1、Designation: E1981 98 (Reapproved 2012)2Standard Guide forAssessing Thermal Stability of Materials by Methods ofAccelerating Rate Calorimetry1This standard is issued under the fixed designation E1981; 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 () indicates an editorial change since the last revision or reapproval.1NOTEEditorial corrections were made to source and reference information in December 2012.2NOTEEdito
3、rial corrections were made throughout in June 2013.INTRODUCTIONThis guide is one of several standards being developed by ASTM Committee E27 for determiningthe physicochemical hazards of chemicals and chemical mixtures. This guide should be used inconjunction with other test methods, as a complete as
4、sessment of the hazard potential of chemicalsmust take into account a number of realistic factors not necessarily considered in this guide. Theexpression hazard potential as used by this committee is defined as the degree of susceptibility ofmaterial to ignition or release of energy under varying en
5、vironmental conditions.It is the intent of this guide to include any calorimetric device consistent with the principles ofadiabatic calorimetry. Device-specific information and specifications are located in appendices to theguide. Any reference to specific devices in the guide are for purposes of il
6、lustration or clarity only.1. Scope1.1 This guide covers suggested procedures for the opera-tion of a calorimetric device designed to obtain temperatureand pressure data as a function of time for systems undergoinga physicochemical change under nearly adiabatic conditions.1.2 This guide outlines the
7、 calculation of thermodynamicparameters from the time, temperature, and pressure datarecorded by a calorimetric device.1.3 The assessment outlined in this guide may be used overa pressure range from full vacuum to the rated pressure of thereaction container and pressure transducer. The temperaturera
8、nge of the calorimeter typically varies from ambient to500C, but also may be user specified (see 6.6).1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This statement does not purport to address all of thesafety concerns,
9、if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety practices and to determine the applicability ofregulatory limitations prior to use. Specific safety precautionsare outlined in Section 7.2. Referenced Documents2.1 ASTM Standards:2E
10、476 Test Method for Thermal Instability of Confined Con-densed Phase Systems (Confinement Test) (Withdrawn2008)3E487 Test Method for Constant-Temperature Stability ofChemical MaterialsE537 Test Method for The Thermal Stability of Chemicalsby Differential Scanning CalorimetryE680 Test Method for Drop
11、 Weight Impact Sensitivity ofSolid-Phase Hazardous MaterialsE698 Test Method for Arrhenius Kinetic Constants forThermally Unstable Materials Using Differential Scan-ning Calorimetry and the Flynn/Wall/Ozawa MethodE1231 Practice for Calculation of Hazard Potential Figures-of-Merit for Thermally Unsta
12、ble Materials3. Terminology3.1 Definitions of Terms Specific to This Standard:1This guide is under the jurisdiction of ASTM Committee E27 on HazardPotential of Chemicals and is the direct responsibility of Subcommittee E27.02 onThermal Stability and Condensed Phases.Current edition approved Dec. 1,
13、2012. Published December 2012. Originallypublished in 1998. Last previous edition approved in 2004 as E1981 98 (2004).DOI: 10.1520/E1981-98R12E02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards
14、 volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1 adiabatic c
15、alorimeter, nan instrument capable ofmaking calorimetric measurements while maintaining a mini-mal heat loss or gain between the sample and its environment,which is verifiable by the capability to continuously measurethe temperature differential between the sample and its sur-roundings.3.1.2 autocat
16、alytic reaction, na chemical reaction inwhich a product or reaction intermediate functions as acatalyst.3.1.3 drift, na gradual unintended increase or decrease inthe system (sample container and surroundings) temperaturedue to limitations in the system calibration, or to changeswhich occur in the sy
17、stem after calibration.3.1.4 final temperature (Tfinal),nthe observed systemtemperature at the end of an exotherm, generally at thetemperature where the self-heat rate of the reaction hasdecreased below the operator-defined slope sensitivity thresh-old.3.1.5 heat of reaction (H), nthe net calculated
18、 heat(energy) liberated during an exothermic reaction.3.1.6 ideal adiabatic temperature rise (Tad), nthe tem-perature rise which would be observed in an exothermicreaction if all of the heat liberated were used to increase thetemperature of only the sample. It is conveniently calculated asthe produc
