1、Designation: F 1868 02Standard Test Method forThermal and Evaporative Resistance of Clothing MaterialsUsing a Sweating Hot Plate1This standard is issued under the fixed designation F 1868; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revi
2、sion, 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.INTRODUCTIONClothing is often made of materials that impede the flow of heat and moisture from the skin to thee
3、nvironment. Consequently, people may suffer from heat stress or cold stress when wearing clothingin different environmental conditions. Therefore, it is important to quantify the thermal resistance andevaporative resistance of clothing materials and to consider these properties when selecting materi
4、alsfor different clothing applications.1. Scope1.1 This test method covers the measurement of the thermalresistance and the evaporative resistance, under steady-stateconditions, of fabrics, films, coatings, foams, and leathers,including multi-layer assemblies, for use in clothing systems.1.2 The ran
5、ge of this measurement technique for thermalresistance is from 0.002 to 0.2 Km2/W and for evaporativeresistance is from 0.01 to 1.0 kPam2/W.1.3 The values in SI units shall be regarded as standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its us
6、e. It is theresponsibility of the user of this standard to consult andestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 177 Test Method for Steady-State Heat Flux Measure-ments and Th
7、ermal Transmission Properties by Means ofthe Guarded-Hot-Plate ApparatusD 1518 Thermal Transmittance of Textile MaterialsE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodF 1291 T
8、est Method for Measuring the Thermal Insulationof Clothing Using a Heated ManikinF 1494 Terminology Relating to Protective Clothing2.2 Other Standards:ISO 11092 TextilesPhysiological EffectsMeasurement ofThermal and Water-Vapour Resistance Under Steady-State Conditions (Sweating Guarded-Hotplate Tes
9、t)3NFPA 1971 Protective Clothing for Structural Fire Fight-ing4NFPA 1977 Protective Clothing and Equipment for Wild-land Fire Fighting43. Terminology3.1 Definitions:3.1.1 clo, nunit of thermal resistance defined as theinsulation required to keep a resting man (producing heat at therate of 58 W/m2) c
10、omfortable in an environment at 21C, airmovement 0.1 m/s, or roughly the insulation value of typicalindoor clothing.3.1.1.1 DiscussionNumerically the clo is equal to 0.155Km2/W.3.1.2 evaporative heat transmittance, ntime rate of undi-rectional evaporative heat transfer per unit area, in the steadyst
11、ate, between parallel planes, per unit difference of watervapor pressure of the planes.3.1.2.1 DiscussionEvaporative heat transmittance is ex-pressed as watts per square metre of test specimen perkilopascal of vapor pressure difference between the test plateand the environment (W/m2kPa). The evapora
12、tive heat trans-mittance may consist of both diffusive and convective compo-nents.1This test method is under the jurisdiction of ASTM Committee F23 onProtective Clothing and is the direct responsibility of Subcommittee F23.60 onHuman Factors.Current edition approved August 10, 2002. Published Octobe
13、r 2002. Originallypublished as F 1868 98. Last previous edition F 1868 98.2For 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
14、ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.4Available from National Fire Protection Assoc., 1 Batterymarch Park, Quincy,MA 02269.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428
15、-2959, United States.3.1.3 evaporative resistance, nreciprocal of evaporativeheat transmittance expressed in kilopascals, square metre oftest specimen per watt.3.1.3.1 DiscussionThe evaporative resistance for severaldifferent cases is determined in this method:RefA= apparent total evaporative resist
16、ance of the fabric testspecimen only, when evaluated non-isothermally. The termapparent is used as a modifier for total evaporative resistanceto reflect the fact that condensation may occur within thespecimen.RetA= apparent total evaporative resistance of the fabric testspecimen, liquid barrier, and
17、 surface air layer when evaluatednon-isothermally. The term apparent is used as a modifier fortotal evaporative resistance to reflect the fact that condensationmay occur within the specimen.Rebp= evaporative resistance of the air layer on the surface ofthe liquid barrier without a fabric test specim
18、en (that is, bareplate). This property reflects the instrument constant and theresistance of the liquid barrier, and in conjunction with Ret,isused in the calculation of Ref.Ref= intrinsic evaporative resistance of the fabric test specimenonly. In the calculation of this value, the assumption is mad
19、ethat the boundary layers of the bare plate and the boundarylayers of the fabric are equal.Ret= total evaporative resistance of the fabric test specimen,the liquid barrier, and the surface air layer.3.1.4 permeability index (im), nthe efficiency of evapora-tive heat transport in a clothing system.3.
