ASTM F1868-23
(Test Method)Standard Test Method for Thermal Resistance, Evaporative Resistance, and Total Heat Loss Measurements of Clothing Materials Using a Sweating Hot Plate
Standard Test Method for Thermal Resistance, Evaporative Resistance, and Total Heat Loss Measurements of Clothing Materials Using a Sweating Hot Plate
SIGNIFICANCE AND USE
4.1 The thermal resistance, evaporative resistance, and total heat loss provided by fabrics, films, coatings, foams, and leathers, including multi-layer assemblies, is of considerable importance in determining their suitability for use in fabricating protective clothing systems.
4.1.1 The thermal resistance, evaporative resistance, and total heat loss can be significantly affected by environmental conditions. Extreme care must be taken when using results measured under standard testing conditions to determine a material’s suitability for use in conditions outside the testing conditions.
4.2 The thermal interchange between people and their environment is an extremely complicated subject that involves many factors in addition to the steady-state resistance values of fabrics, films, coatings, foams, and leathers, including multi-layer assemblies. Therefore, thermal resistance values, evaporative resistance values, and total heat loss measured on a hot plate may or may not indicate relative merit of a particular material or system for a given clothing application. While a possible indicator of clothing performance, measurements produced by the testing of fabrics have no proven correlation to the performance of clothing systems worn by people. Clothing weight, drape, tightness of fit, and so forth, can minimize or even neutralize the apparent differences between fabrics or fabric assemblies measured by this test method.
4.3 The thermal resistance and evaporative resistance of clothing systems and items can be measured with a heated sweating manikin in an environmental chamber in accordance with Test Methods F1291, F2370, and F3426.
SCOPE
1.1 This test method covers the measurement of the thermal resistance, evaporative resistance, and total heat loss under steady-state conditions of fabrics, films, coatings, foams, and leathers, including multi-layer assemblies, for use in clothing systems.
1.2 The range of this measurement technique for intrinsic thermal resistance is from 0.002 to 0.5 K·m2/W and for intrinsic evaporative resistance is from 0.0 to 1.0 kPa·m 2/W. The total heat loss range is from 0.0 to 1300 W/m2.
1.3 The values in SI units shall be regarded as standard. Other units of measurement are provided in this standard but are not regarded as standard.
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F1868 − 23
Standard Test Method for
Thermal Resistance, Evaporative Resistance, and Total Heat
Loss Measurements of Clothing Materials Using a Sweating
Hot Plate
This standard is issued under the fixed designation F1868; 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 (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Clothing is often made of materials that impede the flow of heat and moisture from the skin to the
environment. Consequently, people may suffer from heat stress or cold stress when wearing clothing
in different environmental conditions. Therefore, it is important to quantify the thermal resistance,
evaporative resistance, and total heat loss of clothing materials and to consider these properties when
selecting materials for different clothing applications.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers the measurement of the thermal
C177 Test Method for Steady-State Heat Flux Measure-
resistance, evaporative resistance, and total heat loss under
ments and Thermal Transmission Properties by Means of
steady-state conditions of fabrics, films, coatings, foams, and
the Guarded-Hot-Plate Apparatus
leathers, including multi-layer assemblies, for use in clothing
D1518 Test Method for Thermal Resistance of Batting
systems.
Systems Using a Hot Plate (Withdrawn 2023)
1.2 The range of this measurement technique for intrinsic
E177 Practice for Use of the Terms Precision and Bias in
thermal resistance is from 0.002 to 0.5 K·m /W and for
ASTM Test Methods
intrinsic evaporative resistance is from 0.0 to 1.0 kPa·m /W.
E691 Practice for Conducting an Interlaboratory Study to
The total heat loss range is from 0.0 to 1300 W/m .
Determine the Precision of a Test Method
F1291 Test Method for Measuring the Thermal Insulation of
1.3 The values in SI units shall be regarded as standard.
Clothing Using a Heated Manikin
Other units of measurement are provided in this standard but
F1494 Terminology Relating to Protective Clothing
are not regarded as standard.
