ASTM F2298-03
(Test Method)Standard Test Methods for Water Vapor Diffusion Resistance and Air Flow Resistance of Clothing Materials Using the Dynamic Moisture Permeation Cell
Standard Test Methods for Water Vapor Diffusion Resistance and Air Flow Resistance of Clothing Materials Using the Dynamic Moisture Permeation Cell
SIGNIFICANCE AND USE
The water vapor transport properties of textile materials are of considerable importance in determining the comfort properties of clothing systems. Water vapor transport through porous textiles may occur due to both diffusion (driven by vapor concentration differences) and convection (driven by gas pressure differences).
For air permeable porous materials, a very small pressure gradient can produce large convective flows through the pores in the structure. In many standard water vapor permeability test methods, when used for materials with high air permeability, slight variations in pressure gradient across a specimen will greatly influence the measured water vapor transport properties. Therefore, the water vapor transport properties of the porous and non-porous textile materials cannot be directly compared when the method has no provision for controlling the pressure gradient. This test method determines the diffusion and convection properties from the same test and generates data that allows direct comparison of the results obtained between materials.
SCOPE
1.1 This test method covers the measurement of the moisture vapor transport and gas flow properties of fabrics, membranes, and membrane laminates used for protective materials.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 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.
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Designation:F2298–03
Standard Test Methods for
Water Vapor Diffusion Resistance and Air Flow Resistance
of Clothing Materials Using the Dynamic Moisture
Permeation Cell
This standard is issued under the fixed designation F2298; 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 3.1.1 water vapor diffusion, n—the process by which water
vapor molecules move from a region of high concentration to
1.1 This test method covers the measurement of the mois-
a region of low concentration.
ture vapor transport and gas flow properties of fabrics, mem-
3.1.2 water vapor transmission rate, n—the steady water
branes, and membrane laminates used for protective materials.
vapor flow in unit time through unit area of a material, under
1.2 The values stated in SI units are to be regarded as the
specific conditions of temperature and humidity at each sur-
standard.
face.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Summary of Test Methods
responsibility of the user of this standard to establish appro-
4.1 The testing outlined in this standard consists of measur-
priate safety and health practices and determine the applica-
ingtheamountofwatervaportransportacrossaspecimen.The
bility of regulatory limitations prior to use.
water vapor transport properties can be measured in a pure
2. Referenced Documents diffusion mode and in a diffusion/convection mode.
4.2 Two test methods are presented in this standard:
2.1 ASTM Standards:
4.2.1 Part A (Diffusion Test)—The test is done under the
D737 Test Method for Air Permeability of Textile Fabrics
maximum difference in relative humidity and zero pressure
E96 Test Methods for Water Vapor Transmission of Mate-
gradient across the specimen so that only the water vapor
rials
diffusion transport through the specimen is measured (Fig. 1).
F778 Methods for Gas Flow Resistance Testing of Filtra-
4.2.2 Part B (Combined Convection/Diffusion Test)—A se-
tion
ries of pressure gradients is applied in specified increments to
F1868 Test Method forThermal Evaporative Resistance of
force air through the material (Fig. 1). Thus, the test is
Clothing Materials Using a Sweating Hot Plate
conducted under a combined air pressure gradient and concen-
2.2 Other Standards:
tration gradient that allows examination of the interaction of
ISO 11092 Textiles—Physiological Effects—Measurement
convective and diffusive mass transfer across the specimen.
of Thermal and Water-Vapour Resistance Under Steady-
This method is designed for use on relatively air-permeable
State Conditions (Sweating Guarded-Hotplate Test)
textile materials because for air-impermeable materials, the
JIS L1099 Testing Methods for Water Vapour Permeability
results will be the same as the diffusion test alone.
of Clothes
5. Significance and Use
3. Terminology
5.1 The water vapor transport properties of textile materials
3.1 Definitions:
are of considerable importance in determining the comfort
properties of clothing systems. Water vapor transport through
These test methods are under the jurisdiction of ASTM Committee F23 on porous textiles may occur due to both diffusion (driven by
Personal Protective Clothing and Equipment and are the direct responsibility of
vaporconcentrationdifferences)andconvection(drivenbygas
Subcommittee F23.60 on Human Factors.
pressure differences).
Current edition approved July 10, 2003. Published August 2003.
