ASTM E2046-19

Standard Test Method for Reaction Induction Time by Thermal Analysis

SIGNIFICANCE AND USE
5.1 This test method measures the time to extrapolated onset of an exothermic reaction under constant temperature (isothermal) conditions for reactions which have an induction period, for example, those which are catalytic, autocatalytic, or accelerating in nature or which contain reaction inhibitors.  
5.2 The RIT determined by this test method is an index measurement that is useful for comparing one material to another at the test temperature of interest and in the same apparatus type only.  
5.3 This test method is a useful adjunct to dynamic thermal tests, such as Test Method E537, which are performed under conditions in which the sample temperature is increased continuously at constant rate. Results obtained under dynamic test conditions may result in higher estimates of temperature at which an exothermic reaction initiates because the detected onset temperature is dependent upon the heating rate and because dynamic methods allow insufficient time for autocatalytic reactions to measurably affect the onset temperature.  
5.4 RIT values determined under a series of isothermal test conditions may be plotted as their logarithm versus the reciprocal of the absolute temperature to produce a plot, the slope of which is proportional to the activation energy of the reaction as described in Test Methods E2070.  
5.5 This test method may be used in research and development, manufacturing, process and quality control, and regulatory compliance.  
5.6 This test method is similar to that for oxidation induction time (OIT) (for example, Specification D3350 and Test Methods D3895, D4565, D5483, D6186, and E1858) where the time to the oxidation reaction under isothermal test conditions is measured. The OIT test method measures the presence of antioxidant packages and is a relative measurement of a material’s resistance to oxidation.
SCOPE
1.1 This test method describes the measurement of reaction induction time (RIT) of chemical materials that undergo exothermic reactions with an induction period. The techniques and apparatus described may be used for solids, liquids, or slurries of chemical substances. The temperature range covered by this test method is typically from ambient to 400 °C. This range may be extended depending upon the apparatus used.  
1.2 The RIT is a relative index value, not an absolute thermodynamic property. As an index value, the RIT value may change depending upon experimental conditions. A comparison of RIT values may be made only for materials tested under similar conditions of apparatus, specimen size, and so forth. Furthermore, the RIT value may not predict behavior of large quantities of material.  
1.3 The RIT shall not be used by itself to establish a safe operating temperature. It may be used in conjunction with other test methods (for example, Test Methods E487 and E537, and Guide E1981) as part of a hazard analysis of a particular operation.  
1.4 This test method may be used for RIT values greater than 15 min (as relative imprecision increases at shorter periods).  
1.5 This test method is used to study catalytic, autocatalytic, and accelerating reactions. These reactions depend upon time as well as temperature. Such reactions are often studied by fixing one experimental parameter (that is, time or temperature) and then measuring the other parameter (that is, temperature or time). This test method measures time to reaction onset detection under isothermal conditions. It is related to Test Method E487 that measures detected reaction onset temperature under constant time conditions  
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this test method.  
1.7 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 appl...

General Information

• Status: Published
• Publication Date: 31-Oct-2019
• ICS: 17.200.20 - Temperature-measuring instruments
• Technical Committee: E27 - Hazard Potential of Chemicals
• Drafting Committee: E27.02 - Thermal Stability and Condensed Phases