20、1.4.1 DiscussionAn imof zero indicates that the cloth-ing system allows no evaporative heat transfer. An imof oneindicates that the clothing system achieves the theoreticalmaximum evaporative heat transfer allowed by its insulation.3.1.5 thermal transmittance, ntime rate of unidirectionalheat transf
21、er per unit area, in the steady state, between parallelplanes, per unit difference of temperature of the planes.Thermal transmittance is also known as thermal conductanceand the heat transfer coefficient.3.1.5.1 DiscussionThermal transmittance is expressed aswatts per square metre of test specimen p
22、er kelvin differencebetween the test plate and the environment (W/m2K). The dryheat flux may consist of one or more conductive, convective,and radiant components.3.1.6 thermal resistance, nreciprocal of thermal transmit-tance, expressed in kelvin, square metre of test specimen perwatt.3.1.6.1 Discus
23、sionThermal resistance for several differentcases is determined in this method:It= total insulation value of the test specimen and the air layer,expressed in clo units.Rcbp= thermal resistance of the air layer on the surface of theplate without a fabric test specimen (that is, bare plate). Thisprope
24、rty reflects the instrument constant and is used to stan-dardize the plate, and in conjunction with Rct, is used in thecalculation of Rcf.Rcf= intrinsic thermal resistance of the fabric test specimenonly. In the calculation of this value, the assumption is madethat the boundary layers of the bare pl
25、ate and the boundarylayers of the fabric test specimen are equal.Rct= total thermal resistance of the test specimen and the airlayer.3.1.7 total heat loss, nthe amount of heat transferredthrough a material or a composite by the combined dry andevaporative heat exchanges under specified conditions ex
26、-pressed in watts per square meter,3.1.7.1 DiscussionThis single criterion for comparingfabric assemblies was developed as a special case by theNational Fire ProtectionAssoc. The specific conditions used byNFPA are a 35C fully sweating hot plate surface in a 25C,65 % RH environment.3.2 For definitio
27、ns of other terms related to protectiveclothing used in this test method, refer to Terminology F 1494.4. Significance and Use4.1 The thermal resistance and evaporative resistance pro-vided by a fabric, batting, or other type of material is ofconsiderable importance in determining its suitability for
28、 use infabricating protective clothing systems.4.2 The thermal interchange between people and theirenvironment is, however, an extremely complicated subjectthat involves many factors in addition to the steady-stateresistance values of fabrics and battings. Therefore, thermalresistance values and eva
29、porative resistance values measuredon a hot plate may or may not indicate relative merit of aparticular material or assembly for a given clothing applica-tion. While a possible indicator of clothing performance,measurements produced by the testing of fabrics has no provencorrelation to the performan
30、ce of clothing systems worn bypeople. Clothing weight, drape, tightness of fit, and so forth,can minimize or even neutralize the apparent differencesbetween fabrics or fabric assemblies measured by this testmethod.4.3 The thermal resistance of clothing systems can bemeasured with a heated manikin in
31、 an environmental chamberin accordance with Test Method F 1291.4.4 Departures from the instructions of Test Method F 1868may lead to significantly different test results. Technicalknowledge concerning the theory of heat flow, temperaturemeasurement, and testing practices is needed to evaluate whichd
32、epartures from the instructions are significant. Standardiza-tion of the method reduces, but does not eliminate the need forsuch technical knowledge. Report any departures from theinstructions of Test Method F 1868 with the results.5. Apparatus5.1 Hot PlateThe guarded flat plate shall be composed of
33、a test plate, guard section, and bottom plate, each electricallymaintained at a constant temperature in the range of humanskin temperature (33 to 36C). The guard section shall bedesigned to prevent lateral loss of heat from the test plate. Theguard section shall be wide enough to minimize heat loss
34、andmoisture transport through the edges of the test specimen underthe conditions of the test. The bottom plate shall preventdownward loss of heat from the test plate and guard section. Asystem for feeding water to the surface of the test plate andguard section is also needed. See Test Methods D 1518