5.2 For air permeable porous materials, a very small pres-
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
sure gradient can produce large convective flows through the
Standards volume information, refer to the standard’s Document Summary page on
pores in the structure. In many standard water vapor perme-
the ASTM website.
ability test methods, when used for materials with high air
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036. permeability, slight variations in pressure gradient across a
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F2298–03
FIG. 1 Overview of the Test Methods
specimen will greatly influence the measured water vapor mines the diffusion and convection properties from the same
transport properties. Therefore, the water vapor transport test and generates data that allows direct comparison of the
properties of the porous and non-porous textile materials results obtained between materials.
cannotbedirectlycomparedwhenthemethodhasnoprovision
for controlling the pressure gradient. This test method deter-
F2298–03
FIG. 2 Schematic of DMPC Test System
6. Sampling and Preparation of Test Specimens apparatus requires four mass flow controllers. Two controllers
adjustthedryandsaturatednitrogengasstreamstothetopflow
6.1 Sampling:
cell, and two controllers adjust the dry and wet nitrogen gas
6.1.1 Laboratory Sample—Take test specimens that are
streamstothebottomflowcell.Themassflowcontrollersshall
believedtoberepresentativeofthesampletobetestedandfree
be controlled at an accuracy of 6 1% of full scale, with a
ofabnormaldistortions.Thesamplemaybeapieceoffabricor
response time of less than 5 s, unless stated otherwise in the
a garment.
data report. Electronic mass flow controllers usually indicate
6.1.2 If the material is of nonsymmetrical construction, the
flow rate in terms of volumetric flow rates at standard
two faces shall be designated by distinguishing marks.
conditions of 0°C and atmospheric pressure. The actual volu-
6.2 Sample Preparation:
metricflowrateattheactualtesttemperaturecanbecalculated
6.2.1 Cut three specimens from each laboratory sample.
from the mass flow rate, the temperature, and the pressure of
6.2.2 Specimen Size—Use specimens larger than the area of
the actual flow.
the opening in the clamping plate so that the test area is
7.2.2 Channel Power Supply and Readout, controls and
covered completely.
displays the flow meters and controllers. The display accuracy
7. Test Apparatus of the channel readout shall be within 6 0.2% 6 1 digit,
unless stated otherwise in the data report.
7.1 The procedures in these methods require measurement
7.2.3 Differential Pressure Transducer, directly measures
ofthepressuregradientacrossthespecimenandthemassflow
the pressure gradient across the specimen. The differential
rate. Fig. 2 is a schematic diagram of the basic system for the
pressuretransducercanbeeitherdigitaloranalogtypewithan
dynamic moisture permeation cell (DMPC). This standard is
accuracy of within 6 0.2% of the indicated value. The sensor
written to allow operation of the DMPC system under manual
requires power and signal conditioning electronics. The pres-
control of the test operator. However, the preferred method is
sure in the flow cells is controlled by means of two automated
to automate the data acquisition and control system of the
restrictor valves (7.2.5) at the outlets of the cell.
apparatus so the entire test is performed under the control of a
7.2.4 Signal Conditioner/Display Unit, provides power and
computer.
signal conditioning for the differential pressure transducer
7.2 Control and Measuring Units:
sensors.
7.2.1 Mass Flow Rate Controller,measuresandcontrolsthe
gas flows in a wide variety of applications. Either analog or 7.2.5 Proportioning Valve and Controller, used to continu-
electronic digital type mass flow rate controller can be used. ouslycontrolthegasflows.Therestrictorvalvesattheexitsof
The mass flow rate controllers maintain the correct incoming the cell are used to systematically vary the pressure gradient
relative humidity by adjusting the ratio of the relative mass across the specimen to produce various amounts of convective
flows of a saturated and a dry nitrogen stream. The test flows across the specimen. The valves shall withstand the
F2298–03
FIG. 3 Typical Dimensions of the Specimen Holder for the DMPC
maximumpressureinthetestcellduringthetest.Insteadofthe corrodeanddonotabsorbmoisture.Eachcellsegmentconsists
electronicpressuregaugesandautomatedrestrictorvalves,itis of a flow cell and a sample clamping plate.The size of the cell
acceptable to use analog differential pressure gauges in a
can be as large as practical, so as the size of the duct. The
variety of different full scale ranges, and manual needle or
typical size of the duct in each flow cell segment is 0.025 m
orifice metering valves at the gas flow exit of the cells to
wide, 0.13 m long, and 0.0050 m high. The entrance length of
control the pressure gradient across the test specimen.
the nitrogen gas must be long enough to get a stable fully
7.2.6 Electronic Mass Flow Meter and Power Supply,
developed flow. At 2000 cm /min gas flow rate, more than
connectsoneoftheexitsoftheflowcells(bottomcell)andthe
0.002misrequiredfortheductlengthfromthegasentranceto
proportioning valve. The mass flow meter directly measures
the sample, and from the specimen to the gas exit. The typical
and displays the mass flow rate with a response time of within
duct length is about 0.003 to 0.007 m. Each flow cell segment
5s.
shall have ports for flow inlet and outlet in both ends of the
7.2.7 Humidity Measurement Instrument,measurestherela-
flow cell segment, and a port for differential pressure measure-
tive humidity of the incoming and the outgoing gas flows.The
ment on the front top of the flow cell segment. A specimen is
relativehumidityoftheincominggasflowisdirectlymeasured
held in-between the two flow cell segments (Fig. 3).
