1、Designation: D4920 98 (Reapproved 2003)Standard Terminology Relating toMoisture in Textiles1This standard is issued under the fixed designation D4920; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A num
2、ber 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 terminology is a compilation of definitions oftechnical terms related to moisture in textiles. Terms that aregenerally understood or
3、 adequately defined in other readilyavailable sources are not included.1.2 For other ASTM defined conditioning terms, refer toTerminology E 41. For other terms associated with textiles,refer to Terminology D 123, Relating to Textiles.2. Referenced Documents2.1 ASTM Standards:D 123 Terminology Relati
4、ng to Textiles2E 41 Terminology Relating to Conditioning33. Terminology3.1 Definitions:absolute humidity, nthe mass of water vapor present in aunit volume of air.DISCUSSIONCommon units of measure for absolute humidity aregrams per cubic metre or grains per cubic foot. The amount of watervapor is als
5、o reported in terms of mass per unit mass of dry air, forexample, grams per kilogram, or grains per pound, of dry air. This valuediffers from values calculated on a volume basis and should not bereferred to as absolute humidity. It is designated as humidity ratio,specific humidity, or moisture pick-
6、up.absorption, na process in which one material (the absor-bent) takes in or absorbs another (the absorbate); as theabsorption of moisture by fibers. (See also adsorption, andmoisture equilibrium for testing. Compare desorption andresorption.) D 4772adsorption, na process in which the surface of a s
7、olid takeson or adsorbs in an extremely thin layer molecules of gases,of dissolved substances, or of liquids with which it is incontact. (See also absorption and moisture equilibrium fortesting. Compare desorption and resorption.)atmosphere for testing, nair at ambient conditions ofrelative humidity
8、 and temperature in which tests or experi-ments are conducted. (See also standard atmosphere fortesting.)DISCUSSIONIn the hierarchy of terms, atmosphere is the genericterm where the air is ambient with conditions “controlled” by localweather and therefore variable. Atmosphere for testing is a delimi
9、tedterm in which the use of the atmosphere is restricted for a certainpurpose. In a standard atmosphere for testing, the conditions arespecified (standardized) and controlled for routine testing and fortesting reproducibility. On this basis, there is no real reason for notreferring to the specified
10、atmospheres that have been traditionally usedfor testing glass textiles or tire cords, etc., as standard atmospheresfor testing those mercial allowance (CA), nan arbitrary value, equal tothe commercial moisture regain, plus a specified allowancefor finish, used with the mass of scoured, oven-dried y
11、arn, tocompute (1) yarn linear density, (2) the commercial or legalmass of a shipment or delivery of any specific textilematerial (see also commercial moisture regain), or (3) themass of a specific component in the analysis of fiber blends.D 1907, D 2494, D 3887commercial mass, nbilled mass as deter
12、mined by a gener-ally accepted method or as agreed upon between the pur-chaser and seller. D 2494commercial moisture content, nin wool, the moisturecalculated as a percentage of the mass of the wool, top, noils,yarn, fabric, etc., in the “as-is” condition; that is, containingwhatever moisture, oil,
13、grease, or other extraneous matterthat may be present. D2118commercial moisture regain (CMR), na formally adopted,arbitrary value, to be used with the oven-dried mass oftextile fibers, when calculating the commercial mass of ashipment or delivery.DISCUSSIONThe assigned commercial moisture regain val
14、ue isusually higher than the experimental moisture regain value for the samematerial.condition, vto bring a material to moisture equilibrium witha specified atmosphere.desorption, na process in which a sorbed material isreleased from another material, as the desorption of moisturefrom fibers; the re
15、verse of absorption, adsorption, or both.1This terminology is under the jurisdiction of ASTM Committee D13 on Textilesand is the direct responsibility of Subcommittee D13.51 on Chemical Conditioningand Performance.Current edition approved Oct. 10, 1996. Published February 1997. Originallypublished a
16、s D 4920 89. Last previous edition D 4920 96b.2Annual Book of ASTM Standards, Vol 07.01.3Annual Book of ASTM Standards, Vol 14.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.dew point, nthe temperature below which condensation of
17、water vapor begins to take place when the atmosphere iscooled.DISCUSSIONAs air is cooled, the amount of water vapor which it canhold decreases. If air is cooled sufficiently, the saturation water-vaporpressure becomes equal to the actual water-vapor pressure and anyfurther cooling beyond this point
