1、Designation: F 2298 03Standard Test Methods forWater Vapor Diffusion Resistance and Air Flow Resistanceof Clothing Materials Using the Dynamic MoisturePermeation Cell1This standard is issued under the fixed designation F 2298; the number immediately following the designation indicates the year ofori
2、ginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of the mois-ture vapo
3、r transport and gas flow properties of fabrics, mem-branes, and membrane laminates used for protective materials.1.2 The values stated in SI units are to be regarded as thestandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresp
4、onsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 737 Test Method for Air Permeability of Textile FabricsE 96 Test Methods for Water Vapor
5、Transmission of Mate-rialsF 778 Methods for Gas Flow Resistance Testing of Filtra-tionF 1868 Test Method for Thermal Evaporative Resistance ofClothing Materials Using a Sweating Hot Plate2.2 Other Standards:ISO 11092 TextilesPhysiological EffectsMeasurementof Thermal and Water-Vapour Resistance Unde
6、r Steady-State Conditions (Sweating Guarded-Hotplate Test)3JIS L 1099 Testing Methods for Water Vapour Permeabilityof Clothes33. Terminology3.1 Definitions:3.1.1 water vapor diffusion, nthe process by which watervapor molecules move from a region of high concentration toa region of low concentration
7、.3.1.2 water vapor transmission rate, nthe steady watervapor flow in unit time through unit area of a material, underspecific conditions of temperature and humidity at each sur-face.4. Summary of Test Methods4.1 The testing outlined in this standard consists of measur-ing the amount of water vapor t
8、ransport across a specimen. Thewater vapor transport properties can be measured in a purediffusion mode and in a diffusion/convection mode.4.2 Two test methods are presented in this standard:4.2.1 Part A (Diffusion Test)The test is done under themaximum difference in relative humidity and zero press
9、uregradient across the specimen so that only the water vapordiffusion transport through the specimen is measured (Fig. 1).4.2.2 Part B (Combined Convection/Diffusion Test)A se-ries of pressure gradients is applied in specified increments toforce air through the material (Fig. 1). Thus, the test isco
10、nducted under a combined air pressure gradient and concen-tration gradient that allows examination of the interaction ofconvective and diffusive mass transfer across the specimen.This method is designed for use on relatively air-permeabletextile materials because for air-impermeable materials, there
11、sults will be the same as the diffusion test alone.5. Significance and Use5.1 The water vapor transport properties of textile materialsare of considerable importance in determining the comfortproperties of clothing systems. Water vapor transport throughporous textiles may occur due to both diffusion
12、 (driven byvapor concentration differences) and convection (driven by gaspressure differences).5.2 For air permeable porous materials, a very small pres-sure gradient can produce large convective flows through thepores in the structure. In many standard water vapor perme-ability test methods, when u
13、sed for materials with high airpermeability, slight variations in pressure gradient across aspecimen will greatly influence the measured water vapor1These test methods are under the jurisdiction of ASTM Committee F23 onProtective Clothing and are the direct responsibility of Subcommittee F23.60 onHu
14、man Factors.Current edition approved July 10, 2003. Published August 2003.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe
15、ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.transport properties. Therefore, the water vapor transportpropert
16、ies of the porous and non-porous textile materialscannot be directly compared when the method has no provisionfor controlling the pressure gradient. This test method deter-mines the diffusion and convection properties from the sametest and generates data that allows direct comparison of theresults o
17、btained between materials.6. Sampling and Preparation of Test Specimens6.1 Sampling:FIG. 1 Overview of the Test MethodsF22980326.1.1 Laboratory SampleTake test specimens that arebelieved to be representative of the sample to be tested and freeof abnormal distortions. The sample may be a piece of fab
18、ric ora garment.6.1.2 If the material is of nonsymmetrical construction, thetwo faces shall be designated by distinguishing marks.6.2 Sample Preparation:6.2.1 Cut three specimens from each laboratory sample.6.2.2 Specimen SizeUse specimens larger than the area ofthe opening in the clamping plate so
