1、Designation: D 6942 03 (Reapproved 2008)Standard Test Method forStability of Cellulose Fibers in Alkaline Environments1This standard is issued under the fixed designation D 6942; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、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.1. Scope1.1 This test method describes a procedure for determiningthe effect of exposure to alkaline environments on the s
3、trengthof cellulose fibers. An alkaline environment is defined to beany matrix in which the pH is greater than 8 for a period of 2or more hours.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purpo
4、rt 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 and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 13
5、48 Test Methods for Moisture in CelluloseD 1695 Terminology of Cellulose and Cellulose Derivatives2.2 TAPPI (Technical Association of the Pulp or 1 day, 3 day, 7 day, 14 day).5.2 The specified solution (1N NaOH) is strongly alkaline.Although this alkali concentration is higher than some envi-ronment
6、s that would be simulated by this test, the stronger pHprovides better differentiation between different cellulose fibertypes. Although alkaline stability based on other alkalis (forexample, KOH, Ca(OH)2, etc.) at a different concentrationcould be determined by this method, 1N NaOH is to beconsidere
7、d the standard solution.Alkaline stability results fromother treatments may be reported in addition to the standardsolution if the additional solution(s) provide useful informa-tion.6. Interferences6.1 There are no known interferences for this method.1This test method is under the jurisdiction of AS
8、TM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.36 on Cellulose and Cellulose Derivatives.Current edition approved June 1, 2008. Published June 2008. Originallyapproved in 2003. Last previous edition approved in 2003 as D
9、 6942 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Technical Association of the Pulp an
10、d Paper Industry (TAPPI),15 Technology Parkway South, Norcross, GA 30092, http:/www.tappi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Apparatus7.1 Handsheeting Apparatus, as defined in TAPPI T 205.7.2 Zero-span Tensile Tes
11、ter, as described in TAPPI T 231.7.3 Moisture Balance.7.4 Analytical Balance.8. Reagents and Materials8.1 1N sodium hydroxide (NaOH).9. Hazards9.1 Sodium hydroxide solutions are corrosive, and thusharmful to the skin and eyes. Wear safety glasses or goggles,gloves, and lab coat or chemical apron. wh
12、ile working withcaustic solutions.10. Sampling, Test Specimens, and Test Units10.1 Values stated in SI units are to be regarded as thestandard. Values in parentheses are for information only.10.2 Starting cellulose fibers should be in a dry sheet form(drylap) or in a dry, low-density bulk form. In t
13、his context, theterm dry means at equilibrium moisture content (see 3.1),which is 6 to 8 % moisture for most pulps.11. Calibration and Standardization11.1 Calibration and maintenance of the zero-span tensiletester will be accomplished as prescribed in TAPPI T 231.Inaddition, a control chart of the i
14、nstrument will be maintainedbased on breaking paper strips cut from control sheets of paper.A ream of copy paper can be used for this purpose or any otherpaper with consistent furnish, uniform basis weight, anduniform density (see 3.1). Control paper produced on a papermachine should be tested in th
15、e machine direction.12. Conditioning12.1 Handsheets are to be conditioned prior to testing asdescribed in TAPPI T 205.13. Procedure13.1 For drylap, mechanically disintegrate the pulp sheet toget 150 g of individualized fibers for each sample to be tested.High-density pulp sheets can also be slurried
16、 at low consis-tency, then air-dried to provide a bulk sample of low density.The bulk, air-dry sample can then be disintegrated mechani-cally or by hand to provide individualized fibers.13.2 To 10 g (dry basis) of cellulose fibers, add 23.3 g of 1NNaOH and allow to remain for 24 h. (This corresponds
17、 to a30 % consistency, that is, 10 g pulp/33.3 g total. Moisture inthe pulp is ignored as long as the moisture content (see TAPPIT 231) is 10 %. A fiber sample larger than 10 g can be used,but the starting consistency must still be 30 %.) The samplemay be placed in an uncovered beaker to simulate an
18、 environ-ment that is open to the atmosphere, or placed in a sealed bagto simulate an environment in which the consistency wouldremain constant.13.3 Repeat step 13.2 to prepare five more samples that willbe left to age for time intervals of 3, 7, 14, 21, and 28 days,respectively. Once the time inter
19、val has been met, work-up ofthe samples is accomplished by collecting fibers on a wirescreen (100 mesh), washing with tap water until washings aresubstantially neutral (pH=7to7.5), and then air drying.13.4 Prepare 2 sets of standard handsheets according toTAPPI T 205 for each time interval. One set
20、will be made frompulp that has not been treated with sodium hydroxide and willbe the control set. The other set will be prepared from fibersthat have been exposed to alkali for the designated timeinterval. These 2 sets of handsheets will be prepared on thesame day.13.5 Each set of handsheets will be
21、 tested for zero-spantensile according to TAPPI T 231.14. Calculation or Interpretation of Results14.1 Determine the zero-span stability ratio (that is, ZSSR)by dividing the zero-span tensile result of the alkali treatedsample by the zero-span tensile result from the correspondinguntreated (control)
22、 sample. The results can be reported as adecimal ratio, such as 0.921 or as a percentage, such as 92.1 %.Reporting 3 significant figures is recommended.14.2 The zero-span stability ratios will be reported individu-ally for each time interval sample and/or as an average value ofall the time interval
23、samples tested.14.3 Note that higher ratios will be observed for pulps thathave greater strength stability in an alkaline environment.15. Report15.1 Report the zero-span stability ratios (ZSSR) deter-mined for each time interval sample as a decimal fraction or asa percentage along with the average z
24、ero span stability ratiodetermined from all time interval samples. Since 1N NaOH isthe standard test solution, it need not be specified, but ifanother test solution is used in addition to the standardsolution, its composition must be specified.16. Precision and Bias16.1 Precision and bias for the ze
25、ro-span tensile test aregiven in TAPPI T 231. Repeatability within a laboratory isfrom 3 to 5 %, and reproducibility between laboratories (30samples at 3 laboratories) was 10 %.16.2 Repeatability of zero span tensile tests used to calcu-late stability ratios was found to be 5 % based on 14 sets ofco
26、ntrol handsheets made at different times by 2 operatorswhere each set was tested 4 times by cutting 2 test strips from2 handsheets from each set (64 pulls).16.3 Repeatability of the stability ratio is partly dependenton the type of fibers tested (SSK, NSK, sulfite, mechanical,etc.) and the duration
27、of the test (1 day, 1 week, 4 weeks). Forsamples determined according to section 13 in uncoveredbeakers, the repeatability, expressed as a % coefficient ofvariation, was 5 to 8 %.17. Keywords17.1 alkaline stability; cellulose fibers; zero-span stabilityratio; zero-span tensileD 6942 03 (2008)2ASTM I
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31、Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 6942 03 (2008)3