Relations

• Replaces: ASTM E2046-14 - Standard Test Method for Reaction Induction Time by Thermal Analysis
• Effective Date: 01-Nov-2019
• Refers: ASTM E1445-08(2023) - Standard Terminology Relating to Hazard Potential of Chemicals
• Effective Date: 15-Nov-2023
• Refers: ASTM E2070-23 - Standard Test Methods for Kinetic Parameters by Differential Scanning Calorimetry Using Isothermal Methods
• Effective Date: 01-Oct-2023
• Refers: ASTM E473-23b - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 01-Oct-2023
• Refers: ASTM E537-20 - Standard Test Method for Thermal Stability of Chemicals by Differential Scanning Calorimetry
• Effective Date: 01-Feb-2020
• Refers: ASTM E487-20 - Standard Test Methods for Constant-Temperature Stability of Chemical Materials
• Effective Date: 01-Feb-2020
• Refers: ASTM D6186-19 - Standard Test Method for Oxidation Induction Time of Lubricating Oils by Pressure Differential Scanning Calorimetry (PDSC)
• Effective Date: 01-Jul-2019
• Refers: ASTM E2070-13(2018) - Standard Test Methods for Kinetic Parameters by Differential Scanning Calorimetry Using Isothermal Methods
• Effective Date: 01-Apr-2018
• Refers: ASTM D5483-05(2015) - Standard Test Method for Oxidation Induction Time of Lubricating Greases by Pressure Differential Scanning Calorimetry
• Effective Date: 01-Oct-2015
• Refers: ASTM E473-14 - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 15-Aug-2014
• Refers: ASTM E487-14 - Standard Test Method for Constant-Temperature Stability of Chemical Materials
• Effective Date: 01-Mar-2014
• Refers: ASTM D6186-08(2013) - Standard Test Method for Oxidation Induction Time of Lubricating Oils by Pressure Differential Scanning Calorimetry (PDSC)
• Effective Date: 01-Dec-2013
• Refers: ASTM E2070-13 - Standard Test Method for Kinetic Parameters by Differential Scanning Calorimetry Using Isothermal Methods
• Effective Date: 15-Sep-2013
• Refers: ASTM E1860-13 - Standard Test Method for Elapsed Time Calibration of Thermal Analyzers
• Effective Date: 15-Sep-2013
• Refers: ASTM E1981-98(2012)e1 - Standard Guide for Assessing Thermal Stability of Materials by Methods of Accelerating Rate Calorimetry
• Effective Date: 01-Dec-2012

Overview

ASTM E2046-19: Standard Test Method for Reaction Induction Time by Thermal Analysis defines a reliable approach for measuring the Reaction Induction Time (RIT) of chemical materials undergoing exothermic reactions with an induction period. This test method is widely applied to solids, liquids, or slurries and utilizes isothermal conditions to determine the time before a detectable exothermic reaction begins. RIT is expressed as a relative index value rather than an absolute thermodynamic property. ASTM E2046-19 is critical for quality control, material comparison, process safety, and thermal stability assessment in chemical processing and manufacturing industries.

Key Topics

• Reaction Induction Time (RIT): The interval under controlled isothermal conditions until the onset of an exothermic reaction is detected.
• Isothermal Thermal Analysis: The method operates at a steady temperature, differing from dynamic methods that use continuously increasing temperatures.
• Test Apparatus: Includes differential scanning calorimetry (DSC) or differential thermal analysis (DTA) instruments, suitable for small sample measurements, along with supporting equipment for temperature control and data recording.
• Sample Requirements: Applicable to test specimens ranging from milligrams to grams. The method requires representative and carefully prepared samples to ensure reliable RIT results.
• Relative Measurement: RIT values are only comparable between materials analyzed with the same apparatus and experimental conditions. RIT is not an absolute measure and may vary with specimen size, type of equipment, and other variables.
• Role in Hazard Assessment: While RIT provides useful comparative data, it should not be used alone to establish safe operating temperatures. It is best used alongside other thermal analysis methods for comprehensive hazard analysis.

Applications

ASTM E2046-19 plays a vital role across several fields:

• Research and Development: Used to study the kinetics and hazard potential of new materials, especially those with catalytic or autocatalytic behavior.
• Quality Control: Enables comparison of material stability at critical temperatures, helping ensure batch-to-batch consistency.
• Process and Manufacturing: Informs safe temperature limits, process optimization, and detection of possible inhibitors or accelerators in chemical formulations.
• Regulatory Compliance: Supports documentation and analysis required for compliance with industry safety and environmental standards.
• Thermal Stability Studies: Useful for evaluating how additives, such as inhibitors or antioxidants, affect the thermal reaction behavior of chemical substances.

The test is applicable to a range of substances and industries, including polymers, lubricants, petrochemicals, and materials handling safety.

Related Standards

Several ASTM standards complement or relate to ASTM E2046-19, supporting broader applications in thermal analysis and material stability assessment:

• ASTM E537 - Thermal Stability of Chemicals by Differential Scanning Calorimetry
• ASTM E487 - Constant-Temperature Stability of Chemical Materials
• ASTM E2070 - Kinetic Parameters by Differential Scanning Calorimetry Using Isothermal Methods
• ASTM D3350, D3895, D4565, D5483, D6186, and E1858 - Methods for Oxidation Induction Time (OIT), relevant for materials where antioxidant performance and oxidation resistance are critical factors.
• ASTM E967, E968, E1860 - Standards for calibration of thermal analysis instruments.

