ASTM E476-87(1993)
(Test Method)Standard Test Method for Thermal Instability of Confined Condensed Phase Systems (Confinement Test)
Standard Test Method for Thermal Instability of Confined Condensed Phase Systems (Confinement Test)
SCOPE
1.1 This test method is designed to determine the temperature at which a chemical or mixture of chemicals, confined initially as a solid or liquid in air or other controlled atmosphere under normal laboratory conditions, will start a reaction, generating appreciable heat when subjected to a programmed temperature increase. This test method is also designed to measure the magnitude and rate of heat generation.
1.2 This test method is for use with condensed phases.
1.3 This test method can be used over a temperature range from 0 to 500oC, and a pressure range of 0 to 5000 psi.
1.4 As with any thermal stability test, proper safety precautions should be instituted to protect personnel. See also Section 6.
1.5 Limitations
1.5.1 The threshold temperature determined by this method may be higher than one determined by heating at a lesser rate.
1.5.2 Samples of the same material having different thermal histories may have different threshold temperatures.
1.6 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems 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.
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Designation: E 476 – 87 (Reapproved 1993)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Thermal Instability of Confined Condensed Phase Systems
(Confinement Test)
This standard is issued under the fixed designation E 476; 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.
INTRODUCTION
This test method is one of several methods developed by Committee E-27 for determining the
hazards of chemicals. This test method is to be used in conjunction with other tests to characterize the
hazard potential of chemicals.
1. Scope curve (see Fig. 2) where the slope changes in the direction
indicating an exothermic reaction, that is, the sample is
1.1 This test method is designed to determine the tempera-
beginning to self-heat.
ture at which a chemical or mixture of chemicals, confined
initially as a solid or liquid in air or other controlled atmo-
3. Summary of Method
sphere under normal laboratory conditions, will start a reaction,
3.1 The sample is confined in a specially designed vessel
generating appreciable heat when subjected to a programmed
equipped with a shielded thermocouple. The test assembly is
temperature increase. This test method is also designed to
put into a bath and equilibrated, usually at room temperature.
measure the magnitude and rate of heat generation.
The bath is then heated at a constant temperature rise rate. The
1.2 This test method is for use with condensed phases.
differential temperature (sample temperature minus bath tem-
1.3 This test method can be used over a temperature range
perature) in the vessel is recorded versus bath temperature.
from 0 to 500°C, and a pressure range of 0 to 5000 psi.
Heating is continued until the diaphragm bursts or the upper
1.4 As with any thermal stability test, proper safety precau-
temperature limit is reached. The differential temperature curve
tions should be instituted to protect personnel. See also Section
is then analyzed to determine the threshold temperature for
6.
initiation of measurable reaction as indicated by an exothermic
1.5 Limitations:
temperature rise.
1.5.1 The threshold temperature determined by this method
may be higher than one determined by heating at a lesser rate.
4. Significance and Use
1.5.2 Samples of the same material having different thermal
4.1 The threshold temperature measured by this test method
histories may have different threshold temperatures.
is an indication of the thermal instability of a chemical or
1.6 This standard may involve hazardous materials, opera-
mixture of chemicals, qualitatively expressed by the tempera-
tions, and equipment. This standard does not purport to
ture rise. There is a potential hazard whenever the temperature
address all of the safety problems associated with its use. It is
of the chemical exceeds the threshold temperature unless
the responsibility of the user of this standard to establish
proper design safeguards are utilized. This does not imply that
appropriate safety and health practices and determine the
temperatures lower than the threshold temperature are safe.
applicability of regulatory limitations prior to use.
Since this test is not an adiabatic type and does not indicate the
2. Terminology effect of mass or time, other testing would be needed to
characterize the use or storage of the chemical at lower
2.1 threshold temperature—temperature on the DT versus T
temperatures.
4.2 Because of rate and mass dependent factors, failure to
find evidence of an exothermic reaction does not ensure
This test method is under the jurisdiction of Committee E-27 on Hazard
Potential of Chemicals and is the direct responsibility of Subcommittee E 27.02 on
thermal stability unless substantiated by other test methods.
Thermal Stability.
Current edition approved Sept. 25, 1987. Published November 1987. Originally
5. Apparatus
e2
published as E 476 – 73. Last previous edition E 476 – 73 (1979) .
This test method is a modification of the Thermal Stability Test recommended 5.1 Sample Container—A diagram of a suggested test cell
by the Interagency Chemical Rocket Propulsion Group, published by the Chemical
assembly is shown in Fig. 3 and an engineering drawing is
Propulsion Information Agency in May, 1964, and is the responsibility of E 27.02
shown in Fig. 4. The assembly shall consist of the following
on Thermal Stability.
