Chiparus Dis

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BAGASSEFIBERFORPRODUCTIONOFNONWOVEN

MATERIALS

ADissertationSubmittedtotheGraduateFacultyoftheLouisianaStateUniversityandAgriculturalandMechanicalCollegeInpartialfulfillmentoftherequirementsforthedegreeofDoctorofPhilosophy

in

TheSchoolofHumanEcology

byOvidiuIuliusChiparus

B.S.,TechnicalUniversityGh.Asachi,Iasi,Romania,June1993May,2004


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Acknowledgements

Iwouldliketoexpressmygratitudetomymajoradvisor,Dr.YanChenforhissinceresupervisionandguidancethroughoutthecourseofthisstudy.IalsothanktoDr.BillieJ.CollierandDr.JohnR.Collierfortheirhelpandsupport.Itwasanhonortoknowandtoworkwiththem.

IwouldalsoliketoextendmyappreciationandgratitudetothepersonthatIconsiderittobemysecondfatherandmentor,Dr.IoanI.Negulescu.Hiswordofadviceandsupportmeantalotforme.

Furthermore,Iamgratefultoallthemembersofmycommittee:Dr.BetsyGarrison,Dr.PamMonroe,andDr.KristyReynoldsfortheircooperationandtime.

IalsoacknowledgethefinancialsupportreceivedbytheSchoolofHumanEcology.Specialthankstomycolleaguesandfriendsfromourinterdisciplinaryresearchgroups.

Ideeplyacknowledgetheencouragement,support,guidanceandpatienceofmy

friendsChristianandHoriaNegulescu.

SpecialappreciationgoestoOlenaNesterukforherpermanentmoralandphysicalsupport,forherpatienceandlove.

Iwouldliketoexpressmygratitudeandlovetomyparents,forwhomtheirchildrenshappinessistheirmeaninginlife.

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TableofContents

Acknowledgements.............................................................................................................ii

ListofTables......................................................................................................................v

ListofFigures....................................................................................................................vi

Abstract............................................................................................................................iix

Chapter1ReviewofLiteratureandGeneralProcedures..................................................1

1.1Introduction................................................................

...............................................1

1.2ResearchObjectives..................................................................................................5

1.2.1ToUsetheAtmosphericExtractionProcesstoObtainBagasseFibers............5

1.2.2ToCreateNonwovensBasedonBagasseandOtherAnnualPlants.................5

1.2.3ToDeterminePhysicalProperties,LengthandFineness,ThroughaNewMethodforBagasseandOtherUnconventionalFibers.....................................6

1.2.4ToEstablishTestingProceduresandMethods..................................................6

1.3ArrangementofThisResearchWork.......................................................................7

1.4ReviewofLiterature.................................................................................................8

1.4.1SugarCaneBagasse........................................................................................8

1.4.2OtherPlantFibersKenaf,Ramie,JuteandFlax............................


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...............15

1.4.2.1Kenaf.........................................................................................................15

1.4.2.2Ramie........................................................................................................20

1.4.2.3Flax..........................................................................................................21

1.4.2.4Jute...........................................................................................................23

1.4.3ExtractionandEvaluationofFibers................................................................25

1.4.4NonwovenComposites......................................................

..............................31

1.4.5MechanicalProperties......................................................................................35

1.4.6ImageAnalysis.................................................................................................39

1.4.7ThermalAnalysis.............................................................................................42

1.4.8Biodegradation.................................................................................................47

1.5ExperimentalMethods............................................................................................50

1.5.1ProcessingProcedure.......................................................................................50

1.5.2NonwovensFormation.....................................................................................52

1.5.3Thermal-Bonding.............................................................................................54

1.5.4StaticMechanicalTesting.................................................


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...............................55

1.5.5ImageAnalysis.................................................................................................56

1.5.6Thermo-GravimetricAnalysis.........................................................................57

1.5.7DynamicMechanicalAnalysis(DMA)...........................................................57

1.5.8ThermalConductivityandThermalTransmittance.........................................59

1.5.9Composting......................................................................................................60

Chapter2AnImageMethodtoEvaluateBagasseFiberDimensions..................

...........61

2.1Introduction.............................................................................................................61

2.2Experimental...........................................................................................................63

2.2.1BagasseExtraction...........................................................................................63

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2.2.2VisualizingandMeasuringProcedures...........................................................63

2.2.3DeterminationofFiberLengthandFineness...................................................64

2.2.4StatisticalAnalysis...........................................................................................66

2.3ResultsandDiscussion..........................................................................................67

2.4Conclusions............................................................................................................69

Chapter3ManufactureandAnalysisofNonwovenCompositesBasedonAnnualPlantFibersandPolymers..........................................................................................................71

3.1Introduction............................................................................................................71

3.2Experimental..........................................................................................................73

3.2.1Materials..........................................................................................................73

3.2.2ProcessingProcedures..74

3.3TestingProcedures.................................................................................................75

3.3.1MechanicalDeterminations.............................................................................75

3.3.2ThermalAnalysis.............................................................................................75

3.3.3DynamicMechanicalAnalysis........................................................................76


3.4.1ThermalTransitionsbyDSC...............................................


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............................76

3.4.2Thermo-GravimetricAnalysis.........................................................................76

3.4.3Dynamo-MechanicalAnalysis.........................................................................81

3.4.4MechanicalProperties.....................................................................................83

3.5Conclusions............................................................................................................85

Chapter4BiodegradableNonwovenMaterials...............................................................86

4.1Introduction................................................................

............................................86

4.2MaterialsandMethods...........................................................................................89

4.2.1CellulosicFibers.............................................................................................89

4.2.2BondingSyntheticPolymer............................................................................89

4.2.3CardingandNeedle-punching........................................................................89

4.2.4Thermal-Bonding............................................................................................90

4.2.5ThermalAnalysis............................................................................................90

4.2.6DynamicMechanicalAnalysis.......................................................................91

4.2.7MeasurementofThermalConductivityandThermalTransmission..............91

4.2.8BiodegradationofCompositeNonwovens....................................


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.................92


4.4Conclusions..........................................................................................................101

Chapter5ConclusionsandRecommendations...............................................................102

References......................................................................................................................107

Appendix:LetterofPermission...111

Vita.................................................................................................................................112

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ListofTables

Table1-1AverageBagasseComposition.........................................................................11Table1-2Chemicalcompositionsofvegetablefibers(Batra,1993)...............................24Table1-3Lengthandlineardensityofvegetablefibers...................................................24Table1-4ConventionalFormsofTA...............................................................................45Table2-1DirectdeterminationsfortheAreaandthecorrespondingFineness...............66Table3-1Tensilepropertiesofnonwovencompositematerials......................................84Table4-1Constructioncharacteristicsofnonwovenbagasse/cotton/EBCsamples........90Table4-2Thermalconductivitydataforbagasse/cotton/EBCcompositenonwovens....98Table4-3Mechanicalpropertiesofnonwovenmaterialsbeforeandaftersoildegradation.....................................................................................................................100

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ListofFigures

Figure1-1Currenttechnologicalprocessforextractionofsugarjuice(Elsunni,1993).....2Figure1-2.Bagasse...........................................................................................................10Figure1-3.Land-fillingwithbagasse...............................................................................13Figure1-4.Cross-sectionalviewofkenafplant(Parikh,2002).......................................16Figure1-5.Harvestingkenafcrop(Nimmo,2002)..........................................................17Figure1-6.SEMofkenafbastribboncrosssectionshowingfiberscontainedinbundles(Akinetal.,1999).............................................................................................................19Figure1-7.Flaxharvestingandprocessing(CollierandTortora,2001)..........................22Figure1-8.Hanksofflax...22Figure1-9.Juteplants.......................................................................................................23Figure1-10.SchematicdrawingfortheTilbyMachine(Tilbyetal.,1976)....................26

Figure1-11.BilletsofSugarCaneStalks..26Figure1-12Schematicdrawingofapilotscalecontinuousatmosphericreactorforbagasse..............................................................................................................................28Figure1-13.DelignifiedBagasse.....................................................................................29Figure1-14.Traditionaljutefibersextraction..................................................................30Figure1-15.Kenafbastfibersfromplantharvested180daysafterplanting.(a)Withnotreatment.(b)Treatedwithsodiumacetate(Akinetal.,1999)........................................31

Figure1-16.Strain-stressplot............................................................................................37Figure1-17.Tensilestrengthplot.....................................................................................38Figure1-18.BlockdiagramofaTAinstrument...............................................................44Figure1-19.AtmosphericExtractionReactor..................................................................51Figure1-20.F105DUniversalCardingMachine............................................................52Figure1-21.MorrisonBenkshireNeedle-PunchingMachine..........................................53

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Figure1-22.ThreeLayer(sandwichtype)NonwovenComposite

Ramie/Kenaf/Polypropylene.............................................................................................53Figure1-23.ThreeLayer(sandwichtype)NonwovenCompositeBagasse/Kenaf/Polypropylene..........................................................................................54

Figure1-24.CarverLaboratoryPress...............................................................................54Figure1-25.InstronTesterModel4301...........................................................................55Figure1-26.ElectronScanningMicroscopicImageforBagasseFiberBundleCross-

Section..............................................................................................................................57Figure1-27.Seikodynamo-mechanicalspectrometersDMS200...................................58Figure1-28.Seikodynamo-mechanicalspectrometersDMS110...................................58Figure2-1Length(a1-a3)andcross-sectional(b1-b3)visualizationsfor3samplesof

bagassefibers....................................................................................................................65Figure2-2.Thedependencybetweenthecross-sectionalareaandfineness....................68Figure2-3.Theresiduals(error)distribution...................................................................69Figure3-1.DSCthermogramsofnonwovencompositesandPP.....................................77Figure3-2.Thermogravimetriccurvescorrespondingtoweightlossbydryingof

nonwovencompositesandPP...........................................................................................77

Figure3-3.Thermogravimetriccurvescorrespondingtoweightlossbydryingandthermaldecompositionofkenaf,flaxandjutenonwovencompositesandPP.................78Figure3-4.Firstderivativeofthermogravimetric(tg)curvesofkenaf,flaxandjute

nonwovencompositesshowingthepeakscorrespondingtodegradationofcellulosicsand

individualsyntheticpolymers79

Figure3-5.Secondderivativeofthermogravimetric(TG)curvesofkenaf,flaxandjutenonwovencompositesshowingthepeakscorrespondingtodegradationofcellulosicsandindividualsyntheticpolymers79

Figure3-6.Thermogravimetriccurvescorrespondingtoweightlossbydryingand

thermaldecompositionofRamie/Kenaf/PPnonwovencomposite.....................


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.............80Figure3-7.TGcurvescorrespondingtoweightlossbydryingandthermaldecompositionofBagasse/Kenaf/PPnonwovencomposite...80

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Figure3-8.ThermogravimetriccurvescorrespondingtoweightlossbydryingandthermaldecompositionofRamie/Kenaf/PPnonwovencompositesamplesinairandinertatmosphere(N2)................................................................................................................81

Figure3-9.Dynamo-mechanicalanalysisofKPBPnonwoveninbendingmode.

