ASTM E793-95
(Test Method)Standard Test Method for Enthalpies of Fusion and Crystallization by Differential Scanning Calorimetry
Standard Test Method for Enthalpies of Fusion and Crystallization by Differential Scanning Calorimetry
SCOPE
1.1 This test method covers the determination of the enthalpy (heat) of fusion (melting) and crystallization by differential scanning calorimetry (DSC).
1.2 This test method is applicable to solid samples in granular form or in any fabricated shape from which an appropriate specimen can be cut, or to liquid samples that crystallize within the range of the instrument. Note, however, that the results may be affected by the form and mass of the specimen, as well as by other experimental conditions.
1.3 The normal operating temperature range is from 120 to 600°C. The temperature range can be extended depending upon the instrumentation used.
1.4 This test method is generally applicable to thermally stable materials with well defined endothermic or exothermic behavior.
1.5 Computer or electronic based instruments, techniques, or data treatment equivalent to those in this test method may also be used.
1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: E 793 – 95
Standard Test Method for
Enthalpies of Fusion and Crystallization by Differential
Scanning Calorimetry
This standard is issued under the fixed designation E 793; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope E 1142 Terminology Relating to Thermophysical Proper-
ties
1.1 This test method covers the determination of the en-
thalpy (heat) of fusion (melting) and crystallization by differ-
3. Terminology
ential scanning calorimetry (DSC).
3.1 Definitions—Specialized terms used in this test method
1.2 This test method is applicable to solid samples in
are defined in Terminologies E 473 and E 1142.
granular form or in any fabricated shape from which an
appropriate specimen can be cut, or to liquid samples that
4. Summary of Test Method
crystallize within the range of the instrument. Note, however,
4.1 This test method involves heating (or cooling) a test
that the results may be affected by the form and mass of the
specimen at a controlled rate in a controlled environment
specimen, as well as by other experimental conditions.
through the temperature region of fusion or crystallization. The
1.3 The normal operating temperature range is from −120 to
heat flow associated with fusion, an endothermic process (and
600°C. The temperature range can be extended depending
crystallization, an exothermic process), is recorded and inte-
upon the instrumentation used.
grated over time. Absolute values for the enthalpy of fusion
1.4 This test method is generally applicable to thermally
(and enthalpy of crystallization) or relative values for compara-
stable materials with well defined endothermic or exothermic
tive purposes can thus be obtained.
behavior.
1.5 Computer or electronic based instruments, techniques,
NOTE 1—Melting (or crystallization) temperatures are sometimes de-
termined in conjunction with measurements of the enthalpy of fusion or
or data treatment equivalent to those in this test method may
crystallization. These temperature values may be obtained by Test Method
also be used.
E 794.
1.6 The values stated in SI units are to be regarded as the
standard. The values given in parentheses are for information
5. Significance and Use
only.
5.1 Differential scanning calorimetry provides a rapid
1.7 This standard does not purport to address all of the
method for the determination of enthalpic changes accompa-
safety concerns, if any, associated with its use. It is the
nying first-order transitions of materials.
responsibility of the user of this standard to establish appro-
5.2 This test method is useful for quality control, specifica-
priate safety and health practices and determine the applica-
tion acceptance, and research.
bility of regulatory limitations prior to use.
6. Apparatus
2. Referenced Documents
6.1 Differential Scanning Calorimeter, capable of heating or
2.1 ASTM Standards:
cooling rates up to at least 10°C/min and of automatically
E 473 Terminology Relating to Thermal Analysis
recording the differential heat flow between a specimen and a
E 794 Test Method for Melting Temperatures and Crystal-
reference material, both to the required sensitivity and preci-
lization Temperatures by Thermal Analysis
sion. For comparison, the same heating rate shall be used for all
E 968 Practice for Heat Flow Calibration of Differential
calibrations and test runs. Thermal curves are recorded on a
Scanning Calorimeters
time based recorder for peak area measurements. The instru-
ments should have sufficient heat flow sensitivity to provide
This test method is under the jurisdiction of ASTM Committee E-37 on
precision of 61 %. The instrument shall have a time base
Thermal Measurements and is the direct responsibility of Subcommittee E 37.01on
precision of 61 % over the time base range from 0.1 to 2.0
Test Methods and Recommended Practices.
min/cm (10.0 to 0.5 cm/min) of chart. Some instrument models
Current edition approved Sept. 10, 1995. Published December 1995. Originally
published as E 793 – 81. Last previous edition E 793 – 85 (1989).
allow computer acquisition of heat flow data which may be
Annual Book of ASTM Standards, Vol 14.02.
plotted.
Supporting data for this test method have been filed as ASTM Headquarters.
6.2 Planimeter, or other method of area measurement with
Request RR:E37-1001.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
E 793
precision of 61 % or better. zation exotherm). For digital data storage, select a sufficient
6.3 Specimen Capsule, material composed of aluminum or rate of data collection to minimize interpolation error. Typical
other material of high thermal conductivity. rates are one point/s for polymers and 5 points/s for simple
6.4 Nitrogen, or other inert gas supply for purging purposes. organic or inorganic materials.
6.5 Balance, with capacity greater than 100 mg, capable of
NOTE 2—Preanalysis on a similar specimen may be required to provide
weighing to the nearest 0.01 mg, or better.
this information.
7. Hazards and Interferences
10.5 The specimen may be heated rapidly to 50°C below the
7.1 Since milligram quantities of specimens are used, it is expected melting temperature and allowed to equilibrate. For
some materials, it may be necessary to start the scan substan-
essential that samples are homogeneous.
7.2 Toxic or corrosive effluents, or both, may be released tially lower in termperature, for example, below the glass
transition, in order to establish a baseline where there is no
when heating the material and could be harmful to the
personnel or the apparatus. evidence of melting or crystallization.
7.3 Samples that release volatiles upon heating will change
10.6 Heat the specimen at 10°C/min through the melting
mass and invalidate the test.
range until baseline is reestablished above the melting endot-
7.4 In the use of commercial instrumentation, the operator
herm. Other heating rates may be used but shall be noted in the
should read the manufacturer’s instruction manual to be aware
report. Results may depend on heating rate and equilibration
of potential hazards of operation, such as burn hazards from
times. To allow the system to achieve steady state, provide at
hot surfaces.
least 3 min of scanning time both before and after the peak.
10.7 Hold the specimen at this temperature for 2 min. Other
8. Sampling
periods may be used, but shall be noted in the report.
8.1 Powdered or granular materials should be mixed thor-
10.8 Cool the specimen at 10°C/min through the exotherm
oughly prior to sampling and should be sampled by removing
until baseline is reestablished below the crystallization exo-
portions from various parts of the container. These portions, in
therm. Other cooling rates may be used but must be noted in
turn, should be combined and mixed well to ensure a repre-
the report. To allow the system to achieve steady state, provide
sentative specimen for the determination. Liquid samples may
at least 3 min of scanning time both before and after the peak.
be sampled directly after mixing.
For some materials, it may be necessary to scan several tens of
8.2 In the absence of other information, samples are as-
degrees below the peak maximum in order to attain a constant
sumed to be analyzed as received. If some heat or mechanical
baseline. Record the accompanying thermal curve.
treatment is applied to the sample prior to analysis, this
10.9 Reweigh the specimen after completion of scanning
trea
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.