1、Designation: E 1231 01 (Reapproved 2006)Standard Practice forCalculation of Hazard Potential Figures-of-Merit forThermally Unstable Materials1This standard is issued under the fixed designation E 1231; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、 case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the calculation of hazard potentialfigures-of-merit for exothermi
3、c 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
4、calculation maybe obtained from differential scanning calorimetry (DSC)curves by methods described in other documents.1.3 This technique is the best applicable to simple, singlereactions whose behavior can be described by the Arrheniusequation and the general rate law. For reactions which do notmeet
5、 these conditions, this technique may, with caution, serveas an approximation.1.4 The calculations and results of this practice might beused to estimate the relative degree of hazard for experimentaland research quantities of thermally unstable materials forwhich little experience and few data are a
6、vailable. Comparablecalculations and results performed with data developed for wellcharacterized 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 thispractice are intended to be used only
7、 as a guide for theestimation of the relative thermal hazard potential of a system(materials, container, and surroundings). They are not intendedto predict actual thermokinetic performance. The calculatederrors for these parameters are an intimate part of this practiceand must be provided to stress
8、this. It is strongly recommendedthat those using the data provided by this practice seek theconsultation 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 thesaf
9、ety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 4351 Test Method for Measurin
10、g the Thermal Conduc-tivity of Plastics By the Evaporation-Calorimetric Method3C 177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded-Hot-Plate ApparatusC 518 Test Method for Steady-State Thermal TransmissionProperties by Means of the He
11、at Flow Meter ApparatusE 473 Terminology Relating to Thermal Analysis and Rhe-ologyE 537 Test Method for The Thermal Stability Of ChemicalsBy Differential Scanning CalorimetryE 698 Test Method for Arrhenius Kinetic Constants forThermally Unstable Materials Using Differential ScanningCalorimetry and
12、the Flynn/Wall/Ozawa MethodE 793 Test Method for Enthalpies of Fusion and Crystalli-zation by Differential Scanning CalorimetryE 1269 Test Method for Determining Specific Heat Capac-ity by Differential Scanning CalorimetryE 1952 Test Method for Thermal Conductivity and ThermalDiffusivity by Modulate
13、d Temperature Differential Scan-ning CalorimetryE 2041 Method for Estimating Kinetic Parameters by Dif-ferential Scanning Calorimeter Using the Borchardt andDaniels MethodE 2070 Test Method for Kinetic Parameters by DifferentialScanning Calorimetry Using Isothermal Methods2.2 Other Standards:Publica
14、tion 704, Identification of the Hazards of Materialsfor Emergency Response, 199641This practice is under the jurisdiction of ASTM Committee E27 on HazardPotential of Chemicals and is the direct responsibility of Subcommittee E27.02 onThermal Stability.Current edition approved April 1, 2006. Publishe
15、d May 2006. Originallyapproved in 1988. Last previous edition approved in 2001 as E 1231 01e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document
16、 Summary page onthe ASTM website.3Withdrawn.4Available from the National Fire Protection Association, Quincy, MA.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3. Terminology3.1 Definitions:3.1.1 The definitions relating to thermal
17、analysis appearingin Terminology E 473 shall be considered applicable to thispractice.3.2 Definitions of Terms Specific to This Standard:3.2.1 time-to-thermal-runaway, tcan estimation of thetime required for an exothermic reaction, in an adiabaticcontainer, (that is, no heat gain or loss to the envi
18、ronment), toreach the point of thermal runaway, expressed by Eq 1.3.2.2 critical half thickness, aan estimation of the halfthickness of a sample in an unstirred container, in which theheat losses to the environment are less than the retained heat.This buildup of internal temperature leads to a therm
19、al-runaway reaction, expressed by Eq 2.3.2.2.1 DiscussionThis description assumes perfect heatremoval at the reaction boundary. This condition is not met ifthe reaction takes place in an insulated container such as whenseveral containers are stacked together or when a container isboxed for shipment.
