ASTM E1641-07(2012)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E1641 − 07(Reapproved 2012)
Standard Test Method for
Decomposition Kinetics by Thermogravimetry
This standard is issued under the fixed designation E1641; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E473Terminology Relating to Thermal Analysis and Rhe-
ology
1.1 This test method describes the determination of the
E1142Terminology Relating to Thermophysical Properties
kinetic parameters, Arrhenius activation energy, and preexpo-
E1582Practice for Calibration of Temperature Scale for
nential factor by thermogravimetry, based on the assumption
Thermogravimetry
that the decomposition obeys first-order kinetics.
E1877Practice for Calculating Thermal Endurance of Ma-
1.2 This test method is generally applicable to materials
terials from Thermogravimetric Decomposition Data
with well-defined decomposition profiles, namely, a smooth,
2.2 Other Standard:
continuous mass change with a single maximum rate.
ISO11358-2 Plastics Thermogravimetry (TG) of Polymers
Part 2: Determination of Kinetic Parameters
1.3 This test method is normally applicable to decomposi-
tion occurring in the range from 400 to 1300K (100 to 1000
3. Terminology
°C).The temperature range may be extended depending on the
instrumentation used. 3.1 Definitions:Technical terms used in this test method are
defined in Terminologies E473 and E1142.
1.4 Computer or electronic-based instruments, techniques,
or data treatment equivalent to this test method may also be
4. Summary of Test Method
used.
4.1 This test method consists of heating a series of four or
NOTE 1—Users of this test method are expressly advised that all such
more test specimens, taken from the original sample, each at a
instrumentsortechniquesmaynotbeequivalent.Itistheresponsibilityof
different heating rate between 1 and 10 K/min, through their
the user of this test method to determine the necessary equivalency prior
decompositionregion.Thespecimenmassisrecordedcontinu-
to use.
ously as a function of temperature. The temperatures for
1.5 The values stated in SI units are to be regarded as
constant conversion are determined from the resultant mass
standard. No other units of measurement are included in this
losscurves.TheArrheniusactivationenergyisthendetermined
standard.
from a plot of the logarithm of heating rate versus the
1.6 This method is similar to ISO11358-2 but differs in its
reciprocal of the absolute temperature at constant conversion
mathematical treatment.
level. This activation energy may then be used to calculate
thermal endurance and an estimate of the lifetime of the
1.7 This standard does not purport to address all of the
material at a certain temperature using Test Method E1877.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5. Significance and Use
priate safety and health practices and determine the applica-
5.1 Thermogravimetry provides a rapid method for deter-
bility of regulatory limitations prior to use.
mining the temperature-decomposition profile of a material.
2. Referenced Documents
5.2 This test method can be used for estimating lifetimes of
materials, using Test Method E1877 provided that a relation-
2.1 ASTM Standards:
ship has been established between the thermal endurance test
results and actual lifetime tests.
ThistestmethodisunderthejurisdictionofASTMCommitteeE37onThermal
6. Apparatus
Measurements and is the direct responsibility of Subcommittee E37.01 on Calo-
rimetry and Mass Loss.
6.1 The essential equipment required to provide the mini-
Current edition approved Sept. 1, 2012. Published September 2012. Originally
mum thermogravimetric analytical capability of this test
approved in 1994. Last previous edition approved in 2007 as E1641–07. DOI:
10.1520/E1641-07R12.
method includes:
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1641 − 07 (2012)
NOTE 4—The specimen size and surface-to-volume ratio are known to
6.1.1 A thermobalance, composed of (a)a furnace to
affect the results of this test.Anarrow range of specimen sizes should be
provide uniform controlled heating of a specimen at a constant
used, as noted in 9.5. Uniformity in particle size can be achieved, without
rate within the temperature range from ambient to 1300 K; (b)
the loss of volatiles, by using a liquid nitrogen mill to grind the sample to
a temperature sensor to provide an indication of the specimen/
afinepowder.Topreventthecondensationofmoisture,themillshouldbe
furnace temperature to 60.1 K; (c)an electrobalance to
opened only after returning fully to ambient temperature, or the operation
should be performed in a glove box filled with dry gas.
continuously measure the specimen mass with a minimum
capacityof20mgandasensitivityof 650µg;and(d)ameans
8.2 In the absence of other information, the samples are
of sustaining the specimen/container under atmospheric con-
assumed to be analyzed as received except for the mechanical
trolofaninertorreactivepurgegasof99.99%purityatarate
treatment noted in 8.1. If some heat treatment, such as drying,
of 20 to 50 65 mL/min.
