ASTM E1231-01(2006)
(Practice)Standard Practice for Calculation of Hazard Potential Figures-of-Merit for Thermally Unstable Materials
Standard Practice for Calculation of Hazard Potential Figures-of-Merit for Thermally Unstable Materials
SIGNIFICANCE AND USE
This practice provides eight figures-of-merit which may be used to estimate the relative thermal hazard potential of thermally unstable materials. Since numerous assumptions must be made in order to obtain these figures-of-merit, care must be exercised to avoid too rigorous interpretation (or even misapplication) of the results.
This practice may be used for comparative purposes, specification acceptance, and research. It should not be used to predict actual performance.
SCOPE
1.1 This practice covers the calculation of hazard potential figures-of-merit for exothermic reactions, including:Time-to-thermal-runaway,Critical half thickness,Critical temperature,Adiabatic decomposition temperature riseExplosion potential,Shock sensitivity,Instantaneous power density, andNFPA 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.
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.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information.
Designation:E1231–01(Reapproved2006)
Standard Practice for
Calculation of Hazard Potential Figures-of-Merit for
Thermally Unstable Materials
This standard is issued under the fixed designation E1231; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.6 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
1.1 This practice covers the calculation of hazard potential
standard.
figures-of-merit for exothermic reactions, including:
1.7 There is no ISO standard equivalent to this practice.
(1) Time-to-thermal-runaway,
1.8 This standard does not purport to address all of the
(2) Critical half thickness,
safety concerns, if any, associated with its use. It is the
(3) Critical temperature,
responsibility of the user of this standard to establish appro-
(4) Adiabatic decomposition temperature rise
priate safety and health practices and determine the applica-
(5) Explosion potential,
bility of regulatory limitations prior to use.
(6) Shock sensitivity,
(7) Instantaneous power density, and
2. Referenced Documents
(8) NFPA instability rating.
2.1 ASTM Standards:
1.2 The kinetic parameters needed in this calculation may
D4351 Test Method for Measuring the Thermal Conductiv-
be obtained from differential scanning calorimetry (DSC)
ity of Plastics By the Evaporation-Calorimetric Method
curves by methods described in other documents.
C177 Test Method for Steady-State Heat Flux Measure-
1.3 This technique is the best applicable to simple, single
ments and Thermal Transmission Properties by Means of
reactions whose behavior can be described by the Arrhenius
the Guarded-Hot-Plate Apparatus
equation and the general rate law. For reactions which do not
C518 Test Method for Steady-State Thermal Transmission
meet these conditions, this technique may, with caution, serve
Properties by Means of the Heat Flow Meter Apparatus
as an approximation.
E473 Terminology Relating to Thermal Analysis and Rhe-
1.4 The calculations and results of this practice might be
ology
used to estimate the relative degree of hazard for experimental
E537 Test Method for The Thermal Stability of Chemicals
and research quantities of thermally unstable materials for
by Differential Scanning Calorimetry
whichlittleexperienceandfewdataareavailable.Comparable
E698 Test Method for Arrhenius Kinetic Constants for
calculationsandresultsperformedwithdatadevelopedforwell
Thermally Unstable Materials Using Differential Scanning
characterized materials in identical equipment, environment,
Calorimetry and the Flynn/Wall/Ozawa Method
and geometry are key to the ability to estimate relative hazard.
E793 Test Method for Enthalpies of Fusion and Crystalli-
1.5 The figures-of-merit calculated as described in this
zation by Differential Scanning Calorimetry
practice are intended to be used only as a guide for the
E1269 TestMethodforDeterminingSpecificHeatCapacity
estimation of the relative thermal hazard potential of a system
by Differential Scanning Calorimetry
(materials,container,andsurroundings).Theyarenotintended
E1952 Test Method for Thermal Conductivity and Thermal
to predict actual thermokinetic performance. The calculated
Diffusivity by Modulated Temperature Differential Scan-
errors for these parameters are an intimate part of this practice
ning Calorimetry
andmustbeprovidedtostressthis.Itisstronglyrecommended
E2041 Test Method for Estimating Kinetic Parameters by
that those using the data provided by this practice seek the
DifferentialScanningCalorimeterUsingtheBorchardtand
consultation of qualified personnel for proper interpretation.
Daniels Method
1 2
This practice is under the jurisdiction of ASTM Committee E27 on Hazard For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Potential of Chemicals and is the direct responsibility of Subcommittee E27.02 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Thermal Stability and Condensed Phases. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved April 1, 2006. Published May 2006. Originally the ASTM website.
e1 3
approved in 1988. Last previous edition approved in 2001 as E1231–01 . DOI: Withdrawn. The last approved version of this historical standard is referenced
10.1520/E1231-01R06. on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1231–01 (2006)
E2070 Test Method for Kinetic Parameters by Differential 3.2.7.1 Discussion—This practice calculates the IPD at
Scanning Calorimetry Using Isothermal Methods 250°C (482°F, 523 K).