20、 These figures-of-merit underestimate thehazard as a result of this underestimation of thermal conduc-tivity.3.2.3 critical temperature, Tcan estimation of the lowesttemperature of an unstirred container at which the heat lossesto the environment are less than the retained heat leading to abuildup o
21、f internal temperature expressed by Eq 3. Thistemperature buildup leads to a thermal-runaway reaction. (SeeNote 1.)3.2.4 adiabatic decomposition temperature rise, Tdan es-timation of the computed temperature which a specimen wouldattain if all of the enthalpy (heat) of decomposition reactionwere to
22、be absorbed by the sample itself, expressed by Eq 4.High values represent high hazard potential.3.2.5 explosion potential, EPan index value, the magni-tude and sign of which may be used to estimate the potentialfor a rapid energy release that may result in an explosion.Positive values indicate likel
23、ihood. Negative values indicateunlikelihood. The reliability of this go-no-go indication isprovided by the magnitude of the numerical value. The greaterthe magnitude, the more reliable the go-no-go indication.3.2.6 shock sensitivity, SSan estimation of the sensitivityof a material to shock induced r
24、eaction relative tom-dinitrobenzene reference material.Apositive value indicatesgreater sensitivity; a negative value less sensitivity. The reli-ability of this go-no-go indication is provided by the magnitudeof the numerical value. The greater the magnitude, the morereliable the go-no-go indication
25、.3.2.7 instantaneous power density, IPDthe amount ofenergy per unit time per unit volume initially released by anexothermic reaction.3.2.7.1 DiscussionThis practice calculates the IPD at250C (482F, 523 K).3.2.8 NFPA instability rating, IRan index value for rank-ing, on a scale of 0 to 4, the instant
26、aneous power density ofmaterials.The greater the value, the more unstable the material.4. Summary of Practice4.1 This practice describes the calculation of eight figures-of-merit used to estimate the relative thermal hazard potentialof thermally unstable materials. These figures-of-merit includetime
27、-to-thermal-runaway (tc), critical half thickness (a), criticaltemperature (Tc), adiabatic decomposition temperature rise(Td), explosion potential (EP), shock sensitivity (SS), instanta-neous power density (IPD), and instability rating (IR). Thesecalculations are based upon the determined or assumed
28、 valuesfor activation energy (E), pre-exponential factor (Z), specificheat capacity (Cp), thermal conductivity (l), heat of reaction(H), and density or concentration (r). The activation energyand pre-exponential factor may be calculated using TestMethod E 698, Method E 2041, or Test Method E 2070. T
29、hespecific heat capacity may be obtained from Test MethodE 1269. Thermal conductivity may be obtained from TestMethods C 177, C 518, D 4351,orE 1952. Heat of reactionmay be obtained from Test Method E 793. Values for concen-tration or density may be estimated from known values ofmodel materials or t
30、hrough actual measurement. In addition,certain assumptions, such as initial temperature and containergeometries, must be supplied.5. Significance and Use5.1 This practice provides eight figures-of-merit which maybe used to estimate the relative thermal hazard potential ofthermally unstable materials
31、. Since numerous assumptionsmust be made in order to obtain these figures-of-merit, caremust be exercised to avoid too rigorous interpretation (or evenmisapplication) of the results.5.2 This practice may be used for comparative purposes,specification acceptance, and research. It should not be used t
32、opredict actual performance.6. Interferences6.1 Since the calculations described in this practice arebased upon assumptions and physical measurements whichmay not always be precise, care must be used in the interpre-tation of the results. These results should be taken as relativefigures-of-merit and
33、 not as absolute values.6.2 The values for time-to-thermal-runaway, critical halfthickness, and critical temperature are exponentially dependentupon the value of activation energy. This means that smallimprecisions in activation energy may produce large impreci-sions in the calculated figures-of-mer
34、it. Therefore, activationenergy of the highest precision available should be used (1).56.3 Many energetic materials show complex decomposi-tions with important induction processes. Many materials areused or shipped as an inhibited or stabilized composition,ensuring an induction process. In such case
