ASTM D1348-1994(2003) Standard Test Methods for Moisture in Cellulose《纤维素中湿度的标准测试方法》.pdf

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1、Designation: D 1348 94 (Reapproved 2003)Standard Test Methods forMoisture in Cellulose1This standard is issued under the fixed designation D 1348; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number

2、in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 These test methods cover the determination of moisturein cel

3、lulose using two oven-drying procedures and one KarlFischer procedure.1.2 The test procedures appear in the following order:SectionsTest Method ASpecimen Weighed in Oven 4-10Test Method BSpecimen Weighed Outside of Oven 11-17Test Method CKarl Fischer Method 18-251.3 The values stated in SI units are

4、 to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices

5、 and determine the applica-bility of regulatory limitations prior to use.2. Significance and Use2.1 These test methods determine the amount of moisturecontained in a cellulose sample which determines the amountof bone dry cellulose present in a sample. The actual amount ofcellulose in a sample is an

6、 essential entity when using celluloseas a starting material for the production of cellulose deriva-tives.3. Sampling3.1 Cellulose in a variety of forms is sampled for moisture,and no single set of directions can be given that is applicableto all types of cellulose material. The following generalcon

7、siderations should be borne in mind.3.1.1 Cellulose, either in compact form, such as wood,sheeted pulp or paper, baled cotton or baled staple rayon, or inloose form such as sawdust or chips, may have an appreciablydifferent moisture content in sections lying relatively closetogether. In order to sec

8、ure representative samples, therefore, abulk sample should be made up of small portions taken fromvarious parts of the lot and having the proper proportion ofedge and center material.3.1.2 Except for those samples taken in an atmosphere withwhich the sample is in equilibrium, the moisture content of

9、 thesample will begin to change immediately after it is removedfrom its original surroundings. This change can be reduced bytaking extra layers of sheeted material and discarding a fewlayers from the top and bottom before weighing, folding, orrolling the sample to reduce the exposed area, and by pla

10、cingsmall samples in cans or bottles and protecting larger samplesby wrapping in rubber sheets, moistureproof cellophane, orother protective wrappings. These means do not providecontinuous protection, and the test samples should be weighedas soon as possible.3.1.3 When possible, bulk samples should

11、be taken. Thesesamples should weigh from 100 to 300 g (3.5 to 10.5 oz), thelarger samples being taken when the moisture content is low orvariable. Following the initial weighing, the bulk samplesshould be cut up or torn into small pieces and then mixed andallowed to stand overnight or longer in a se

12、aled container toobtain moisture equilibrium before weighing out test speci-mens; or the sample may be allowed to come to approximateequilibrium with the laboratory air and reweighed to determinemoisture change before weighing test specimens. The latterprocedure is recommended since it permits routi

13、ne weighing ofsamples without the use of special weighing bottles or boxes,and a series of accumulated samples can be weighed simulta-neously. Predrying is very desirable on samples with a highmoisture content (more than 5 % above equilibrium value).When samples have been predried, calculate the moi

14、sture lost,as follows:R 5 M A/A 3 100 (1)where:R = moisture, air-dry sample basis, %,M = original mass of the sample, g, andA = air-dry mass of sample, g.3.1.4 The apparent moisture subsequently observed whentesting a predried sample must be calculated on the basis of theoriginal sample mass in orde

15、r to get the original moisturecontent. Calculate the original mass of the air-dried sample asfollows:1These test methods are under the jurisdiction of ASTM Committee D01 onPaint and Related Coatings, Materials, and Applications and are the directresponsibility of Subcommittee D01.36 on Cellulose and

16、 Cellulose Derivatives.Current edition approved Oct. 1, 2003. Published October 2003. Originallyapproved in 1954. Last previous edition approved in 1994 as D 1348 94 (1998).1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Original sam

17、ple mass, g 5 A 3 100 1 R!#/100 (2)NOTE 1ExampleIf 1000 g (35 oz) of bulk (wet) sample on exposureto air lose 200 g (7 oz) of water, the apparent moisture content is 20 % andequivalent regain is 25 %. If an 8-g (0.28-oz) specimen of the air-drymaterial is taken for drying in the oven, the original m

18、ass is 8 3 1.25 = 10g (0.35 oz).TEST METHOD ASPECIMEN WEIGHED IN OVEN4. Scope4.1 This test method for moisture determination is appli-cable to a variety of cellulose types and can be used in mostcases where a sample does not contain nonaqueous materialvolatile at 105C. The test method can be used fo