Dependenceoftanduponthetemperature........................................................................82Figure3-10.Dynamo-mechanicalanalysisofKPBPnonwoveninbendingmode.DependenceoftheviscouscomponentEuponthetemperature.....................................82

Figure3-11.Dynamo-mechanicalanalysisofRPKPnonwoveninbendingmode.........83

Figure3-12.Dynamo-mechanicalanalysisofKPBPnonwoveninbendingmode.DependenceoftheelasticcomponentEuponthetemperature.......................................84Figure4-1.Layeredcompositenonwovensmadeofbagasse/cottonwebsandEBCmelt

blownnonwovensbeforeandafterhot-pressing..............................................................90

Figure4-2.Thermaldegradationofnonwovenmaterialsininertatmosphere(nitrogen).......................................................................................................93Figure4-3.DependenceofEoftheEBCupontemperatureandfrequency..................93Figure4-4.DependenceofEofthecompositenonwovenupontemperatureand

frequency..........................................................................................................................94Figure4-5.Glasstransition,meltingandsofteningoftheEBCpolyesterasreflectedby

DSCandDMA(E)dataforthebondingpolymer(EBC)andfortheEBCbondednonwoven.........................................................................................................................96Figure4-6.DependenceoftheEBCglasstransitionuponfrequency..............................96Figure4-7.ThermaltransitionsofEBCpolyesterincompositenonwovens...................97Figure4-8.Blow-upofFigure4athighertemperatures:glasstransitionofcell

ulosic

chains................................................................................................................................97Figure4-9.Decayingintimeofthecomplexelasticmodulusofelasticity(E*)ofbagasse/cotton/EBCcompositenonwovensaftersoilburial..........................................101

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Abstract

Rawmaterialsusedinnonwovenproductsvarygreatly,coveringtheentirespectrumfromsynthetictonaturalfibers.Thelimitationofuseforindustrialapplicationsofnonwovenproductshaslongbeensurpassed,todaynonwovensbeingfoundindiverseapplicationsrangingfromintimateappareltogeotextiles.

Thepresentworkhasasitsultimategoaltodevelopacommercialmethodforcharacterizingsomeofthephysicalpropertiesofbagasseorotherunconventionalfibersobtainedthroughanewatmosphericextractionmethod,andalsotocreateandanalyzedifferentnonwovenstructuresbasedonbagasse,kenafandotherannualplants.

Bagassefiberswereextractedfromsugarcanerindintwodifferentsteps:mechanicalseparationandchemicalextraction.Severalfactorswereconsideredsuchassolutionsofsodiumhydroxidewithdifferentconcentrationsandtimeofreaction.Asimilarprocesswasusedforkenaf.Thekenafrindcontainingouterbastfiberwas

mechanicallyseparated(usingaTilbyseparator)andchemicallytreatedwithanalkalisolution.

Eventhoughunderratedasapotentialfiber,bagassedrawsmoreandmoreattentionbecauseoftheincreasingconcernfordisposalofagriculturalresiduesandtheneedforenhancingthesugarcaneindustrysprofitability.However,thereisalackofaninstrumentalmethodtoevaluatebagassefiberlengthandfineness.Thispaperpresentsastudyonmeasuringbagassefiberfinenessusingimageanalysismethod.Cross-section

imagesofbagassefiberswerevisualizedusingScanningElectronicMicroscopy(SEM).Therelationshipbetweenfiberfinenessandcross-sectionalareawasanalyzedusingthestatisticalmethodofregression.Themodelusedinthismethodcanbeextendedfor

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evaluatingconveselythecross-sectionalareawhenthefinessisknown,and/orforevaluatingotherunconventionalfibers.

Differentstructuresofnonwovenmaterialswerecreatedthroughcarding,needle-punching,andthermal-bonding.Asbondingagents,differenttypesofsyntheticpolymershavebeenuseddependingonthefinalproductusage.

Thefinalproductsweresubjectedtotestingprocedures(accordingwiththeirusage)suchasmechanicaldeterminations,thermalanalysis,dynamo-mechanicalanalysis,biodegradability.Theresultsprovidedinformationregardingthepossibilitytousethenonwovenstructurescreatedindifferentapplications.

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Chapter1ReviewofLiteratureandGeneralProcedures

1.1IntroductionIntropicalregionsoftheworldsugarcanerepresentsamajorcrop.Becauseoftheincreasingdemandforsugarinthelastcentury,largeareasinthetropicalandsubtropicalcountriesallaroundtheworldwereallottedforsugarcanecrops.Lowlevelofmaintenanceandgoodproductivitymadesugarcaneanattractivecropforfarmersintheseregions.

IntheUSthesugarcaneindustrystartedtodevelopinthesecondhalfofthe19thcenturyoncesteampowerwasavailableforagriculturemachinery.Today,LouisianaisthesecondlargestproducerofsugarcaneintheUS,onlybehindFlorida.Besidesthemainproduct,sugarjuice,severalby-productsareavailableinthesugarcaneextractionprocess.Themostimportantisconsideredtobebagasse(Paturau,1989).

AsitcanbeseeninFigure1-1,caneiscrushedinaseriesofmills,each

consistingofatleastthreeheavyrollers.Duetothecrushing,thecanestalkwillbreakinsmallpieces,andsubsequentmillingwillsqueezethejuiceout.Thejuiceiscollectedandprocessedforproductionofsugar.Theresultingcrushedandsqueezedcanestalk,namedbagasse,isconsideredtobeaby-productofthemillingprocess(Elsunni,1993).Bagasseisessentiallyawasteproductthatcausesmillstoincuradditionaldisposalcosts.

CurrentresearchintheUSagriculturalandforestryindustryisconcernedwiththe

developmentofnewusesandaddedvaluetofarmandforestryproductsforgreatereconomicbenefits.Processingandrecyclingofthenaturalproductsisdoneinanenvironmentallyresponsiblemanner,usingtheseresourcesefficiently.Utilizationoftheagriculturalcropsasalternaterawmaterialsformanyindustriesismorethananoption.

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Sugarcanebagasseisestablishedasthefuturefiberintropicalandsubtropicalregionsforpulpandpapermaking.

Figure1-1Currenttechnologicalprocessforextractionofsugarjuicefromcaneinasugarcanemill(Elsunni,1993).AccordingtoAtchinson(1995),bagassewillbeaheadofothercropsasasourceforthepulpinpaperindustry.Itisestimatedthattheamountofbagasseproducedannuallyisabout80,000,000metrictons(MT),fromwhich25,000,000metrictonswillbeusedforpulping(equalto13%ofthetotalpaper-makingpulpcapacity).Also,kenafisaverypromisingmaterialforpaperpulpsandtextileapplications(KPProductsInc.,1993).Structurallysugarcane(SaccharumOfficinarum)stalkiscomposedofanouterrindandaninnerpith.AccordingtoPaturau(1989)themajorityofsucrosetogetherwithbundlesofsmallfibersisfoundintheinnerpith.Theouterrindcontainslongerandfiner

fibers,inarandomarrangementthroughoutthestemandboundtogetherbyligninand

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hemicellulose.Previousstudiesontheextractionofthefibersfromsugarcanerinddemonstratedthatcontrolledamountsofligninandhemicellulosecouldberemovedthroughalkalineandmechanicaltreatments,resultinginbundlesofrelativelythinfibers(Collieretal.,1992).

Kenaf(HibiscusCannabinus),nativetosoutheasternAsiaandpartsofAfrica,hasbeenusedasanaturalfiberforhundredsofyears.ItcameintotheUnitedStatesonacommercialscaleatthebeginningofWorldWarII.Itisconsideredtobeanalternativeannualcrop,usedprimarilyforindustrialtextileapplicationsascordage,rope,andburlapcloth(Moreauetal,1995).Kenafissimilartojute,butifthetechnologicalprocessisconductedproperly,kenafismorelustrous,hasgreatertensilestrength,andhasgreaterresistancetorotthanjute.Thepriceforkenaffibersbecamereasonablewiththelatestimprovementsinthegrowing,harvesting,andmechanicalseparationoffiberand

core.Eventheleavesandstemsofthekenafcultivarshavepotentialaslivestockfeed(Webber,1993).Driedleavescontain30%crudeprotein,comparedwithalfalfas1621%(USDA,1993).Thekenafplanthastwofibertypes:theouterbarkorthebastportion(40%oftheplant)andtheinnerwoodycorematerial(60%)(Sellersetal.,1993).Oneareathatoffersopportunityistheincorporationofkenaffiberintononwovencomposites.Kenafalsofoundgroundforapplicationinpulpandpaperindustries.

Besidessugarcanebagasseandkenaf,otherbastfiberslikejute,ramie,andflaxwereconsideredbythescientistsinthenonwovenindustry.Duetotheirphysicalandmechanicalcharacteristicsthesefiberscanbringimprovementintotheoverallpropertiesofnonwovencomposites.Also,theycouldbeareplacementforthesyntheticfibersthat

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dominatenonwovenindustry.Theirbiodegradationpropertiesmakethemmoreandmoreappealinginthecontextofnewregulationsforenvironmentprotection.

Furtherdevelopmentofvalueaddedagriculturalproductswillrequirenotonlyoptimizationoftheextractionprocessanddeterminationoftheeffectofprocessparametersonfiberproperties,butalsothedevelopmentofavalidsamplingandmeasuringtechniqueforthefiberslengthandlineardensity(Romanoschi,1998).Newmethodsinvolvingimageanalysiswillallowdeterminingphysicalparametersforunconventionalfibersuchasbagasseandkenafinaneasyandinexpensiveway.

Extractingsugarcaneandkenaffibersfromtheplantstalkswasconsideredtobeadifficultandcostlytask.Theextractionprocessshouldbeoptimizedintermsofchemicaluseandtimetomaximizethepotentialforcommercialuse(Romanoschi,1998).Theprimarygoalistoremovecontrolledamountsofligninandhemicellulose,soastoobtainfiberswithuniformlength,weight,andfineness.Anothergoalsetbythi

sworkwastodevelopanextractionprocessthatwasasenvironmentallyfriendlyaspossible.

Inthelastdecadesnonwovenproductsconqueredseveralsegmentsofthetextilemarketmakingthenonwovenindustryasuccessstoryinacrumblingworldoftextiles.Nowadays,nonwovensareeverywherefromchilddiaperstocarinteriors.Inthiscontextnewdesignandcharacterizationofnonwovenproductsrepresentaneedforthisnewindustry.Aparticularareaofinterestistheuseofcheapalternativecropsinmaking

nonwovencomposites.Biodegradation,asoneoftheimportantcharacteristicsfornonwovenmaterials,isinvestigated.Thedesireforuseofnonwovencompositesindiversenewapplicationsalsorequiresfurthertestingfordifferentspecificconditions.Thermalanalysisanddynamicmechanicalanalysisaretoolsusedbythescientists

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nowadaysinordertogivecomprehensiveinformationregardingmaterialbehaviorunderthermalandmechanicalfactors.

ThisresearchwillhaveanimpactoneconomicdevelopmentinLouisianaandothersouthernstatesbyprovidingagriculturistswithalternativesincropchoicesandaddingvaluetothesugarcanecrop.Also,thesugarcanemillscanextendtheirworkperiodbeyondthetraditionalfallseason.Convertingagriculturalby-productstovalueaddedproductswillbenefittheeconomyofLouisiana,andnewmarketswillbedevelopedforagriculturalcrops(Romanoschi,1998).

1.2ResearchObjectives1.2.1ToUsetheAtmosphericExtractionProcesstoObtainBagasseFibersFrompreviouswork,itwasdeterminedthatthemostinfluentialfactorsfortheextractionprocesswerealkalineconcentration,timeofthereaction,mixing,andpresenceorabsenceofsteamexplosion(Romanoschi,1998).Inthisstudy,theextractionprocesstookplaceatatmosphericpressure.Thegoalwastodesignanextractionprocessas

affordableandasenvironmentallyfriendlyaspossible.

