Significance and Use
5.1 Test Methods D2654, Procedure 1, is used in the trade as a basis for rejecting abnormally wet material, but it is not recommended for routine acceptance testing of commercial shipment. Procedure 2 is used by the trade and is recommended for acceptance testing of commercial shipments except as stated in Note 1 . Procedure 3 is used to determine the moisture in a material in a given moisture-equilibrium situation and is not used for acceptance testing of commercial shipments. Procedure 4 is for research and development and is recommended for determining the standard moisture regain of a material although there will usually be a bias between buyer and producer data because the produce is usually able to obtain material without surface material, mostly finishes.
5.1.1 In case of a dispute arising from differences in reported test results when using Test Method D2654 for acceptance testing of commercial shipments, the purchaser and the supplier shall conduct comparative tests to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties shall take a group of test specimens that are as homogeneous as possible and that are from a lot of material of the type in question. The test specimens shall then be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories shall be compared using student's l-test for unpaired data and an acceptable probability level chosen by the two parties before the testing is begun. If a bias is found, either its cause must be found and corrected or the purchaser and the supplier must agree to interpret future test results in the light of the known bias.
5.2 The measurement of moisture is important for several reasons, including the following:
5.2.1 Large quantities of fibers and manufactured textile products containing some water are bought and sold on the basis of mass. The value of a particular commodity varies over a significant range with a variation in the amount of water it contains.
5.2.2 Besides the effect of the moisture present when the material is received, the moisture present at the time of testing and subsequent handling and processing can be quite important.
5.2.2.1 Some textile fibers, particularly cellulosic fibers and wool, have physical properties that vary significantly with the amount of moisture present, such as tensile strength, crimp, torsional rigidity, etc.
5.2.2.2 Optimum conditions for processing, such as in carding, include moisture as an important parameter.
5.2.2.3 Control of blends during processing is sometimes critically dependent on the moisture present in the components.
5.2.2.4 Production of textile products to meet specifications for mass per unit area of fabric and the linear density of yarn depends on control of moisture.
5.2.2.5 Quantitative analysis of fiber mixtures requires information on moisture present. (See Test Methods D629.)
5.3 Between Procedures 1 and 2, the choice for use is dependent primarily on the degree of accuracy required in the result. They are oven-drying procedures and have the virtue of simplicity and economy, with Procedure 1 having the added feature of not requiring a special drying atmosphere for the oven. Both are subject to certain limitations, however, that are avoided by toluene distillation (Note 2).
5.3.1 Because Procedure 1 uses ambient air and Procedure 2 uses air from the standard atmosphere for testing textiles, the mass of the oven-dry specimen is somewhat greater than it would be if the air were without water. This is due to the establishment of moisture-equilibrium between the moisture in the air supply and the moisture in the specimen. The error is usually slight, but in the case of wool dried at 105 °C with the use of ambient air that is hot and humid, the residual moisture in the oven-dry specimen can be as high as 1 % or more (see Tables 1 and 2 of Test Method D584). When the temperature and relative humidity of the ambient air are known, the amount of moisture retained by a specimen of wool, cotton, silk, viscose rayon, cuprammonium rayon, or acetate shall be estimated data.4 An additional source of potential error in oven-drying is the loss of volatile matter other than water when such material is present.
5.4 It is sometimes possible, and preferable, when sampling a material for the determination of moisture to select sampling units of a size which coincide with the size required by the method for a test specimen. In these instances, the mass shall be determined immediately, and if the mass of the oven-dry material is to be determined, no intermediate steps are necessary. However, in other instances, it will be necessary to perform some intermediate manipulation with the material, such as compositing or subsampling. For such instances to circumvent the problem of moisture loss or gain after sampling, provisions are made in these methods to stabilize the material in the working laboratory atmosphere, and equations are provided with correction terms to relate the measured moisture to the amount which existed at the time when the sample was taken.
5.5 While moisture regain is not a frequently tested property, it has an importance, once established. Commercial moisture regains (see Table 1 in D1909) are values adopted for use in determining commercial mass and fiber blends which meet government regulations. These values are usually slightly higher than experimental standard moisture regain values or an average for a class which has a range.
5.6 The measurement of moisture regain of a fiber is affected by any surface material present, the procedure (technique, solvent) used to remove the material, the dryness achieved and the atmosphere (temperature, humidity) in which the dry material is conditioned.
Scope
1.1 These test methods cover measurement of moisture in textile materials as (1) moisture content or pick-up using ambient air for oven-drying, (2) moisture content or pick-up using standard atmosphere for testing textiles for oven-drying, (3) moisture content or pick-up at moisture equilibrium, and (4) moisture regain. These test methods are applicable to all fibers natural or man-made, and in all forms from fiber or filament to finished fabric, subject to the limitations set forth in 1.1.1 through 1.1.4. Blends of fibers shall also be tested by these methods.
1.1.1 Procedure 1—This oven-drying technique, using ambient air heated to 105 °C, shall be used in any situation in which a simple and convenient method for routine process control or when in-plant evaluation is needed to determine an approximation of the moisture content or pickup. It is not recommended for jute or grease wool, or for acceptance testing in commercial transactions.
1.1.2 Procedure 2—Oven-drying technique, using air from the standard atmosphere air for testing textiles that is heated to 105 °C and other refinements in technique, shall be used as a basis for commercial transactions for all materials for which it is known that no significant quantity of non-aqueous volatile matter is present on, or in, the material to be tested.
Note 1: The air supply for Procedure 2 has been changed from desiccated air to the air from the standard atmosphere for testing textiles because the latter is in common use and is prescribed in Test Method D494 for commercial mass of a shipment. By agreement, however, desiccated air may be used.
1.1.3 Procedure 3—This oven-drying technique uses specimens in moisture-equilibrium under specified conditions and an oven with an air supply of specified temperature and relative humidity heated to 105 °C, and other refinements in technique. The procedure is used to determine the moisture content or pickup of a material in equilibrium conditions, usually the standard atmosphere for testing textiles.
Note 2: The previous Procedure 3 for determining moisture using distillation with toluene has been dropped from this method because it is essentially the same as Test Method D2462 which is the preferred method for jute and grease wool in any circumstance. Test Method D2462 is the preferred method for any material in which it is known, or suspected, that a significant quantity of nonaqueous and non-water miscible volatile matter is present.
1.1.4 Procedure 4—This new technique is for determination of actual moisture regained by a material under specified conditions after the material has been extracted by a suitable procedure, if surface materials are present, and dried in vacuum at a low temperature
1.2 In Procedures 1, 2, and 3, alternative techniques are described for weighing oven-dried specimens: in the oven while hot, and outside the oven at room temperature.
1.3 The word water refers to the chemical compound H20. The terms water and moisture are frequently used interchangeably in the literature and in the trade even when the “moisture” is known to contain other volatile materials. When the loss during oven exposure is not known to be all water, it shall be considered a “volatiles loss” rather than a “moisture loss” for technical accuracy.
1.4 Moisture calculations commonly involve the mass of a specimen that has been dried by heating in an oven. If the air in the oven contains moisture, the oven-dried specimen will contain moisture (in equilibrium with that in the oven air) even when it no longer shows a significant change in mass. Therefore, if a very precise measurement of the moisture present is required and oven drying is used, the mass must be exposed to desiccated air until it shows no further significant change in mass.
Note 3: Other ASTM Standards related to the determination of moisture of textile materials are Test Methods D1576, D2495, and D2118.
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.
1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