isappliedtothesamplepriortoanalysis,thistreatmentandany
6.1.2 A temperature controller, capable of executing a
resulting mass loss must be noted in the report.
specifictemperatureprogrambyoperatingthefurnacebetween
8.3 Certain materials require more sophisticated
selected temperature limits at a rate of temperature change
conditioning, such as maintaining the sample at a specified
between 1 and 10 K/min to within 60.1 K/min.
roomtemperatureandrelativehumidityforanextendedperiod
6.1.3 A recording device, capable of recording and display-
of time. Such conditioning may be conducted, but procedural
inganyportion(includingnoise)ofthechangeinmassandany
details shall be included in the report.
portion (including noise) of the temperature.
6.1.4 Containers (pans, crucibles, and so forth) which are
9. Procedure
inert to the specimen and which will remain dimensionally
stable over the temperature range from ambient to 900 K.
9.1 Prepare the thermogravimetric analyzer using any pro-
cedures described in the manufacturer’s Operations manual.
6.2 High-Purity (99.99 %) Nitrogen Supply, for purge gas.
9.2 Placethetemperaturesensorwithin2mmoftheoutside
NOTE 2—Other atmospheres may be used but shall be specified.
of the specimen holder. Care must be taken to ensure that the
7. Precautions specimen holder is not touched in any way by the sensor and
that it is not moved after temperature calibration.
7.1 It is essential that the samples be representative since
milligram quantities of specimen are to be used.
9.3 Maintain a constant flow rate of purge gas in the range
from 20 to 50 mL/min throughout the experiment.
7.2 The value of the calculated activation energy is inde-
pendent of reaction order in the early stages of decomposition.
NOTE 5—In the case of samples that may be sensitive to oxidative
This assumption does not hold for the later stages and shall be degradation, it will be necessary to maintain inert gas purging for a time
sufficient to ensure that all residual oxygen is removed from the system
used with caution. An upper limit of 10% decomposition is
prior to the start of the temperature program. It may be necessary to
suggested, although 20% is justified in certain cases. It is
evacuate the system prior to initiating inert gas purging for some
strongly suggested that calculations be made at several differ-
instruments.
ent levels of decomposition, for example, 5, 10, 15, and 20%.
9.4 Calibrate the instrument furnace temperature in accor-
Variations in the results among these determinations could
dance with the calibration procedure in Practice E1582 using
indicate the inapplicability of one of them. For instance,
the same heating rate, purge gas, and flow rate to be used for
volatile, low-level impurities would affect the results of the
the specimens. The temperature calibration shall be performed
lowest conversion determination more than those at higher
both prior to every change in heating rate and at that heating
conversions. Consistent results for all conversions validate the
rate.
method for the range of conversions examined.
9.5 Place 3 61 mg of the specimen under test into a clean,
7.3 Toxic or corrosive effluents, or both, may be released
tared instrument specimen holder. Other specimen sizes may
duringtheheatingprocessandmaybeharmfultothepersonnel
be used but shall be indicated in the report.
or apparatus.
NOTE 6—The specimen holder should be tared in the fully assembled
8. Sampling
system, with the purge gas flowing.
NOTE 7—Powdered or granular specimens should be distributed evenly
8.1 Powdered or granular specimens, which have a high
over the specimen holder so as to maximize the exposed surface. A
surface-to-volume ratio, are preferred, although films, fibers,
one-grain thick layer would be optimal.
andfabricsmaybeusedprovidingthatcareistakentomakeall
9.6 Equilibrate the specimen at a temperature, in kelvins
of the specimens uniform in size and shape. Under circum-
(K), of ten times the heating rate in kelvins per minute below
stances in which material parts are available, the specimens
the known decomposition temperature. If the percentage mass
should be prepared by filing or rasping the part.All specimens
loss is to be recorded, establish zero percent loss at this time.
should be mixed thoroughly prior to sampling if possible, and
they should be sampled by removing portions from various
NOTE8—Ifzeropercentmasslossisestablishedatthetimeatwhichthe
parts of the container. These portions should in turn be
specimen is placed into the instrument, the specimen mass at the
equilibration temperature can be greater than 100% due to buoyancy
combinedandmixedwelltoensurearepresentativesamplefor
effects.Ablank should be run for accurate determination of the buoyancy
the determination.
effect throughout the temperature range of the experiment. The blank can
NOTE 3—Care should be exercised during sample preparation to avoid beapieceofplatinumofapproximatelythesamevolumeasthespecimen.
contamination. The balance drift at any temperature can be determined in this manner.