1.2.2ToCreateNonwovensBasedonBagasseandOtherAnnualPlantsDifferentmethodologiescanbeusedtocreateavarietyofstructuresofnonwovenmaterials.Dependingonthefinalsoughtproduct,aspecifictechniquecanbeemployed.Bycomparingthefinalproductsaccordingtothephysicalandthermo-mechanicalcharacteristics,acertainpathforthetechnologicalprocessofcreatingnonwovenscanbedesigned.Thewebformationfollowsadrylaidcardedmethod.Thewebbondingaccordingtotherawmaterialsusedisaccomplishedthroughamechanicalneedle-punchingmethodfollowedbyathermalbonding.Thedesireistodesignasimple,

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reliable,andeconomicaltechnologicalprocessthatwillcreatenonwovenswithcharacteristicsinaccordancewiththefinalproductproperties.

1.2.3ToDeterminePhysicalProperties,LengthandFineness,ThroughaNewMethodforBagasseandOtherUnconventionalFibersInstrumentsusedtodeterminecottonslengthandfinenesseffectivelycannotbeemployedforthecoarsefiberswithunevenstructureascanbefoundinunconventionalfiberslikebagasseandkenaf.Acombinationofimageanalysisandstatisticalregressionanalysisprovidesaconvenientapproachformeasurementsofsomeofbagassesphysicalcharacteristics.Thismethodcanbeextendedtootherunconventionalfibers.

1.2.4ToEstablishTestingProceduresandMethodsOneoftheresearchgoalswastoidentifytestingmethodsandtechniquesthatwouldallowassessmentofperformanceofthematerialsused.Inindustrialapplicationnonwoven-basedmaterialsmustsatisfycertainbehavioralexpectationsthatcanbequantifiedthroughmechanicalorthermalproperties.Standardtensilestrengtht

estingevaluatedthestaticmechanicalpropertiesfordifferentnonwovencomposites.Severalparameterswereregistered-themostimportantbeingmodulus,strain,andstress.Thesewillallowassessmentofperformanceofacertaintypeofnonwovencompositeaccordingtothespecificationsforthefinalproductandincomparisonwithotherstructure-compositioncombinations.Theuseofnonwovensinproductsundertheeffectofvariablestressandtemperaturerecommendedthethermalanalysisanddynamicmechanicaltesting.Conductivityandthermaltransmittanceweredeterminedinordertoanal

yzetheheattransferfordifferentstructure-compositioncombinationsofnonwovenasapplicationsforheatinsulation.Biodegradationisanotherimportantpropertyandwasusedtoassesthecapacityofnonwovenmaterialstodecomposeinaspecificamountof

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time.Theresultswereanalyzedtodeterminethemostcriticaltestsandtoeliminateanyunnecessaryorrepetitivetests.

1.3ArrangementofThisResearchWorkThisdissertationisorganizedinthreeparts.Thefirstpartdealswithexperimentalaspectsofdevelopingnonwovencompositesusedinindustrialapplications.Theliteraturereviewsubchapterpresentsdifferentapplicationsofsugarcaneandkenaf,anextendedoverviewofthepreviouslyusedbagasseextractionprocess,theemploymentofimageanalysisandthermalanalysisincharacterizingtextilescomponents,andanoverviewofbiodegradation.Intheexperimentalmethodssubchapter,alltheprocessingandtestingproceduresarediscussed.

Inthesecondpartthreeproposedarticlesarepresented.ThefirstoneinChapter2,AnImageMethodtoEvaluateBagasseFiberDimensions,proposesanewmethodindeterminingsomeofthephysicalcharacteristicsforbagassefibers.Thesecond

oneinChapter3,ManufactureandAnalysisofNonwovenCompositesBasedonAnnualPlantFibersandPolymers,describesthetechnologicalprocessofmakingnonwovensusingablendofnaturalandsyntheticfibers,andanalyzesthefinalmechanicalandthermalproperties.ThethirdoneinChapter3,BiodegradableNonwovensMaterials,isanextensionofthebiodegradabilitystudyinthepreviouschapter.Thisgoalisaccomplishedbyusingasabondingagentabiodegradablepolymer.Again,abatteryoftestsisconductedinordertoassessthephysical,mechanical,thermal,andbiodegradationproperties.Thethirdpart,Chapter5,presentsconclusionsandrecommendations.

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1.4ReviewofLiterature1.4.1SugarCaneBagasseBastfibersrepresentfibersthatareobtainedfromthestemorstalkoftheplants.Grassessuchassugarcanehavestemswhichcontainbundlesoffibers,buttheyarenotclassifiedasbastfibers(Romanoschi,1998).Thedifferencecomesfromthearrangementpatternofthefiberbundles;inregularbastfibersthebundlesareinadefiniteringpattern,whileinsugarcanetheyaremorerandomlydispersed.Nowadaysseveralvarietiesofsugarcaneareusedinagriculture.Thesugarcaneplantsareknowntogrowbestintropicalandsubtropicalregions.

Sugarcanestalkcharacteristicsvaryconsiderablydependingonvariety.Typicalcommercialvarietiesgrownundernormalfieldconditionshaveaheightof1.5to3metersandare1.8to5cmindiameter.Thestalksurfacecanbegreenish,yellowishorreddishincolorandiscoveredwithathinwaxylayer(vanDillewijn,1952).

Thecanestalkismadeupofshortersegmentsandjoints.Thesejointsvaryinlengthfrom5to25cm.Thelowerjointsarelonger,largerindiameter,andolderthantheupperjoints.Eachjointhastwodistinctiveparts,thenodeandtheinternode(Elsunni,1993).Atthenodeandimmediatelyarounditaretheimportantstalkstructures:therootband,thebud,thegrowthring,andtheshoulderwheretheleafattachestothestalk(Clements,1980).Inacrosssectionintheinternodewecanobservetwodistinctiveareas.Thefirstone,knownastherind,istheouterdensehardlayer.Theinsidelayer,

knownasthepith,isthesoftlightcoloredregionwherethefibrovascularbundlesareembedded.Therindvariesinthicknessandtexturealongthestalklength.

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Thefibrovascularbundlesareratherwidelyspacedinthecentralpartofthestalk,buttowardstheperipherytheirnumbersincreasewhiletheirsizesdecrease.Thebundlesarecomposedofsmallerultimatefibercellswhichareboundtogetherbyligninandhemicellulose.Asthecaneages,thereisincreaseddepositionoflignin-likecompoundsinandaroundfibrovasculartissues(vanDillewijn,1952).Thisphenomenonresultsinwhatiscalledfiberhardeninguptothetimeofflowering.Afterthat,asthecaneageadvances,theprocessisreversedandtheligninisremovedfromthebundlescausingthemtobecomesoftandweak.Thesofterrindisprimarilycellulosicinnature(Elsunni,1993).Thefibrovascularbundlesarefibrousstrandswhichextendforlongdistancesinthestem.Attheinternodetheyareseparatedfromeachotherandeachissurroundedbypithtissue.Withintheinternodethesebundlesrunparalleltotheaxisofthestalkanddonotbranch.Althoughthefibrovascularbundlesarescatteredthroughouttheint

eriorofthestalk,theyaremoreabundantintherindregionthantheyarenearertothecenterofthestalk.Thisbundlearrangementincreasesthestrengthandtherigidityofthestalk.

Thehardnessofthecanestalkisapropertyofconsiderableconcernbothinthemillandinthefield.Hardcanevarietieshavebeenresponsibleformanymechanicalproblems(vanDillewijn,1952).Inthefield,thesugarcanevarietieswithhardrindsareknowntobedifficultformanualcanecutters,andaredirectcauseofexcessive

breakdownsofmechanicalharvestingunits,resultinginlossofpartsandvaluablecrushingtime(Barnes,1964).Atthesametime,varietiesofhardrindhavesomeadvantagesoversoftercanevarieties.Rindhardnessiscloselyassociatedwithresistancetoattacksbyanimalssuchasrats,pigs,andmongooses.

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Thegoalofsugarcaneharvestingistoproducesugarcanestalksofhighquality.Qualityisreducedbydamagedcane,increasedtrashindeliveredcane,anddelayincanedelivery(Meade,1977).Mostofthehighsucrosevarietiesarefullyripenedandreadyforharvestwhentheyare10to15monthsold.However,insomepartsoftheworldtherearevarietieswhichgrowfor22to26monthsbeforetheyarereadyforharvesting.Thelongerthegrowingseason,themorelikelyitisthatthecropmaylodgeandbecomeentangled,makingharvestingdifficult(Barnes,1964).Formorethan60yearstheentiresugarcanecropinLouisianahasbeenharvestedmechanically.However,muchoftheworldssugarcaneisstillharvestedandloadedmanually,andinsomepartsoftheworldtraditionaltransportofsugarcanebydomesticanimalsisstillinuse(Meade,1977).

Baggasseisafibrousresiduethatremainsaftercrushingthestalks,andcontainsshortfibers(seeFigure1-2).Basically,itisawasteproductthatcausesmill

stoincuradditionaldisposalcosts.Itconsistsofwater,fibers,andsmallamountsofsolublesolids.Percentcontributionofeachofthesecomponentsvariesaccordingtothevariety,maturity,methodofharvesting,andtheefficiencyofthecrushingplant.InTable1-1(Elsunni,1993)atypicalbagassecompositionispresented.

Figure1-2.Bagasse

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Table1-1AverageBagasseComposition

ITEMBAGASSE(%)Moisture49.0Fiber48.7SolubleSolids2.3

Fibersinbagasseconsistmainlyofcellulose,pentosans,andlignin.Celluloseisanaturallinearpolymerandhaspolymerchainsof2000to3000units(Paturau,1989)andaspecificgravityabout1.55(Elsunni,1993).Celluloseishighlycrystallineregardlessofthesource.Theorderedchainsaretightlypackedandhavestrongintermolecularhydrogenbondingbecauseofthepreponderanceofhydroxylgroups(Romanoschi,1998).Thecelluloseispresentinthreetypes:a,,and..Theacelluloseisknownaspurecellulose,whereasand.cellulosecombinedarecalledhemicellulose(Marthur,1975).Thehemicellulosesarechemicallylinkedwithcellulosemolecules.Theothermain

compoundinsugarcanefiberbundlesisligninwhichisahighmolecularweightsubstance.Becauseitisnotpossibletoisolateligninquantitativelyfromplantmaterialswithoutchemicalormechanicaldegradation,itstruemolecularweightisnotknown.Theamountofligninthatnaturallyoccursinsugarcanedependstoagreatextentonthevarietyandageofthecane.Theamountsofsugar,lignin,andlignin-likecompoundsincreaseastheplantadvancesinageuntilthefloweringtime,whentheplantisconsideredtobefullymature.Beyondthefloweringtime,thesugarcaneplanttendsto

consumeitsstockofsucroseandligninasaresultofphysiologicalchangesdueto

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flowering.Thedepletionoftheorganiccompoundsmakestherindandthefiberbundlessofterandspongy(vanDillewijn,1952).

Forafibertobesuitablefortextilepurposescertainqualitiesareessentialandothersaredesirable.Thelengthofthefibershouldbeseveralhundredtimesthewidth,whichenablesfiberstobetwistedtogethertoformayarn.Theactuallengthofthefiberisalsoimportant.Itcanbeinfinitelylong,butshouldnotbeshorterthan6to12mm,oritmaynotholdtogetheraftersinning(Batra,1983).Theapparentlimitationonlengthofthesugarcanerindistheinternodelength,andthisvariesfrom5to25cm.Thelengthoftheultimatefibercellsisfrom2to4mm(Paturau,1989).Thelengthofextractedfiberbundlesdependsonextractionconditionsandtheextractionprocess.Thewidthofthefiberbundlescanvarybetweenconsiderablelimits,andeventuallydeterminesthefineness.Theresultantsugarcanefiberbundlesconsistofseveraltohundreds

ofultimatefibercells,withthewidthofthefiberbundlesbeingdependentonextractionconditionsandextractionprocesses.Theamountofligninremovedfromtherindaffectsthesizeofthefiberbundlesaswellastheirtensileandbendingproperties(Collieretal,1992).

