ASTM D2326-70

Method of Test for Thermal Conductivity of Cellular Plastics by Means of a Probe (Withdrawn 1975)

General Information

• Status: Withdrawn
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.20 - Plastic Lumber

Standards Content (Sample)

American National Standard K65.123-1971
~~l~ Designation: D 2326- 10
Approved May 20. 1971
By American National Standards Institute
Standard Method of Test for
THERMAL CONDUCTIVITY
OF CELLULAR
1
PLASTICS BY MEANS OF A
PROBE
This Standard_ i~ issued u~der the_ fixed designation. ~ 2326: the number immediately following the designation indicates
the year of ongmal adopt1on or, m the case of revLsLon, the year of last revision. A number in parentheses indicates the
year of last reapproval.
The cm:unillee respo~siblefor this sra~dard has roted its withdrawal. In the absence of substantial reasons rhat it should
be co/11/f/ut'd. the Socmy w1/l approve wuhdrawal from publication in April/977.
I. Scope for this·method are shown in Fig. I. It consists
of a heater and thermocouple in a protective
1.1 This method covers the determination,
sheath that terminates in a plastic handle. The
by means of a probe, of the thermal conduc­
layout and eleCtrical schematic drawing for
tivity of cellular plastics having thermal con­
the probe is shown in Fig. 2. In addition, a
ductivities that are not in excess of 0.058
constant-temperature enclosure as specified in
W fm · K (0.4 Btu . in./h . ft' . deg F). The test
4.6 is required.
may be run over a range of temperatures
4.2 The heating element shall be made in
within the temperature limits of the material
the form of a bifilar coil. This construction
being tested.
eliminates inductive effects and makes possi­
1.2 The probe method is a transient
ble high resistance which greatly simplifies
method for determining thermal conductivity.
the problem of supplying a constant voltage
Heat is applied at a constant rate along a line.
for the power source. At the same time, it
The temperature rise of the line source is pro­
places the heater nearer the surface of the
portional to the logarithm of time and in­
probe arld decreases the axial heat flow along
versely proportional to the thermal conductiv­
the heater wire.
ity of the surrounding medium.
4.3 The 'probe need not be of specified
NOTE !-The values stated in SI units are to be
length or diameter and need not have a speci­
regarded as the standard.
fied length-to-diameter ratio; however, in
practice it has been found that a protective
2. Significance
sheath 0.5 I mm (0.020 in.) in diameter, a
2.1 The probe method is an absolute
length of approximately 200 mm (8 in.), and a
method for determination of k values directly,
heater resistance of approximately 1800 n has
so that no calibration based on a specimen of
proved satisfactory for cellular plastics. The
known thermal conductivity is required. Low
resistance. and length of the heater coil (ohms
cost and simplicity of operation makes the
per unit length) must be known with an accu-
method especially useful for screening pur­
3
racy of at least ' ±0.5 percent.
poses in laboratory and in plant use. In cases
4.4 The power source (see Fig. 2) shall con­
of dispute ASTM Method C 177, Test for
sist of a battery and variable series resistor, a
Thermal Conductivity of Materials by Means
precision inilliammeter, and a resistance
of the Guarded Hot Plate/ shall be used.
'This method is. under the jurisdiction of ASTM Com­
3. Symbols and Definitions
mittee D-?0 on Plastics and is the direct responsibility of
Subcommittee D-20.22 on Cellular Plastics
3.1 For symbols and definitions, see
Effective Jan. 22, 1970. Originally is~ued 1964. Re­
Method C 177.
places D 2326- 64 T.
2
Annual Book of ASTM Standards, Part 35.
1
: A commercially availp.ble probe which has proven to be
4. Apparatus
satisfactory for cellular plastics is available from Custom
4.1 The general features of a suitable probe Scientific Instruments, Inc., P.O. Box A, Whjppany. N.J.
311

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02326
equal to that of the probe to stabilize the bat­ mally not be tested for at least 24 h after
tery before placing a voltage across the probe. foaming. In the event that at least one dimen­
The precision of the milliammeter (or poten­ sion of a sample is not less than 200 mm (8
tiometer and Standard resistance) must be at in.), the sample size should be reduced ac­
least ±0.25 percent of full scale. A milliam­ cordingly and conditioned at room tempera­
meter with a range from 0 to 10 rnA has been ture for at least 4 h prior to cutting the test
satisfactory for most cellular plastics. The specimens.
power source shall be capable of holding the 5.2 In the event that the foam is not iso­
current constant to at least ±0.2 percent over
tropic, the direction of test shall be spec~fied
the duration of the test. The test current shall
or as agreed upon by the seller and the pur­
1
match the warm-up current within ± / per­ chaser.
2
cent. 5.3 The minimum size of specimen is de­
pendent upon the properties of the sample, the
NoTE 2-A lead storage battery or mercury bat­
teries will hold their voltage level under hea
...