1、Designation: F1868 14Standard Test Method forThermal and Evaporative Resistance of Clothing MaterialsUsing a Sweating Hot Plate1This standard is issued under the fixed designation F1868; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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 theenvi
3、ronment. 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 materials
4、for 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 range
5、of this measurement technique for intrinsicthermal resistance is from 0.002 to 0.5 Km2/W and forintrinsic evaporative resistance is from 0.0 to 1.0 kPam2/W.1.3 The values in SI units shall be regarded as standard. Noother units of measurement are included in this standard.1.4 This standard does not
6、purport to address all of thesafety concerns, if any, associated with its use. 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
7、Standards:2C177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded-Hot-Plate ApparatusD1518 Test Method for Thermal Resistance of BattingSystems Using a Hot PlateE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691
8、 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodF1291 Test Method for Measuring the Thermal Insulation ofClothing Using a Heated ManikinF1494 Terminology Relating to Protective ClothingF2370 Test Method for Measuring the Evaporative Resis-tance of Clothing
9、 Using a Sweating Manikin2.2 Other Standards:ISO 11092 TextilesPhysiological EffectsMeasurement ofThermal and Water-Vapour Resistance Under Steady-State Conditions (Sweating Guarded-Hotplate Test)33. Terminology3.1 Definitions:3.1.1 clo, na unit of thermal resistance (insulation) equalto 0.155 Km2/W
10、.3.1.1.1 DiscussionThe value of the clo was selected asroughly the insulation value of typical indoor clothing, whichshould keep a resting man (producing heat at the rate of 58W/m2) comfortable in an environment at 21C, air movement0.1 m/s.3.1.2 evaporative resistance, nThe resistance to the flowof
11、moisture vapor from a saturated surface (high vaporpressure) to an environment with a lower vapor pressure.3.1.2.1 Discussion The evaporative resistance in units ofkPam2/W can be calculated for several different cases.RefA= apparent total evaporative resistance of the fabric testspecimen only, when
12、evaluated non-isothermally. The termapparent is used as a modifier for total evaporative resistance to1This test method is under the jurisdiction ofASTM Committee F23 on PersonalProtective Clothing and Equipment and is the direct responsibility of SubcommitteeF23.60 onHuman Factors.Current edition a
13、pproved Feb. 1, 2014. Published February 2014. Originallyapproved in 1998. Last previous edition approved in 2012 as F1868 - 12. DOI:10.1520/F1868-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStand
14、ards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
15、 PA 19428-2959. United States1reflect the fact that condensation may occur within the speci-men.RetA= apparent total evaporative resistance of the fabric testspecimen, liquid barrier, and surface air layer when evaluatednon-isothermally. The term apparent is used as a modifier fortotal evaporative r
16、esistance 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 specimen (that is, bareplate). This property reflects the instrument constant and theresistance of the liquid barrier,
17、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 madethat the boundary layers of the bare plate and the boundarylayers of the fabric are equal.Ret= total evaporative
18、 resistance of the fabric test specimen,the liquid barrier, and the surface air layer.3.1.3 permeability index (im), nthe efficiency of evapora-tive heat transport in a clothing system.3.1.3.1 DiscussionAn imof zero indicates that the clothingsystem allows no evaporative heat transfer. An imof onein
19、dicates that the clothing system achieves the theoreticalmaximum evaporative heat transfer allowed by its insulation.The permeability index is calculated one of two ways.im= permeability index calculated using the total thermalresistance and the total evaporative resistance of a material.The U.S. mi
20、litary uses this value in their databases on fabricsand clothing systems.imf= permeability index calculated using the intrinsic thermalresistance and the intrinsic evaporative resistance of a material.ISO 11092 uses this value.3.1.4 thermal resistance, nthe resistance to the flow ofheat from a heate
21、d surface to a cooler environment.3.1.4.1 DiscussionThermal resistance in units of Km2/Wcan be calculated for several different cases.It= total insulation value of the test specimen and the air layer,expressed in clo units.If= intrinsic thermal resistance of the fabric test specimen only,expressed i
22、n clo units.Rcbp= thermal resistance of the air layer on the surface of theplate without a fabric test specimen (that is, bare plate). Thisproperty 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 the
23、rmal resistance of the fabric test specimenonly. In the calculation of this value, the assumption is madethat the boundary layers of the bare plate and the boundarylayers of the fabric test specimen are equal.Rct= total thermal resistance of the test specimen and the airlayer.3.1.5 total heat loss,
24、nthe amount of heat transferredthrough a material or a composite by the combined dry andevaporative heat exchanges under specified conditions ex-pressed in watts per square metre.3.1.5.1 DiscussionThis single criterion for comparing fab-ric assemblies was developed as a special case by the NationalF
25、ire Protection Assoc. The specific conditions used by NFPAare a 35C fully sweating hot plate surface in a 25C, 65 % RHenvironment.3.2 For definitions of other terms related to protectiveclothing used in this test method, refer to Terminology F1494.4. Significance and Use4.1 The thermal resistance an
26、d evaporative resistance pro-vided by fabrics, films, coatings, foams, and leathers, includingmulti-layer assemblies, is of considerable importance in deter-mining their suitability for use in fabricating protective cloth-ing systems.4.2 The thermal interchange between people and theirenvironment is