19、t of the observed adiabatic temperature rise, Tobs,and the thermal inertia factor, .3.1.7 observed adiabatic temperature rise (Tobs), ntheobserved temperature rise in the system during an exotherm;mathematically, it is equal to the temperature difference be-tween the final temperature and the onset
20、temperature of anexotherm.3.1.8 onset temperature (Tstart),nthe observed systemtemperature at the start of an exotherm where the self-heatingrate first exceeds the operator-defined slope sensitivitythreshold, usually 0.02C/min; the onset temperature is not afundamental property of a substance, but i
21、s apparatus-dependent, based upon the inherent sensitivity of the calori-metric system.3.1.9 self-heating, adjany exothermic process which in-creases the temperature of the system by the self absorption ofthe liberated heat.3.1.10 thermal inertia factor (), n a correction factorapplied to time and t
22、emperature differences observed in exo-thermic reactions in the system (sample and container) undertest, which accounts for the sensible heat absorbed by thesample container that otherwise would lead to erroneously lowheats of reaction and adiabatic temperature rise, as well as toerroneously high ti
23、me to maximum rates (TMRs) (see 3.1.12).See also 10.1 for a mathematical formula definition of thethermal inertia factor.3.1.11 thermal runaway reaction, na chemical reaction inwhich the heat generation rate in a system exceeds the heatremoval rate of that system.3.1.12 time-to-maximum rate (TMR), n
24、the amount of timethat is needed for a reaction to reach its maximum self-heatingrate or pressure rate in a thermal runaway reaction, normallyreferenced from the time corresponding to the onsettemperature, but may also be referenced from any time-temperature point to the time at which the maximum se
25、lf-heating or pressure rate occurs. The experimentally observedTMR is normally divided by the thermal inertia factor (see3.1.10) to obtain a more conservative assessment of TMR.(TMR divided by the thermal inertia factor is often referred toas the “-corrected” TMR).4. Summary of Guide4.1 A sample is
26、placed in a reaction container and posi-tioned in the calorimeter (see Fig. 1).4.2 The bomb is heated to a user-specified initial tempera-ture and allowed to come to equilibrium, whereupon a searchfor evidence of an exothermic reaction is undertaken. Anexotherm is considered to have occurred when th
27、e user-specified rate of temperature rise is first exceeded. If noexotherm is detected, the system temperature is raised aspecified increment and the system allowed to equilibrateagain. This heat-wait-search cycle is repeated until either anexotherm is detected or the upper temperature limit of the
28、testis reached. If an exotherm is detected, the surroundings arekept at the same temperature as the reaction container, allowingthe system to be maintained without heat loss as the tempera-ture of the system increases due to the heat evolved during theexotherm.4.3 Time, temperature, and pressure dat
29、a are recorded atspecified temperature intervals as a function of time. Addi-tional user-selected parameters may also be recorded or stored.4.4 The recorded data are used to calculate the time rates ofchanges of pressure and temperature. These data may also beused to calculate a time-to-maximum rate
30、 (as defined in 3.1.12)and to obtain kinetic parameters (1-4)4for simple, non-autocatalytic exothermic reactions using the equations speci-fied in the vendors manual (subject to the limitations of 6.5).These data may also be adjusted for the sample- and container-specific heats to calculate an adiab
31、atic temperature rise andheat of reaction.5. Significance and Use5.1 The data from this guide seldom, if ever, directlysimulate thermal and pressure events in the processing, storage,and shipping of chemicals. However, the data obtained fromthis guide may be used, with suitable precautions, to predi
32、ct thethermal and pressure hazards associated with processing,storage, and shipping of a chemical or mixture of chemicalsafter appropriate scaling of the data. This has been addressed inthe literature (1-4) but is beyond the scope of this guide.5.2 This guide is suitable, under the proper conditions
33、, forthe investigation of the effects of catalyst, inhibitors, initiators,reaction atmospheres, materials of construction, or, ifavailable, agitation (see 6.1.2).4The boldface numbers in parentheses refer to the list of references found at theend of this practice.E1981 98 (2012)225.3 Interpretation
34、of the time-temperature or time-pressuredata may be possible for relatively simple systems through theuse of suitable temperature-dependent kinetic theories such asthe Arrhenius and Absolute Reaction Rate theories (5-6).6. Limitations6.1 This guide requires good heat transfer within the sampleand be