2.2 Other Standards: 3.2.8 NFPA instability rating, IR—an index value for rank-
Publication 704, Identification of the Hazards of Materials ing, on a scale of 0 to 4, the instantaneous power density of
for Emergency Response, 1996 materials.Thegreaterthevalue,themoreunstablethematerial.
3. Terminology 4. Summary of Practice
3.1 Definitions: 4.1 This practice describes the calculation of eight figures-
3.1.1 The definitions relating to thermal analysis appearing of-merit used to estimate the relative thermal hazard potential
in Terminology E473 shall be considered applicable to this of thermally unstable materials.These figures-of-merit include
practice. time-to-thermal-runaway(t ),criticalhalfthickness(a),critical
c
3.2 Definitions of Terms Specific to This Standard: temperature (T ), adiabatic decomposition temperature rise
c
3.2.1 time-to-thermal-runaway, t —an estimation of the (T ), explosion potential (EP), shock sensitivity (SS), instanta-
c d
time required for an exothermic reaction, in an adiabatic neous power density (IPD), and instability rating (IR). These
container, (that is, no heat gain or loss to the environment), to
calculations are based upon the determined or assumed values
reach the point of thermal runaway, expressed by Eq 1. for activation energy (E), pre-exponential factor (Z), specific
3.2.2 critical half thickness, a—an estimation of the half
heat capacity (C ), thermal conductivity (l), heat of reaction
p
thickness of a sample in an unstirred container, in which the (H), and density or concentration (r). The activation energy
heat losses to the environment are less than the retained heat.
and pre-exponential factor may be calculated using Test
This buildup of internal temperature leads to a thermal- MethodE698,TestMethodE2041,orTestMethodE2070.The
runaway reaction, expressed by Eq 2.
specific heat capacity may be obtained from Test Method
3.2.2.1 Discussion—This description assumes perfect heat E1269. Thermal conductivity may be obtained from Test
removal at the reaction boundary. This condition is not met if Methods C177, C518,or D4351. Heat of reaction may be
the reaction takes place in an insulated container such as when obtained from Test Method E793. Values for concentration or
several containers are stacked together or when a container is density may be estimated from known values of model
boxed for shipment. These figures-of-merit underestimate the materials or through actual measurement. In addition, certain
hazard as a result of this underestimation of thermal conduc- assumptions, such as initial temperature and container geom-
tivity. etries, must be supplied.
3.2.3 critical temperature, T —an estimation of the lowest
c
5. Significance and Use
temperature of an unstirred container at which the heat losses
to the environment are less than the retained heat leading to a
5.1 This practice provides eight figures-of-merit which may
buildup of internal temperature expressed by Eq 3. This
be used to estimate the relative thermal hazard potential of
temperature buildup leads to a thermal-runaway reaction. (See
thermally unstable materials. Since numerous assumptions
Note 1.)
must be made in order to obtain these figures-of-merit, care
3.2.4 adiabatic decomposition temperature rise, T —an es-
must be exercised to avoid too rigorous interpretation (or even
d
timationofthecomputedtemperaturewhichaspecimenwould
misapplication) of the results.
attain if all of the enthalpy (heat) of decomposition reaction
5.2 This practice may be used for comparative purposes,
were to be absorbed by the sample itself, expressed by Eq 4.
specification acceptance, and research. It should not be used to
High values represent high hazard potential.
predict actual performance.
3.2.5 explosion potential, EP—an index value, the magni-
6. Interferences
tude and sign of which may be used to estimate the potential
for a rapid energy release that may result in an explosion.
6.1 Since the calculations described in this practice are
Positive values indicate likelihood. Negative values indicate
based upon assumptions and physical measurements which
unlikelihood. The reliability of this go-no-go indication is
may not always be precise, care must be used in the interpre-
provided by the magnitude of the numerical value.The greater
tation of the results. These results should be taken as relative
the magnitude, the more reliable the go-no-go indication.
figures-of-merit and not as absolute values.
3.2.6 shock sensitivity, SS—an estimation of the sensitivity
6.2 The values for time-to-thermal-runaway, critical half
of a material to shock induced reaction relative to
thickness,andcriticaltemperatureareexponentiallydependent
m-dinitrobenzenereferencematerial.Apositivevalueindicates
upon the value of activation energy. This means that small
greater sensitivity; a negative value less sensitivity. The reli-
imprecisions in activation energy may produce large impreci-
abilityofthisgo-no-goindicationisprovidedbythemagnitude
sions in the calculated figures-of-merit. Therefore, activation
of the numerical value. The greater the magnitude, the more
energy of the highest precision available should be used (1).
reliable the go-no-go indication.
