ASTM E1231-96a

Standard Practice for Calculation of Hazard Potential Figures-of-Merit for Thermally Unstable Materials

SCOPE
1.1 This practice covers the calculation of hazard potential figures-of-merit for exothermic reactions, including:(1)Time-to-thermal-runaway,
(2)Critical half thickness,
(3)Critical temperature,
(4)Adiabatic decomposition temperature rise
(5)Explosion potential,
(6)Shock sensitivity,
(7)Instantaneous power density, and
(8)NFPA instability rating.
1.2 The kinetic parameters needed in this calculation may be obtained from differential scanning calorimetry (DSC) curves by methods described in other documents.
1.3 This technique is the best applicable to simple, single reactions whose behavior can be described by the Arrhenius equation and the general rate law. For reactions which do not meet these conditions, this technique may, with caution, serve as an approximation.
1.4 The calculations and results of this practice might be used to estimate the relative degree of hazard for experimental and research quantities of thermally unstable materials for which little experience and few data are available. Comparable calculations and results performed with data developed for well characterized materials in identical equipment, environment, and geometry are key to the ability to estimate relative hazard.
1.5 The figures-of-merit calculated as described in this practice are intended to be used only as a guide for the estimation of the relative thermal hazard potential of a system (materials, container, and surroundings). They are not intended to predict actual thermokinetic performance. The calculated errors for these parameters are an intimate part of this practice and must be provided to stress this. It is strongly recommended that those using the data provided by this practice seek the consultation of qualified personnel for proper interpretation.
1.6 The SI units are standard.
1.7 There is no ISO standard equivalent to this practice.
1.8 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-Feb-2001
• ICS: 13.230 - Explosion protection
• Technical Committee: E27 - Hazard Potential of Chemicals
• Drafting Committee: E27.02 - Thermal Stability and Condensed Phases

Relations

• Replaced By: ASTM E1231-01 - Standard Practice for Calculation of Hazard Potential Figures-of-Merit for Thermally Unstable Materials
• Effective Date: 10-Feb-2001
• Referred By: ASTM E2012-06(2020) - Standard Guide for the Preparation of a Binary Chemical Compatibility Chart
• Effective Date: 10-Feb-2001
• Referred By: ASTM E1952-23 - Standard Test Method for Thermal Conductivity and Thermal Diffusivity by Modulated Temperature Differential Scanning Calorimetry
• Effective Date: 10-Feb-2001
• Referred By: ASTM E698-23 - Standard Test Method for Kinetic Parameters for Thermally Unstable Materials Using Differential Scanning Calorimetry and the Flynn/Wall/Ozawa Method
• Effective Date: 10-Feb-2001
• Referred By: ASTM E2160-04(2018) - Standard Test Method for Heat of Reaction of Thermally Reactive Materials by Differential Scanning Calorimetry
• Effective Date: 10-Feb-2001
• Referred By: ASTM E1445-08(2015) - Standard Terminology Relating to Hazard Potential of Chemicals
• Effective Date: 10-Feb-2001
• Referred By: ASTM E1981-22 - Standard Guide for Assessing Thermal Stability of Materials by Methods of Accelerating Rate Calorimetry
• Effective Date: 10-Feb-2001
• Referred By: ASTM E2890-21 - Standard Test Method for Determination of Kinetic Parameters and Reaction Order for Thermally Unstable Materials by Differential Scanning Calorimetry Using the Kissinger and Farjas Methods
• Effective Date: 10-Feb-2001