F2370 Test Method for Measuring the Evaporative Resis-
1.4 This standard does not purport to address all of the
tance of Clothing Using a Sweating Manikin
safety concerns, if any, associated with its use. It is the
F3426 Test Method for Measuring the Thermal Insulation of
responsibility of the user of this standard to establish appro-
Clothing Items Using Heated Manikin Body Forms
priate safety, health, and environmental practices and deter-
2.2 Other Standards:
mine the applicability of regulatory limitations prior to use.
ISO 11092 Textiles – Physiological Effects – Measurement
1.5 This international standard was developed in accor-
of Thermal and Water-Vapour Resistance Under Steady-
dance with internationally recognized principles on standard-
State Conditions (Sweating Guarded-Hotplate Test)
ization established in the Decision on Principles for the
3. Terminology
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.1 Definitions:
Barriers to Trade (TBT) Committee.
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
This test method is under the jurisdiction of ASTM Committee F23 on Personal Standards volume information, refer to the standard’s Document Summary page on
Protective Clothing and Equipment and is the direct responsibility of Subcommittee the ASTM website.
F23.60 on Human Factors. The last approved version of this historical standard is referenced on
Current edition approved June 1, 2023. Published June 2023. Originally www.astm.org.
approved in 1998. Last previous edition approved in 2017 as F1868 – 17. DOI: Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/F1868-23. 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
F1868 − 23
3.1.1 clo, n—a unit of thermal resistance (insulation) equal plate without a fabric test specimen (that is, bare plate). This
to 0.155 K·m /W. property reflects the instrument constant and is used to stan-
3.1.1.1 Discussion—The value of the clo was selected as dardize the plate, and in conjunction with R , is used in the
ct
roughly the insulation value of typical indoor clothing, which calculation of R .
cf
should keep a resting person (producing heat at the rate of R = intrinsic thermal resistance of the fabric test specimen
cf
58 W ⁄m ) comfortable in an environment at 21 °C, air move- only. In the calculation of this value, the assumption is made
ment 0.1 m/s. When clo was developed, typical indoor clothing that the boundary layers of the bare plate and the boundary
consisted of a three-piece suit and light underclothes. layers of the fabric test specimen are equal.
R = total thermal resistance of the test specimen and the air
ct
3.1.2 evaporative resistance, n—the resistance to the flow of
layer.
moisture vapor from a saturated surface (high vapor pressure)
to an environment with a lower vapor pressure. 3.1.5 total heat loss, n—the amount of heat transferred
3.1.2.1 Discussion— The evaporative resistance in units of through a material or a composite by the combined dry and
kPa·m /W can be calculated for several different cases. evaporative heat exchanges under specified conditions ex-
A
R = apparent intrinsic evaporative resistance of the fabric pressed in watts per square meter.
ef
test specimen only, when evaluated non-isothermally. The term 3.1.5.1 Discussion—This single criterion for comparing fab-
ric assemblies was developed as a special case by the National
apparent is used as a modifier for intrinsic evaporative resis-
tance to reflect the fact that the properties of the specimen may Fire Protection Association. The specific conditions used by
NFPA simulate skin at 35 °C fully sweating in a 25 °C, 65 %
be altered in the testing condition and that condensation may
occur within the specimen. RH environment, with a 2 m/s wind flowing parallel to the
A
surface of the skin.
R = apparent total evaporative resistance of the fabric test
et
specimen, liquid barrier, and surface air layer when evaluated
3.2 For definitions of other terms related to protective
non-isothermally. The term apparent is used as a modifier for
clothing used in this test method, refer to Terminology F1494.
total evaporative resistance to reflect the fact that the properties
of the specimen may be altered in the testing condition and that
4. Significance and Use
condensation may occur within the specimen.
4.1 The thermal resistance, evaporative resistance, and total
R = evaporative resistance of the air layer on the surface of
ebp
heat loss provided by fabrics, films, coatings, foams, and
the liquid barrier without a fabric test specimen (that is, bare
leathers, including multi-layer assemblies, is of considerable
plate). This property reflects the instrument constant and the
importance in determining their suitability for use in fabricat-
resistance of the liquid barrier, and in conjunction with R , is
et
ing protective clothing systems.
used in the calculation of R .
ef
4.1.1 The thermal resistance, evaporative resistance, and
R = intrinsic evaporative resistance of the fabric test specimen
ef
total heat loss can be significantly affected by environmental
only. In the calculation of this value, the assumption is made
conditions. Extreme care must be taken when using results
that the boundary layers of the bare plate and the boundary
measured under standard testing conditions to determine a
layers of the fabric are equal.
material’s suitability for use in conditions outside the testing
R = total evaporative resistance of the fabric test specimen,
et
conditions.
the liquid barrier, and the surface air layer.