35、tween the sample and the container and, therefore, issubject to the following limitations:6.1.1 Solid samples or systems where heat transfer couldbecome rate-limiting may not yield quantitatively reliable orconsistent results, and6.1.2 Heterogeneous systems may not give meaningfulresults. A qualitat
36、ive indication of change in reaction rate maybe obtained by (optional) agitation, but the observed reactionrates may be strongly dependent on the rate and efficiency ofthe agitation. Loss of agitation may also affect observedreaction rates.6.2 Accurate tracking of very high or very low self-heatrate
37、s may not be quantitatively reliable and is equipmentdependent.6.3 Endothermic reactions can be observed but generally arenot quantitatively measured.6.4 The determination of enthalpies of reaction is based onan accurate knowledge of the (temperature-dependent) heatcapacities of the reactants, produ
38、cts, and container. The calcu-lation is also dependent on the temperature tracking accuracyof the system (see 6.2).6.5 The use of the equations specified for the determinationof kinetic parameters (see, for example, Appendix X1) may notbe suitable in many instances, especially when multiple reac-tio
39、ns are involved.6.6 Data may be obtained in the temperature range consis-tent with the calorimeters specifications and at pressures up tothose consistent with the limitation of the pressure transduceror the material of construction of the bomb.6.7 Modifications to the calorimeter can significantly a
40、lterthe performance of the instrument. It is the users responsibilityto assure that modifications do not alter the precision oraccuracy of the instrument.6.8 If the thermal inertia () factor for the experiment differssignificantly from that of the system it is intended to simulate,any reaction mecha
41、nism observed experimentally may not bethe same as the true reaction mechanism that exists in thesystem being simulated.6.9 In the determination of kinetic parameters, the possibil-ity of autocatalytic reaction mechanisms must be considered.7. Hazards7.1 The thermal stability characteristics, impact
42、characteristics, (see Test Method E476, E487, E537, E680, andE698, Practice E1231 and Ref. 7), or friction sensitivitycharacteristics of the sample, or a combination thereof, shouldbe assessed, as it is often necessary to grind (see Note 1)orcompact the sample prior to or during loading into the sam
43、plecontainer. Additional physical properties of the sample mayalso need to be determined, such as sensitivity to electrostaticdischarge.NOTE 1Caution should be used in grinding sample materials, aspolymorphic changes can occur, thus altering the nature of the sample.7.2 If the device incorporates a
44、pressure-relief device, itshould be periodically inspected for possible corrosion orphysical damage, which may result in improper operation.FIG. 1 Example Calorimeter and Reaction ContainerE1981 98 (2012)237.3 Operation of the relief device or rupture of the bombmay result in the release of toxic or
45、 noxious fumes, which mayescape into the immediate operating area. The calorimeter,therefore, should be properly vented.7.4 When venting the sample container at the end of the test,suitable precautions should be taken prior to lifting the topcover of the calorimeter in order to prevent exposure of t
46、heoperator to a potentially highly pressurized container capableof rupture without warning.7.5 Bombs and transducer lines may become plugged,preventing normal operation of any relief device or vent valve.Therefore, exercise caution and use appropriate personal pro-tective equipment and shielding dev
47、ices prior to attempts torelieve the pressure. Depressurization and subsequent openingof the sample container at the end of the test should beperformed in a safe manner, taking into consideration potential,unanticipated pressure releases or exposure to the operator, orboth.7.6 The toxicity of the co
48、ntents of the sample container,especially after reaction, should be considered and handled ina manner consistent with local safety and regulatory proce-dures.7.7 Material incompatibilities, including that with the sili-cone oil or other fluids in the pressure transducer or lines,should be considered
49、 in any test.7.8 The mass of the sample and total energy release poten-tial (see Test Methods E476, E487, E537, E680, and E698,Practice E1231, and Ref. 7) should always be sufficientlylimited so as to minimize the potential for rupture of the samplecontainer due to overpressurization.7.9 Any safety interlock on the device should not bedefeated.8. Apparatus8.1 The equipment used in this guide shall be capable ofmeasuring and recording changes of temperature and pressureoccurring within a sample (placed inside a suitable container)as a function of e