Fibersmustbestrongtowithstandspinningandweavingprocesses.Fiberstrengthistypicallynormalizedbyreportingtensilestrengthastenacity.Tenacityisthebreakingloadingramsdividedbythelineardensity.Lineardensity,themasso

rweightofaunitlengthoffiber,isgivenasgramsper1000mandcalledtex,orasgramsper9000mandcalleddenier.Thetenacityofthesugarcanefibersextractedunderdifferentconditionsisvariableaccordingtoextractionconditions.

Bendingpropertiesofthefiberareofgreatinterestinthespinningprocess.FiberbendingresistanceandhysteresiscanbemeasuredontheKawabataPureBendingTester

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(Collier,1991).Theresultsofapreviousstudyshowedthatthebendingpropertiesofsugarcanefiberaresignificantlyaffectedbyextractionvariables(Collieretal,1992).Thosevariablesincludepretreatmenttime,temperature,concentrationofalkalisolution,andpresenceofsteamexplosion.

Nowadaysbagasseismainlyusedasaburningrawmaterialinthesugarcanemillfurnaces.Thelowcaloricpowerofbagassemakesthisalowefficiencyprocess.Also,thesugarcanemillmanagementencountersproblemsregardingregulationsofcleanairfromtheEnvironmentalProtectionAgency,duetothequalityofthesmokereleasedintheatmosphere.Presently85%ofbagasseproductionisburnt.Evenso,thereisanexcessofbagasse(Figure1-3).Usuallythisexcessisdepositedonemptyfieldsalteringthelandscape.

Approximately9%ofbagasseisusedinalcohol(ethanol)production.Ethanolisnotjustagoodreplacementforthefossilfuels,butitisalsoanenvironmenta

llyfriendlyfuel.Apartfromthis,ethanolisaveryversatilechemicalrawmaterialfromwhichavarietyofchemicalscanbeproduced(Sharma,1989).Butagain,duetothelowlevelofsucroseleftinbagasse,theefficiencyoftheethanolproductionisquitelow.

Figure1-3.Land-fillingwithbagasse.

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Bagassepulpsareusedforallgradesofpaper:writing,toilettissue,toweling,glassine,andothers.Bagassenewsprintpaperisalow-gradeandlow-pricedsheetappropriateforhigh-speedprintingpresses,withresistancetodeformation,quickoiladsorption,highopacity,andsmoothprintingsurfaces.BagassenewsprintpaperisacommerciallysuccessfulproductinIndia,Mexico,andIndonesia(Romanoschi,1998).Researchhasshownthatsomekeyfactorsshouldbeconsideredintheproductionofbagassenewsprint.Theserelatetotheuseofahighcontentofmechanicalpulp(allorpartofwhichcanbeproducedfrombagasse),theuseofhighlyefficientdepithingsystems,andtheuseofastoragemethodthatassuresexcellentpreservationofthebagasseproperties,includingcolorandbrightness.

ResearchatLouisianaStateUniversity(LSU)hasbeenconductedtodeterminethefeasibilityofsugarcanerindfibersfortextileandgeotextileapplications(Elsunni&

Collier,1996).Oneproductisanonwovenmatformedbysuspendingthefiberbundlesonascreeninwater,thendewateringanddrying.Thematshavebeentestedasgeotextilesforsoilerosioncontrolincivilengineeringapplications(Romanoschi,1998).Asuitablenonwovenmatforgeotextilesshouldsustain,oratleast,preventerosion.Atthesametimeitshouldbepenetrablebygrowingplants,becapableofpermittinginteractionbetweenairandsoil,andallowraintopenetratethesoilanddrainexcesswater(Collieretal.,1995).Thus,alow-cost,biodegradablegeotextilecanbeproducedin

localsugarcanemills,providinganeconomicbenefittoboththetransportationindustryandthesugarcaneindustry.

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1.4.2OtherPlantFibersKenaf,Ramie,JuteandFlax1.4.2.1KenafKenafbastfibersarederivedfromthebarkoftheHibiscusCannabinusLplant.Kenafisanannualplantgrowninareaswithtemperateortropicalclimate.AtpresentitisgrownintheSunbeltregionoftheUS,southernRussia,China,Thailand,Indonesia,Bangladesh,India,andinsomeLatinAmericancountries.ItcanalsobepotentiallygrownthroughoutsouthandsoutheastAsia,Australia,andAfrica,aswellasinsouthernEurope,orwherevertherearenotsufficientorsuitableforestresources(Kalgrenetal.,1989).Thereareverylowrequirementsforgrowingkenaf.Theannualproductioncanbeuptosixtotentonsofrawfibersperacre.USDAfieldtrialsshowedthatkenafcouldyieldthreetofivetimesmorefiberperacreperyearthansouthernpine(KPProductsInc.,1993).

Whenharvestedtheplantstemsaredecorticatedtoremovetheinnerpartofthestalkandthenrettedtoobtainthefiberbundles(Collier,2001).Thebastfibe

rsareconstructedofthick-and-thinwalledcells(lengthof:2to7mm,anddiameterof:10to30m)thatareoverlappedandgluedtogetherbynoncellulosicmaterials(lignin,pectins,andhemicellulose)toformcontinuousribbons(Figure1-4).Theribbonsmayruntheentirelengthof3to4.5m(10to14ft)oftheplantstem.(Parikhetal,2002).Therefinedouterbastfibersmeasure3.6mmandaresimilartothebestsoftwoodfibersinstrengthandbursttests.Therefinedinnercorefibersmeasure0.6mm(Kaldor,1992).Theplants

compositioniswellsuitedformakingnewsprint.Aswasdetermined,forkenaftobeaviablesourceforchemicalpulping,itwouldbenecessarytoseparateandtoprocessthe

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bastandcorefibersindependently(Jeyasingam,1990).Thetwokindsoffiberscanbeblendedindifferentproportionstoproducenearlyanygradeofpaper.

Figure1-4.Cross-sectionalviewofkenafplant(Parikh,2002)

Theprocessofseparatingthelongandshortfibersdependsuponthemethodofharvesting.Infrost-freeregions,thekenafstalkiscutwhilegreenwithspecialequipment.Incoolerregions,theplantistypicallyfrost-killedandanaturaldryingofthestalkoccurs,makingharvestingwithconventionalfarmequipmentpossible.Theseparationequipmentisdesignedtoaccommodatetherawmaterialineitherwholestalkorchopped(KPProducts,1993).

Fromaneconomicpointofview,akenafpulpmillwouldrequireahigherinvestmentforrawmaterialstorageandfiberseparationthantheregularwoodpulpmill;however,thisisoffsetbylowercostsinrawmaterialpreparation(Kalgren,1989).Becauseofthelowerlignincontentthanwood(7.7%),fewerchemicalsarerequir

edforpulping,and,inaddition,thefibersrequirelessbleaching.Thus,thewastewatercontaminationisalsoreduced,andfewerchemicalby-productsareproducedinthepaper-makingprocess.Anotherfactorthatdistinguisheskenafbastmaterialfromwoodmaterialsistheorientationofthefibrils.Inbastfibers,thefibrilslieparalleltotheplantaxis,whereasinwoodthefibrilsarespirallywound.Thus,thekenaf,aswellasotherbast

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fibers,canbesplitlengthwisebymechanicalaction,toyieldfineandlongfibrousbundles.Thehighhot-watersolubilityandthe1%NaOHsolubilityofkenafexplainalsothelossofyieldafteranythermalorchemi-thermo-mechanicalpulpingprocess,ascomparedwithwood.Thefungaltreatmentofkenaffollowedbypressurizedmechanicalpulpingresultsinenhancementofstrengthproprieties.Thecontrolledfibrillationthatrestrictstheformationoffinesisresponsibleforthisbehavior(Sabharwal,1994).

Kenafplantscangrowtoaheightof3to4.5m(10to14ft)in5to6months,whichmakethemanabundant,renewableresource(Figure1-5).Kenafcancompeteincost,quality,andavailability,ifsuitableconditionsandlandareasexist.IntheUS,kenafisalsoacomplementarycropforsoybeans,cotton,andsugarcane.InAustraliaitcanreplacewheatorrice,dependingonlocation.InThailandkenafisanalternativetoplantationeucalyptusandcassava.Alsothereislandavailabilityinmostcount

riesthatrelyontheimportoflongfiberpulpsforwhichtheyneedforeigncurrency(Romanoschi,1998).

Figure1-5.Harvestingkenafcrop(Nimmo,2002)

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Aswasstatedearlier,forkenaftobecomeaviablesourceforpulppaper,itisnecessarytoseparatethebastandcorefractions.Asaresult,thecorefibersgeneratedhavebeeninvestigatedassourcesforlow-densitycomposites(Sellersetal.,1993).Panelsofcorematerialwereconstructedandtestedforstrengthproprieties,dimensionalstability,waterabsorbanceproperties,andacousticalproperties.Phenol-formaldehyde,urea-formaldehyde,andpolymericdiphenylmethanediisocyanateresinswereusedasbinders.Theresultsshowedthatthepanelswouldbesuitableforsoundabsorption-typeproducts.Also,kenafcorepanelswereproducedforceilingtiles,decorativepanelsubstrates,floortilesubstrates,andcertainstructuralcomponents(Sellersetal.,1995).Kenafcanbeusedasreinforcingfibersintheformationofsynergisticpropertyenhancedfiber/thermoplasticcompositematerials.Ablendofkenaf/polypropylenehasgoodtensileproperties.

Researchhasdeterminedalsothatkenaffibersareexcellentoilabsorbentmaterialsandpreventtheoilfromleakingafterabsorption.Allthesepropertieswillbebeneficialinminimizingindustrialwaste(Goforth,1994).Kenafcanplayasignificantroleinfluid/particleseparationoperationssuchasoiladsorption,coalescence,deep-bedfiltration,andasfilteraidsfordecreasingtheresistanceoffiltercakes.Fiberscanbeusedtoimprovefilteringcharacteristicsofmunicipalwastewater(Tiller&Zhon,1995).

Becauseofthecoarsenessandstiffnessofthebastfiberbundles,theycanbecardedonlythroughacoarsewoolsystemorthroughamodifiedcottoncard.Forthefiberstobecardedonacottoncard,itisnecessarytoremovecontrolledamountsofthebindingligninandmakethefiberssufficientlyfineandpliable.Bycontrollingthelignin

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thatisremoveditshouldbepossibletoobtainfibersthataresuitabletothecottoncardingsystem(Parikhetal,2002).

Kenaffibershavebeenincorporatedintovarioustypesofnonwoventextiles,likekenaf/PPorkenaf/cotton/PPblends,whichmaybeusedforproductssuchasfabricsoftenersheets,furnitureunderlays,coverstocks,andbarriertextilesformedicalandagriculturalprotectiveclothing(Ramaswami&Boyd,1994).Kenaffiberswerealsobleachedtoagoodwhitewithhydrogenperoxide,andthendyedwithdirectandbasicdyes(Romanoschi,1997).Kenaffiberstreatedwithsodiumhydroxidehavebeencardedandneedlepunchedinto100%kenafandkenaf/cottonblendedmats.Thesematsarealsobiodegradableandhavepotentialinthepreventionofsoilerosion,thecontrolofweeds,andcleanupofwasteliquids(Tao&Moreau,1994).Kenaffibers,cleanedofcorefibers,havebeenmixedwithrefinedwood,syntheticandothernaturalfiberstomakeva

riousnonwovenneedle-punchedproducts:lightweightseededgrassmats,wildflowermats,vegetablestrips,erosioncontrolmats,oilabsorptionmats,padsandpillows,substratesformoldedautomobileparts,andcomposites(Fisher,1994).