with the humidity sensor. Relative humidity can be measured
7.3.2 Specimen Clamping Plate, can be made of plastic,
in different ways, such as a condensation type dew point
metal, or steel, and attached to the flow cell segments by using
hygrometer, capacitance type relative humidity probe, or gas
a sealing agent or mounting bolts. The thickness of clamping
chromatography. Capacitance type humidity probe is recom-
-5
plate shall be 5 3 10 m (0.5 mm). The hole opening in the
mendedbecauseitprovidessmallsizeandafastresponsetime.
clamping plate that determines the test area of the specimen
The relative humidity probes shall have a measurement accu-
shall have the size of 0.05 m long by 0.02 m wide (0.001 m ).
racy of 6 3% R.H. over the range in use, unless stated in the
Aspecimenmustbebiggerthantheholeofaclampingplateto
report.
cover the clamping plate completely.
7.2.8 Temperature Measurement Instrument—The tempera-
7.3.3 Clamping System,preventsleakageofthenitrogengas
ture measurement sensor shall measure the temperature within
through the test cell unit. The sealing other than the clamping
6 0.1°C with a time constant not exceeding 1 min. The
force provided by the mounting bolts is unnecessary for most
temperature measurement shall be made at the same place as
thinmaterialssuchaslaminatedandwoventextilematerials.If
the humidity measurement.
7.3 Moisture Permeation Cell: there is any leakage from the edges of the specimen, special
sealing methods such as molten wax, curable sealant, rubber
7.3.1 Flow Cell Unit, consists of two identical flow cell
segmentsmadeofplastic,glass,orothermaterialsthatwillnot sealing gaskets may be required.
F2298–03
7.3.4 Bubblers, used to saturate nitrogen gas in water. a mass flow controller. Appropriate sizing of the needle valve
Bubblers of 500 mL or 1000 mL are appropriate for this test. or orifice opening, and the pressure transducer range, will give
The first bubbler completes the primary saturation of the gas a measured pressure gradient across the valve or orifice which
stream. The second bubbler ensures full saturation, and brings is indicative of whether each mass flow controller set at a
the gas stream back to deviation from the test temperature that particular flow is actually delivering identical gas flow rates.
may have occurred due to evaporative cooling in the first 8.3 Humidity Calibration—Requirementsforhumiditycali-
bubbler. The saturated and the dry nitrogen gas controlled by
bration will also depend on the humidity measurement system
separate mass flow meters shall merge into one gas tube and selected for the test. Humidity calibration procedures may be
enter to the top flow cell. The ratio of dry and saturated
supplied by the manufacturer for the specific instrument, or
nitrogen gas determines the relative humidity in the flow cell. may not be necessary for a high-accuracy system such as a gas
An identical set of two flow controllers and bubblers are chromatograph, infrared diode laser sensor, or a chilled-mirror
neededtocontroltherelativehumidityofthebottomflowcell. dew point hygrometer.
7.3.5 Data Acquisition System—Itispossibletoconductthe
8.4 Reference Material Calibration—Before starting test
tests manually by reading the outputs from the relative humid- withaspecimen,conductatestwithareferencematerialunder
itymeasurementdevices,flowmeters,andpressuretransducers
the condition specified in 9.2. An expanded polytetrafluoreth-
and performing the necessary calculations. However, it is
ylene (ePTFE) film is used as a reference material for the
recommended to conduct the tests under the control of a
system. The ePTFE membranes are microporous and hydro-
computertoautomatethetasksofdatacollectionandcontrolof
phobic, thus vapor transport takes place only through the
the mass flow controllers and valves.
interconnectedairspacesofthemembrane.Theydonotchange
7.4 Materials:
the transport properties as a function of membrane water
7.4.1 Reference Material, required for the calibration to
content or test conditions.
check the instrument before testing. Use microporous ex-
8.4.1 Test Conditions—Use the test conditions directed in
panded polytetrafluorethylene (ePTFE) membrane as a refer-
9.1.
ence material.
8.4.2 Place an ePTFE film in between the top and the
7.4.2 Nitrogen Gas, pure nitrogen gas with technical grade
bottom flow cell segments.
of 99% is used.
8.4.3 Follow the same procedures in 9.2.2-9.2.4.
8.4.4 Calculate total water vapor diffusion resistance Rdtot
8. Calibration Procedures
described in 9.3.
8.1 Threecalibrationproceduresmaybenecessary.Thefirst
8.4.5 The water vapor diffusion resistance of the reference
two procedures (flow and humidity calibration) may not be
material shall be 170 6 10%.
required for all systems, depending on the accuracy and
8.4.6 If t
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