包装盒专业英语3.ppt
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包装盒专业英语3.ppt
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UNITTWOPACKAGINGMATERIALSANDCONTAINER第二单元第二单元包装材料和容器包装材料和容器Lesson3PaperandPaperboard第第3课课纸与纸板纸与纸板IntroductionDefinitionofpaper:
Paperisdefinedasamattedorfeltedsheetusuallycomposedofplantfiber.Paperhasbeencommerciallymadefromsuchfibersourcesasrags(linen),bagasse(sugarcane),cotton,andstraw.Modernpaperismadealmostexclusivelyfromcellulosefiberderivedfromwood.Althoughtheword“paper”isderivedfromtheEgyptianterm,“papyrus”wasnotatruepaperinthemodernsense.-InventionofpaperTheinventionofpaperbyblendingcellulosefibersdidntoccuruntilthebeginningofthesecondcenturyA.D.IntroductionTsaiLun,amemberofthecourtofthelaterHanDynasty,isgenerallycreditedwithdevelopingthefirstrealpapermakingprocessin105A.D.The“Fourdriniermachine”wasthefirstonthemarketandproducedahomogenous(single-ply)sheetofboxboardinvariousthicknesses.Itwassoonjoinedbythe“Cylindermachine”whichformedamulti-layered(multi-ply)typeofpaperboard.ThesemachineswerefirstinstalledintheUnitedStatesaround1830.IntroductionPaperandpaperboardPaperboard,boxboard,cardboard,andcartonboardarealltermsusedtodescribeheavierpaperstock.TheInternationalOrganizationforStandardization(ISO)statesthatmaterialweighingmorethan250gramspersquaremetre(511bper1,000sq.ft.)shallbeknownaspaperboard.U.S.practicecallsmaterialthatismorethan300(0.012in.)thickpaperboard.RepresentativePapermakingMachinesFourdrinierMachinesFourdriniermachines(Figure3.1)pumpfurnishfromaheadboxdirectlyontoamovingwirescreenthroughwhichthewateriscontinuouslydrained.Fourdriniermachinesmayhaveasecondheadbox(Figure3.2)situateddownstreamofthefirstheadboxtoaddfurtherquantitiesoffurnishontothepartiallydewateredinitiallay-down.RepresentativePapermakingMachinesFigure3.1Furnishpoursoutoftheheadboxofafourdriniermachineandontoanendlesswireorscreenwhereexcesswatercanbedrained.ThefibersremaintrappedonthescreenRepresentativePapermakingMachinesFigure3.2PaperisdewateredatthewetendofafourdriniermachineRepresentativePapermakingMachinesCylinderMachinesAcylindermachine(Figure3.3)rotatesascreendruminavatoffurnish.(Thepaperissometimescalledvatpaper.)Asthewaterpoursthroughthescreen,fiberaccumulatesontheoutsideofthescreen.Thisthinlayerofmattedfiberistransferredontoamovingfeltbeltthatpassessequentiallyoverfurtherrotatingcylinders,eachofwhichdepositsanotherfiberlayer.RepresentativePapermakingMachinesFigure3.3Asinglecylinderstationonacylinder-typemachineRepresentativePapermakingMachinesCylindermachinesdewaterfurnishatthecylinderandpasteathinlayeroffiberagainstthefelt.(Figure3.4.)Figure3.4AcylindermachinewithsixcylindersatwhichapaperlayercanbeformedRepresentativePapermakingMachinesThefibersofsubsequentlayersdonotintermingle,andthereforethebondbetweenthelayersisweak.Thedryendissimilartothatofthefourdriniermachine.Cylindermachinesdonothavethefourdriniermachineslimitationonthenumberofstations,andsix-orseven-stationmachinesarecommon.Higher-caliperboardsforfoldingandsetupcartonsareusuallycylinderboards.Generally,papersaremadeonfourdrinierortwin-wireformers,whereasheavierpaperboardproductsaremadeoncylinder-typemachines.Extremelyheavyboardsaremadebylaminatingseveralthinnersheets.Atypicalcylinderboardconstruction(Figure3.5):
RepresentativePapermakingMachinesFigure3.5Cylinderboardsaremultiplyboards.AnadvantageisthatthepliescanallbedifferentRepresentativePapermakingMachinesTwin-WireMachinesVertiformersandtwin-wireformers(Figure3.6)injectthefurnishbetweentwomovingwirescreens.Theadvantageisthatdewateringtakesplaceonbothsidesofthepaperandisthereforefast.Thesemachinescanproducesingleandmulti-plysheetswithidenticalformationatbothfaces.MachineDirectionandCrossDirectionDepositingafiber-and-waterslurryontoamovingwirebelttendstoalignfibersinthedirectionoftravel,knownasthemachinedirection(MD).Thedirectionacrosstheapermakingmachineandacrossthefiberalignmentisthecrossdirection(CD)(Figure3.7).Becauseofthisfiberalignment,paperisananisotropicmaterial;measuredpropertiesdifferdependingonthedirectioninwhichthepropertyismeasured.RepresentativePapermakingMachinesFigure3.6Watercanbesimultaneouslyremovedfrombothsidesofthepaperonatwin-wirepaperformerRepresentativePapermakingMachinesFigure3.7FibersinamanufacturedpapersheettendtoalignthemselvesinthemachinedirectionRepresentativePapermakingMachinesFigure3.8showstherelationshipoftear,stiffness,andfoldendurancetomachinedirection.Paperspecificationsheetsnormallyshowphysicalvaluesmeasuredinbothdirections.Packagedesignersneedtobeawareofpapersdirectionality.Cylindermachinestendtoalignfibersmorethanfourdriniermachines.TensilestrengthratiosinMDandCDforatypicalfourdrinierboardareabout2:
