ASTM D4442-2015 Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based Materials《木材和木基材料含水量直接测量的标准试验方法》.pdf

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1、Designation: D4442 07D4442 15Standard Test Methods forDirect Moisture Content Measurement of Wood and Wood-BaseWood-Based Materials1This standard is issued under the fixed designation D4442; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re

2、vision, 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.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 These test m

3、ethods cover the determination of the moisture content (MC) of solid wood, veneer, and other wood-basewood-based materials, including those that contain adhesives and chemical additives. The test methods below describe primary (A) andsecondary (B through D) procedures to measure moisture content:Met

4、hod APrimary Oven-Drying MethodMethod BSecondary Oven-Drying MethodMethod CDistillation (Secondary) MethodMethod DOther Secondary Methods.1.2 The primary oven-drying method (Method A) is intended as the sole primary method. It is structured for research purposeswhere the highest accuracy or degree o

5、f precision is needed.1.3 The secondary methods (B through D) are intended for special purposes or under circumstances where the primaryprocedure is not desired or justified. In these procedures, moisture content values cannot be reported with an accuracy greater thaninteger percentage values. Howev

6、er, a greater level of accuracy may be reported if the appropriate primary procedures are used.1.4 Distillation (secondary) method is intended for use with materials that have been chemically treated or impregnated suchthat the oven-drying procedures introduce greater error than desired in the resul

7、ts.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced

8、Documents2.1 ASTM Standards:2D9 Terminology Relating to Wood and Wood-Based ProductsD4933 Guide for Moisture Conditioning of Wood and Wood-Based Materials3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method, refer to Terminology D9.3.1.2 moisture contentthe amount of

9、 water contained in the wood, usually expressed as a percentage of the mass of theoven-dry wood (in accordance with Terminology D9).3.1.2.1 DiscussionThe moisture content of wood or other wood-based materials can be expressed on either as a percentage of oven-dry mass of thesample (oven-dry basis) o

10、r as a percentage of initial the original mass (wet basis). The methods described in this standard refer1 These test methods are under the jurisdiction ofASTM Committee D07 on Wood and are the direct responsibility of Subcommittee D07.01 on Fundamental Test Methodsand Properties.Current edition appr

11、oved Nov. 15, 2007June 1, 2015. Published December 2007August 2015. Originally approved in 1984. Last previous edition approved in 20032007as D4442 92 (2003).D4442 07. DOI: 10.1520/D4442-07.10.1520/D4442-15.These test methods replace, in part, Test Methods D2016, for Moisture Content of Wood, discon

12、tinued 1989.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is inte

13、nded only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the curre

14、nt versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1to the oven-dry basis. Because oven-dry mass is used, moisture content values may exceed 100 %. T

15、he term moisture content whenused with wood or other wood-based materials can be misleading since untreated wood they frequently containscontain varyingamounts of volatile compounds (extractives whichthat are evaporated when determining moisture content). Definition of themoisture content of wood is

16、 further complicated when determined by a thermal method because of thermal degradation, whichcauses the final moisture-free mass to decrease from small but continuous losses.4. Significance and Use4.1 Moisture content is one of the most important variables affecting the properties of wood and wood-

17、basewood-basedmaterials. The procedures in these test methods are structured to permit the full range of use from fundamental research toindustrial processing. Method A is designed for obtaining the most precise values of moisture content consistent with the needsof the user. It also provides means

18、of assessing variability contributed by the oven or specimen hygroscopicity, or both. In addition,criteria are described for defining the endpoint in oven-drying. Method A is the reference (primary) standard for determiningmoisture content of wood and wood-basewood-based materials. Methods B through

19、 D are secondary methods to permit relativelysimple procedures of measuring moisture content, but with less precision than Method A. However, greater precision may beobtained with supporting data by using the appropriate procedures in Method A.5. Method AOven-Drying (Primary)5.1 Apparatus:5.1.1 Oven

20、A forced-convection oven that can be maintained at a temperature of 103 6 2C throughout the drying chamberfor the time required to dry the specimen to the endpoint shall be used. Ovens shall be vented to allow the evaporated moistureto escape.NOTE 1The ratio of sample mass to chamber volume and the

21、air velocity within the oven are not critical as long as temperature and relative humiditywithin the oven are constant. Room relative humidity should be less than 70 % relative humidity, at which condition the oven is at 1.7 % relative humidity.For best precision, drying should be carried out in a c

