1、Designation: E1231 10Standard Practice forCalculation of Hazard Potential Figures-of-Merit forThermally Unstable Materials1This standard is issued under the fixed designation E1231; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the calculation of hazard potentialfigures-of-merit for exothermic reactions, includin
3、g:(1) Time-to-thermal-runaway,(2) Time-to-maximum-rate,(3) Critical half thickness,(4) Critical temperature,(5) Adiabatic decomposition temperature rise,(6) Explosion potential,(7) Shock sensitivity,(8) Instantaneous power density, and(9) NFPA instability rating.1.2 The kinetic parameters needed in
4、this 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 no
5、tmeet 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
6、are available. 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
7、 only 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 st
8、ress this. It is strongly recommendedthat those using the data provided by this practice seek theconsultation of qualified personnel for proper interpretation.1.6 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 There is no I
9、SO standard equivalent to this practice.1.8 This standard does not purport to address all of thesafety 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
10、limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded-Hot-Plate ApparatusC518 Test Method for Steady-State Thermal TransmissionProperties by Means of the Heat Flow Meter
11、 ApparatusE473 Terminology Relating to Thermal Analysis and Rhe-ologyE537 Test Method for The Thermal Stability of Chemicalsby Differential Scanning CalorimetryE698 Test Method for Arrhenius Kinetic Constants forThermally Unstable Materials Using Differential ScanningCalorimetry and the Flynn/Wall/O
12、zawa MethodE793 Test Method for Enthalpies of Fusion and Crystalli-zation by Differential Scanning CalorimetryE1269 Test Method for Determining Specific Heat Capacityby Differential Scanning CalorimetryE1952 Test Method for Thermal Conductivity and ThermalDiffusivity by Modulated Temperature Differe
13、ntial Scan-ning CalorimetryE2041 Test Method for Estimating Kinetic Parameters byDifferential Scanning Calorimeter Using the Borchardt andDaniels MethodE2070 Test Method for Kinetic Parameters by DifferentialScanning Calorimetry Using Isothermal Methods1This practice is under the jurisdiction of AST
14、M Committee E27 on HazardPotential of Chemicals and is the direct responsibility of Subcommittee E27.02 onThermal Stability and Condensed Phases.Current edition approved April 15, 2010. Published May 2010. Originallyapproved in 1988. Last previous edition approved in 2006 as E1231 01 (2006).DOI: 10.
15、1520/E1231-10.2For 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 Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor
16、Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2.2 Other Standards:NFPA 704 Identification of the Hazards of Materials forEmergency Response, 199633. Terminology3.1 Definitions:3.1.1 The definitions relating to thermal analysis appearingin Terminology E473 shall be considered ap
17、plicable to thispractice.3.2 Definitions of Terms Specific to This Standard:3.2.1 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 be absorbed by the sample itself, expre
18、ssed by Eq 5.High values represent high hazard potential.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 thermal-runawa
19、y reaction, expressed by Eq 3.3.2.2.1 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. These fi
20、gures-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 of interna
21、l temperature expressed by Eq 4. Thistemperature buildup leads to a thermal-runaway reaction. (SeeNote 3.)3.2.4 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 indi
22、cate likelihood. 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.3.2.5 instantaneous power density, IPDthe amount ofenergy per unit time per unit
23、volume initially released by anexothermic reaction.3.2.5.1 DiscussionThis practice calculates the IPD at250 C (482 F, 523 K).3.2.6 NFPA instability rating, IRan index value for rank-ing, on a scale of 0 to 4, the instantaneous power density ofmaterials.The greater the value, the more unstable the ma
24、terial.3.2.7 shock sensitivity, SSan estimation of the sensitivityof a material to shock induced reaction 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 ma
25、gnitudeof the numerical value. The greater the magnitude, the morereliable the go-no-go indication.3.2.8 time-to-maximum-rate, TMRan estimate of the timerequired for an exothermic reaction, in an adiabatic container(that is, no heat gain or loss to the environment), to reach themaximum rate of react
26、ion, expressed by Eq 2.3.2.9 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 environment), toreach the point of thermal runaway, expressed by Eq 1.4. Summary of Practice4.1 This practice describes
27、 the calculation of nine figures-of-merit used to estimate the relative thermal hazard potentialof thermally unstable materials. These figures-of-merit includetime-to-thermal-runaway (tc), time-to-maximum-rate (TMR),critical half thickness (a), critical temperature (Tc), adiabaticdecomposition tempe
28、rature rise (Td), explosion potential (EP),shock sensitivity (SS), instantaneous power density (IPD), andinstability rating (IR). These calculations are based upon thedetermined or assumed values for activation energy (E),pre-exponential factor (Z), specific heat capacity (Cp), thermalconductivity (
