ASTM_D_643_-_97_2002.pdf

Designation:D 643 97(Reapproved 2002)An American National StandardStandard Test Method forFolding Endurance of Paper by the Schopper Tester1This standard is issued under the fixed designation D 643;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number 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 test method describes the use of the Schopper typeof folding apparatus.It is suitable for papers having a thicknessof 0.25 mm(0.010 in.)or less.1.2 The procedure for the M.I.T.-type apparatus is given inTest Method D 2176.1.3 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 and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:D 585 Practice for Sampling and Accepting a Single Lot ofPaper,Paperboard,Fiberboard,and Related Product2D 685 Practice for Conditioning Paper and Paper Productsfor Testing2D 776 Test Method for Determination of Effect of Dry Heaton Properties of Paper and Board2D 1968 Terminology Relating to Paper and Paper Products2D 2176 Test Method for Folding Endurance of Paper by theMIT Tester2D 4714 Test Method for Determination of Effect of MoistHeat(50%Relative Humidity and 90C)on Properties ofPaper and Board2E 122 Practice for Calculating Sample Size to Estimate,with a Specified Tolerable Error,the Average for a Char-acteristic of a Lot or Process32.2ISO Standard:ISO 5626 Paper Determination of Folding Endurance43.Terminology3.1 DefinitionsDefinitions shall be in accordance withTerminology D 1968 and the Dictionary of Paper.54.Significance and Use4.1 Folding endurance is not a measure of the foldability ofpaper,but a measure of the strength of paper.In many cases,itis a better measure of strength than the conventional tests fortensile strength,bursting strength,and tearing resistance.Theuniqueness of the folding endurance tests leads to many specialuses for this test method.4.2 Folding endurance is determined by the number of timesthat the paper can be folded before it loses enough tensilestrength to break under the conditions of the test.It is the onlyone of the four strength tests that uses a repetitive mechanicaltreatment to weaken the sheet.Therefore,it is the only one ofthe strength tests that measures the durability of paper sub-jected to repeated or rough handling.It is an important test forpaper that will be subjected to continued folding and unfoldingduring use.Examples are maps and printed materials such asmusic,pamphlets,folded prints,and blueprints.It is also animportant test for any paper that will be handled repeatedly orwhich might be subjected to rough treatment when it is beingused.4.3 The ratio between the machine direction and crossdirection folding endurance is a good measure of the fiberorientation in the sheet.For most papers,the machine directiontest will be higher than the cross direction test,and the morethe fibers are oriented in the machine direction,the greater thedifference will be.If the cross direction is higher than themachine direction,the paper has an unusually large number offibers oriented in the cross direction.This information may alsobe obtained from tests for tensile strength and tearing resis-tance but the folding endurance test is much more sensitive tothese differences than the other two tests.4.4 Folding endurance is more sensitive to the flexibility inthe paper than the other strength tests.Because flexibility islost with aging,folding endurance is commonly used as anindicator of strength loss in accelerated aging tests.1This test method is under the jurisdiction of ASTM Committee D06 on Paperand Paper Products and is the direct responsibility of Subcommittee D06.92 on TestMethods.Current edition approved Dec.10,1997.Published November 1998.Originallypublished as D 643 41 T.Last previous edition D 643 95.2Annual Book of ASTM Standards,Vol 15.09.3Annual Book of ASTM Standards,Vol 14.02.4Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036.5Available from the Technical Association of the Pulp and Paper Industry,P.O.Box 105113,Atlanta,GA 30348.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.4.5 The folding endurance test is made on a very smallsection of the paper(15 mm by approximately 1 mm).The testis sensitive to very small changes in the paper,and as a resultthere will be a significant variation in the tests made on thesame sheet using these very small test areas.The better theformation,the smaller this variation will be.Therefore,thevariation in individual fold numbers is an indirect indication ofthe uniformity of the formation