22、onstant relative humidity room with the relative humidity as low as possible.5.1.2 BalanceBased on a 10-g (oven-dry) specimen, minimum readability of the balance shall be determined by the desiredreporting level of precision:Reporting Precision Level, MC, % Minimum Balance Readability, mg0.01 10.05

23、50.1 100.5 501.0 100For other oven-dry mass levels, the sensitivity requirement shall be scaled appropriately.5.2 Test MaterialAny conveniently sized wood or wood-based material can be used, consistent with the use of closedweighing jars (5.4.65.4.7) and the balance readability (5.1.2).NOTE 2If spec

24、imens contain any degree of volatilizable material other than water, it may be necessary to either use Method C or run Method A andC concurrently.5.3 Calibration and StandardizationDetermination of specimen variability requires a separate measurement of thecontribution of variability within the oven

25、.5.3.1 Determination of Oven VariabilityThis section permits a separate evaluation of the oven variability from that ofspecimens distributed in the oven.5.3.1.1 Specimen Selection and PreparationDouglas-fir shall be ground to sawdust and that fraction contained in a 40/60mesh screen used. The sample

26、 origin or drying history is not critical. The sawdust shall be tumbled in a closed container untilthoroughly mixed. All replicates shall be prepared at the same time from the same batch of material. All material shall betransferred and stored in air-tight weighing jars.5.3.1.2 EquilibrationThe mois

27、ture content of the specimen is not important if the preparation techniques described under5.3.1.1 are used. Equilibration is not required, although it is preferable that the material be as uniform as possible in moisturecontent.5.3.1.3 Number and Location of SpecimensEach test shall consist of a se

28、t of eight replicated specimens. These shall be locatedat third-point positions with respect to height, width, and depth of the oven cavity.With this scheme four samples will be positionedon each of two shelves at one third and two thirds of the cavity height.5.3.2 Determination of Combined Specimen

29、 and Oven VariabilityProcedures are the same as 5.3.1.1 5.3.1.3 except thatspecimens of any origin and size or shape can be used. Calculate variability by the equation in 5.5.2.5.3.3 ProcedureUse the primary oven-drying procedure (5.4).5.4 Procedure:5.4.1 Specimens to be equilibrated shall be proces

30、sed as in Guide D4933.5.4.2 Store specimens in individual vapor-tight containers if any delay could occur between sampling and weighing.D4442 1525.4.3 Weigh the specimens using a balance consistent with the desired precision (see 5.1.2).5.4.4 Preheat the oven to a temperature of 103 6 2C5.4.5 Place

31、specimens in the oven within the volume tested for oven precision.5.4.6 EndpointAssume that the endpoint has been reached when the mass loss in a 3-h interval is equal to or less than twicethe selected balance sensitivity. For example, given a specimen weight of 10-g and for a balance sensitivity of

32、 1 mg chosen in 5.1.2to allow reporting to a 0.01 % MC precision, the endpoint is assumed to have been reached when the change in weight is 2 mgor less in a 3-h period.5.4.7 Handling and Weighing ProceduresDried samples shall be stored in a desiccator with fresh desiccant until they havereached room

33、 temperature. All weighings shall be carried out using closed weighing jars.5.5 Calculations:5.5.1 Calculate moisture content as follows:MC,%5A 2B!/B 3100 (1)where:A = original mass, g, andB = oven-dry mass, g.ExampleA specimen of wood weighs 56.70 g. After oven-drying, the mass is 52.30 g.MC,%556.7

34、0252.30!/52.303100 (2)54.40/52.30!310058.4%NOTE 3If wood has been treated with a nonvolatile chemical chemical, or if a wood-based material contains a large amount of non-wood chemicalsthat cannot be neglected, and if the mass of the retained chemicalchemical(s) is known, the moisture content may be

35、 determined as follows:MC,%5A 2B!/D 3100 (3)where:D = B minus mass of retained chemical in sample.D4442 1535.5.2 Calculate variance of the specimens as follows:Sw25Sow 2 2So 2 (4)where:Sw2 = specimen material variance,So2 = oven variance (from 5.3.1), andSo2 = oven variance (from 5.3.1), andSow2 = c

36、ombined specimen and oven variance (5.3.2).5.6 ReportReport: Report the following information: nominal oven-dry mass, type of material, oven variance, specimenvariance, balance sensitivity, oven model and type, and any deviation from the prescribed method. The number of decimal placesreported shall