29、l), heat of reaction (H), heat flow rate (q) anddensity or concentration (r). The activation energy and pre-exponential factor may be calculated using Test Methods E698,E2041,orE2070. The specific heat capacity may be obtainedfrom Test Method E1269. Thermal conductivity may beobtained from Test Meth
30、ods C177, C518,orE1952. Heat ofreaction may be obtained from Test Method E793. Heat flowrate may be obtained from Test Method E2070, 13.5, where itis called dH/dt. Values for concentration or density may beestimated from known values of model materials or throughactual measurement. In addition, cert
31、ain assumptions, such asinitial temperature and container geometries, must be supplied.5. Significance and Use5.1 This practice provides nine figures-of-merit which maybe used to estimate the relative thermal hazard potential ofthermally unstable materials. Since numerous assumptionsmust be made in
32、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 topredict actual performance.6. Interferences
33、6.1 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 not as absolute values.6.2 The values for t
34、ime-to-thermal-runaway, critical halfthickness, and critical temperature are exponentially dependent3Available from National Fire Protection Association (NFPA), 1 BatterymarchPark, Quincy, MA 02169-7471, http:/www.nfpa.org.E1231 102upon the value of activation energy. This means that smallimprecisio
35、ns in activation energy may produce large impreci-sions in the calculated figures-of-merit. Therefore, activationenergy of the highest precision available should be used (1).46.3 Many energetic materials show complex decomposi-tions with important induction processes. Many materials areused or shipp
36、ed as an inhibited or stabilized composition,ensuring an induction process. In such cases, 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 pa
37、rameters and follow different rate-law expressions.6.4 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).6.5 Extrapolation of TMR to temperatures below thoseactually
38、 measured shall be done only with caution due to thepotential changes in kinetics (activation energy), the potentialfor autocatalysis, and the propagation of errors.7. Apparatus7.1 No special apparatus is required for this calculation.8. Calculation8.1 Time-to-thermal-runaway from sample initial tem
39、pera-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 = pre-exponential factor, s1,H = enthalpy (heat) of reaction, J/g, andT = initial temperature, K.NOTE 1
40、Time-to-thermal-runaway is related to time-to-maximum-ratebut assumes a first order reaction.8.2 Time-to-maximum-rate, TMR, is defined by (see Refs(1) and (3):CpRT12/ Eq (2)where:T1= initial temperature, K (that is, the temperature atwhich TMR is to be estimated), andq = mass normalized heat flow ra
41、te at (T1), W/g.NOTE 2Time-to-maximum-rate is related to time-to-thermal-runawaybut assumes a zeroth order reaction.8.3 Critical half thickness at environmental temperature Tois defined by (see Ref (4):a 5 SdlRTo2eE/RToHZErD12(3)where:a = critical half-thickness, cm;l = thermal conductivity, W/(cm K
42、);To= environment temperature, K;r = density or concentration, g/cm3; andd = form factor (dimensionless) (4, 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.8.4 Critical temperature Tcis defined by (see Refs (1) and(6):Tc5SRElnSd2r
43、HZET2cldRDD21(4)where:Tc= critical temperature, K, andd = shortest semi-thickness, cm.8.5 Adiabatic decomposition temperature rise Tdis definedby:Td5HCp(5)where:Td= adiabatic decomposition temperature rise, K.8.6 Explosion potential EP is defined by (7, 8):EP 5 logH 2 0.38 log Tonset2 298 K# 2 2.29
44、(6)where:EP = explosion potential, andTonset= onset temperature by DSC, K.8.7 Shock sensitivity SS is defined by (7):SS 5 logH 2 0.72 logTonset2 298 K# 2 1.60 (7)where:SS = shock sensitivity relative to m-dinitrobenzene.8.8 Instantaneous power density at 250 C is defined by(NFPA 704):5IPD 5 HZr exp2
45、E/523 K R (8)8.9 Instability rating is defined by Table 1 (NFPA 704).4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.5Reprinted with permission from NFPA 7041996, “Identification of the Haz-ards of Materials for Emergency Response,” copyright r 1996, N
46、ational FireProtectionAssociation, Quincy, MA. This reprinted material is not the complete andofficial position of the NFPAon the referenced subject which is represented only bythe standard in its entirety.TABLE 1 NPFA Instability RatingInstability Rating Instantaneous Power Density at 523 K4 1000 W
47、 mL1or greater3 at or greater than 100 W mL1and below 1000 WmL12 at 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 mL1E1231 1038.10 Methods of Obtaining Parameters:8.10.1 The activation energy E and frequency factor Z maybe obtained by Test
48、 Methods E698, E2041,orE2070. Othermethods may be used but shall be reported.NOTE 3In Test Methods E698 and E2041, the activation energy andpre-exponential are mathematically related and must be determined fromthe same experimental study.8.10.2 The enthalpy (heat) of reaction H may be obtained byTes
49、t Methods E793 or E537. Other methods may be used butshall be reported.8.10.3 Room temperature specific heat capacity, Cp, may beobtained by Test Method E1269.8.10.4 Environment temperature Tois taken to be thetemperature of the air space surrounding the unstirred con-tainer.8.10.5 Concentration or density of material r is the amountof reactive material per unit volume. The value of 1.28 g/cm3may be assumed for many organic materials.8.10.6 The form factor d is a dimensionless unit used tocorrect for the type of geometry for the unstirred co
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