These referenced documents contribute to an integrated approach in thermal analysis, ensuring precise calibration, consistent methodology, and comprehensive safety analysis within laboratories and industrial settings.

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Keywords: reaction induction time, RIT, ASTM E2046-19, isothermal thermal analysis, exothermic reaction, differential scanning calorimetry, chemical hazard assessment, thermal stability, quality control, material comparison, oxidation induction time.

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: E2046 − 19
Standard Test Method for
Reaction Induction Time by Thermal Analysis
This standard is issued under the fixed designation E2046; 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 1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method describes the measurement of reaction
responsibility of the user of this standard to establish appro-
induction time (RIT) of chemical materials that undergo
priate safety, health, and environmental practices and deter-
exothermic reactions with an induction period. The techniques
mine the applicability of regulatory limitations prior to use.
and apparatus described may be used for solids, liquids, or
1.8 This international standard was developed in accor-
slurriesofchemicalsubstances.Thetemperaturerangecovered
dance with internationally recognized principles on standard-
by this test method is typically from ambient to 400 °C. This
ization established in the Decision on Principles for the
range may be extended depending upon the apparatus used.
Development of International Standards, Guides and Recom-
1.2 The RIT is a relative index value, not an absolute
mendations issued by the World Trade Organization Technical
thermodynamicproperty.Asanindexvalue,theRITvaluemay
Barriers to Trade (TBT) Committee.
change depending upon experimental conditions. A compari-
2. Referenced Documents
son of RITvalues may be made only for materials tested under
similar conditions of apparatus, specimen size, and so forth.
2.1 ASTM Standards:
Furthermore, the RIT value may not predict behavior of large
D3350 Specification for Polyethylene Plastics Pipe and Fit-
quantities of material.
tings Materials
D3895 Test Method for Oxidative-Induction Time of Poly-
1.3 The RIT shall not be used by itself to establish a safe
olefins by Differential Scanning Calorimetry
operating temperature. It may be used in conjunction with
D4565 Test Methods for Physical and Environmental Per-
other test methods (for example,Test Methods E487 and E537,
formance Properties of Insulations and Jackets for Tele-
and Guide E1981) as part of a hazard analysis of a particular
communications Wire and Cable
operation.
D5483 Test Method for Oxidation Induction Time of Lubri-
1.4 This test method may be used for RIT values greater
catingGreasesbyPressureDifferentialScanningCalorim-
than 15 min (as relative imprecision increases at shorter
etry
periods).
D6186 Test Method for Oxidation Induction Time of Lubri-
1.5 Thistestmethodisusedtostudycatalytic,autocatalytic,
cating Oils by Pressure Differential Scanning Calorimetry
and accelerating reactions. These reactions depend upon time
(PDSC)
as well as temperature. Such reactions are often studied by
E473 Terminology Relating to Thermal Analysis and Rhe-
fixing one experimental parameter (that is, time or tempera-
ology
ture) and then measuring the other parameter (that is, tempera-
E487 Test Method for Constant-Temperature Stability of
ture or time). This test method measures time to reaction onset
Chemical Materials
detection under isothermal conditions. It is related to Test
E537 Test Method for The Thermal Stability of Chemicals
Method E487 that measures detected reaction onset tempera-
by Differential Scanning Calorimetry
ture under constant time conditions
E967 Test Method for Temperature Calibration of Differen-
tial Scanning Calorimeters and Differential Thermal Ana-
1.6 The values stated in SI units are to be regarded as
lyzers
standard. No other units of measurement are included in this
E968 Practice for Heat Flow Calibration of Differential
test method.
Scanning Calorimeters
E1445 Terminology Relating to Hazard Potential of Chemi-
cals
This test method is under the jurisdiction ofASTM Committee E27 on Hazard
Potential of Chemicals and is the direct responsibility of Subcommittee E27.02 on
Thermal Stability and Condensed Phases. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2019. Published November 2019. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1999. Last previous edition approved in 2014 as E2046 – 14. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E2046-19. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2046 − 19
E1858 Test Methods for Determining Oxidation Induction which an exothermic reaction initiates because the detected
Time of Hydrocarbons by Differential Scanning Calorim- onset temperature is dependent upon the heating rate and
etry because dynamic methods allow insufficient time for autocata-
E1860 Test Method for Elapsed Time Calibration of Ther- lytic reactions to measurably affect the onset temperature.
mal Analyzers
5.4 RIT values determined under a series of isothermal test