35、s, time-to-thermal-runaway will be determined largely by the induction processwhile critical temperature will be determined by the maximum-rate process. These two processes typically have very differentkinetic parameters and follow different rate-law expressions.5The boldface numbers in parentheses
36、refer to the list of references at the end ofthis standard.E 1231 01 (2006)26.4 It is believed that critical temperature, using the samesize and shape container, provides the best estimate of relativethermal hazard potential for different materials (see Section10).7. Apparatus7.1 No special apparatu
37、s is required for this calculation.8. Calculation8.1 Time-to-thermal-runaway from sample initial tempera-ture T is defined by (see Ref (2):tc5CpRT2eE/RTEZH(1)where:tc= time-to-thermal-runaway, s,Cp= specific heat capacity, J/(g K),R = gas constant = 8.314 J/(K mol),E = activation energy, J/mol,Z = p
38、re-exponential factor, s1,H = enthalpy (heat) of reaction, J/g, andT = initial temperature, K.8.2 Critical half thickness at environmental temperature Tois defined by (see Ref (3):a 5 SdlRTo2eE/RToHZErD12(2)where:a = critical half-thickness, cm,l = thermal conductivity, W/(cm K),To= environment temp
39、erature, K,r = density or concentration, g/cm3, andd = form factor (dimensionless) (3, 5):0.88 for infinite slab,2.00 for infinite cylinder,2.53 for a cube,2.78 for a square cylinder, and3.32 for sphere.8.3 Critical temperature Tcis defined by (see Refs (1) and(4):Tc5SRElnSd2r HZET2cldRDD21(3)where:
40、Tc= critical temperature, K, andd = shortest semi-thickness, cm.8.4 Adiabatic decomposition temperature rise Tdis definedby:Td5HCp(4)where:Td= adiabatic decomposition temperature rise, K.8.5 Explosion potential EP is defined by (Refs 7 and 8):EP 5 logH 2 0.38 log Tonset2 298 K# 2 2.29 (5)where:EP =
41、explosion potential, andTonset= onset temperature by DSC, K.8.6 Shock sensitivity SS is defined by (Ref 7):SS 5 logH 2 0.72 logTonset2 298 K# 2 1.60 (6)where:SS = shock sensitivity relative to m-dinitrobenzene.8.7 Instantaneous power density at 250C is defined by(NFPA 704):6IPD 5 HZr exp2E/523 K R (
42、7)8.8 Instability rating is defined by Table 1 (NFPA 704).8.9 Methods of Obtaining Parameters:8.9.1 The activation energy E and frequency factory Z maybe obtained by Test Method E 698, Method E 2041, or TestMethod E 2070. Other methods may be used but shall bereported.NOTE 1In Test Method E 698, Met
43、hod E 2041, or Test MethodE 2070, the activation energy and pre-exponential are mathematicallyrelated and must be determined from the same experimental study.8.9.2 The enthalpy (heat) of reaction H may be obtained byTest Method E 793 or E 537. Other methods may be used butshall be reported.8.9.3 Roo
44、m temperature specific heat capacity, Cp, may beobtained by Test Method E 1269.8.9.4 Environment temperature Tois taken to be the tem-perature of the air space surrounding the unstirred container.8.9.5 Concentration or density of material r is the amount ofreactive material per unit volume. The valu
45、e of 1.28 g/cm3maybe assumed for many organic materials.8.9.6 The form factor d is a dimensionless unit used tocorrect for the type of geometry for the unstirred container.Five cases are ordinarily used, including:(1) 0.88 for an infinite slabessentially a two dimensionalplane,(2) 2.00 for a cylinde
46、r of infinite height,(3) 2.53 for a cube,(4) 2.78 for a square cylinder, and(5) 3.32 for a sphere.6Reprinted with permission from NFPA704-1996, “Identification of the Hazardsof Materials for Emergency Response,” copyright r 1996, National Fire ProtectionAssociation, Quincy, MA. This reprinted materi
47、al is not the complete and officialposition of the NFPA on the referenced subject which is represented only by thestandard in its entirety.TABLE 1 NPFA Instability RatingInstability Rating Instantaneous Power Density at 523 K4 1000 W mL1or greater3 at or greater than 100 W mL1and below 1000 WmL12 at
48、 or greater than 10 W mL1and below 100 W mL11 at or greater than 0.01 W mL1and below 10 W mL10 below 0.01 W mL1E 1231 01 (2006)38.9.7 Thermal conductivity l may be obtained by TestMethods E 1952, D 4351, C 177, or C 518 or by estimationfrom literature values of model compounds.Avalue of 0.00040Wcm1K
49、1may be assumed for many organic solid materials.NOTE 2The actual thermal conductivity of a material is quite depen-dent upon the form of the materialpowder, fiber, solid, etc.The value maybe as much as a factor of 10 lower than literature values depending uponpacking.8.9.8 The shortest half-thickness d is the distance from thecenter of the container to the outside in its shortest dimension.8.9.9 Onset temperature, Tonset, shall be obtained by TestMethod E 537 or similar DSC methods.8.10 The values for time-to-thermal-runaway, critical thick-n