4.2 The thermal interchange between people and their
3.1.3 permeability index (i ), n—the efficiency of evapora-
m
environment is an extremely complicated subject that involves
tive heat transport in a clothing system.
many factors in addition to the steady-state resistance values of
3.1.3.1 Discussion—An i of zero indicates that the clothing
m
fabrics, films, coatings, foams, and leathers, including multi-
system allows no evaporative heat transfer. An i of one
m
layer assemblies. Therefore, thermal resistance values, evapo-
indicates that the clothing system achieves the theoretical
rative resistance values, and total heat loss measured on a hot
maximum evaporative heat transfer allowed by its insulation;
plate may or may not indicate relative merit of a particular
however, a value of one is not approached in practice. The
material or system for a given clothing application. While a
permeability index is calculated one of two ways.
possible indicator of clothing performance, measurements
i = permeability index calculated using the total thermal
m
produced by the testing of fabrics have no proven correlation to
resistance and the total evaporative resistance of a material.
the performance of clothing systems worn by people. Clothing
i = permeability index calculated using the intrinsic thermal
mf
weight, drape, tightness of fit, and so forth, can minimize or
resistance and the intrinsic evaporative resistance of a material.
even neutralize the apparent differences between fabrics or
ISO 11092 uses this value.
fabric assemblies measured by this test method.
3.1.4 thermal resistance, n—the resistance to the flow of
4.3 The thermal resistance and evaporative resistance of
heat from a heated surface to a cooler environment.
clothing systems and items can be measured with a heated
3.1.4.1 Discussion—Thermal resistance in units of K·m /W
sweating manikin in an environmental chamber in accordance
can be calculated for several different cases.
with Test Methods F1291, F2370, and F3426.
I = total insulation value of the test specimen and the air layer,
t
expressed in clo units.
5. Interferences
I = intrinsic thermal resistance of the fabric test specimen only,
f
expressed in clo units. 5.1 Departures from the instructions of this test method lead
R = thermal resistance of the air layer on the surface of the to different testing results. Technical knowledge concerning the
cbp
F1868 − 23
theory of heat flow, temperature measurement, and testing electronic humidity-measuring device shall be used to measure
practices is needed to evaluate which departures from the the relative humidity and calculate the dew point temperature
instructions are significant. Standardization of the method inside the chamber. The relative humidity-sensing devices shall
reduces but does not eliminate the need for such technical have an overall accuracy of at least 64 %.
knowledge. Report any departures from the instructions of Test 6.6.2 Air Temperature Sensors—Shielded air temperature
Method F1868 with the results. sensors shall be used. Any sensor with an overall accuracy of
60.1 °C is acceptable. The sensor shall have a time constant
6. Apparatus
not exceeding 1 min. The sensor(s) is suspended with the
measuring point exposed to air inside the chamber at a point in
6.1 Hot Plate—The guarded hot plate shall be composed of
the air stream such that the air temperature sensor is not
a test plate, guard section, and bottom plate, each electrically
influenced by the plate temperature.
maintained at a constant temperature in the range of human
6.6.3 Air Velocity Indicator—Air velocity shall be measured
skin temperature (33 to 36 °C). The guard section shall be
with an accuracy of 60.1 m/s using a hot wire anemometer. Air
designed to prevent lateral loss of heat from the test plate. The
velocity is measured at a point 15 mm (nominal) from the plate
guard section shall be wide enough to minimize heat loss and
surface or from the top of the test specimen surface to the
moisture transport through the edges of the test specimen under
bottom of the anemometer sensing element. The air velocity
the conditions of the test. The bottom plate shall prevent
shall be measured at one position perpendicular to the airflow,
downward loss of heat from the test plate and guard section. A
at the center of the plate.
system for feeding water to the surface of the test plate and
6.6.3.1 The air velocity is to be measured 15 mm above the
guard section is also needed for testing Parts B and C. See Test
plate surface for bare plate measurements. The air velocity is to
Methods D1518, C177, and ISO 11092 for additional informa-
be measured 15 mm above the test specimen surface when
tion on hot plates.