19、r sampleshaving either high or low moisture content.5. Summary of Test Method5.1 The specimen is heated to constant mass at 105C in aventilated gravity-convection oven, in a current of dry air, fora period of 2 h. If no dry air is used, the specimen is heated for4h.6. Apparatus6.1 Oven with Built-In

20、 Weighing EquipmentSuch an ovenemploys a system of tared containers mounted on a table ortrack that can be rotated to bring specimens to a specific pointin the oven, where the specimen and container can be placed ona hook or a tray connected to an outside balance. The ovenmust be capable of maintain

21、ing a constant temperature of 1056 3C, with an average temperature of 105C; continuousoperation below 105C is not satisfactory.NOTE 2In ovens having heating elements at the bottom only, and nocross circulation, the temperature of the lower shelves should be checkedbefore they are used.6.2 Dry Air St

22、reamAir, dried by passing through silicagel, aluminum oxide, concentrated sulfuric acid, or othersuitable drying agent, should be passed through the oven at arate sufficient to effect a complete change once every 2 min. Ifthe air is dried by means of concentrated sulfuric acid,adequate traps must be

23、 provided. The use of sulfuric acidfollowed by perchloric drying agents should be avoided.6.3 Shallow Glass Weighing BottlesBottles with groundglass stoppers, measuring 30 mm high, and having a capacityof 30 mL.6.4 Seamless Metal Weighing Boxes, having a wall height,when open, preferably not over 25

24、.4 mm (1 in.).7. Procedure7.1 Remove the basket, shallow pan, or other containersupplied for use with the oven (Note 3). Weigh the containerand place in it a specimen of 10 to 50 g (0.35 to 1.75 oz)weighed to the nearest 0.005 g. Designate this mass as M. Placethe specimen in a tared container in th

25、e oven in such a mannerthat it can be reweighed without removal from the oven.NOTE 3Experience has shown that when yarn and fiber specimens areleft in comparatively deep weighing bottles in the oven, relativelydiscordant results are obtained and the drying period is unnecessarily long.To avoid these

26、 difficulties specimens should be dried in containers thatgive the cellulose free access to the air. For fibrous or bulky materials tobe weighed in an oven, use containers such as open wire grills or baskets.For small specimens to be weighed out of the oven, use wire screenbaskets that will fit in w

27、eighing bottles, but if the specimen is powdery ortends to shed lint or fine short fibers, use a small weighing bottle or metalboxes.7.2 Dry the specimen for 2 h at 105 6 3C, passing acurrent of dry air into the bottom of the oven during the dryingperiod. (If dry air is not forced through the oven,

28、dry for 4 h.)NOTE 4Reproducible but less accurate values (under unfavorableconditions the absolute error may be as high as 1 %) will be obtained if thecurrent of predried air is omitted. Since the error will be identical for allsimilar samples in the oven at one time, the results obtained in these c

29、aseswill be comparable. The magnitude of error will vary directly with therelative humidity of the air entering the oven and with the equilibriummoisture content of samples at low relative humidity. Thus, the error willbe higher on regenerated cellulose than on wood pulp or cotton, but it stillwould

30、 not usually be greater than 0.2 %, absolute.7.3 At the end of the specified period, cut off the flow of airand weigh the specimen without removing it from the oven.Continue drying for 2 h longer, with the normal air flow, andreweigh the specimen. Repeat the drying and weighing untilthe mass loss be

31、tween successive weighings is not more than0.005 g, or until the specimen shows a gain in mass. Designatethis mass as D.7.4 Additional specimens should not be placed in the ovenuntil the first specimens have attained constant mass.8. Calculation8.1 Calculate moisture, as measured in the oven, as fol

32、lows:Moisture content, % 5 M D/M 3 100 (3)Moisture, dry basis regain!,% 5 M D!/D 3 100 (4)where:M = original mass of specimen, and .D = mass of oven-dry specimen.9. Report9.1 Report the moisture in the cellulose on either or both ofthe following bases:9.1.1 On the basis of the original sample, when

33、it is termed“moisture content,” “moisture as received,” or “moisture as is”basis.9.1.2 On the basis of the oven-dry cellulose, when it istermed “moisture, dry basis” or “moisture regain.”9.2 In order to avoid confusion always use the appropriateterm.10. Precision and Bias10.1 Precision:10.1.1 Statis

34、tical analysis of intralaboratory (repeatability)test results on samples containing 5 to 15 % moisture indicatesa precision of 60.14 % at the 95 % confidence level.10.1.2 Statistical analysis of interlaboratory (reproducibil-ity) test results on samples containing 5 to 15 % moistureindicates a preci