Figure1-6.SEMofkenafbastribboncrosssectionshowingfiberscontainedinbundles(Akinetal.,1999)

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Thefeasibilityofkenafforyarnsandfabricswasalsoevaluated.Sincejuteandpineapplefibershavebeenusedtomakecoarserfabrics,itwasexpectedthatkenafsgoodtensilepropertiesanditsresistancetomildewandrotmightmakekenafanalternativecropforindustrialtextiles.Thefiberswererettedbothchemicallyandbacterially,followedbyadegummingprocess.Thenthefiberswereblendedwithcotton,successfullyspunintoyarns,andknitted(Ramaswami&Boyd,1994).

1.4.2.2RamieRhea,ramieorChinaGrasshasbeengrowninthefareastformanycenturiesanditsfiberusedformakingclothevenbeforetheintroductionofcotton.Ramiehasthelookandfeeloflinenbutishigherintenacityandlowerinprice.Itisstrongerwetthandry,doesnotshrink,andismildewandrotresistant.Ramiefiberisexceptionallylongandlustrouslikesilk.

Recentresearchwasfocusedoncontrollingfiberquality.Bycontrollingthe

growthandtheprocessing,fiberswithsimilarphysicalcharacteristicswereobtained.Despiteitsmanyexcellentpropertiesanddiverseuses,ramiefailedtobecomeahighlytradedtextilebecauseoflaborandotherproductioncostsassociatedwiththeprocessingofthefiber.Untilthechemicalrettingprocesswasdeveloped,onlyhandmethodscouldbeemployedtoremovethefiberfromthestem(Collier&Tortora,2001).Thedevelopmentofnewtechnologiesreducedthecostofproductionandincreasedtheattractivenessofthisfiber.Loweringproductioncostwillextenditsend-usesnotonlyin

high-valuefinalproducts,butalsoinlow-valueproductslikenonwovens.Goodpropertiesoftheramiefibermayenhanceend-useperformanceofcotton-baseddiverseindustrialapplications.

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1.4.2.3FlaxFlaxisabastfiberderivedfromthestrawofanannualplantofLinaceaefamilyoftheLinumgenus(Smithetal,2001).Theflaxplantisaggressivelycultivatedinseveralareasoftheworld(Russia,Canada,Belgium,Ireland,NewZealand,andothers),asitisthesourceofusefulcomponents:thestemgivesrisetotheflaxfiber,whichisthebasisforlinentextiles;theseedisthesourceforlinseedoilandlinseedcake,ananimalfeed;theremainingleavesandcoreofthestemaregenerallyreferredtoasbract,whichisalsoaproductofcommerce(deJong,1999).

Itisinterestingtonotethatflaxwasthemajorsourceofclothfiberforcenturies,untiltherapidgrowthofthecottonindustry,whichoccurredafter1800.Priortothattime,flaxwasthekingoffibers.FineandcoarselinenmaterialswerepreservedinthedryclimateofEgypt,datingbackto4000B.C.

Flaxplantsgrowupto0.6to1.5m(2to4ft)inheight.Stalksaredriedenoughsothattheycanbethreshed,combed,orbeatentoremovetheflaxseeds(Collier&Tortora,2001).Thefirststepistoloosenthebarkfromthestemandiscalledretting.Therettingprocesscanbedonenaturallyorchemically(Figure1-7).Afterrettingtheflaxstrawispassedoverflutedrollersorcrushedbetweenslattedframes.Thiswillbreakupthebrittlestemsbutdoesnotharmthefiber(Collier&Tortora,2001).

Flaxfibercanbecomparedwithcottoninseveralrespects(Figure1-8).Ithas

thesamespecificgravity(1.54g/d)ascotton,butbecauseofahigherdegreeofpolymerizationandahighlyorientedstructure,itisstrongerthancotton.Linenproductscanbefoundalmosteverywhereinthetextilecomplexfromextremelyfineproductsto

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coarseindustrialapplications.Linenproductsarepresentinhouseholdtextilessuchasbedsheets,tablecloths,andwearingapparel.

Figure1-7.Flaxharvestingandprocessing(CollierandTortora,2001)

Figure1-8.Hanksofflax

Theuseofflaxfibersforindustrialapplicationsissomewhatlimitedbytheproductioncost(18to35centsperpound).Withnewtechnologiesemployedtoprocessflax,itspricecandropmakingflaxaffordableforselectednonwovencomposites.Aninterestingapplicationforflaxnonwovencompositesisinaqua-culture.Thisinvolvesgrowingvegetablesandplantsinanutrientsolutionwithoutsoil.Thetraditionalsupport

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usedinthismethodinvolvesmineralfibersthatcannotbeusedformorethanfiveyears,andtheirdisposalisamajorproblem.Flax,abiodegradablefiber,isanalternativesolution.

1.4.2.4JuteJuteisthenameofthefiberextractedfromthestemsoftheplantsbelongingtothegenusCorchorus(Cook,1994).JuteisanotherbastplantmainlygrowninsouthernpartsofAsia.Theplantrequiresafertilesoil,andahotandhumidclimate.Theprocessofgettingthefibersoutofthestemfollowsbasicallythesametechnologicalprocessusedfortheotherbastfibers.Firstthestalksarerettedusinganaturalorchemicalprocess,andafterthatthestemsarebrokenandthefibersareremoved(Collier&Tortora,2001).

Figure1-9.Juteplants

Basedonthefiberstructureandcompositionthesefibersaremostsimilarwiththoseextractedfromsugarcanerind.Duetoitsphysicalandmechanicalcharacteristics,juteneverfoundgroundsforapplicationinapparel.Morethanthat,afterexposuretoairthejutefibersbecomebrittle.Foralongtimejutehasbeenusedforindustrialtextileslikebags,ropes,andcordage.Cheappolypropylenereplacedjuteinseveralapplications,primarilycarpetbacking.Recentfocusonbiodegradabilityoftheindustrialtextilemadejutefibersagainofinterest.Possibleusesareforgeotextilesinerosioncontrol.

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Developingnewtechnologiesforfiberextractionwouldmakejuteamorecompetitiveplantinthetextilecomplex.Tables1-2&1-3provideancomparativeviewofthecompositionandsomeofthephysicalpropertiesforthemainbastandgrassfibersthatarethesubjectofthiswork.Table1-2Chemicalcompositionsofvegetablefibers(Batra,1993)

FiberCellulose(%)Hemicellulose(%)Lignin(%)SugarCane50.030.018.0Kenaf65.713.221.6Ramie68.613.10.6Jute64.412.118.8Flax56.515.42.5(unretted)Flax(retted)64.116.72.0

Table1-3Lengthandlineardensityofvegetablefibers

FiberLength(cm)Lineardensity(tex)Celllength(mm)Cotton1.55.60.110.3715-56Sugarcane2.5-206.5014.002-4Kenaf7-151.504.501-7

Flax201400.191.984-77Ramie401000.510.7140-250Jute1503601.443.000.8-6

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extractionconditionsinfluencedthelineardensityofthefiberbundles,withalkalineconcentrationbeingthemostsignificantfactor.

Figure1-10.SchematicdrawingfortheTilbyMachine(Tilbyetal.,1976)

Figure1-11.BilletsofSugarCaneStalks

Higheralkalineconcentrationyieldedfiberswithlowertexvalues.Also,itwasobservedthatthemostsevereconditionsyieldedfiberswithlowertenacityandtoughnessvalues,andlowerbendingrigidityandhysteresis(Collieretal.,1992).

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Steamexplosionisatechniquedevelopedforseparationoffibersfromeachotherinlignocellulosiccomposites.Applicationofthistechniqueenablesasimplenonreactivesolventextractionofthefiberbondingcompoundswhileretainingthestructuralintegrityofthefiberbundles(DeLong,1990).Thepurposeofthesteamexplosionprocesswastoreplacetheconventionalchemicalandmechanicalpulpingforproducingfiberswithcertaincharacteristics.Themainchemicalcomponentsofthefiberarelignin,xylan,andcellulose(DeLong,1990).Ligninisaneasilyhydrolyzedpolymerwithameltingpointofabout125Candadegradationpointofabout195C.Ligninandxylanareheavilycrosslinkedwithinthefiberbundle.Above166Cthestrengthofthecross-linkisconsiderablyweakened.Atthistemperaturelevel,ligninbecomeshighlysolubleinalcoholandmildcausticsoda.Meanwhile,thecellulosehasatransitionorsofteningtemperatureof234Candadegradationtemperatureof260C.Thesetwotemperaturelimitsarewellabov

ethoseofligninandxylan,allowingcellulosetoretainitsfullstructuralstrength(DeLong,1990).Steamexplosioncaneitherbeperformedbatch-wiseorinacontinuousmanner.

Inlaterworka20-Lreactorfittedwithanoscillatingagitatorwasused(Elsunni&Collier,1996).Thebestfiberswereproducedbyasteamexplosionprocessmodifiedfromonethatwasusedforwoodfibers(Wolfgang&Sarkanen,1989).Steamwasinjectedinthereactoruntilapressureof100-150psiwasachieved.Afterafewseconds

thedischargevalvelocatedatthebottomofthereactorwasopened,creatingasuddenreleaseofpressure,whichblewthefibersout,andalsoblewthemapart.Dry,separatedfiberswereobtained.FiberswiththebestproprietiesforspinningintoyarnswereobtainedwithsteamexplosionandlowerNaOHconcentration(Elsunni&Collier,1996).

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Duetothesafetyconcernsinoperatingasteamexplosionreactor,atechnologicalextractionprocessthatwouldtakeplaceatatmosphericpressurewasdeveloped.Theextractionparametersinthiscasewerealkalineconcentration,tumblingspeed,andtime.InFigure1-12ispresentedtheschematicdrawingofacontinousatmosphericreactor.Theextractionprocesscanbecontinuous,improvingtheproductivity.Similarresultswiththesteamexplosionprocessregardingfiberquality(seeFigure1-13)canbeachievedbyincreasingthealkalineconcentrationofthesolutionandthetimeofreaction.Highlyconcentratedsolutionsofsodiumhydroxidethoughcreatedisposalproblems.

Figure1-12Schematicdrawingofapilotscalecontinuousatmosphericreactorforbagasse.Thephysicalcharacteristicsofthesugarcanefibersextractedwereexaminedusing

anenvironmentalscanningelectronmicroscope(Tao&Collier,1994).Thefiberswerecutto5-10mmlength,mountedonastub,andviewedwithoutdryingandcoating.

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Figure1-13.DelignifiedBagasse

Themicrographsobtainedshowedthelongitudinalandcross-sectionalmorphologyofthesugarcanefibersafterhightemperaturewaterpretreatment.Theamountofencrustingmaterialsbetweentheultimatefibers,aswellasthesizeofthefibers,wasobserved.TheSEMexaminationallowedunderstandingoftheeffectofhightemperaturewaterpretreatmentonthepresenceofencrustingmaterials.Tensileandbendingpropertieswerealsoevaluated.Itwasobservedthatthemostsevereconditionsyieldedthefinestfibersbutwithlowertenacityandtoughnessvaluesandlowerbendingrigidityandhysteresis(Collieretal.,1992).

