pulp and paper testing

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1、Chapter7Generalphysicalpropertiesofpaperandboard(3)whereFistheforceandlisthecorrespondingelongation.Figure3.Measuringtensilestrengthpropertiesofpaper.ThetensileenergyabsorptionunitsareJ/m2.Calculationofthemodulusofelasticityalsousestheloadelongationcurve.Itcorrespondstoth

2、emaximumslope,(linearpart)ofthiscurveasFig.3shows.Acloselyrelatedconceptistensilestiffness.Figure3illustratescalculationoftensilestrength,tensileindex,elongation,modulusofelasticity,andtensilestiffnessfromaload-elongation(stress-strain)curveforpaperasfollows:(4)(5)(6)(7)w

3、herewisbasisweightbwidthofthetestpiecetthicknessofthetestpiecel0originallengthofthetestpieceEmodulusofelasticityTStensilestiffness.Tensilestrengthofapaperdependsonfiberstrengthbutprimarilyonthedegreeofbondingbetweenfibers.Itthereforehasfrequentuseinpulptestingasageneralch

4、aracteristicforthePulpandPaperTesting-Page90Chapter7Generalphysicalpropertiesofpaperandboardcapabilityofbondingbetweenfibers.Theresultobtainedalsodependsonthetestingconditions.Anincreaseintherateofloadingwillincreasethetensilestrength.Anincreaseinmoisturecontentofthepaper

5、willdecreasethetensilestrengthwhileincreasingelongation14.Thetensilestrengthishighlydependantondirectionalityofthepaper.Thetensilestrengthmeasuredindifferentdirectionsofthesheetisoftenusedasanindicatoroffiberorientation.Tensiletestsometimesusestestpiecessaturatedwithaliqu

6、idsuchaswater,ISO3781.Thiswetstrengthvalueindicatestheretentionofstrengthofthepaperafterwetting.Wetstrengthvaluediffersfromtheinitialwetwebstrengthvaluethatgivesthetensilestrengthofthewebbeforeitsfirstdryingcycle.Thismeasurementisatensilevalueoflaboratorysheetsatacertains

7、olidscontentoratthesolidscontentobtainedwithastandardizeddewateringprocedure.Itisapulporfurnishpropertythatrelatestotherunnabilityofapapermachine,SCAN-C31andC35.7.3.2BurstingstrengthBurstingstrengthisthemaximumpressurethatthepapercanresistwithoutbreakingwithpressureapplie

8、dperpendiculartotheplaneofthetestpiece.Theunitforburstingstrengthiskilopascal,kPa.Calculationoft