1、Designation: E 1981 98 (Reapproved 2004)Standard Guide forAssessing Thermal Stability of Materials by Methods ofAccelerating Rate Calorimetry1This standard is issued under the fixed designation E 1981; 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.INTRODUCTIONThis guide is one of several standards being developed by ASTM Committee E27 for deter
3、miningthe physicochemical hazards of chemicals and chemical mixtures. This guide should be used inconjunction with other test methods, as a complete assessment of the hazard potential of chemicalsmust take into account a number of realistic factors not necessarily considered in this guide. Theexpres
4、sion hazard potential as used by this committee is defined as the degree of susceptibility ofmaterial to ignition or release of energy under varying environmental conditions.It is the intent of this guide to include any calorimetric device consistent with the principles ofadiabatic calorimetry. Devi
5、ce-specific information and specifications are located in appendices to theguide. Any reference to specific devices in the guide are for purposes of illustration or clarity only.1. Scope1.1 This guide covers suggested procedures for the opera-tion of a calorimetric device designed to obtain temperat
6、ureand pressure data as a function of time for systems undergoinga physicochemical change under nearly adiabatic conditions.1.2 This guide outlines the calculation of thermodynamicparameters from the time, temperature, and pressure datarecorded by a calorimetric device.1.3 The assessment outlined in
7、 this guide may be used overa pressure range from full vacuum to the rated pressure of thereaction container and pressure transducer. The temperaturerange of the calorimeter typically varies from ambient to500C, but also may be user specified (see 6.6).1.4 This statement does not purport to address
8、all of thesafety concerns, 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 Doc
9、uments2.1 ASTM Standards:2E 476 Test Method for Thermal Instability of ConfinedCondensed Phase Systems (Confinement Test)E 487 Test Method for Constant-Temperature Stability ofChemical MaterialsE 537 Test Method for The Thermal Stability of ChemicalsBy Differential Scanning CalorimetryE 680 Test Met
10、hod for Drop Weight Impact Sensitivity OfSolid-Phase Hazardous MaterialsE 698 Test Method for Arrhenius Kinetic Constants forThermally Unstable MaterialsE 1231 Practice for Calculation of Hazard PotentialFigures-of-Merit for Thermally Unstable Materials3. Terminology3.1 Definitions of Terms Specific
11、 to This Standard:3.1.1 adiabatic calorimeter, 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
12、and its sur-roundings.3.1.2 autocatalytic 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,
13、 or to changeswhich occur in the system after calibration.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 April 1, 2004. Published May
14、 2004. Originallypublished in 1998. Last previous edition approved in 1998 as E 1981 - 98.2For 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 Sum
15、mary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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 rea
16、ction hasdecreased below the operator-defined slope sensitivity thresh-old.3.1.5 heat of reaction (DH), nthe net calculated heat(energy) liberated during an exothermic reaction.3.1.6 ideal adiabatic temperature rise (DTad), nthe tem-perature rise which would be observed in an exothermicreaction if a
17、ll of the heat liberated were used to increase thetemperature of only the sample. It is conveniently calculated asthe product of the observed adiabatic temperature rise, DTobs,and the thermal inertia factor, f.3.1.7 observed adiabatic temperature rise (DTobs), ntheobserved temperature rise in the sy
18、stem during an exotherm;mathematically, it is equal to the temperature difference be-tween the final temperature and the onset 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
19、-defined slope sensitivity thresh-old, usually 0.02C/min; the onset temperature is not a funda-mental property of a substance, but is apparatus-dependent,based upon the inherent sensitivity of the calorimetric system.3.1.9 self-heating, adjany exothermic process which in-creases the temperature of t
20、he system by the self absorption ofthe liberated heat.3.1.10 thermal inertia factor (f), n a correction factorapplied to time and temperature differences observed in exo-thermic reactions in the system (sample and container) undertest, which accounts for the sensible heat absorbed by thesample conta
21、iner that otherwise would lead to erroneously lowheats of reaction and adiabatic temperature rise, as well as toerroneously high time 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 rea
22、ction inwhich the heat generation rate in a system exceeds the heatremoval rate of that system.3.1.12 time-to-maximum rate (TMR), nthe 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 co
23、rresponding to the onset tempera-ture, but may also be referenced from any time-temperaturepoint to the time at which the maximum self-heating orpressure rate occurs. The experimentally observed TMR isnormally divided by the thermal inertia factor (see 3.1.10) toobtain a more conservative assessment