Delignificationofjuteisoftencarriedoutbyretting(Figure1-14).Theactionofrettinginvolvesmicroorganismsandenzymes,andtakesseveraldaystocomplete-theactualtimebeingdependentonthetemperatureofthewater(Batra,1983).

Thesameprocess,usedfortheextractionofthefiberbundlesfromtherindofsugarcane,wasadaptedtokenaf(Collieretal.,1994).Differentkenafrindsourceswereused:greenwholestalk,drywholestalk,andpeeled,strippedandtwo-year-storedkenaf.

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Figure1-14.Traditionaljutefibersextraction

Theprocessconsistedoffourdistinctsteps:mechanicalseparation,chemicalextraction,steamexplosion,andproductformation.Usingthisprocessitispossibletoobtainfiberbundlesreducedincrosssectionandwithsufficientlengthfortextileapplications.Bychangingtheextractionparameters,thefinalpropertiesofthefiberbundlecanbecontrolled.

ThefirststepformechanicalseparationisaccomplishedwiththeTilbycaneseparator.NextaRandoCleanermachinecanbeusedinordertofurtherseparatethefiberbundlesandtodisposeoftheveryshortfibersandotherimpurities.Thesecondprocessstepcanbeabacterialorchemicalretting.Bacterialrettingisasimpleprocessbasedonthenaturalactionofanaerobicbacteriaoraerobicfungi.Chemicalrettingisalow-concentrationalkalinesolution,hightemperatureandpressureprocess.Thisprocessisdifferentfromtheusualpulpingactionssincetheintentistoextractcontr

olledlengthfiberbundlesfromrindstripswithminimalreductionofthefiberbundlelengthwhilereducingitscrosssection(Figure1-15).Asupplementalmechanicalaction,thatcanbeanoscillatoryagitationand/oratumblingmotion,isresponsibleforapreferentialreductionofthecross-sectionratherthanthelengthofthefiberbundles.

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(a)(b)Figure1-15.Kenafbastfibersfromplantharvested180daysafterplanting.(a)Withnotreatment.(b)Treatedwithsodiumacetate(Akinetal.,1999)Thechemicalrettingisfasterthanthebacterialretting,butithassomeharmfulconsequencesforthefinalfibercharacteristics:lossintenacity,color,andluster.Bothchemicalandbacterialrettingencounterssomeenvironmentalproblemsregardingairqualityandchemicaldisposal.Intheoptionalthirdstepthekenaffiberbundlesaresteamexplodedtofurtherreducethecrosssections.Inthisprocess,asinthesugarcanefibercase,livesteamisinjectedintothereactorandthenthepressureisquicklyreleased.Themoistureinthefibersevaporatessuddenly,blowingthemapartintodryseparatedfiberbundles.Resultsshowedsimilarreactionconditionstothoseappliedtothecanerindcouldalsobeemployedtoobtainkenaffiberbundlesthatcanbeusedfornonwovenmatsoryarnapplications(Romanoschi,1998).Also,asinthecaseofbagassecase,t

heextractioncantakeplaceinanatmosphericreactor.

1.4.4NonwovenCompositesNonwovenasanindustry-especiallycomparedwithitstraditionaltextileandpaperrelatives-hasproventobeaninterestingandall-encompassingbusinesswithhundredsofendusesandproductniches.Forthosenewtotheindustry,themanyfacetsofnonwovensarewhatmakeittheinterestingandgrowingbusinessthatitis.

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Themajorareasinnonwovenscangenerallybesplitintodisposable,orshortlife,anddurable,orlong-life,enduses.TheU.S.marketisdivided,60%fordisposablemarketsand40%fordurables,whileinEurope,salesleanmoretowarddurables.AccordingtoconsultantJohnR.StarrInc.,Naples,FL,disposableapplicationsaccountfor53%ofworldwiderollgoodssaleswhiledurablesrepresent47%.ThedevelopedmarketsoftheU.S.,Canada,WesternEuropeandJapanaccountedfor73%ofnonwovenssaleslastyear.Salesinthesemarketsareexpectedtoincreaseby7.4%eachyearforthenextfiveyears,accordingtoMr.Starr.Meanwhile,salesinthedevelopingareasbeyondtheseregionsareexpectedtogrow9.6%peryearduringthenextfiveyears.Paperprocessesandpolymerextrusiontechnologyhavebecomeimportantcontributorstononwovensmanufacturing.Theelectronicsindustrysdevelopmentofmicroprocessorsandthesubsequentdevelopmentofaffordable,high-speedcomputingarealsocontributingtothegrowingsophisticationofnonwovenprocessesandproducts(Mansfield,2001).

IntheU.S.,theoverwhelmingvolumeofnonwovensisutilizedintheabsorbentproductmarketsofdisposablebabydiapers,femininehygieneitems(sanitarynapkinsandtampons),adultincontinenceproductsandmedicalfabrics.Themostinfluentialmarketfornonwovensisbabydiapers,amorethan$4billionmarketwithabout16billiondiapersproducedannually(Bitz,2001).Recentproductinnovations,suchasupstandinglegcuffsandcloth-likebacksheets,havedramaticallyincreasedtheuseofnonwovenfabricperdiaper,whilelineextensionsintotrainingpantsanddispos

ableswimwearproductsarebroadeningthecategoryforbothbrandedandprivatelabelsuppliers.Relatedtothebabydiapermarketarethefemininehygieneandadult

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incontinenceindustries,wherecomplementaryproductsandmachinerymeansimilarcompaniesinvolvementinthebusiness.Likewise,themarketforbabywipesisalsorelatedtothebabydiapermarketinthatwipesaresometimeslineextensionsofbabydiaperproducts.Wipeproductsarealsofindingapplicationsinthehouseholdcleaning,personalcareandpharmaceutical/cleanroomcategories.Anotherdisposablenonwovensendusemarket,onethathaswithstoodtheupsanddownsofeconomichardtimesandconcernsoverdisposingofdisposables,ismedicalnonwovens,wherethelife-threateningimpactofAIDSandothercontagiousdiseaseshaveputworkerprotectionaboveeconomicandenvironmentalconcerns.IntheU.S.,themedicalnonwovenrollgoodssegmenthasapplicationinarangeofproductsforuseintheoperatingroomonmedicalpersonnel,patients,andinmyriadotherusesthroughoutthehospital(Bitz,2001).

Protectiveapparelisanothergrowingdisposablesmarketwhich,inadditiontomedicalapplications,alsoincludesmarketsinindustrialandcleanroomapparel,hazardouswasteandasbestosclean-upapplications,andagriculturalprotectiveapparel.

Onthedurablessideofthenonwovensindustry,majormarketsaregeotextiles,whichobviouslyarethehighestvolumesegmentsfornonwovens.TheNorthAmericangeotextilemarketisfamousforitsvastopportunities.Yearsago,therewereextensivebattlesbetweenwovenandnonwovenfabricmanufacturers.Wovenmanufacturerstouted

thehigheststrengthperweightandhighmodulus.Nonwovenmanufacturersproclaimedtheadvantageofhigherpermeability,betterfriction,betterconformability,andconstructionsurvivability.Thelargestsegmentofthegeotextilemarketisseparation/stabilizationgeotextiles.Theuseofseparation/stabilizationgeotextileskeeps

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thesubgradesoilfrompumpingupintoaggregatethatsupportsthepavementorunpavedaggregatesurface.Recentdevelopmentsintheseparation/stabilizationmarkethaveincludedstudiesongeotextileinstallationandconstructionsurvivabilityandlongtermsurvivability(Marienfield,1995).Thenextlargestmarketisthepavingfabric.Pavingfabricisthegenerictermfornonwovengeotextilescombinedwithasphaltcementinthefield.Placedbetweenlayersofasphaltconcrete,thisinterlayersystemwaterproofsandretardsreflectiveandfatiguecrackinginpavements.Thethirdlargestandfastestgrowingsegmentofthegeotextilemarketisthelinerfabrics.Heregeotextilesareusedinlayeredgeosyntheticandnaturallineranddrainagesystem.Thepurposeofthegeotextilescanbegeomembraneprotection,drainageandfiltration,orsimpleseparationofmaterials.Veryheavynonwovensupto16oz/squareyardarenecessarywhereprotectionistheprimaryfunction(Marienfield,1995).Thenextsegmentincludesapplicationsintrenchd

rainage,drainboards,drainpipewraps,andhighwayedgedrains.Thedrainagemarketsegmentwillcontinuetogrow.Thereisanincreasingawarenessbythepavementdesignersandmaintainersthatwaterinpavementscausesthemostdamageandshortensthepavementlife.Thelastsignificantgeotextilemarketsegmentwhichusespredominantlynonwovensistheerosioncontrolandslopeprotectionapplication.Thegeotextilesactasfilterstoallowwatertopasswhileretainingsoil.Thisretardserosiononslopes,shorelines,and

streambanksbeneathrip-rapstoneoranotherarmorsystem.Themarketwillcontinuetogrowinthisareaduetoincreasinglystrictlawsonpollutionandenvironmentalprotection(Marienfield,1995).

Besidesgeotextiles,nonwovenscanbefoundinautomotiveapplications,whichencompassanythingfromtrunklinersandpackageshelvestodoorpanelsandheadliner

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materialsandfiltration.Compositesreinforcedwithnaturalfibernonwovenshavesuccessfullyproventheirqualitiesinthisfieldbecauseoftheirexcellentproperties,e.g.,highstrengthandstiffness,lowweight,etc.Oneoftheirmostimportantadvantages,however,isthepossibilityofdesigningthematerialitselfbyarranginglongfibersinthedirectionoftheappliedforcesinordertocreatelightweightstructureswithanisotropicpropertiesoptimallytailoredtoeachspecificrequirement(Mueller,2002).

Alsoincludedonthedurablesideareapparelinterlinings,althoughheremorewovensthannonwovensareused.Interliningsegmentsincludewomensdresses,blouses,sportswear,shoes,hatsandhandbagsandmenstailoredclothing,tuxedos,waistbandsandlapels,collarsandpocketflaps.

Despitecontinuingconsolidation,intensecompetitionandseveraleconomictroublespotsaroundtheglobe,nonwovenscompaniescontinuetoexpandandgrowthroughcapitalinvestments,capacityexpansions,jointventuresandacquisitions.Geographicandendusemarketexpansionalsocontinues,withcompaniesclaiming

newglobalmarketsalmostdaily.

1.4.5MechanicalPropertiesStrengthisamechanicalpropertythatweareabletorelateto,butwemightnotknowexactlywhatwemeanbytheword"strong.Thereismorethanonekindofstrengthdependingonthetypeofdeformationamaterialundergo.Thereistensilestrength.Tensilestrengthisimportantforamaterialthatisgoingtobestretchedorundertension.Fibersneedgoodtensilestrength.Thenthereiscompressionalstrength.Concrete

isanexampleofamaterialwithgoodcompressionalstrength.Anythingthathastosupportweightfromunderneathhastohavegoodcompressionalstrength.Thereisalso

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flexuralstrength,torsionalstrength,andimpactstrength.Asamplehastorsionalstrengthifitisstrongwhenonetriestotwistit.Asamplehasimpactstrengthifitisstrongwhenonehitshitsharplyandsuddenly,aswithahammer.

Thereisaprecisedefinitionforstrength.Tomeasurethetensilestrengthofamaterial,asamplemustbestretched.Thestretchingisperformedbyatensiletestingmachine.Thismachineclampseachendofthesample,then,stretchesthesamplemeasuringtheamountofforce(F)neededtoresisttheextension.Dividingthisforcebythecross-sectionalarea(A)yieldsthesamplestress.Ifthesampleisstretchedtothebreakingpoint,thebreakingstressisobtained.