E 476
FIG. 1 Connector, Gasket, and Burst Diaphragm
function of bath temperature. A suitable recorder for this test is
a standard 8.5 by 11 in. X-Y plotter. Two recorders are required
if pressure versus bath temperature is monitored. Dual-pen
plotters are suitable, provided the temperature pens do not
interact at any critical junction of the reaction.
5.2.2 The maximum reaction rates that can be followed
using the recommended instrumentation are limited by the
writing speeds of the mechanical writing recorders. When
these are calibrated as described in Section 8, rates of reaction
producing temperature changes of 5°C per s can be determined.
Certain reactions may cause temperature changes in excess of
FIG. 2 Idealized Thermogram these. If more exact resolution for rapid reactions is desired, it
is necessary to use a recording oscillograph in place of the: X-Y
recorder.
parts: basic test cell, sample thermocouple, compression fitting,
5.3 Low-Range Heating Bath—For temperatures from 0 to
sealing ring, burst diaphragm, modified Army-Navy specifica-
370°C the bath may be a conventional 2-L silicon oil unit with
tion union (AN union), vent tube and flare fitting. Detailed
heaters (1800 W), stirring motor, and temperature programmer.
dimensions of all parts are given in Fig. 4 with the exception of
The bath container shall be metal with strip heaters on the
those parts readily available from manufacturers. The parts are
outside. The bath shall be well insulated. A cooling coil shall be
listed in Table 1. The internal volume ofthe assembled test cell
wrapped around the container to reduce the time lost between
3,4
is approximately 1.1 mL.
tests (optional). The coolant shall be tap water. The nominal
5.2 Instrumentation:
heating rate for the bath shall be 8 to 10°C per min.
5.2.1 One recorder is used for recording the difference
5.4 High-Range Heating Bath—For temperatures between
between the sample temperature and the bath temperature as a
100 and 500°C a bath of a low-melting alloy may be employed.
The bath medium may be cerrobend/Alloys or Woods’ metal
(Caution. Woods’ metal may contain cadmium and should be
Apparatus of similar designs with a total volume of 1 to 10 mL can be used.
This revised test method, when used with its provision for optional pressure
measurement, is essentially similar to earlier versions of this in which pressure
measurement was an integral part. Dow Corning 710 has been found satisfactory for this purpose.
E 476
of impact sensitivity has previously been made and has shown
sufficient insensitivity to permit powdering or compaction.
6.3 Upon rupture of the diaphragm, noxious fumes may be
released into the laboratory. To prevent escape of the reaction
products into the laboratory atmosphere, conduct tests either in
a fume hood or pipe the vent line to a suitable exhaust system.
6.4 The bath of hot oil or molten metal may inadvertently be
spilled or ruptured and cause personnel burns or laboratory
fires. To prevent such accidents, the test unit should be located
in a separate fume hood constructed of non-combustible
materials. The use of a fluidized sand bath minimizes this
particular hazard.
6.5 During the test, certain sensitive chemicals may deto-
nate resulting in destruction of the basic test cell assembly and
possible destruction of the bath. Such violent reactions fre-
quently hurl fragments through the surroundings at high
velocity with great danger to personnel. To prevent injury from
possible shrapnel, conduct tests in a barricaded enclosure or
behind a blast shield contained within a fume hood.
6.6 All controls and switches should be on the operator side
of the blast shield or enclosure so that during emergencies,
steps can be taken to turn off heaters and shut down the system
without exposing personnel to danger.
6.7 A loud report accompanies the rupture of a burst
diaphragm; this may cause accidents by startling personnel
engaged in other tasks. Although the use of fume hoods and
blast shields muffles the sound, all nearby personnel should be
warned that the test is in progress prior to running the test.
6.8 Give thought to procedures for cooling. If water is to be
used for cooling, care is needed since in most instances, the
FIG. 3 Thermal Stability Bomb Assembly
temperatures of the bath will be much higher than the boiling
point of water.
used with adequate ventilation to remove toxic fumes). A
6.9 In some cases the pressure may not be sufficient to burst
temperature programmer is also employed with the metal bath.
the pressure diaphragm. On cooling to room temperature, there
The nominal heating rate for the metal bath is 8 to 10°C per
may still be a high residual pressure in the test cell. Take care
min. This heating rate may prove difficult to maintain above
in relieving pressure from the cell. The operator should be
400°C unless the bath is well protected from air currents.
protected by a shield and have protective covering for eyes,
5.5 Full-Range Heating Bath—A fluidized sand bath
arms and hands.
equipped with vacuum dust ring may be conveniently used for
NOTE 1—It would be jud
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