35、, C 177,and ISO 11092 for information on hot plates.F18680225.2 Temperature ControlSeparate independent tempera-ture control is required for the three sections of the hot plate(test plate, guard section, and bottom plate). Temperaturecontrol may be achieved by independent adjustments to thevoltage o
36、r current, or both, supplied to the heaters using solidstate power supplies, solid-state relays (proportional time on),adjustable transformers, variable impedances, or intermittentheating cycles. The three sections of the plate shall becontrolled to the same temperature to within 60.1C.5.3 Power Mea
37、suring InstrumentsPower to the hot platetest section shall be measured to provide an accurate averageover the period of the test. If time proportioning or phaseproportioning is used for the power control, then devices thatare capable of averaging over the control cycle are required.Integrating devic
38、es (watt-hour transducers) are preferred overinstantaneous devices (watt meters). Overall accuracy of thepower monitoring equipment must be within 62 % of thereading for the average power for the test period.5.4 Temperature SensorsTemperature sensors may bethermistors, thermocouples, resistance temp
39、erature devices(RTDs), or equivalent sensors. The test plate, guard section,and bottom plate shall each contain one or more temperaturesensors that are mounted flush with the hot plate surface and insuch a manner that they measure the surface temperaturewithin 60.1C.5.5 Controlled Atmosphere Chamber
40、The hot plate shallbe housed in an environmental chamber that can be maintainedat selected temperatures between 20 and 35C. The walls of thetest chamber shall not be highly reflective, and the walltemperature shall be 60.5C of the air in the chamber. Therelative humidity shall be maintained at selec
41、ted levels be-tween 40 and 65 %.5.6 Measuring Environmental ParametersThe air tem-perature, relative humidity, and air velocity shall be measuredas follows:5.6.1 Relative Humidity Measuring EquipmentEither awet-and-dry bulb psychrometer or a dew point hygrometershall be used to measure the relative
42、humidity and calculate thedew point temperature inside the chamber. The relative humid-ity sensing devices shall have an overall accuracy of at least64%.5.6.2 Air Temperature SensorsShielded air temperaturesensors shall be used. Any sensor with an overall accuracy of60.1C is acceptable. The sensor s
43、hall have a time constant notexceeding 1 min. The sensor(s) is suspended with the measur-ing point exposed to air inside the chamber at a point just priorto the air passing over the hot plate.5.6.3 Air Velocity IndicatorAny calibrated means of mea-suring air velocity with an accuracy of 60.1 m/s is
44、acceptable(for example, anemometer).Air flow speed is measured 15 mmabove the plate surface. The air flow velocity shall be measuredat three positions located along a horizontal line perpendicularto the air flow, including a point at the center of the plate andat points at the centers of the guard s
45、ection on both sides of theplate. Spatial variations in air velocity shall not exceed 610 %of the mean value.5.6.4 Temporal VariationsTemporal variations shall notexceed the following air temperature 60.1C, relative humid-ity 64 %, and air velocity 610 % of the mean value for dataaveraged over 5 min
46、.6. Materials6.1 WaterFor the evaporative resistance measurements inParts B, C, and E, distilled water shall be used to wet the testplate surface.6.2 Liquid BarrierFor the evaporative resistance mea-surements in Parts B, C, and E, a liquid barrier shall be used tocover the test plate so that water d
47、oes not contact the testspecimen. The permeability index of the liquid barrier shall begreater than 0.7, where im= .061 (Rcbp/Rebp). Examples includeuntreated cellophane film, microporous polytetraflouroethylenefilm, and so forth.6.3 Calibration Fabrics5A calibration fabric is requiredfor the calibr
48、ation in Part C. Sources for the calibration fabricare given in Footnote 8.7. Sampling and Preparation of Test Specimens7.1 SamplingTest three specimens from each laboratorysampling unit.7.2 Specimen PreparationUse test specimens largeenough to cover the surface of the hot plate test section and the
49、guard section completely. Remove any undesirable wrinklesfrom the test specimens. Possible techniques for removingwrinkles include smoothing, free-hanging, pressing, steaming,ironing, and so forth.7.3 ConditioningAllow the test specimens to come intoequilibrium with the atmosphere of the testing chamber byconditioning them in the chamber for a least 4 h.8. Part A - Thermal Resistance8.1 Test Conditions:8.1.1 Temperature of the Test Plate, Guard Section, andBottom PlateMaintain the temperature of these sections at 356 0.5C and without