testing fabric or systems. The 15 mm distance is to be the
6.2 Temperature Control—Separate, independent tempera-
distance from the plate or test specimen to the anemometer
ture control is required for the three sections of the hot plate
sensing element (wire)—not to the bottom of the sensing
(test plate, guard section, and bottom plate). Temperature
element housing.
control is achieved by independent adjustments to the voltage
6.6.3.2 At a minimum, annually verify that air velocity
or current, or both, supplied to the heaters using solid-state
spatial variation does not exceed 610 % of the mean value.
power supplies, solid-state relays (proportional time on), ad-
Measurements of air velocity shall be measured at three
justable transformers, variable impedances, or intermittent
positions located along a horizontal line perpendicular to the
heating cycles. The test plate, guard, and bottom plate sections
airflow, including a point at the center of the plate and at points
shall be controlled to measure the same temperature to within
at the centers of the guard section on both sides of the plate.
60.1 °C of each other.
6.6.3.3 The additional two anemometers needed for spatial
6.3 Power-Measuring Instruments—Power to the hot plate
variation must meet the same requirements as defined in 6.6.3
test section shall be measured to provide an accurate average
and shall be permitted to be external anemometers or integral
over the period of the test. If time proportioning or phase
anemometers to the system.
proportioning is used for the power control, then devices that
6.6.4 Air Temperature Variations—Air temperature varia-
are capable of averaging over the control cycle are required.
tions during testing shall not exceed 60.1
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F1868 − 17 F1868 − 23
Standard Test Method for
Thermal and Evaporative Resistance Resistance,
Evaporative Resistance, and Total Heat Loss Measurements
of Clothing Materials Using a Sweating Hot Plate
This standard is issued under the fixed designation F1868; 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 (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Clothing is often made of materials that impede the flow of heat and moisture from the skin to the
environment. Consequently, people may suffer from heat stress or cold stress when wearing clothing
in different environmental conditions. Therefore, it is important to quantify the thermal resistance and
evaporative resistance resistance, evaporative resistance, and total heat loss of clothing materials and
to consider these properties when selecting materials for different clothing applications.
1. Scope
1.1 This test method covers the measurement of the thermal resistance and the evaporative resistance, under steady-state
conditions,resistance, evaporative resistance, and total heat loss under steady-state conditions of fabrics, films, coatings, foams, and
leathers, including multi-layer assemblies, for use in clothing systems.
1.2 The range of this measurement technique for intrinsic thermal resistance is from 0.002 to 0.5 K·m /W and for intrinsic
2 2
evaporative resistance is from 0.0 to 1.0 kPa·m /W. The total heat loss range is from 0.0 to 1300 W/m .
1.3 The values in SI units shall be regarded as standard. No other Other units of measurement are included in this provided in this
standard but are not regarded as standard.
1.4 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 consult and establish appropriate safety and healthsafety, health, and environmental practices and
determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
This test method is under the jurisdiction of ASTM Committee F23 on Personal Protective Clothing and Equipment and is the direct responsibility of Subcommittee
F23.60 on Human Factors.
Current edition approved June 1, 2017June 1, 2023. Published June 2017June 2023. Originally approved in 1998. Last previous edition approved in 20142017 as
F1868 – 14.F1868 – 17. DOI: 10.1520/F1868-17.10.1520/F1868-23.
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 the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1868 − 23
C177 Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the
Guarded-Hot-Plate Apparatus
D1518 Test Method for Thermal Resistance of Batting Systems Using a Hot Plate (Withdrawn 2023)
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
F1291 Test Method for Measuring the Thermal Insulation of Clothing Using a Heated Manikin
F1494 Terminology Relating to Protective Clothing
F2370 Test Method for Measuring the Evaporative Resistance of Clothing Using a Sweating Manikin
F3426 Test Method for Measuring the Thermal Insulation of Clothing Items Using Heated Manikin Body Forms
2.2 Other Standards:
ISO 11092 Textiles – Physiological Effects – Measurement of Thermal and Water-Vapour Resistance Under Steady-State
Conditions (Sweating Guarded-Hotplate Test)
3. Terminology
3.1 Definitions:
3.1.1 clo, n—a unit of thermal resistance (insulation) equal to 0.155 K·m /W.