.Likewise,onecanimaginesimilartestsforcompressionalorflexuralstrength.Inallcases,thebreakingstrengthisthestressneededtobreakthesample.Sincetensilestressistheforceplacedonthesampledividedbythecross-sectionalareaof

thesample,tensilestress,andtensilestrengthaswell,arebothmeasuredinunitsofforcedividedbyunitsofarea,usuallyN/cm2.StressandstrengthcanalsobemeasuredinEnglishunits,commonlyusedarepoundspersquareinch.

Allstrengthtellsusishowmuchstressisneededtobreaksomething.Itdoesnottellusanythingaboutwhathappenstooursampleduringdeformation.Thatiswhyitisusefultostudytheelongationbehaviorofthematerial.Elongationisthedeformationthat

occurswhenatensileforceisapplied.Understress,thesampledeformsbystretching,becominglonger.Usuallyelongationismeasuredinpercentage,whichisthelengthof

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thestretchedsample(L),dividedbytheoriginallengthofthesample(L0),multipliedby

100.Thereareanumberofthingswemeasurerelatedtoelongation.Whichismostimportantdependsonthetypeofmaterialoneisstudying.Therearetwoimportantmeasuresofelongation:ultimateorbreakingelongationandelasticelongation.Ultimateelongationisimportantforanykindofmaterial.Itistheamountonecanstretchthesamplebeforeitbreaks.Elasticelongationisthepercentelongationonecanreachwithoutpermanentlydeformingthesample;thatis,howmuchcanonestretchit,andstillhavethesamplereturnstoitsoriginallengthoncethestressisreleased.

Ifthegoalistoknowhowwellamaterialresistsdeformation,wemeasureitsmodulus.Tomeasuretensilemodulus,thesamethingisdoneasitwastomeasurestrengthandultimateelongation.Thestressismeasured,justasitwasdonefortensilestrength.Theamountofstressisincreasedataconstantrate,andtheelongati

onthesampleundergoesateachstresslevelismeasured.Theprocesscontinuesuntilthesamplebreaks.Aplotofstressversuselongation,isshowninFigure1-16:

Figure1-16.Stress-strainplot

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Thisplotiscalledastress-straincurve.Strainisanykindofdeformation,includingelongation.Theheightofthecurvewhenthesamplebreaksisthetensilestrength,andthetensilemodulusistheslopeofthisplot.Iftheslopeissteep,thesamplehasahightensilemodulus,whichmeansitresistsdeformation.Iftheslopeisgentle,thenthesamplehasalowtensilemodulus,whichmeansitiseasilydeformed.

Therearetimeswhenthestress-straincurveisnotlinear,suchastheplotinFigure1-17.Forsomematerials,especiallyflexibleplastics,wegetoddcurvesthatlooklikethis:

Figure1-17.Tensilestrengthplot

Theslopeisnotconstantasstressincreases.Theslope,thatisthemodulus,ischangingwithstress.Inacaselikethistheinitiallinearportionofthecurveisusedtodeterminethemodulus.Ingeneral,fibershavethehighesttensilemoduli,elastomers

havethelowest,andplasticshavetensilemodulisomewhereinbetweenfibersandelastomers.Modulusismeasuredinunitsofstressdividedbyunitsofelongation.Sinceelongationisdimensionless,howeverithasnounits.Somodulusisexpressedinthesameunitsasstrength,suchasN/cm2.

Tensilestrengthassessmentisdoneaccordingtoanestablishedtestmethodorstandard.Thetermstandardcanrefertotheactualmethodofassessment,tominimum

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levelsafety,ortoperformancerequirements.Aproblemoftenoccurringinstandardtextiletestmethodsishowtosimulatereal-lifeenduse.Inthelaboratory,usuallyitcanbetestedonlyonepropertyatatime.Howeverinactualuseatextileproductissubjectedtomanyforcesatthesametime.Itishardtosimulatethiscombinationofeffectsinonestandardlaboratorytest.

Thereareseveralorganizationsinvolvedintextiletesting.

1.AmericanSocietyforTestingandMaterials(ASTM).Thepurposeofthisorganizationistodevelopstandardsoncharacteristicsandperformanceofmaterials,products,systems,andservices.ThestandardsdevelopedbyASTMincludetestmethods,specifications,anddefinitions,andusuallydealwithphysicalpropertiesofmaterials.2.AmericanAssociationofTextileChemistsandColorists(AATCC).Thisorganizationwasformedtopromotetheincreaseofknowledgeoftextiledyesandchemicals,and

thereforeitisconcernedspecificallywithtextileproducts.Inadditiontodevelopmentoftestmethods,AATCCsponsorsscientificmeetingsandpromotestextileeducation.Alloftheactivitiesareconcernedwiththechemicalpropertiesoftextiles,incontrasttoASTMsphysicalemphasis.3.AmericanNationalStandardsInstitute(ANSI).ThepurposeofANSIistocoordinatevoluntarystandardsdevelopmentanduseintheU.S.ItalsoservesasliaisonbetweenstandardsorganizationsintheU.S.andothercountries.ANSIisconcernedwithphysical

andchemicalpropertiesformanydifferentproducts.1.4.6ImageAnalysisSeeingisbelieving.Sightisfundamentaltoourunderstandingoftheworld.Thisisastrueinscienceasitisineverydaylife.Thecollectionofmuchstatisticaldatais

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dependentuponhumanvision.Forexample,theexaminationofsamplesunderamicroscope,observinganimalbehavior,andtheidentificationandcountingofplantspeciesinafieldareallformsofimageanalysis.Humansdoagreatjobinprojectingimagesinourretinas,usingathirdofourbrainsforvision.However,computersarebeingusedmoreandmoretoautomateandextendthepotentialofimageanalysis.Computersarebetteratextractingquantitativeinformationfromimagesthanhumanobservers-theycanbemoreaccurateandmoreconsistentfromdaytoday.Furthermore,computersmayspareusfromtediousimageinterpretation.Progresswasexpectedtoberapidwhenresearchcommencedinthe1960soncomputer-basedimageanalysis.Thetask,however,hasprovedtobefarmoredifficult.Inpart,thisisbecausescientistswerenotconsciousoftheprocesseshumansgothroughinseeing.Biologicalobjectspresentanevengreaterchallengetocomputerinterpretationthanman-madeones,becausetheytend

tobemoreirregularandvariableinshape.

Manufacturingproductsthatadheretostrictindustryandcorporatequalitystandardsisnoeasytask.Withcompetitiongettingmorefierce,smarter,andincreasinglyglobaleveryday,organizationsmustdealwiththinningmarginsandpotentiallysevererepercussionsifinefficienciesandpoorproductivityarenotaddressed.

Inthequalityassurancelab,thesituationisnodifferent.Manuallaboratoryproceduresarebeingslowlyreplacedwithinnovativeautomatedsolutionsthatprovideconsistentlyaccurate,objectiveandreproducibleresults.Onesuchtechnologyb

eingimplementedintoleadinglabsaroundtheworldisimageanalysis.

AtypicalPC-basedimageanalysissystemconsistsofacameramountedonamicroscopeandattachedtoaframegrabber.Withtheuseofsophisticatedimageanalysis

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software,laboratorytechniciansareabletoeasilymanipulateimagesintotheiraccuratebinarycomponentsofinterest,andthenanalyzetheirbinarystructuresfromananalytical,statisticalpointofview(Glasbyetal.,1998).

Withtheadventofthecomputerrevolution,today'simageanalysissystemshavecomealongwaysincetheirearlybeginnings.Thesesystemsusedintegratedlightpentechnologytodigitizeandquantifysingleobjectsofinterestwhenpointedatascreen.Significantadvancementsinhardwarecoupledwithnewdevelopmentsinmathematicalalgorithmsappliedtoimageprocessinghavecontributedtothegrowingacceptanceofimageanalysistechnologyasaneffectivetoolforimagequantification.Imageanalysisisnotatoolusedexclusivelyinqualitycontrollaboratories.Theuseofimageanalysisindifferentfieldsofsciencecreatednewdomainsofresearchandapplications:biomedicalimaging,industrialvision,remotesensing,scientificvisualization,andvirtualreality.

Imageanalysishasbeenversatileinmeasuringvariouspropertiesinthetextileworld.Qualitycontrolspecificationsforyarnandfabricdensity,yarnconfigurationandtheknitgeometrywerecheckedbyimageanalysis(Zhang,1996).Thecompositesindustryusedimageanalysistostudythefiberbreakageinsomeinjectionmoldedplastics(ShortallandPennington,1982).Innonwovens,poresizesaswellasstructuralparametersofindividualfibersandbundleshavebeensuccessfullymeasuredwiththistechnology(Xu,1996).

Thereisaneedinthetextileindustryforobjectivedetectionofnonuniformcolorationindyedblendedtextiles.Animageanalysissystemcanbeusedtofollowtheeffectsofvaryingcertainconditionsforthepretreatingoftextiles.Dyedfabricswereimagedandtheimagedatadigitized.Dataanalysisgavevaluesthatwereusedtoobtain

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dynamicmechanicalanalysis(DMA).TAiswidelyemployedinbothscientificandindustrialdomains.Theabilityofthesetechniquestocharacterize,quantitativelyandqualitatively,alargevarietyofmaterialsoveraconsiderabletemperaturerangehasbeenpivotalintheiracceptanceasanalyticaltechniques.UndernormalconditionsonlylimitedtrainingofpersonnelisrequiredtooperateaTAinstrument.This,coupledwiththefactthatresultscanbeobtainedrelativelyquicklyandareaccurateandreproducible,meansthatTAisemployedinanever-increasingrangeofapplications(Hassel,1991).However,theoperationalsimplicityofTAinstrumentsbeliesthesubtletyoftechniqueswhich,ifimproperlypracticed,cangiverisetomisleadingorerroneousresults.Theabundanceofresultsofdubiousintegrityinboththeacademicliteratureandindustrialperformancereportsunderlinestheextentandseriousnessofthisproblem(Hatakeyama,1999).

TheadvantagesofTAoverotheranalyticalmethodscanbesummarizedas

follows(Hatakeyama,1999):

(i)Thesamplecanbestudiedoverawidetemperaturerangeusingvarioustemperatureprograms;(ii)Almostanyphysicalformofsample(solid,liquidorgel)canbeaccommodatedusingavarietyofsamplevesselsorattachments;(iii)Asmallamountofsample(0.1g-10mg)isrequired;(iv)Theatmosphereinthevicinityofthesamplecanbestandardized;(v)

Thetimerequiredtocompleteanexperimentrangesfromseveralminutestoseveralhours;(vi)TAinstrumentsarereasonablypriced.43


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Inpolymerscience,preliminaryinvestigationofthesampletransitiontemperaturesanddecompositioncharacteristicsisroutinelyperformedusingTAbeforespectroscopicanalysisisbegun.TAdataareindirectandmustbecollatedwithresultsfromspectroscopicmeasurements,beforethemolecularprocessesresponsiblefortheobservedbehaviorcanbeelucidated.Irrespectiveoftherateoftemperaturechange,asamplestudiedusingaTAinstrumentismeasuredundernoequilibriumconditions,andtheobservedtransitiontemperatureisnottheequilibriumtransitiontemperature.Therecordeddataareinfluencedbyexperimentalparameters,suchasthesampledimensionsandmass,theheating/coolingrate,thenatureandcompositionoftheatmosphereintheregionofthesampleandthethermalandmechanicalhistoryofthesample(Pierce,1996).