18、will normally result in the conden-sation of moisture.humidity, nthe condition of the atmosphere in respect towater vapor. (Compare absolute humidity and relativehumidity.)hygrometer, nany instrument for measuring the humidity ofthe atmosphere.moisture, nas used with textiles, water absorbed, adsorb
19、ed,or resorbed by a material. (See also water.)moisture as-is, ndeprecated term. See moisture content.moisture as-received, ndeprecated term. See moisturecontent.moisture content, nthat part of the total mass of a materialthat is absorbed or adsorbed water, compared to the totalmass. (Compare moistu
20、re pick-up and moisture regain.)DISCUSSIONMoisture is usually expressed as a percentage and iscalculated using the equation:C 5 100 A 2 D!/Awhere:C = moisture content, %,A = mass of material before drying, andD = mass of the dried material.There is a relationship between moisture content and mois-tu
21、re pick-up since both may be calculated from the same data.The difference is in the bases used for calculating the percent-ages, original versus dried material mass. The relationshipbetween moisture content and moisture pick-up is shown bythe equations:C 5 100 P/100 1 P!P 5 100 C/100 2 C!where:C = m
22、oisture content, %, andP = moisture pick-up, %.moisture content, nat moisture-equilibrium, the moisturecontent of a material in equilibrium with air of known, orspecified, temperature and relative humidity.DISCUSSIONA frequently prescribed condition for determiningmoisture content at moisture-equili
23、brium is use of a standard atmo-sphere, for example, 21 6 1C (70 6 2F) and 65 6 2 % relativehumidity, for textiles, both in establishing the equilibrium and as airsupply for the drying oven.moisture content (dry-basis), ndeprecated term. See mois-ture pick-up.moisture (dry-basis), ndeprecated term.
24、See moisturepick-up.moisture equilibrium, nthe condition reached by a materialwhen it no longer takes up moisture from, or gives upmoisture to, the surrounding atmosphere. (Comparemoisture-free.)DISCUSSIONThe establishment of equilibrium between a materialand the surrounding atmosphere is dependent
25、upon the exposure time,the difference in moisture levels between the material and the atmo-sphere, and motion of the air about the material. The level at which themoisture in the textile reaches equilibrium depends upon the side fromwhich equilibrium is approached. Because of this difference, equili
26、b-rium for textiles should be approached from the dry (but not moisture-free) side which is faster. Equilibrium with air in motion is consideredto be achieved when successive weighings at specified time intervals donot show a change in mass greater than the tolerance established for thematerial. If
27、there is no established tolerance, consider 0.1 % of the massafter a 2-h exposure as satisfactory.moisture equilibrium, nfor preconditioning, the moisturecondition reached by a material during free exposure tomoving air in the standard atmosphere for preconditioning.D 1776moisture equilibrium, nfor
28、testing, the condition reachedby a material during free exposure to moving air in aspecified atmosphere for testing. D 885, D 885M, D 1776moisture-free, adjin textiles, a descriptive term for a mate-rial that (1) has been exposed to a flow of desiccated air ata specified temperature until there is n
29、o further significantchange in mass, or (2) has been treated by a distillationprocess using a suitable solvent. (Syn. zero-moisture.)(Compare moisture equilibrium.)DISCUSSIONMoisture determinations frequently involve the changein mass of an oven-dried specimen. If the air in the oven containsmoistur
30、e, the oven-dried specimen will also contain some moistureeven though it no longer shows a significant change in mass. This is dueto the establishment of moisture equilibrium under the existing condi-tions. To ensure that the specimen is actually moisture-free, it must beexposed to desiccated air un
31、til it shows no further significant change inmass. Although heating textiles in dessicated air to temperatures as highas 110C increases the rate of moisture loss without changing the finalequilibrium mass of the moisture-free textile, heating also increases thepossibility of removing other matter. T
32、he distillation process may besubstituted provided the textile does not contain any distillable,water-soluble matter.moisture pick-up, nthe mass of absorbed and adsorbedwater that is held by a material, compared to the mass of thedried material. (Compare moisture content and moistureregain.)DISCUSSI
33、ONMoisture pick-up is usually expressed as a percentagebased on the dried mass of the material and is calculated using theequation:P 5 100 A 2 D!/Dwhere:P = moisture pick-up, %A = mass of material before drying, andD = mass of the material after drying under specifiedconditions.There is a relationsh