37、not exceed the precision level (5.1.2).5.6.1 Report the following information:5.6.1.1 Type of material,5.6.1.2 Description of specimens and their nominal oven-dry mass,5.6.1.3 Oven variance,5.6.1.4 Specimen variance,5.6.1.5 Balance sensitivity,5.6.1.6 Oven model and type, and5.6.1.7 Any deviation fr

38、om the prescribed method.5.6.2 The number of decimal places reported shall not exceed the precision level (5.1.2).5.7 Precision and Bias:5.7.1 Precision of MeasurementBy definition, the accuracy of measurement has been set equal to the determined precision oftest measurement, that is, there is no as

39、sumed bias of measurement due to the inability to accurately assess moisture content. Withthis approach the actual accuracy may be poorer than the stated accuracy. At this time, no data are available from which to reporttypical variances in ovens or from specimen material.6. Method BOven-Drying (Sec

40、ondary)6.1 Apparatus:6.1.1 OvenAn oven that can maintain 103 6 2C near the drying endpoint shall be used.6.1.2 BalanceThe sensitivity shall be a minimum of 0.1 % of the nominal oven-dry mass of the specimen (see 5.1.2).6.2 Test MaterialAny conveniently sized wood or wood-based material can be used,

41、however, the balance readability shallbe consistent with the desired precision (see 5.1.2 and 5.3).NOTE 4If specimens contain any degree of volatilizable material other than water, it may be necessary to either use Method C, or run Methods Band C concurrently.6.3 Calibration and StandardizationNo sp

42、ecific tests are required unless greater precision than integer moisture contentvalues are desired. See 6.7.6.4 Procedure:6.4.1 Specimens to be equilibrated shall be processed as in Guide D4933.6.4.2 Store specimens in individual vaportight containers or wrapping if any delay could occur between sam

43、pling and weighing.6.4.3 Weigh the specimens using a balance consistent with the desired precision (see 6.1.2).6.4.4 Preheat the oven to a temperature of 103 6 2C and place specimens in the oven.6.4.5 EndpointAssume that the endpoint has been reached when no appreciable change is noted in final mass

44、 readings madeat approximately 4-h intervals.NOTE 5As a guide, an air-dry solid wood specimen about 50 by 100 mm in cross section and 25 mm along the grain will usually attain “constantmass” within 24 h when dried in a forced convection oven using this procedure.6.4.6 Handling and Weighing Procedure

45、sDried samples shall be weighed as soon as possible to minimize moisture uptake.6.5 Calculation of Moisture Content:6.5.1 Calculate moisture content as follows:MC,%5A 2B!/B 3100 (5)where:A = original mass, g, andB = oven-dry mass, g.ExampleA specimen of wood weighed 56.7 g. After oven-drying, the ma

46、ss was 52.3 g.D4442 154MC,%556.7252.3!/52.33100 (6)54.4/52.3!310058.4Round to 8 % (see 1.3 and 6.7.1)NOTE 6If wood has been treated with a nonvolatile chemical chemical, or if a wood-based material contains a large amount of non-wood chemicalsthat cannot be neglected, and if the mass of the retained

47、 chemicalchemical(s) is known, the moisture content may be determined as follows:MC,%5A 2B!/D 3100 (7)where:D = B minus the mass of retained chemical in sample.6.6 ReportReport: Report the following information: Mean, standard deviation, number of specimens, and any deviation fromthe method. Moistur

48、e content values shall be integer only (see 6.7.1).6.6.1 Report the following information:6.6.1.1 Type of material,6.6.1.2 Description of specimens and their nominal oven-dry mass,6.6.1.3 Mean,6.6.1.4 Standard deviation,6.6.1.5 Number of specimens, and6.6.1.6 Any deviation from the method.6.6.2 Mois

49、ture content values shall be integer only (see 6.7.1).6.7 Precision and Bias:6.7.1 The precision is assumed to be no greater than 61 % moisture content for any measurement unless the appropriateprocedures in Section 5 are used.6.7.2 No bias calculations may be made from this procedure.7. Method CDistillation7.1 Apparatus:7.1.1 Extraction FlaskA 500-mL flask and thimble holder, as shown in Fig. 1. The flask and holder may be combined in oneunit.7.1.2 CondenserA water-cooler condenser of the cold-finger type, as shown in Fi