24、 of TMR. (TMR dividedby the thermal inertia factor is often referred to as the“f-corrected” TMR).4. Summary of Guide4.1 A sample is 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 eq
25、uilibrium, whereupon a searchfor evidence of an exothermic reaction is undertaken. Anexotherm is considered to have occurred when the 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
26、equilibrateagain. This heat-wait-search cycle is repeated until either anexotherm is detected or the upper temperature limit of the testis reached. If an exotherm is detected, the surroundings arekept at the same temperature as the reaction container, allowingFIG. 1 Example Calorimeter and Reaction
27、ContainerE 1981 98 (2004)2the 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 data are recorded atspecified temperature intervals as a function of time. Addi-tional user-selected para
28、meters 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 (as defined in 3.1.12)and to obtain kinetic parameters (1-9)3for simple, non-autocatalytic exothermic
29、 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 adiabatic temperature rise andheat of reaction.5. Significance and Use5.1 The data from this guide seldom,
30、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 predict thethermal and pressure hazards associated with processing,storage, and shipping of a chemical or m
31、ixture of chemicalsafter appropriate scaling of the data. This has been addressed inthe literature (1-9) but is beyond the scope of this guide.5.2 This guide is suitable, under the proper conditions, forthe investigation of the effects of catalyst, inhibitors, initiators,reaction atmospheres, materi
32、als of construction, or, if avail-able, agitation (see 6.1.2).5.3 Interpretation 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 (10-1
33、1).6. Limitations6.1 This guide requires good heat transfer within the sampleand between 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
34、 results, and6.1.2 Heterogeneous systems may not give meaningfulresults. A qualitative 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
35、observedreaction rates.6.2 Accurate tracking of very high or very low self-heatrates 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 accur
36、ate knowledge of the (temperature-dependent) heatcapacities of the reactants, products, 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, A
37、ppendix X1) may notbe suitable in many instances, especially when multiple reac-tions 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 o
38、f construction of the bomb.6.7 Modifications to the calorimeter can significantly alterthe 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 (f) factor for the experimentdiffers
39、 significantly from that of the system it is intended tosimulate, any reaction mechanism observed experimentallymay not be the same as the true reaction mechanism that existsin the system being simulated.6.9 In the determination of kinetic parameters, the possibil-ity of autocatalytic reaction mecha
40、nisms must be considered.7. Hazards7.1 The thermal stability characteristics, impact character-istics, (see Test Method E 476, E 487, E 537, E 680, and E 698,Practice E 1231 and Ref. 12), or friction sensitivity character-istics of the sample, or a combination thereof, should beassessed, as it is of
41、ten necessary to grind (see Note 1) orcompact the sample prior to or during loading into the samplecontainer. 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, aspolymor
42、phic changes can occur, thus altering the nature of the sample.7.2 If the device incorporates a pressure-relief device, itshould be periodically inspected for possible corrosion orphysical damage, which may result in improper operation.7.3 Operation of the relief device or rupture of the bombmay res
43、ult in the release of toxic or 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
44、order to prevent exposure of theoperator 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-tecti
45、ve equipment and shielding devices 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, orb
46、oth.3The boldface numbers in parentheses refer to the list of references found at theend of this practice.E 1981 98 (2004)37.6 The toxicity of the contents of the sample container,especially after reaction, should be considered and handled ina manner consistent with local safety and regulatory proce
47、-dures.7.7 Material incompatibilities, including that with the sili-cone oil or other fluids in the pressure transducer or lines,should be considered in any test.7.8 The mass of the sample and total energy release poten-tial (see Test Methods E 476, E 487, E 537, E 680, and E 698,Practice E 1231, an
48、d Ref. 12) 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 change
49、s of temperature and pressureoccurring within a sample (placed inside a suitable container)as a function of either time or temperature, or both.8.2 The accelerating rate calorimetric device may be pur-chased4or custom built to various degrees of precision andsensitivity. The basic components of an apparatus suitable forthis guide include:8.2.1 Calorimeter,8.2.2 Sample (reaction) container,8.2.3 Programmable temperature controller,8.2.4 Heating unit, and8.2.5 Temperature and pressure measuring and recordingdevices.8.3 Optional components include provision for stirri
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