ThegeneralconformationofTAapparatus(consistingofaphysicalpropertysensor,acontrolled-atmospherefurnace,atemperatureprogrammerandarecording

device)isillustratedinFigure1-18.Table1-4liststhemostcommonformsofTA.

Figure1-18.BlockdiagramofaTAinstrument.

ModernTAapparatusisgenerallyinterfacedtoacomputer(workstation)whichoverseesoperationoftheinstrumentcontrollingthetemperaturerange,heatingandcoolingrate,flowofpurgegasanddataaccumulationandstorage.

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Table1-4ConventionalFormsofTA

PropertyTAMethodAbbreviationMassThermogravimetryTGDifferenceofTemperatureDifferentialthermalanalysisDTADifferenceofTemperatureAlternatingcurrentcalorimetryACCEnthalpyDifferentialscanningcalorimetryDSCLength,VolumeDilatometryDeformationThermomechanicalanalysisTMADynamicmechanicalanalysisDMAElectricCurrentThermostimulatedcurrentTSCLuminescenceThermoluminescenceTL

Varioustypesofdataanalysiscanbeperformedbythecomputer.AtrendinmodernTAistouseasingleworkstationtooperateseveralinstrumentssimultaneously.

Thermo-gravimetry(TG)isthebranchofthermalanalysiswhichexaminesthemasschangeofasampleasafunctionoftemperature(scanningmode)orasafunctionoftime(isothermalmode).Notallthermaleventsbringaboutachangeinthemassofthesample.Melting,crystallization,andglasstransitiondonotexhibitmasschange

whereasdesorption,absorption,sublimation,vaporization,oxidation,reductionanddecompositiondo.TGisusedtocharacterizethedecompositionandthermalstabilityofmaterialsunderavarietyofconditionsandtoexaminethekineticsofthephysicochemicalprocessesoccurringinthesample.Themasschangecharacteristicsofamaterialarestronglydependentontheexperimentalconditionsemployed.Factorssuch

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assamplemass,volumeandphysicalform,theshapeandnatureofthesampleholder,thenatureandpressureoftheatmosphereinthesamplechamberandthescanningrateallhaveimportantinfluencesonthecharacteristicsoftherecordedTGcurve.

DifferentialScanningCalorimetry(DSC)isabranchofTAwherethedifferentialenergysuppliedbetweenasampleandreferencetomaintainaminimumtemperaturedifferencebetweenthesampleandreferenceinresponsetoatemperatureprogramisusedtoinvestigatethenatureofthesample.TheDSCcurveisagraphicrepresentationofthedatacollected,wherethedifferentialenergysuppliedisplottedasafunctionoftemperature(scanningmode)ortime(isothermalmode).Both,sampleandreferencearesubjectedtocontinuoustemperatureincrease(Negulescu,2001).

Dynamicmechanicalanalysis(DMA)isabranchofthermalanalysiswherethebehaviorofasamplesubjectedtoanoscillatingstressinresponsetoatemperature

programisusedtoinvestigatethenatureofthesample.MostDMAmeasurementsaremadeusingasinglefrequencyandconstantdeformationamplitudewhilevaryingtemperature(Foreman,1997).Thevalueofadynamictestismostsignificant,inthata30to60minuteexperimentyieldsatremendousamountofinformationonthesampleinquestion.Themodulusvaluebelowtheglasstransitionwilltellaboutlevelsofmolecularorientationandcrystallinity.Transitionsoccurringcanberelatedtothepolymersstructureandmaybeparticularlyusefulwhereamultiplecomponentblendisunder

investigation.Dynamicmechanicalmethodsarethemostsensitivewayofmeasuringtheglasstransitionitself,whichisoneofthekeypropertiesofapolymerfromboththestructuralandprocessingviewpoint.Abovetheglasstransitiontherubberybehavioryieldsimportantfactorssuchastheeffectivecross-linkdensityandcluesto

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processability.Finallydatacanbeobtainedinshearmodeafterthemeltingpoint.Thistechniqueiscomplementarytoinfra-redorNMRresultsonchemicalcomposition.Thesetestsyieldcomprehensivedetailonthemolecularmoietiespresent,whilstthemechanicaldatarevealhowtheyareconnectedtogether(www.triton-technology.co.uk).

1.4.8BiodegradationConcernsforacleanenvironmenthaveimpactednotonlytextilemanufacturersbutalsoconsumersinthechoiceofrawmaterialstofinalproducts.Publicawarenessincreasinglydemandsbiodegradableorenvironmentallyfriendlytextiles,especiallydisposablenonwovenproducts.Thepossibilityofcompostingdisposablenonwovenproducts,suchasdiapers,incontinenceproducts,surgicalgowns,andlandfillshasattractedspecialattentioninanefforttosolvethesolidwastecrisis.Othernichesofthenonwoventextileindustry,suchasgeotextiles,dealwiththesameproblem.Unfortunately,thereareonlyafewbiodegradablefibersavailablethatcanserveasrawmaterialsinnonwovenproduction,andinmostcasesnewlydevelopedbiodegradabl

efibersareexpensive(Suhetal.,1996).

Biodegradationbydefinitionisabiologicalprocessandrequiresmicroorganismssuchasbacteria,fungi,algae,andacetinomyecetes(Suhetal.,1996).Biodegradationoftextilematerialsisusuallyassociatedwiththepresenceofnaturalfibers.Duetotherelativelymodestphysicalandmechanicalpropertiesofthenaturalfibers,theiruseinnonwovensislimited.Evenso,presenceofsyntheticmaterialsisrequiredasabonding

agent,exceptforneedlepunchingbonding.Cotton,forcenturiesthemostimportantoffibers,isnowtakingsecondplacetosynthetics.Viscoserayonstaplefiberswere,in

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1966,thecheapestmanufacturedfiber.Nowtheyarearoundtwicethepriceofthemainsyntheticwithouttheabilitytobeeasilyspun-laidorthermalbonded(Woodings,2001).

Thebiodegradationmechanismisgenerallyexplainedbytheenzymaticcatalyzedprocess,whereenzymesareproducedbyvariousmicroorganismsinthepresenceofdegradablesubstrates.Requirementsformicrobialgrowthvarywithtemperature,pH,andoxygenavailability(Suhetal.,1996).Usuallythepresenceofmoistureandnutrientsisnecessary.Thebiodegradationprocessinvolvesanumberofdifferentmechanisms,includinghydrolysisandoxidation,whichresultinpolymerchainscission(Cooke,1990).Intermediateproductsfromthecontinuationofthechainbreakagesarewater-solublefragments.Astotalmineralizationproceeds,furtherdegradationproductsarecarbondioxide(CO2),water(H2O),methane(CH4),andbiomass(Cooke,1990).Thebiodegradationofcellulose-basedfibershasbeenintensivelystudied.Cellulose

isbelievedtobereadilybiodegradedbymanymicroorganismsduetotheactivityofcelluloseenzymescatalyzingthehydrolysisandoxidation(FinchandRoberts,1985).Thecelluloseenzymesareclassifiedintothreegroupsaccordingtotheircatalyzedreactions:hydrolases,oxidases,andphosphorylases(FinchandRoberts,1985).Enzymaticactivitiesoncellulosicsareinfluencedbymanyfactorsdependingontheirmorphologicalandphysicalstructures.Theseenzymesactbyhydrolyzingoroxidizingthepolymer,andcanworkattheendofthechains(exo-enzymes)orrandomlyalo

ngtheirlength(endo-enzymes).Thehigherthedegreeofpolymerizationandthegreaterthedegreeofcrystallinityandorientation,thelesssusceptibilitytomicrobialattackduetolimitedaccessibility.Themostbiodegradablefibersthereforetendtobehydrophilic,andmadeupofshort,flexiblechainswithlowlevelsofcrystallization.Theywilloftenhave

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chainbackboneswithoxygenornitrogenlinks.Thisdescriptionclearlyfitsmostnaturalfibersandmanynaturalpolymers.

Biodegradationwithinaspecifiedtimeframeinasolidcompostmediumiscalledcomposting.Compostingisamanagedprocessthatcontrolsthebiologicaldecompositionandtransformationofbiodegradablematerialintoahumus-likesubstancecalledcompost.Amaterialiscompostableifitiscapableofundergoingbiologicaldecompositioninacompostsiteasapartofanavailableprogramsuchthatthematerialisnotvisuallydistinguishableandbreaksdownintocarbondioxide,water,inorganiccompounds,andbiomassatarateconsistentwiththeknowncompostablematerials(ASTMD600296).

Populationandsocialconcerns,theGreenmovementandgovernmentmandateshaveprovidedanincentivetodevelopandusebiodegradablepolymers(Hailleetal.,2001).Polymerscientistshavefacilitatedaparadigmshiftintheuseoftextiles,fromthe

historicaldesiretoimprovedurability,weatherabilityandotherlonglifecharacteristics,toatriggeredorreproduciblebreakdownunderprescribedconditions.

Biodegradationinfibers,includingsyntheticones,occurswhentheirconstituentpolymersaredepolymerized.Biodegradation-resistantpolymershavetheoppositecharacteristicsandunsurprisinglyareusedtomakethestrongermoredurablefibers.Oxygen-freepolymerssuchaspolypropyleneandpolyethyleneresistbiodegradationtotally.Polyester,despiteitsoxygencontentisdegradation-resistantprobablybecauseit

hasrigid,rod-likechains.Thesameistrueforpolyamidesdespitetheirnitrogencontent.Unlikearomatics,aliphaticpolyestersaregenerallybiodegradable.Manufacturedbiodegradablealiphaticpolyestersare,however,stillbasedmainlyonindustrial

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polymerizationofmonomerssuchasglycolicacid(PGA),lacticacid(PLA),butyricacid(PHB),valericacid(PHV)andcaprolactone(PCL)(Woodings,2001).Despitethesenewachievementsinbiodegradablepolymerdevelopment,theuseofthesematerialsislimitedbytheproductioncosts.Itisforecastthatbytheendofthisdecade,advancementsintechnologywillallowmanufactureofbiodegradablepolymersatapricelevelcomparablewiththeregularpolymers.

1.5ExperimentalMethods1.5.1ProcessingProcedureBagassefiberusedinthisstudywasprovidedbyalocalsugarmill,fromthe2001crop.Therawbagassewasalreadycrushedatdifferentlengthsasanoutputfromthesugarextractionprocess.Toextractthebagassefibers,aseriesofmechanicalandchemicalprocedureswasused.WastebagassewaslaidoutonthegroundofanopenbutroofedareaintheLSUAudubonSugarFactoryforaperiodoftwoweeks.Toassur

eauniformdryingprocessthelayerofbagassewasturnedoveronceaday.Themoisturecontentwasmeasuredforrandomlyselectedsamplesoffibers.Theresultsindicatedaconsistentlevelofmoisturelessthan15%.Smallfibersandimpuritieswereremovedthroughasiftingprocessusinga2ftby2ftwoodenframesievehavingascreenwith1/16ineyedimension.

Forthealkalineextraction,anatmosphericprocesswasemployed.AnLSU-designed,previouslybuiltatmosphericreactorwasused(Figure1-19).Fromprev

iousstudies,itwasdeterminedthata2.0NNaOHsoulutionisrequiredtoremoveasignificantamountoflignin.Themeasuredvolumeofthereactorwas200liters.Certified

A.C.S.NaOHpelletswereused.Thesolutionwasheateduptotheboilingpoint50


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(approximately100C).Siftedbagassewasfedintoreactorgradually.Thefiber/liquidratiousedwas1:10.Inapproximately90minutesthewholeamountofbagasse,intendedfordelignification,wascollectedattheotherendofthereactor.Theextractedfiberswerer

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