information. Users should be aware that selling mercury and/or mercury containing products into your state or country may be
prohibited by law.
1.5 This standard should be is used to measure and describe the propertiesresponse of material,materials, products, or
assemblies in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise
theconditions, but does not by itself incorporate all factors required for fire hazard or fire risk assessment of the materials,
products, or assemblies under actual fire conditions. However, results of this test may be used as elements of a fire risk assessment
which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use.
1.6 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
This test method is under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and is the direct responsibility of
Subcommittee D01.21 on Chemical Analysis of Paints and Paint Materials.
Current edition approved Dec. 15, 2014June 1, 2020. Published January 2015June 2020. Originally approved in 1980. Last previous edition approved in 20072014 as
D3941 – 90 (2007).D3941 – 14. DOI: 10.1520/D3941-14.10.1520/D3941-20.
*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
D3941 − 20
1.7 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:
D56 Test Method for Flash Point by Tag Closed Cup Tester
D93 Test Methods for Flash Point by Pensky-Martens Closed Cup Tester
E1 Specification for ASTM Liquid-in-Glass Thermometers
E1137 Specification for Industrial Platinum Resistance Thermometers
E2251 Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids
E2877 Guide for Digital Contact Thermometers
2.2 ISO Standard:
ISO 1523 Paints, varnishes, petroleum, and related products—Determination of flash point—Closed cup equilibrium method
3. Terminology
3.1 Definitions:
3.1.1 flash point, n—the lowest temperature corrected to a pressure of 760 mm Hg (101.3 kPa) (1013 millibars) at which
application of an ignition source causes the vapor of the specimen to ignite under specified conditions of test.
4. Summary of Test Method
4.1 A specimen is heated in a closed cup of standard design in a suitable liquid bath at the rate of 0.5°C (1.0°F) in not less than
1.5 min so that the difference in temperature between the specimen in the cup and bath never exceeds 2.0°C (3.5°F). Flash
determinations are made at intervals of not less than 1.5 min.
5. Significance and Use
5.1 This test method, using a slow rate of heating, provides a uniform temperature throughout the specimen. The slow rate of
heating is necessary because of the low thermal conductivity of some liquids such as paints, resins, and related products, and also
because of the poor heat transfer by convection in high-viscosity products. Since the specimen is being heated at a reduced rate,
the longer time interval between each determination is necessary to reestablish after each flash test the saturation concentration of
vapor in the air space above the specimen.
NOTE 1—ISO 1523 is used in United Nations Recommendations for Transportation of Dangerous Goods and in the International Civil Aviation
Organization (ICAO) regulations and for similar regulations in the International Maritime Dangerous Goods (IMDG) code. Test Method D3941, which
is similar to ISO 1523, is used in the United States Department of Transportation (USDOT) regulations. The ICAO and IMDG codes are used for
transshipment of hazardous materials through the United States to other countries.
6. Apparatus
6.1 Test Cups, equipped with their lid as specified in Test Methods D56 (Tag) and D93 (Pensky-Martens). Remove the test cup
assembly (including lid and specimen thermometer) from the Tag and Pensky-Martens apparatus to permit either to be used in a
separate water bath.
6.1.1 If a stirrer is fitted to the test cup used, it shall operate during the heating period but must be stopped during the flashing
determination. If the stirrer originally fitted to the test cup is removed, the aperture in the cover shall be securely plugged before
starting the test.
6.2 Liquid Bath—Any suitable liquid bath capable of being adjusted to the required temperature and of adequate heat capacity
to meet the requirements of the test. A bath fitted with a stirrer and an adjustable thermostat is convenient (see 4.1).
NOTE 2—The bath should be fitted with a cover, especially when the specified temperature is above 160°F. At about this temperature the inerting effect
of the water vapor may prevent or delay the flashing of the liquid under test.
6.3 Thermometers—Standard thermometers as specified in Test Methods D56 and D93. Alternative temperature measuring
devices are permitted providing they have a similar response time and meet the respective performance and immersion depth
specifications of thermometers listed in Specification E1. See Specifications E1137 and E2251, and Guide E2877 when selecting
alternative temperature measuring devices. One thermometer shall be used to measure the temperature of the water bath and one
shall be used for measuri
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