1,whereasforacylinderboardtheratiomightbe4:
1orhigher,meaningthattheMDtensilestrengthisfourtimesgreaterthantheCDtensilestrength.Thegreaterthedegreeoffiberalignment,thegreaterthedifferenceinagivenpropertywhenmeasuredinMDandCD.Theratioofapropertyinthetwodirectionsisoftenusedasagaugeoffiberalignment.RepresentativePapermakingMachinesFigure3.8TherelationshipbetweenMDandtear,stiffness,andfoldendurancepropertiesRepresentativePapermakingMachinesCylindermachinestendtoalignfibersmorethanfourdriniermachines.TensilestrengthratiosinMDandCDforatypicalfourdrinierboardareabout2:
1,whereasforacylinderboardtheratiomightbe4:
1orhigher,meaningthattheMDtensilestrengthisfourtimesgreaterthantheCDtensilestrength.Thegreaterthedegreeoffiberalignment,thegreaterthedifferenceinagivenpropertywhenmeasuredinMDandCD.TheratioofapropertyinthetwodirectionsisoftenusedasagaugeoffiberalignmentRepresentativePapermakingMachinesSurfaceorDry-End,TreatmentsandCoatingsAfterthepaperisformedanddried,itisusuallypassedbetweenmultiplesetsofheavyrolls(Figure3.9.).Thiscalenderingoperationhasmanyvariations,buttheprimeobjectiveistoironandsmoothoutthesurfaceofthepaperstocktomakeitmoresuitableforprinting.Calenderingalsocompressesthepapersheet,givingadenserproductandaglossiersurface.Starchisatypicalsurfacesizingusedtofillsurfacevoidsandreduceliquidpenetrationrate.RepresentativePapermakingMachinesFigure3.9Calenderingconsistsofpassingtheformeddriedpaperbetweensetsofheavyrolls.ThepapersurfacemaybedampenedtohelpinsmoothingitRepresentativePapermakingMachinesTomeetthehighestopacity,gloss,brightness,andprinting-detailrequirements,papersarecoatedwithpigmentssuchasclay,calciumcarbonate,andtitaniumdioxide.Coatedpapersareusuallycalledclay-coatedregardlessoftheactualformulation.Coatedpapersarecalenderedtomaintainahigh-quality,smoothsurface.Inaddition,highlysizedandclay-coatedboardscanbedifficulttobondwithwater-basedadhesivebecauseofpoorliquidpenetrationandtheinabilityoftheadhesivetobondtotheunderlyingfibers.Wherenecessary,coatedboardsshouldhaveperforationsintheadhesive-bondareassothatadhesivecanpenetratetothebodyofthepaper.RepresentativePapermakingMachinesPaperCharacterizationCaliperandWeightIninch/poundunits:
Caliperisexpressedinthousandthsofaninchorinpoints.Onethousandthofaninchis1point.(Forexample,a0.020-in.boardwouldbe20points.)Containerboardforthecorrugatedboardindustryandmostpaperboardsarespecifiedbytheweightinpoundsper1,000sq.ft.,thebasisweight.Finepaperscanbespecifiedbytheweightinpoundsperream.Areamis500sheets,buttheactualsheetsizecanvarydependingontheproduct.Inmostinstancesareamistakentobe3,000sq.ft.RepresentativePapermakingMachinesInmetricunits:
Caliperisexpressedinm.Papermass/unitarearelationshipisreportedasgrammage,definedasbeingthemass(weight)ofpaperin1squaremetre(m2).Themetricconversionfactorsarelbs./l,000sq.ft.4.88=grams/m20.001inch25.4=(usuallyroundedto25)1mm=1,000BrightnessBrightnessisameasureofthetotalreflectanceofwhitelight.RepresentativePapermakingMachinesPaperandMoistureContentPaperishygroscopicandabsorbsandlosesmoistureaccordingtotheambientrelativehumidity(R.H.)andtemperature.Thephysicalpropertiesofpapervarydramaticallywithmoisturecontent,andinsomeapplicationsthemoisturecontentofthepaperduringprocessingmustbecontrolled.Becausephysicalcharacterizationvaluesdependonmoisturecontent,allpapertestingmustbedoneatapreciselycontrolledtemperatureandhumidity.Internationally,thestandardconditionsarespecifiedas23Cand50%R.H.Paperishygroexpansive:
whenitabsorbsmoisture,itexpands;whenitdriesout,itshrinks.Between0and90%R.H.,thedimensionscanchange0.8%intheMDand1.6%intheCD.RepresentativePapermakingMachinesPaper/foillaminatePaper/foillaminatePaper/foillaminateat40%R.H.at20%R.H.at80%R.H.Figure3.10PapershygroexpansivenaturecancauseunwantedcurlingwhenpaperisbondedtoanenvironmentallystablesurfaceRepresentativePapermakingMachinesWheneverapapersheetislaminatedtoorcoatedwithamaterialthatisnotaffectedbymoisture(forexample,plasticfilm,aluminumfoil,orheavyprintorvarnish),thereisthepotentialforcurlingwhenthehumiditychanges.ViscoelasticityPaperismoreorlessviscoelastic,dependingontherateatwhichloadisapplied.Simply
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