19、that the test area iscovered completely.7. Test Apparatus7.1 The procedures in these methods require measurementof the pressure gradient across the specimen and the mass flowrate. Fig. 2 is a schematic diagram of the basic system for thedynamic moisture permeation cell (DMPC). This standard iswritte
20、n to allow operation of the DMPC system under manualcontrol of the test operator. However, the preferred method isto automate the data acquisition and control system of theapparatus so the entire test is performed under the control of acomputer.7.2 Control and Measuring Units:7.2.1 Mass Flow Rate Co
21、ntroller, measures and controls thegas flows in a wide variety of applications. Either analog orelectronic digital type mass flow rate controller can be used.The mass flow rate controllers maintain the correct incomingrelative humidity by adjusting the ratio of the relative massflows of a saturated
22、and a dry nitrogen stream. The testapparatus requires four mass flow controllers. Two controllersadjust the dry and saturated nitrogen gas streams to the top flowcell, and two controllers adjust the dry and wet nitrogen gasstreams to the bottom flow cell. The mass flow controllers shallbe controlled
23、 at an accuracy of 6 1 % of full scale, with aresponse time of less than 5 s, unless stated otherwise in theFIG. 2 Schematic of DMPC Test SystemF2298033data report. Electronic mass flow controllers usually indicateflow rate in terms of volumetric flow rates at standardconditions of 0C and atmospheri
24、c pressure. The actual volu-metric flow rate at the actual test temperature can be calculatedfrom the mass flow rate, the temperature, and the pressure ofthe actual flow.7.2.2 Channel Power Supply and Readout, controls anddisplays the flow meters and controllers. The display accuracyof the channel r
25、eadout shall be within 6 0.2 % 6 1 digit,unless stated otherwise in the data report.7.2.3 Differential Pressure Transducer, directly measuresthe pressure gradient across the specimen. The differentialpressure transducer can be either digital or analog type with anaccuracy of within 6 0.2 % of the in
26、dicated value. The sensorrequires power and signal conditioning electronics. The pres-sure in the flow cells is controlled by means of two automatedrestrictor valves (7.2.5) at the outlets of the cell.7.2.4 Signal Conditioner/Display Unit, provides power andsignal conditioning for the differential p
27、ressure transducersensors.7.2.5 Proportioning Valve and Controller, used to continu-ously control the gas flows. The restrictor valves at the exits ofthe cell are used to systematically vary the pressure gradientacross the specimen to produce various amounts of convectiveflows across the specimen. T
28、he valves shall withstand themaximum pressure in the test cell during the test. Instead of theelectronic pressure gauges and automated restrictor valves, it isacceptable to use analog differential pressure gauges in avariety of different full scale ranges, and manual needle ororifice metering valves
29、 at the gas flow exit of the cells tocontrol the pressure gradient across the test specimen.7.2.6 Electronic Mass Flow Meter and Power Supply,connects one of the exits of the flow cells (bottom cell) and theproportioning valve. The mass flow meter directly measuresand displays the mass flow rate wit
30、h a response time of within5s.7.2.7 Humidity Measurement Instrument, measures the rela-tive humidity of the incoming and the outgoing gas flows. Therelative humidity of the incoming gas flow is directly measuredwith the humidity sensor. Relative humidity can be measuredin different ways, such as a c
31、ondensation type dew pointhygrometer, capacitance type relative humidity probe, or gaschromatography. Capacitance type humidity probe is recom-mended because it provides small size and a fast response time.The relative humidity probes shall have a measurement accu-racy of 6 3 % R.H. over the range i
32、n use, unless stated in thereport.7.2.8 Temperature Measurement InstrumentThe tempera-ture measurement sensor shall measure the temperature within6 0.1C with a time constant not exceeding 1 min. Thetemperature measurement shall be made at the same place asthe humidity measurement.7.3 Moisture Permea
33、tion Cell:7.3.1 Flow Cell Unit, consists of two identical flow cellsegments made of plastic, glass, or other materials that will notcorrode and do not absorb moisture. Each cell segment consistsof a flow cell and a sample clamping plate. The size of the cellcan be as large as practical, so as the si
34、ze of the duct. Thetypical size of the duct in each flow cell segment is 0.025 mwide, 0.13 m long, and 0.0050 m high. The entrance length ofthe nitrogen gas must be long enough to get a stable fullydeveloped flow. At 2000 cm3/min gas flow rate, more than0.002 m is required for the duct length from t