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: E 1231 – 96a
Standard Practice for
Calculation of Hazard Potential Figures-of-Merit for
Thermally Unstable Materials
This standard is issued under the fixed designation E 1231; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This practice covers the calculation of hazard potential 2.1 ASTM Standards:
figures-of-merit for exothermic reactions, including: C 177 Test Method for Steady-State Heat Flux Measure-
(1) Time-to-thermal-runaway, ments and Thermal Transmission Properties by Means of
(2) Critical half thickness, the Guarded Hot Plate Apparatus
(3) Critical temperature, and C 518 Test Method for Steady-State Heat Flux Measure-
(4) Adiabatic decomposition temperature rise. ments and Thermal Transmission Properties by Means of
1.2 The kinetic parameters needed in this calculation may the Heat Flow Meter Apparatus
be obtained from differential scanning calorimetry (DSC) D 4351 Test Method for Measuring the Thermal Conduc-
curves by methods described in other documents. tivity of Plastics by the Evaporation-Calorimetric Method
1.3 This technique is the best applicable to simple, single E 473 Terminology Relating to Thermal Analysis
reactions whose behavior can be described by the Arrhenius E 698 Test Method for Arrhenius Kinetic Constants for
equation and the general rate law. For reactions which do not Thermally Unstable Materials
meet these conditions, this technique may, with caution, serve E 793 Test Method for Heats of Fusion and Crystallization
as an approximation. by Differential Scanning Calorimetry
1.4 The calculations and results of this practice might be
3. Terminology
used to estimate the relative degree of hazard for experimental
and research quantities of thermally unstable materials for 3.1 Definitions:
3.1.1 The definitions relating to thermal analysis appearing
which little experience and few data are available. Comparable
calculations and results performed with data developed for well in Terminology E 473 shall be considered applicable to this
practice.
characterized materials in identical equipment, environment,
and geometry are key to the ability to estimate relative hazard. 3.2 Definitions of Terms Specific to This Standard:
3.2.1 time-to-thermal-runaway, t —an estimation of the
1.5 The figures-of-merit calculated as described in this
c
practice are intended to be used only as a guide for the time required for an exothermic reaction, in an adiabatic
container, (that is, no heat gain or loss to the environment), to
estimation of the relative thermal hazard potential of a system
(materials, container, and surroundings). They are not intended reach the point of thermal runaway, expressed by Eq 1.
to predict actual thermokinetic performance. The calculated 3.2.2 critical half thickness, a—an estimation of the half
thickness of a sample in an unstirred container, in which the
errors for these parameters are an intimate part of this practice
and must be provided to stress this. It is strongly recommended heat losses to the environment are less than the retained heat.
This buildup of internal temperature leads to a thermal-
that those using the data provided by this practice seek the
consultation of qualified personnel for proper interpretation. runaway reaction, expressed by Eq 2.
1.6 This standard does not purport to address all of the
NOTE 1—This description assumes perfect heat removal at the reaction
safety concerns, if any, associated with its use. It is the
boundary. This condition is not met if the reaction takes place in an
responsibility of the user of this standard to establish appro-
insulated container such as when several containers are stacked together or
priate safety and health practices and determine the applica- when a container is boxed for shipment. These figures-of-merit underes-
timate the hazard as a result of this underestimation of thermal conduc-
bility of regulatory limitations prior to use.
tivity.
3.2.3 critical temperature, T —an estimation of the lowest
c
temperature of an unstirred container at which the heat losses
This practice is under the jurisdiction of ASTM Committee E-27 on Hazard
Potential of Chemicals and is the direct responsibility of Subcommittee E27.02 on
Thermal Stability. Annual Book of ASTM Standards, Vol 04.06.
Current edition approved Nov. 10, 1996. Published January 1997. Originally Annual Book of ASTM Standards, Vol 08.03.
published as E 1231 – 88. Last previous edition E 1231 – 96. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
E 1231
to the environment are less than the retained heat leading to a while critical temperature will be determined by the maximum-
buildup of internal temperature expressed by Eq 3. This rate process. These two processes typically have very different
temperature buildup leads to a thermal-runaway reaction. (See kinetic parameters and follow different rate-law expressions.