6.3 Many energetic materials show complex decomposi-
3.2.7 instantaneous power density, IPD—the amount of
tions with important induction processes. Many materials are
energy per unit time per unit volume initially released by an
used or shipped as an inhibited or stabilized composition,
exothermic reaction.
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
Available from the National Fire Protection Association, Quincy, MA. this standard.
E1231–01 (2006)
ensuring an induction process. In such cases, time-to-thermal-
where:
runaway will be determined largely by the induction process
T = adiabatic decomposition temperature rise, K.
d
whilecriticaltemperaturewillbedeterminedbythemaximum-
8.5 Explosion potential EP is defined by (Refs 7 and 8):
rate process.These two processes typically have very different
EP 5log@H] 20.38log[T 2298K# 22.29 (5)
onset
kinetic parameters and follow different rate-law expressions.
6.4 It is believed that critical temperature, using the same
where:
EP = explosion potential, and
size and shape container, provides the best estimate of relative
T = onset temperature by DSC, K.
thermal hazard potential for different materials (see Section
onset
8.6 Shock sensitivity SS is defined by (Ref 7):
10).
SS 5log@H] 20.72log@T 2298K# 21.60 (6)
onset
7. Apparatus
where:
7.1 No special apparatus is required for this calculation.
SS = shock sensitivity relative to m-dinitrobenzene.
8.7 Instantaneous power density at 250°C is defined by
8. Calculation
(NFPA 704):
8.1 Time-to-thermal-runaway from sample initial tempera-
IPD 5HZ rexp@2E/523K R] (7)
ture T is defined by (see Ref (2)):
8.8 Instability rating is defined by Table 1 (NFPA 704).
2 E/RT
C RT e
p
t 5 (1)
c
EZH
TABLE 1 NPFA Instability Rating
Instability Rating Instantaneous Power Density at 523 K
where: −1
4 1000 W mL or greater
−1
t = time-to-thermal-runaway, s, 3 at or greater than 100 W mL and below 1000 W
c
−1
mL
C = specific heat capacity, J/(g K),
p
−1 −1
2 at or greater than 10 W mL and below 100 W mL
R = gas constant=8.314 J/(K mol),
−1 −1
1 at or greater than 0.01 W mL and below 10 W mL
E = activation energy, J/mol, −1
0 below 0.01 W mL
−1
Z = pre-exponential factor, s ,
H = enthalpy (heat) of reaction, J/g, and
T = initial temperature, K.
8.9 Methods of Obtaining Parameters:
8.2 Critical half thickness at environmental temperature T
o
8.9.1 The activation energy E and frequency factory Z may
is defined by (see Ref (3)):
be obtained byTest Method E698,Test Method E2041, orTest
Method E2070. Other methods may be used but shall be
2 E/RT
o
dlRT e 2
o
reported.
a 5 (2)
S D
HZE r
NOTE 1—In Test Method E698 and Test Method E2041, the activation
energy and pre-exponential are mathematically related and must be
where:
determined from the same experimental study.
a = critical half-thickness, cm,
8.9.2 The enthalpy (heat) of reaction H may be obtained by
l = thermal conductivity, W/(cm K),
Test Method E793 or E537. Other methods may be used but
T = environment temperature, K,
o
shall be reported.
r = density or concentration, g/cm , and
8.9.3 Room temperature specific heat capacity, C , may be
d = form factor (dimensionless) (3, 5): p
obtained by Test Method E1269.
0.88 for infinite slab,
8.9.4 Environment temperature T is taken to be the tem-
o
2.00 for infinite cylinder,
perature of the air space surrounding the unstirred container.
2.53 for a cube,
8.9.5 Concentrationordensityofmaterial ristheamountof
2.78 for a square cylinder, and
reactivematerialperunitvolume.Thevalueof1.28g/cm may
3.32 for sphere.
be assumed for many organic materials.
8.3 Critical temperature T is defined by (see Refs (1) and
c
8.9.6 The form factor d is a dimensionless unit used to
(4)):
correct for the type of geometry for the unstirred container.
2 21
R d rHZE Five cases are ordinarily used, including:
T 5 ln (3)
c S S DD
E
(1) 0.88 for an infinite slab—essentially a two dimensional
T ld R
c
plane,
(2) 2.00 for a cylinder of infinite height,
where:
(3) 2.53 for a cube,
T = critical temperature, K, and
c
d = shortest semi-thickness, cm.
8.4 Adiabatic decomposition temperature rise T is defined
ReprintedwithpermissionfromNFPA704-1996,“IdentificationoftheHazards
d
of Materials for Emergency Response,” copyright r 1996, National Fire Protection
by:
Association, Quincy, MA. This reprinted material is not the complete and official
H
position of the NFPA on the referenced subject which is represented only by the
T 5 (4)
d
C standard in its entirety.
p
E1231–01 (2006)
(4) 2.78 for a square cylinder, and
...
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