35、he gas entrance tothe sample, and from the specimen to the gas exit. The typicalduct length is about 0.003 to 0.007 m. Each flow cell segmentshall have ports for flow inlet and outlet in both ends of theflow cell segment, and a port for differential pressure measure-ment on the front top of the flow
36、 cell segment. A specimen isheld in-between the two flow cell segments (Fig. 3).7.3.2 Specimen Clamping Plate, can be made of plastic,metal, or steel, and attached to the flow cell segments by usinga sealing agent or mounting bolts. The thickness of clampingplate shall be 5 3 10-5m (0.5 mm). The hol
37、e opening in theclamping plate that determines the test area of the specimenshall have the size of 0.05 m long by 0.02 m wide (0.001 m2).Aspecimen must be bigger than the hole of a clamping plate tocover the clamping plate completely.7.3.3 Clamping System, prevents leakage of the nitrogen gasthrough
38、 the test cell unit. The sealing other than the clampingforce provided by the mounting bolts is unnecessary for mostFIG. 3 Typical Dimensions of the Specimen Holder for the DMPCF2298034thin materials such as laminated and woven textile materials. Ifthere is any leakage from the edges of the specimen
39、, specialsealing methods such as molten wax, curable sealant, rubbersealing gaskets may be required.7.3.4 Bubblers, used to saturate nitrogen gas in water.Bubblers of 500 mL or 1000 mL are appropriate for this test.The first bubbler completes the primary saturation of the gasstream. The second bubbl
40、er ensures full saturation, and bringsthe gas stream back to deviation from the test temperature thatmay have occurred due to evaporative cooling in the firstbubbler. The saturated and the dry nitrogen gas controlled byseparate mass flow meters shall merge into one gas tube andenter to the top flow
41、cell. The ratio of dry and saturatednitrogen gas determines the relative humidity in the flow cell.An identical set of two flow controllers and bubblers areneeded to control the relative humidity of the bottom flow cell.7.3.5 Data Acquisition SystemIt is possible to conduct thetests manually by read
42、ing the outputs from the relative humid-ity measurement devices, flow meters, and pressure transducersand performing the necessary calculations. However, it isrecommended to conduct the tests under the control of acomputer to automate the tasks of data collection and control ofthe mass flow controll
43、ers and valves.7.4 Materials:7.4.1 Reference Material,4required for the calibration tocheck the instrument before testing. Use microporous ex-panded polytetrafluorethylene (ePTFE) membrane as a refer-ence material.7.4.2 Nitrogen Gas, pure nitrogen gas with technical gradeof 99 % is used.8. Calibrati
44、on Procedures8.1 Three calibration procedures may be necessary. The firsttwo procedures (flow and humidity calibration) may not berequired for all systems, depending on the accuracy andstability of the specific instrumentation incorporated into theparticular DMPC design used.8.2 Flow Controller Cali
45、bration and CheckIt is importantto ensure that the flow controllers are all checked and adjustedto give the same flow. For high accuracy electronic mass flowcontrollers, this step may be unnecessary since there is verylittle drift of high quality stable controllers. The flow controllercheck is carri
46、ed out using only dry nitrogen. Any method ofverifying that the flows at a specific indicated flow rate of thefour controllers are equal is acceptable.8.2.1 Test each flow controller individually by connecting itto a flow measurement device. The mass flow meter requiredfor the diffusion/convection t
47、est is sufficient for this purpose.Adjust each mass flow controller to the mass flow rate to beused in the actual test. They should all give the same flow towithin the control and measurement accuracy specifications ofthe mass flow controllers. If there are deviations, the full rangeoutput for elect
48、ronic mass flow controllers can be manually orelectronically adjusted so that each flow controller gives thesame flow rate as all the other mass flow controllers. Analternate flow rate measurement method is to use a needlevalve or orifice, with a differential pressure sensor connectedacross the valv
49、e or orifice, which is connected to the output ofa mass flow controller. Appropriate sizing of the needle valveor orifice opening, and the pressure transducer range, will givea measured pressure gradient across the valve or orifice whichis indicative of whether each mass flow controller set at aparticular flow is actually delivering identical gas flow rates.8.3 Humidity CalibrationRequirements for humidity cali-bration will also depend on the humidity measurement systemselected for the test. Humidity calibration procedures may besupplied by the manufacturer for the speci