35、sion of 60.2 % at the 95 % confidence level.10.2 BiasNo justifiable statement can be made on the biasof the procedure for measuring moisture in cellulose becauseno suitable reference material exists.D 1348 94 (2003)2TEST METHOD BSPECIMEN WEIGHED OUTSIDEOF OVEN11. Scope11.1 The scope and application

36、of this test method are thesame as those of Test Method A (see Section 4).12. Summary of Test Method12.1 See Test Method A (Section 5).13. Apparatus13.1 Oven Without Built-In Weighing EquipmentAnyventilated oven capable of maintaining a constant temperatureof 105 6 3C, with an average temperature of

37、 105C;continuous operation below 105C is not satisfactory.NOTE 5In ovens having heating elements at the bottom only, and nocross circulation, the temperature of the lower shelves should be checkedbefore they are used.13.2 Dry Air StreamSee 6.2.13.3 Shallow Glass Weighing BottlesSee 6.3.13.4 Seamless

38、 Metal Weighing BoxesSee 6.4.13.5 Weighing Bottles, glass with ground-glass stoppers,approximately 40 mm wide and 80 mm high.13.6 Wire BasketsFitted baskets for weighing bottlesmade from approximately 15-mesh stainless steel, Monel, orother suitable screen. The height and depth of the basket will be

39、determined by the weighing bottle used; the basket must slideinto and out of the bottle without binding. The basket shouldhave a solid bottom, but no top is required.14. Procedure14.1 If the sample is free of lint, dust, or short fibers, placeapproximately 10 g (0.35 oz) of the sample into a previou

40、slydried and desiccated wire basket (Note 2) contained in a dryweighing bottle. Stopper the weighing bottle, and weigh to thenearest 0.001 g. Designate this mass as M. Remove the basketcontaining the specimen from the weighing bottle and place thebasket, weighing bottle, and stopper in the oven. If

41、thespecimen includes powder-like material, transfer the specimendirectly into a small weighing bottle or can. Stopper the bottleand weigh to the nearest 0.001 g (M). Remove the stopper fromthe bottle and place the bottle containing the specimen and thestopper in the oven.14.2 Dry for2hat1056 3C, pas

42、sing a current of dry airinto the bottom of the oven during the drying period. (If dry airis not forced through the oven, dry for 4 h.)14.3 At the end of the specified period, quickly place thebasket and specimen in the weighing bottle again and stopperit (or stopper directly). Remove the weighing b

43、ottle from theoven and place it in a desiccator containing an efficientdesiccant, such as anhydrous calcium sulfate. Allow it to coolfor 1 h, momentarily open the weighing bottle to equalize thepressure, and weigh to the nearest 0.001 g.14.4 Return the specimen to the oven, exposing it asdirected ab

44、ove, and dry for at least 1 h more. Place it in adesiccator to cool and weigh in accordance with 14.3. Repeatthe drying and weighing until the mass loss between twosuccessive weighings is not more than 0.005 g (or until thespecimen shows a gain in mass). Designate the lowest ob-served mass as D.14.5

45、 When constant mass has been obtained, discard thespecimen and weigh the weighing bottle (plus basket) or can.Designate this mass as T.14.6 Do not place additional specimens in the oven until thefirst specimens have attained constant mass.15. Calculation15.1 Calculate moisture, as measured outside o

46、f the oven, asfollows:Moisture content, % M D!/M T!# 3 100 (5)Moisture, dry basis, regain!,% 5 M D!/D T!# 3 100 (6)where:M = original mass of the specimen (plus basket) andweighing bottle,D = oven-dry mass of the specimen (plus basket), andT = mass of the empty weighing bottle (plus basket).16. Repo

47、rt16.1 Report the moisture in the cellulose as directed inSection 9.17. Precision and Bias17.1 See Section 10.TEST METHOD CKARL FISCHER METHOD18. Scope18.1 This test method covers the determination of moisturein cellulose by titration with Karl Fischer reagent. The testmethod is applicable to all ty

48、pes and forms of cellulose. It isespecially useful with samples containing nonaqueous materialvolatile at 110C, since such substances interfere in theoven-drying methods. Anhydrides, alkalies, and large amountsof aldehydes and ketones interfere.18.2 The Karl Fischer titration method is especially va

49、lu-able where only small amounts of samples are available. Theprocedure lends itself to multiple determinations.18.3 It is essential that the Karl Fischer reagent, standardwater solution, and anhydrous methanol be protected fromatmospheric moisture at all times. During the titration a streamof dry air or nitrogen will protect the contents of the titrationflask from atmospheric moisture pick-up.19. Summary of Test Method19.1 An excess of Karl Fischer reagent is added to thespecimen suspended in anhydrous methanol. After sh