1、Designation: E1981 98 (Reapproved 2012)1Standard 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.INTRODUCTI
3、ONThis 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 assessment of the hazard potential of chemicalsmust take into a
4、ccount 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 environmental conditions.It is the intent of this guide to incl
5、ude 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 illustration or clarity only.1. Scope1.1 This guide covers sugg
6、ested 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 calculation of thermodynamicparameters from the time, temper
7、ature, 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 temperaturerange of the calorimeter typically varies from ambient to500C,
8、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, if any, associated with its use. It is theresponsibility of t
9、he 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:2E476 Test Method for Thermal Instability of Confined Con-dense
10、d 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 Weight Impact Sensitivity ofSolid-Phase Hazardous MaterialsE
11、698 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 Unstable Materials3. Terminology3.1 Definitions of Terms Specific
12、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, 2012. Published December 2012. Originallypublished in 1998. L
13、ast previous edition approved in 2004 as E1981 98 (2004).DOI: 10.1520/E1981-98R12.2For 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 pag
14、e 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 calorimeter, nan instrument capable ofmaking calorimetric measure
15、ments 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 autocatalytic reaction, na chemical reaction inwhich a product or react
16、ion 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 system after calibration.3.1.4 final temperature (Tfinal),nthe obs
17、erved 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 heat(energy) liberated during an exothermic reaction.3.1.6 idea
18、l 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 product of the observed adiabatic temperature rise, Tobs,and the therm
19、al 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 temperature of anexotherm.3.1.8 onset temperature (Tstart),nthe
20、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 is apparatus-dependent, based upon the inherent sensitivity of th
21、e 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 temperature differences observed in exo-thermic reactions in the
22、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 time to maximum rates (TMRs) (see 3.1.12).See also 10.1 for a math
23、ematical 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), nthe amount of timethat is needed for a reaction to reach its max
24、imum 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 self-heating or pressure rate occurs. The experimentally observedT
25、MR 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 placed in a reaction container and posi-tioned in the calorimete
26、r (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 the user-specified rate of temperature rise is first exceeded. If
27、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 testis reached. If an exotherm is detected, the surroundings are
28、kept 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 data are recorded atspecified temperature intervals as a function o
29、f 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 (as defined in 3.1.12)and to obtain kinetic parameters (1-4)4fo
30、r 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 adiabatic temperature rise andheat of reaction.5. Significance and Us
31、e5.1 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 predict thethermal and pressure hazards associated with processing,st
32、orage, 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, forthe investigation of the effects of catalyst, inhibitors, i
33、nitiators,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)125.3 Interpretation of the time-temperature or time-pressuredata may be possible for
34、 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 between the sample and the container and, therefore, issubject to
35、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 qualitative indication of change in reaction rate maybe obtained by (opt
36、ional) 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-heatrates may not be quantitatively reliable and is equipmentdependent.6
37、.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, products, and container. The calcu-lation is also dependent on the te
38、mperature 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-tions are involved.6.6 Data may be obtained in the temperature rang
39、e 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 alterthe performance of the instrument. It is the users responsib
40、ilityto 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 mechanism observed experimentally may not bethe same as the true reac
41、tion 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, impactcharacteristics, (see Test Method E476, E487, E537, E680, andE69
42、8, 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 samplecontainer. Additional physical properties of the sample mayal
43、so 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 pressure-relief device, itshould be periodically inspected for p
44、ossible corrosion orphysical damage, which may result in improper operation.FIG. 1 Example Calorimeter and Reaction ContainerE1981 98 (2012)137.3 Operation of the relief device or rupture of the bombmay result in the release of toxic or noxious fumes, which mayescape into the immediate operating are
45、a. 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 theoperator to a potentially highly pressurized container capable
46、of 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 devices prior to attempts torelieve the pressure. Depressurization
47、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 contents of the sample container,especially after reaction, should
48、 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 in any test.7.8 The mass of the sample and total energy release
49、 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 either time or temperature, or both.8.2 The accelerating rate calor
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1