E1641 − 07 (2012)
FIG. 1 Examples of Mass Loss Curves at the Following Heating Rates: 1°C/min, 2°C/min, 5°C/min, 10°C/min
FIG. 2 Arrhenius Plot of Heating Rate, Temperature of Constant Conversion Data
NOTE9—Theuseofheatingratesgreaterthan10K/minaffectsboththe
9.7 Heat the specimen at a constant rate through the
precision of the temperature measurement and the kinetics of the
decomposition profile until a constant mass is obtained or the
decomposition. Diffusion of volatiles from the sample may become the
temperature is well beyond the useful temperature range of the
rate-controlling process at high heating rates.
material tested. Record the accompanying thermal curve, with
mass or percentage mass loss displayed on the ordinate and
10. Calculation
specimen temperature on the abscissa.
10.1 From each of the thermal curves obtained in 9.5-9.9,
9.8 Once the decomposition of the test specimen is
determine the absolute temperature at constant conversion, α,
complete, cool the instrument to room temperature, remove,
for each of the constant conversion values to be used in the
clean, and replace the specimen holder, and retare the instru-
calculations as noted in 7.2. For example, see Fig. 1. The
ment in preparation for additional experiments. Use the same
temperature corresponding to other conversion levels (not
specimen holder for the entire series of runs to eliminate
greater than 20%) may be used in the determination, but it
buoyancy problems.
must be noted in the report.
9.9 Repeat the procedures described in 9.4-9.8 at three
NOTE 10—These calculations are simplified if the percent mass loss
additionalheatingratescoveringtherangefrom1to10K/min.
rather than actual mass is recorded on the ordinate.
Other heating rates, and more than four, may be used but shall
NOTE11—Thevalueisdeterminedfromthedifferenceoftheinitialand
be noted in the report. final sample conversion, with the initial mass taken as the mass at the
E1641 − 07 (2012)
equilibration temperature and the final mass taken once the plateau has TABLE 1 Numerical Integration Constants
been reached at the end of weight loss. For example, if the initial mass is
E/RT a b (1/K)
100.3% and the final mass is 80%, 100% decomposition corresponds to
8 5.3699 0.5398
(100.3 to 80.0) or 20.3% mass loss. Thus, 5% decomposition occurs at
9 5.8980 0.5281
(0.05×20.3)or1.02%massloss,whichoccursontheordinateat99.3%
10 6.4167 0.5187
(100.3%−1.02%=99.28%).
11 6.928 0.511
12 7.433 0.505
10.2 Plot the logarithm of the heating rate expressed as
13 7.933 0.500
kelvins per minute against the reciprocal of the absolute
14 8.427 0.494
15 8.918 0.491
temperature at which the conversion level, selected in 10.1,
16 9.406 0.488
was reached. A straight line, similar to that in Fig. 2, should
17 9.890 0.484
result. This test procedure is not applicable if the curve is
18 10.372 0.482
19 10.851 0.479
nonlinear.
20 11.3277 0.4770
NOTE 12—An apparent nonlinearity may result from erroneous deter- 21 11.803 0.475
22 12.276 0.473
minations. It is recommended that any nonlinear points be repeated for
23 12.747 0.471
verification.
24 13.217 0.470
10.3 Using the least-squares method fit a straight line to
25 13.686 0.469
26 14.153 0.467
these data without weighing factors, and determine the slope:
27 14.619 0.466
∆ logβ /∆ 1/T 28 15.084 0.465
~ ! ~ !
29 15.547 0.463
NOTE13—Ifthevaluesobtainedfromthistestmethodaretobeusedin
30 16.0104 0.4629
TestMethodE1877,anestimationoftheuncertaintyforactivationenergy
31 16.472 0.462
(E) and preexponential factor (A) is required. These uncertainties may be
32 16.933 0.461
derived from the uncertainty in the slope value of m= ∆ (log β)/∆ (1/T).
33 17.394 0.461
Ifthecalculationtoolusedtoobtaintheslopeofthestraightlineprovides
34 17.853 0.459
an estimation of uncertainty in the determined slope (δm), record it.
35 18.312 0.459
Oth
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