E1981 Guide for Assessing Thermal Stability of Materials
conditions may be plotted as their logarithm versus the
by Methods of Accelerating Rate Calorimetry
reciprocal of the absolute temperature to produce a plot, the
E2070 Test Methods for Kinetic Parameters by Differential
slope of which is proportional to the activation energy of the
Scanning Calorimetry Using Isothermal Methods
reaction as described in Test Methods E2070.
5.5 This test method may be used in research and
3. Terminology
development, manufacturing, process and quality control, and
3.1 The specialized terms used in this test method are
regulatory compliance.
described in Terminologies E473 and E1445, including differ-
5.6 This test method is similar to that for oxidation induc-
ential scanning calorimetry, differential thermal analysis, ex-
tion time (OIT) (for example, Specification D3350 and Test
trapolated onset value, first-deviation-from-baseline, onset
MethodsD3895,D4565,D5483,D6186,andE1858)wherethe
value, isothermal, and reaction.
time to the oxidation reaction under isothermal test conditions
3.2 Definitions of Terms Specific to This Standard:
is measured. The OIT test method measures the presence of
3.2.1 constant temperature stability (CTS) value, n—the
antioxidant packages and is a relative measurement of a
maximum temperature at which a chemical compound or
material’s resistance to oxidation.
mixture may be held for a minimum of two hours without
exhibitingameasurableexothermicreaction.(SeeTestMethod
6. Apparatus
E487.)
6.1 The design and complexity of the apparatus required for
3.2.2 reaction induction time (RIT) value, n—the time a
this test method depends upon the size of the specimen to be
chemical compound or mixture may be held under isothermal
used.Ingeneral,observationofanexothermicreactioninsmall
conditions until it exhibits a specified exothermic reaction.
specimens (less than 50 mg) is performed using differential
scanningcalorimetryordifferentialthermalanalysisequipment
4. Summary of Test Method
and techniques. Large samples (up to 2 g) may be tested using
4.1 A specimen of the chemical compound or mixture is
devices such as the Kuhner Micro CTS apparatus.
placed in an inert container that is then heated to an operator-
6.2 The following items are required to obtain the appro-
selected test temperature of interest.The specimen temperature
priate experimental data.
and the difference in heat flow or temperature between the test
specimen and an inert reference are monitored until an exo-
NOTE 1—Commercially available differential scanning calorimetry
apparatus may be used. Alternatively, the apparatus may be assembled or
thermic reaction is recorded. The time from the attainment of
fabricated from commercially available components.
the isothermal test temperature until the extrapolated onset to
the exothermic reaction is taken as the RIT. 6.2.1 Test Chamber, composed of the following:
6.2.1.1 Furnace(s),toprovideuniformcontrolledheatingof
4.2 Using fresh specimens measurements at more than one
a specimen and reference to a constant temperature.
isothermal test temperature may be made.
6.2.1.2 Temperature Sensor, to provide an indication of
4.3 The RIT is expressed as time at a specific test tempera-
specimen/furnace temperature readable to 60.1 K.
ture. For example:
6.2.1.3 DifferentialSensor,todetectadifferenceinheatflow
RIT 5 120 min at 100 °C (or temperature) between the specimen and the reference
specimen equivalent to 10 µW or 0.01 mK.
5. Significance and Use
NOTE 2—A reference material is used when differential heat flow or
5.1 Thistestmethodmeasuresthetimetoextrapolatedonset
differential temperature measurements are made. The reference material
of an exothermic reaction under constant temperature (isother- should match the physical state and heat capacity of the specimen as
closely as practical. Typical reference materials include calcined alumi-
mal) conditions for reactions which have an induction period,
num oxide, glass beads, silicone oil, or combinations thereof.
for example, those which are catalytic, autocatalytic, or accel-
6.2.1.4 Means of Sustaining a Test Chamber Environment,
erating in nature or which contain reaction inhibitors.
through the use of an air purge gas at a rate of 10 mL/min to
5.2 The RIT determined by this test method is an index
100 6 5 mL/min.
measurement that is useful for comparing one material to
another at the test temperature of interest and in the same NOTE 3—Typically, air or inert 99.9+ % pure nitrogen, argon, or helium
is employed (when oxidation in air is a concern). Unless effects of
apparatus type only.
moisture are to be studied, use of dry purge gas is recommended.
5.3 This test method is a useful adjunct to dynamic thermal
NOTE 4—For the Kuhner Micro CTS apparatus, the purge gas is
providedbyoperationinalaboratoryhoodwiththedoor(s)approximately
tests, such as Test Method E537, which are performed under
50 % closed.
conditions in which the sample temperature is increased
continuously at constant rate. Results obtained under dynamic 6.2.2 Temperature Controller, capable of heating from am-
test conditions may result in higher estimates o
...