3.1.1.1 Discussion—
The value of the clo was selected as roughly the insulation value of typical indoor clothing, which should keep a resting manperson
(producing heat at the rate of 58 W ⁄m ) comfortable in an environment at 21 °C, air movement 0.1 m/s. When clo was developed,
typical indoor clothing consisted of a three-piece suit and light underclothes.
3.1.2 evaporative resistance, n—Thethe resistance to the flow of moisture vapor from a saturated surface (high vapor pressure)
to an environment with a lower vapor pressure.
3.1.2.1 Discussion—
The evaporative resistance in units of kPa·m /W can be calculated for several different cases.
A
R = apparent totalintrinsic evaporative resistance of the fabric test specimen only, when evaluated non-isothermally. The term
ef
apparent is used as a modifier for totalintrinsic evaporative resistance to reflect the fact that the properties of the specimen may
be altered in the testing condition and that condensation may occur within the specimen.
A
R = apparent total evaporative resistance of the fabric test specimen, liquid barrier, and surface air layer when evaluated
et
non-isothermally. The term apparent is used as a modifier for total evaporative resistance to reflect the fact that the properties of
the specimen may be altered in the testing condition and that condensation may occur within the specimen.
R = evaporative resistance of the air layer on the surface of the liquid barrier without a fabric test specimen (that is, bare plate).
ebp
This property reflects the instrument constant and the resistance of the liquid barrier, and in conjunction with R , is used in the
et
calculation of R .
ef
R = intrinsic evaporative resistance of the fabric test specimen only. In the calculation of this value, the assumption is made that
ef
the boundary layers of the bare plate and the boundary layers of the fabric are equal.
R = total evaporative resistance of the fabric test specimen, the liquid barrier, and the surface air layer.
et
3.1.3 permeability index (i ),n—the efficiency of evaporative heat transport in a clothing system.
m
3.1.3.1 Discussion—
An i of zero indicates that the clothing system allows no evaporative heat transfer. An i of one indicates that the clothing system
m m
achieves the theoretical maximum evaporative heat transfer allowed by its insulation. insulation; however, a value of one is not
approached in practice. The permeability index is calculated one of two ways.
i = permeability index calculated using the total thermal resistance and the total evaporative resistance of a material. The U.S.
m
military uses this value in their databases on fabrics and clothing systems.
i = permeability index calculated using the intrinsic thermal resistance and the intrinsic evaporative resistance of a material.
mf
ISO 11092 uses this value.
3.1.4 thermal resistance, n—the resistance to the flow of heat from a heated surface to a cooler environment.
3.1.4.1 Discussion—
Thermal resistance in units of K·m /W can be calculated for several different cases.
I = total insulation value of the test specimen and the air layer, expressed in clo units.
t
I = intrinsic thermal resistance of the fabric test specimen only, expressed in clo units.
f
The last approved version of this historical standard is referenced on www.astm.org.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
F1868 − 23
R = thermal resistance of the air layer on the surface of the plate without a fabric test specimen (that is, bare plate). This property
cbp
reflects the instrument constant and is used to standardize the plate, and in conjunction with R , is used in the calculation of R .
ct cf
R = intrinsic thermal resistance of the fabric test specimen only. In the calculation of this value, the assumption is made that the
cf
boundary layers of the bare plate and the boundary layers of the fabric test specimen are equal.
R = total thermal resistance of the test specimen and the air layer.
ct
3.1.5 total heat loss, n—the amount of heat transferred through a material or a composite by the combined dry and evaporative
heat exchanges under specified conditions expressed in watts per square metre.meter.
3.1.5.1 Discussion—
This single criterion for comparing fabric assemblies was developed as a special case by the National Fire Protection
Assoc.Association. The specific conditions used by NFPA are a simulate skin at 35 °C fully sweating hot plate surface in a 25 °C,
65 % RH environment.environment, with a 2 m/s wind flowing parallel to the surface of the skin.