34、ip between moisture pick-up and mois-ture content since both may be calculated from the same data.The difference is in the bases used for calculating the percent-ages, original versus dried material mass. The relationshipbetween moisture content and moisture pick-up is shown bythe equations:C 5 100
35、P/100 1 P!P 5 100 C/100 2 C!D4920 98 (2003)2where:C = moisture content, %, andP = moisture pick-up, %.Since moisture pick-up, like moisture content, involves theoriginal mass, or “as-is, where-is” (from a location withunknown temperature and humidity conditions) state of thematerial, it is generally
36、 unknown if the loss in mass on dryingis caused by the loss of any materials other than water.moisture pick-up, nat moisture-equilibrium, the moisturepick-up of a material in equilibrium with air of known, orspecified, temperature and relative humidity.DISCUSSIONA frequently prescribed condition for
37、 determiningmoisture content at moisture-equilibrium is use of a standard atmo-sphere, for example, 21 6 1C (70 6 2F) and 65 6 2 % relativehumidity, for textiles, both in establishing the equilibrium and as airsupply for the drying oven.moisture regain, nthe amount of water resorbed by a driedmateri
38、al at specified equilibrium conditions of temperatureand humidity, compared to the mass of the dried material.(See standard moisture regain.) (Compare commercialmoisture regain, moisture content, and moisture pick-up.)DISCUSSIONMoisture regain is usually expressed as a percentageand is calculated us
39、ing the equation:R5100B2D!/Dwhere:R = moisture regain, %,B = mass of material in moisture-equilibrium at specifiedconditions,D = mass of material dried under specified conditions.Since most surface matter can be extracted without appreciablyaffecting the textile material, or the textile material can
40、 beproduced without surface matter (except natural fibers), any-thing removed by drying or distillation after moisture-equilibrium is established is water. This is a key differencebetween moisture regain and moisture pick-up, which havebeen traditionally, but incorrectly, used synonymously.moisture,
41、 wet-basis, ndeprecated term. See moisture con-tent.oven-dried, adja descriptive term for a material that hasbeen heated under prescribed conditions of temperature andhumidity until there is no further significant change in themass of the material.DISCUSSIONAn oven-dried material retains a small amo
42、unt ofmoisture which is dependent upon the temperature and relative humid-ity of the air supplied to the oven. An oven-dried material will only bemoisture-free if the air supplied to the oven has been desiccated.psychrometer, na variety of hygrometer comprising a drybulb temperature indicator and a
43、wet bulb temperatureindicator which is cooled to the wet bulb temperature by thespontaneous evaporation of moisture.relative humidity, nof air, the ratio of the pressure of watervapor present to the pressure of saturated water vapor at thesame temperature.DISCUSSIONThe ratio of the vapor pressures i
44、s expressed as adecimal fraction or, more generally, as a percentage. For normal testingconditions, the ratio of the actual absolute humidity to the maximumpossible humidity at the same temperature does not differ appreciablyfrom the ratio of the pressures used in the above definition. Theagreement
45、holds for temperatures up to 93C (200F) and belowsaturation.resorption, nthe process by which a material that has givenup another material by desorption takes up some more ofthe material given up.sorption, nthe process of taking up or holding a material byadsorption, absorption, or both.standard atm
46、osphere for preconditioning, na set of con-trolled conditions having a temperature not over 50C(122F), with respective tolerances of 61C (62F), and arelative humidity of 525 % 6 2 % for the selected humiditythat drying can be achieved prior to conditioning in thestandard atmosphere for testing texti
47、les. D 1776standard atmosphere for testing, nan atmosphere fortesting in which the conditions for relative humidity andtemperature are specified and controlled. (Compare atmo-sphere for testing.)standard atmosphere for testing, nin glass textiles,anatmosphere for testing in which the air is maintain
48、ed at arelative humidity of at least 45 % and no greater than 67 %,tolerance of 62 % for the selected relative humidity, and atemperature of at least 20C (68F) and no greater than 25C(77F), with a tolerance of 61C (62F) at the selectedtemperature. (Compare atmosphere for testing.) D 578,D 580, D 579
49、, D 581standard atmosphere for testing, nin textiles, an atmo-sphere for testing in which the air is maintained at a relativehumidity of 65 6 2 % and at a temperature of 21 6 1C(70 6 2F). (See atmosphere for testing.)DISCUSSIONSpecial conditions of humidity and temperature aresometimes prescribed for the testing of certain textiles for specificservice predictions, resistance to water or biological action, etc. Wheninternational testing is involved, a standard temperature of 20 6 2C,or, by agre