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: E2046 − 14 E2046 − 19
Standard Test Method for
Reaction Induction Time by Thermal Analysis
This standard is issued under the fixed designation E2046; 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
1.1 This test method describes the measurement of Reaction Induction Timereaction induction time (RIT) of chemical materials
that undergo exothermic reactions with an induction period. The techniques and apparatus described may be used for solids,
liquids, or slurries of chemical substances. The temperature range covered by this test method is typically from ambient to 400°C.
400 °C. This range may be extended depending upon the apparatus used.
1.2 The RIT is a relative index value, not an absolute thermodynamic property. As an index value, the RIT value may change
depending upon experimental conditions. A comparison of RIT values may be made only for materials tested under similar
conditions of apparatus, specimen size, and so forth. Furthermore, the RIT value may not predict behavior of large quantities of
material.
1.3 The RIT shall not be used by itself to establish a safe operating temperature. It may be used in conjunction with other test
methods (for example, Test Methods E487, and E537, and Guide E1981) as part of a hazard analysis of a particular operation.
1.4 This test method may be used for RIT values greater than 15 min (as relative imprecision increases at shorter periods).
1.5 This test method is used to study catalytic, autocatalytic, and accelerating reactions. These reactions depend upon time as
well as temperature. Such reactions are often studied by fixing one experimental parameter (that is, time or temperature) and then
measuring the other parameter (that is, temperature or time). This test method measures time to reaction onset detection under
isothermal conditions. It is related to Test Method E487 that measures detected reaction onset temperature under constant time
conditions
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.test
method.
1.7 There is no ISO standard equivalent to this test method.
1.7 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 consult and establish appropriate safety safety, health, and healthenvironmental practices and
determine the applicability of regulatory limitations prior to use.
1.8 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:
D3350 Specification for Polyethylene Plastics Pipe and Fittings Materials
D3895 Test Method for Oxidative-Induction Time of Polyolefins by Differential Scanning Calorimetry
D4565 Test Methods for Physical and Environmental Performance Properties of Insulations and Jackets for Telecommunications
Wire and Cable
D5483 Test Method for Oxidation Induction Time of Lubricating Greases by Pressure Differential Scanning Calorimetry
D6186 Test Method for Oxidation Induction Time of Lubricating Oils by Pressure Differential Scanning Calorimetry (PDSC)
E473 Terminology Relating to Thermal Analysis and Rheology
This test method is under the jurisdiction of ASTM Committee E27 on Hazard Potential of Chemicals and is the direct responsibility of Subcommittee E27.02 on Thermal
Stability and Condensed Phases.
Current edition approved Jan. 1, 2014Nov. 1, 2019. Published February 2014November 2019. Originally approved in 1999. Last previous edition approved in 20082014
as E2046 – 08.E2046 – 14. DOI: 10.1520/E2046-14.10.1520/E2046-19.
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’sstandard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2046 − 19
E487 Test Method for Constant-Temperature Stability of Chemical Materials
E537 Test Method for The Thermal Stability of Chemicals by Differential Scanning Calorimetry
E967 Test Method for Temperature Calibration of Differential Scanning Calorimeters and Differential Thermal Analyzers
E968 Practice for Heat Flow Calibration of Differential Scanning Calorimeters
E1445 Terminology Relating to Hazard Potential of Chemicals
E1858 Test Methods for Determining Oxidation Induction Time of Hydrocarbons by Differential Scanning Calorimetry
E1860 Test Method for Elapsed Time Calibration of Thermal Analyzers
E1981 Guide for Assessing Thermal Stability of Materials by Methods of Accelerating Rate Calorimetry
E2070 Test Methods for Kinetic Parameters by Differential Scanning Calorimetry Using Isothermal Methods
3. Terminology
3.1 The specialized terms used in this test method are described in Terminologies E473 and E1445, including differential
scanning calorimetry, differential thermal analysis, extrapolated onset value, first-deviation-from-baseline, onset value,
isothermal, and reaction.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 constant temperature stability (CTS) value, n—the maximum temperature at which a chemical compound or mixture may
be held for a minimum of two hours without exhibiting a measurable exothermic reaction. (See Test Method E487.)