27、, however, an extremely complicated subjectthat involves many factors in addition to the steady-stateresistance values of fabrics, films, coatings, foams, andleathers, including multi-layer assemblies. Therefore, thermalresistance values and evaporative resistance values measuredon a hot plate may o
28、r may not indicate relative merit of aparticular material or system for a given clothing application.While a possible indicator of clothing performance, measure-ments produced by the testing of fabrics have no provencorrelation to the performance of clothing systems worn bypeople. Clothing weight, d
29、rape, 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 and evaporative resistance ofclothing systems can be measured with a heated manikin in anenvironmental chamber in a
30、ccordance with Test MethodsF1291 and F2370.5. Interferences5.1 Departures from the instructions of this test method maylead to significantly different test results. Technical knowledgeconcerning the theory of heat flow, temperature measurement,and testing practices is needed to evaluate which depart
31、uresfrom the instructions are significant. Standardization of themethod reduces, but does not eliminate the need for suchtechnical knowledge. Report any departures from the instruc-tions of Test Method F1868 with the results.6. Apparatus6.1 Hot PlateThe guarded flat plate shall be composed ofa test
32、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 andmois
33、ture 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 for testing Parts B and C. See
34、TestMethods D1518, C177, and ISO 11092 for additional informa-tion on hot plates.F1868 1426.2 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 independe
35、nt adjustments to thevoltage or 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 test plate, guard, and bottom plate sectionsshall be controlled to mea
36、sure the same temperature to within60.1C of each other.6.3 Power Measuring 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 capabl
37、e of averaging over the control cycle are required.Integrating devices (watt-hour transducers) are preferred overinstantaneous devices (watt metres). Overall accuracy of thepower monitoring equipment must be within 62 % of thereading for the average power for the test period.6.4 Temperature SensorsT
38、emperature sensors shall bethermistors, thermocouples, resistance temperature 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
39、 the surface temperaturewithin 60.1C.6.5 Controlled Atmosphere ChamberThe hot plate shallbe housed in an environmental chamber that can be maintainedat selected temperatures between 20 and 35C. The testchamber wall temperature shall be 60.5C of the air in thechamber. The relative humidity shall be m
40、aintained as speci-fied in the individual procedure section.6.6 Measuring Environmental ParametersThe airtemperature, relative humidity, and air velocity shall be mea-sured as follows:6.6.1 Relative Humidity Measuring EquipmentEither awet-and-dry bulb psychrometer, a dew point hygrometer, orother el
41、ectronic humidity measuring device shall be used tomeasure the relative humidity and calculate the dew pointtemperature inside the chamber. The relative humidity sensingdevices shall have an overall accuracy of at least 64%.6.6.2 Air Temperature SensorsShielded air temperaturesensors shall be used.
42、Any sensor with an overall accuracy of60.1C is acceptable.The sensor shall 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 in the airstream such that the air temperature sensor is not influenced bythe plate te
43、mperature.6.6.3 Air Velocity IndicatorAir velocity shall be measuredwith an accuracy of 60.1 m/s using a hot wire anemometer.Airvelocity is measured at a point 15 mm (nominal) from the platesurface or from the top of the test specimen surface to thebottom of the anemometer sensing element. The air v
44、elocityshall be measured at three positions located along a horizontalline perpendicular to the airflow, including a point at the centerof the plate and at points at the centers of the guard section onboth sides of the plate. Spatial variations in air velocity shallnot exceed 610 % of the mean value
45、.NOTE 1The air velocity is to be measured 15 mm above the platesurface for bare plate measurements. The air velocity is to be measured 15mm above the test specimen surface when testing fabric or systems. The15 mm distance is to be the distance from the plate or test specimen to theanemometer sensing
46、 element (wire)not to the bottom of the sensingelement housing.6.6.4 Air Temperature VariationsAir temperature varia-tions during testing shall not exceed 60.1C6.6.5 Relative Humidity VariationsRelative humidityvariations during testing shall not exceed 64%.6.6.6 Air Velocity VariationsAir velocity
47、variations shallnot exceed 610 % of the mean value for data averaged over 5min.7. Materials7.1 WaterFor the evaporative resistance measurements inParts B and C distilled, de-ionized, or reverse osmosis-treatedwater shall be used to wet the test plate surface.7.2 Liquid BarrierFor the evaporative res
48、istance measure-ments in Parts B and C, a liquid barrier shall be used to coverthe test plate so that water does not contact the test specimen.The permeability index of the liquid barrier shall be greaterthan 0.7, where im= 0.060 (Rcbp/Rebp). Examples includeuntreated cellophane film and microporous
49、 polytetraflouroeth-ylene film.7.3 Verification Fabrics4A verification fabric is requiredfor the verification in Part C. The verification fabric is 7.5oz/yd2, plain weave, yellow color with a fiber blend of 93 %meta-aramid, 5 % para-aramid, and 2 % anti-static with adurable water-repellent finish. Sources for the verificationfabric are given in Footnote 4.8. Sampling and Preparation of Test Specimens8.1 SamplingTest three specimens from each laboratorysampling unit.8.2 Specimen PreparationUse test specimens largeenough to cover the surfac