3.2 For definitions of other terms related to protective clothing used in this test method, refer to Terminology F1494.
4. Significance and Use
4.1 The thermal resistance and evaporative resistance resistance, evaporative resistance, and total heat loss provided by fabrics,
films, coatings, foams, and leathers, including multi-layer assemblies, is of considerable importance in determining their suitability
for use in fabricating protective clothing systems.
4.1.1 The thermal resistance, evaporative resistance, and total heat loss can be significantly affected by environmental conditions.
Extreme care must be taken when using results measured under standard testing conditions to determine a material’s suitability
for use in conditions outside the testing conditions.
4.2 The thermal interchange between people and their environment is, however, is an extremely complicated subject that involves
many factors in addition to the steady-state resistance values of fabrics, films, coatings, foams, and leathers, including multi-layer
assemblies. Therefore, thermal resistance values and evaporative resistance values values, evaporative resistance values, and total
heat loss measured on a hot plate may or may not indicate relative merit of a particular material or system for a given clothing
application. While a possible indicator of clothing performance, measurements produced by the testing of fabrics have no proven
correlation to the performance of clothing systems worn by people. Clothing weight, drape, tightness of fit, and so forth, can
minimize or even neutralize the apparent differences between fabrics or fabric assemblies measured by this test method.
4.3 The thermal resistance and evaporative resistance of clothing systems and items can be measured with a heated sweating
manikin in an environmental chamber in accordance with Test Methods F1291, F2370and , and F2370F3426.
5. Interferences
5.1 Departures from the instructions of this test method may lead to significantly different testtesting results. Technical knowledge
concerning the theory of heat flow, temperature measurement, and testing practices is needed to evaluate which departures from
the instructions are significant. Standardization of the method reduces,reduces but does not eliminate the need for such technical
knowledge. Report any departures from the instructions of Test Method F1868 with the results.
6. Apparatus
6.1 Hot Plate—The guarded flathot plate shall be composed of a test plate, guard section, and bottom plate, each electrically
maintained at a constant temperature in the range of human skin temperature (33 to 36 °C). The guard section shall be designed
to prevent lateral loss of heat from the test plate. The guard section shall be wide enough to minimize heat loss and moisture
transport through the edges of the test specimen under the conditions of the test. The bottom plate shall prevent downward loss
of heat from the test plate and guard section. A system for feeding water to the surface of the test plate and guard section is also
needed for testing Parts B and C. See Test Methods D1518, C177, and ISO 11092 for additional information on hot plates.
6.2 Temperature Control—Separate, independent temperature control is required for the three sections of the hot plate (test plate,
guard section, and bottom plate). Temperature control may be is achieved by independent adjustments to the voltage or current,
or both, supplied to the heaters using solid-state power supplies, solid-state relays (proportional time on), adjustable transformers,
variable impedances, or intermittent heating cycles. The test plate, guard, and bottom plate sections shall be controlled to measure
the same temperature to within 60.1 °C of each other.
F1868 − 23
6.3 Power-Measuring Instruments—Power to the hot plate test section shall be measured to provide an accurate average over the
period of the test. If time proportioning or phase proportioning is used for the power control, then devices that are capable of
averaging over the control cycle are required. Integrating devices (watt-hour transducers) are preferred over instantaneous devices
(watt metres).meters). Overall accuracy of the power-monitoring equipment must be within 62 % of the reading for the average
power for the test period.
6.4 Temperature Sensors—Temperature sensors shall be thermistors, thermocouples, resistance temperature devices (RTDs), or
equivalent sensors. The test plate, guard section, and bottom plate shall each contain one or more temperature sensors that are
mounted flush with the hot plate surface and in such a manner that they measure the surface temperature within plate surface. Each
temperature sensor shall have an overall accuracy of 60.1 °C.
6.5 Controlled Atmosphere Chamber—The hot plate shall be housed in an environmental chamber that can be maintained at
selected temperatures at a minimum between 20 and 35 °C. The test chamber wall temperature shall be 60.5 °C of the air in the
chamber. The relative humidity shall be maintained as specified in the individual procedure section.
6.6 Measuring Environmental Parameters—The air temperature, relative humidity, and air velocity shall be measured as follows:
6.6.1 Relative Humidity Measuring Equipment—Either a wet-and-dry A wet and dry bulb psychrometer, a dew point hygrometer,
or other electronic humidity-measuring device shall be used to measure the
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.