3.2.2 reaction induction time (RIT) value, n—the time a chemical compound or mixture may be held under isothermal
conditions until it exhibits a specified exothermic reaction.
4. Summary of Test Method
4.1 A specimen of the chemical compound or mixture is placed in an inert container that is then heated to an operator-selected
test temperature of interest. The specimen temperature and the difference in heat flow or temperature between the test specimen
and an inert reference are monitored until an exothermic reaction is recorded. The time from the attainment of the isothermal test
temperature until the extrapolated onset to the exothermic reaction is taken as the Reaction Induction Time.RIT.
4.2 Using fresh specimens measurements at more than one isothermal test temperature may be made.
4.3 The RIT is expressed as time at a specific test temperature. For example:
RIT
RIT 5 120 min at 100 °C
= 120 min at 100°C
5. Significance and Use
5.1 This test method measures the time to extrapolated onset of an exothermic reaction under constant temperature (isothermal)
conditions for reactions which have an induction period, for example, those which are catalytic, autocatalytic, or accelerating in
nature or which contain reaction inhibitors.
5.2 The RIT determined by this test method is an index measurement that is useful for comparing one material to another at
the test temperature of interest and in the same apparatus type only.
5.3 This test method is a useful adjunct to dynamic thermal tests, such as Test Method E537, which are performed under
conditions in which the sample temperature is increased continuously at constant rate. Results obtained under dynamic test
conditions may result in higher estimates of temperature at which an exothermic reaction initiates because the detected onset
temperature is dependent upon the heating rate and because dynamic methods allow insufficient time for autocatalytic reactions
to measurably affect the onset temperature.
5.4 RIT values determined under a series of isothermal test conditions may be plotted as their logarithm versus the reciprocal
of the absolute temperature to produce a plot, the slope of which is proportional to the activation energy of the reaction as described
in Test MethodMethods E2070.
5.5 This test method may be used in research and development, manufacturing, process and quality control, and regulatory
compliance.
5.6 This test method is similar to that for Oxidation Induction Timeoxidation induction time (OIT) (for example, Specification
D3350 and Test Methods D3895, D4565, D5483, D6186, and E1858) where the time to the oxidation reaction under isothermal
test conditions is measured. The OIT test method measures the presence of antioxidant packages and is a relative measurement of
a material’smaterial’s resistance to oxidation.
6. Apparatus
6.1 The design and complexity of the apparatus required for this test method depends upon the size of the specimen to be used.
In general, observation of an exothermic reaction in small specimens (less than 50 mg) is performed using differential scanning
calorimetry or differential thermal analysis equipment and techniques. Large samples (up to 2 g) may be tested using devices such
as the Kuhner Micro CTS apparatus.
E2046 − 19
6.2 The following items are required to obtain the appropriate experimental data.
NOTE 1—Commercially available differential scanning calorimetry apparatus may be used. Alternatively, the apparatus may be assembled or fabricated
from commercially available components.
6.2.1 Test Chamber, composed of the following:
6.2.1.1 Furnace(s), to provide uniform controlled heating of a specimen and reference to a constant temperature.
6.2.1.2 Temperature Sensor, to provide an indication of specimen/furnace temperature readable to 60.1 K.
6.2.1.3 Differential Sensor, to detect a difference in heat flow (or temperature) between the specimen and the reference specimen
equivalent to 10 μW or 0.01 mK.
NOTE 2—A reference material is used when differential heat flow or differential temperature measurements are made. The reference material should
match the physical state and heat capacity of the specimen as closely as practical. Typical reference materials include calcined aluminum oxide, glass
beads, silicone oil, or combinations thereof.
6.2.1.4 Means of Sustaining a Test Chamber Environment, through the use of an air purge gas at a rate of 10 mL/min to 100
6 5 mL/min.
NOTE 3—Typically, air or inert 99.9+ % pure nitrogen, argon, or helium is employed (when oxidation in air is a concern). Unless effects of moisture
are to be studied, use of dry purge gas is recommended.
NOTE 4—For the Kuhner Micro CTS apparatus, the purge gas is provided by operation in a laboratory hood with the door(s) approximately 50 % closed.
6.2.2 Temperature Controller, capable of hea
...