Note 1.) 6.4 It is believed that critical temperature, using the same
3.2.4 adiabatic decomposition temperature rise, T —an es- size and shape container, provides the best estimate of relative
d
timation of the computed temperature which a specimen would thermal hazard potential for different materials (see Section
attain if all of the enthalpy (heat) of decomposition reaction 10).
were to be absorbed by the sample itself, expressed by Eq 4.
7. Apparatus
High values represent high hazard potential.
7.1 No special apparatus is required for this calculation.
4. Summary of Practice
8. Calculation
4.1 This practice describes the calculation of four figures-
8.1 Time-to-thermal-runaway from sample initial tempera-
of-merit used to estimate the relative thermal hazard potential
ture T is defined by (see Ref (2)):
of thermally unstable materials. These figures-of-merit include
2 E/RT
C RT e
p
time-to-thermal-runaway (t ), critical half thickness (a), critical
c t 5 (1)
c
EZH
temperature (T ), and adiabatic decomposition temperature rise
c
(T ). These calculations are based upon the determined or
d where:
assumed values for activation energy (E), pre-exponential
t 5 time-to-thermal-runaway, s,
c
factor (Z), specific heat capacity (C ), thermal conductivity (l),
C 5 specific heat capacity, J/(g K),
p
p
and density or concentration (r). The activation energy and R 5 gas constant 5 8.314 J/(K mol),
pre-exponential factor may be calculated using Test Method E 5 activation energy, J/mol,
−1
Z 5 pre-exponential factor, s ,
E 698. Values for specific heat, thermal conductivity, and
H 5 enthalpy (heat) of reaction, J/g, and
concentration or density may be estimated from known values
T 5 initial temperature, K.
of model materials or through actual measurement. In addition,
8.2 Critical half thickness at environmental temperature T
certain assumptions, such as initial temperature and container o
is defined by (see Ref (3)):
geometries, must be supplied.
2 E/RT
o
dl RT e
5. Significance and Use
o
a 5 (2)
S D
HZE r
5.1 This practice provides four figures-of-merit which may
be used to estimate the relative thermal hazard potential of
where:
thermally unstable materials. Since numerous assumptions
a 5 critical half-thickness, cm,
must be made in order to obtain these figures-of-merit, care
l5 thermal conductivity, W/(cm K),
must be exercised to avoid too rigorous interpretation (or even
T 5 environment temperature, K,
o
r5 density or concentration, g/cm , and
misapplication) of the results.
d5 form factor (dimensionless) (3, 5):
5.2 This practice may be used for comparative purposes,
0.88 for infinite slab,
specification acceptance, and research. It should not be used to
2.00 for infinite cylinder,
predict actual performance.
2.53 for a cube,
6. Interferences
2.78 for a square cylinder, and
3.32 for sphere.
6.1 Since the calculations described in this practice are
8.3 Critical temperature T is defined by (see Refs (1) and
based upon assumptions and physical measurements which c
(4)):
may not always be precise, care must be used in the interpre-
2 21
tation of the results. These results should be taken as relative
R d rHZE
T 5 ln (3)
figures-of-merit and not as absolute values. c S S DD
E
T ld R
c
6.2 The values for time-to-thermal-runaway, critical half
thickness, and critical temperature are exponentially dependent
where:
upon the value of activation energy. This means that small T 5 critical temperature, K, and
c
d 5 shortest semi-thickness, cm.
imprecisions in activation energy may produce large impreci-
sions in the calculated figures-of-merit. Therefore, activation 8.4 Adiabatic decomposition temperature rise T is defined
d
by:
energy of the highest precision available should be used (1).
6.3 Many energetic materials show complex decomposi-
H
T 5 (4)
d
tions with important induction processes. Many materials are
C
p
used or shipped as an inhibited or stabilized composition,
where:
ensuring an induction process. In such cases, time-to-thermal-
T 5 adiabatic decomposition temperature rise, K.
d
runaway will be determined largely by the induction process
8.5 Methods of Obtaining Parameters:
8.5.1 The activation energy E may be obtained in accor-
dance with Test Method E 698. Other methods may be used but
The boldface numbers in parentheses refer to the list of references at the end of
this standard. must be indicated in the report.
E 1231
NOTE 2—The activation energy and pre-exponential factor are math-
H 5 2.40 kJ/g,
ematically related and must be determined from the same experimental
l5 0.00160 W/(cm K),
study.
r5 1.280 g/cm ,
d5 2.0 (for cylinder),
8.5.2 The pre-exponential factor Z may be obtained in
C 5 1.80 J/(g K),
accordance with Test Method E 698. other methods may be
p
R 5 8.314 J/(K mol),
used but must be indicated in the report. (See Note 2.)
T 5 330 K,
8.5.3 The enthalpy
...