造纸专业英语教材

PAGEword文档可自由复制编辑Lesson1ThehistoryofpapermakingPaperderivesitsnamefromthereedyplant,papyrus.TheancientEgyptiansproducedtheworld’sfirstwritingmaterialbybeatingandpressingtogetherthinlayersofplantstem.ThefirstauthenticpapermakingoriginatedinChinaasearlyas100AD,utilizingasuspensionofbambooormulberryfibers.TheChinesesubsequentlydevelopedpapermakingintoahighlyskilledart.Afteraperiodofseveralcenturies,theartofpapermakingextendedintotheMiddleEastandlaterreachedEurope,wherecottonandlinenragsbecamethemainmaterials.PaperwasfirstmadeinEnglandin1496.byheendofthe15thcentury,anumberofpapermillsexistedinSpain,Italy,GermanyandFrance.ThefirstpapermillinNorthAmericawasestablishednearPhiladelphiain1690.Thedevelopmentofthepapermachineisthemostimportantmilestoneoftheindustry.LouisRobert,workingatthepapermillownedbyLedgerDidot,madehisfirstmodelofthecontinuouspapermachinein1796nearParisandreceivedaFrenchpatentforhismachinein1799attheageof37.In1803,apatentwasissuedtoFourdrinierbrothersfortheimprovedcontinuouspapermachinedesignedbyBryanDonkin.Ataboutthesametime,JohnDickson,acolleagueandfriendofDonkin,wasworkinghiscylindermachine,whichwasrefinedby1809.In1840,groundwoodpulpingmethodwasdevelopedinGermany.ThefirstmanufactureofpulpfromwoodusingsodaprocesswaspatentedonJuly1,1854toanEnglandinventornamedHughBurgess.In1867,aPhiladelphiachemist,BenjaminTilgham,wasawardedtheU.S.patentforthesulfitepulpingprocess;thefirstcommercialsulfitepulpwasproducedinSwedenin1874.C.F.Dahliscreditedwiththedevelopmentofthekraftprocesswasoriginallypatentedin1854.Alaterpatentin1865coveredtheincinerationofthespentsodaliquortorecovermostofhealkaliusedintheprocess.Theseinventionsandpioneeringprototypesprovidedthebasisforthemodernpaperindustry.Thetwentiethcenturyhasbeentherapidrefinementandmodificationoftheearlyandrathercrudetechnology,alongwiththedevelopmentoftechniquesasrefinermechanicalpulping,continuouscooking,continuousmultistagebleaching,on-machinepapercoating,twin-wireforming,andcomputerprocesscontrol.WordsandExpressionsPaper纸，纸张papyrus纸莎草beating打浆pressing压榨，压合papermaking抄纸，造纸fiber纤维papermachine纸机groundwoodpulping磨木法制浆sodaprocess烧碱法制浆sulfitepulpingprocess亚硫酸盐法制浆kraft（sulfate）process硫酸盐法制浆refinermechanicalpulping盘磨机械法制浆continuouscooking连续蒸煮continuousmultistagebleaching连续多段漂白on-machinepapercoating机内涂布twin-wireforming双网成形computeprocesscontrol计算机过程控制Lesson2FibrousmaterialsofpapermakingTheoretically,pulpfibercanbeextractedfromalmostanyvascularplantfoundinnature.Sofar,woodisstillthemostabundantsourceofpapermakingfibers.Besides,about10%ofthefiberusedtomakepapereachyearworldwideisfromnon-woodplant,includingstraws(wheat,rye,riceandbarley)，grasses（bamboo，espartoandpapyrus)，canesandreeds(bagasse,cornstalksandkenaf),bast(flax,hemp,jute,ramieandmulberry),andseedhairs(cotton).Nonvegetablefiberssuchaspolyethyleneandglassfibersarealsoused.Inrecentyears,secondaryfiberutilizationisincreasingatarapidpace.Botanically,woodsareclassifiedintotwomajorgroups:softwoodsorconifersandhardwoodsorbroad-leafed-trees,eitherdeciduousorevergreen.Theverticalstructureofconifersiscomposedalmostentirelyoflong,tappingcellscalledtracheids.Thewallofatypicaltrachiedorfiberiscomposedofseverallayers.Themiddlelamellawithveryhighlignincontentseparatestwocontiguoustrachieds.Eachtrachiedhasprimarywallandathree-layeredsecondarywallwithspecificalignmentsofmicrofibrils.Microfibrilsarebundlesofcellulosemolecules,andtheirorientationcaninfluencethecharacteristicsofapulpfiber.Theprincipalverticalstructureofhardwoodiscomposedofbothrelativelylong,narrowcells,calledlibriformfibers,andmuchshorter,widecells,calledvessels.Hardwoodsalsohaveaverticalparenchymasystemandahorizontalorrayparenchymasystem.Generally,softwoodhashigheramountoffiberswhilehardwoodhashigherpercentageofvessels.Softwoodfibersaremorethantwiceaslongashardwoodfibers.Technically,woodisxylemtissue,whichconsistsofcellulose,hemicellulose,ligninandextractives,hencealignocellulosicmaterial.Sapwoodistheouterpartofthetrunkandcontainssomelivingcells.Heartwoodisfoundinthecentreofoldertrees,containingonlydeadcells,andisgenerallydrierthansapwood.Eachannualgrowthringcontainsearlywood,whichischaracterizedbylargecellswiththincellwalls,andlatewood,whichischaracterizedbysmallcellsandthickwalls.Someoftheimportantpulpingvariablesofwoodandwoodchipsare:moisturecontent,specificgravity,tensionandcompressionstrength,barkcontent,chemicalcomposition,woodspecies,chipdimensions,andlengthofstorage.Wordsandexpressionsstraws稻麦草wheat小麦rye黑麦rice稻谷barly大麦grasses草类bamboo竹子esparto西班牙草canesandreeds蔗苇类bagasse蔗渣cornstalks玉米茎秆kenaf洋麻bast韧皮类flax亚麻hemp大麻jute黄麻ramie苎麻mulberry桑树seedhairs种毛类polyethylene聚乙烯glassfibers玻璃纤维softwood软木，针叶木conifer针叶树，针叶木hardwood硬木，阔叶木broad-leafed-tree阔叶树tracheid管胞middlelammela胞间层lignin木素primarywall初生壁secondarywall次生壁microfibril微纤丝cellulose纤维素libriformfiber韧皮纤维vessels导管parenchymasystem薄壁组织系统hemicellulose半纤维素extractive抽提物sapwood边材heartwood心材earlywood早材latewood晚材moisturecontent水分含量specificgravity比重tensionandcompressionstrength抗张与抗压强度Readingmaterial:ChemicalcompositionofrawmaterialsChemicalcompositionofthecandidateplantgivesanideaofhowfeasibletheplantisasrawmaterialforpapermaking.Thefibrousconstituentisthemostimportantpartoftheplant.Sinceplantfibresconsistofcellwalls,thecompositionandamountoffibresisreflectedinthepropertiesofcellwalls.Celluloseistheprincipalcomponentincellwallsandinfibres.Thenone-cellulosecomponentsofthecellwasincludehemicelluloses,pectins,ligninandproteins,andintheepidermalcellsalsocertainminerals.Theamountandcompositionofthecellwallcompoundsdifferamongplantspeciesandevenamongplantparts,andtheyaffectthepulpingpropertiesoftheplantmaterial.Someofnon-woodyfibreplantscontainmorepentosans(over20%),holocellulose(over70%)andlesslignin(about15%)comparedwithhardwoods.Theyhavealsohigherhotwatersolubility,whichisapparentfromtheeasyaccessibilityofcookingliquors.Thelowlignincontentingrassesandannualslowerstherequirementofchemicalsforcookingandbleaching.Exceptforthefibrousmaterial,plantsalsoconsistofothercellularelements,includingmineralcompounds.Whiletheinorganiccompoundsareessentialforplantgrowthanddevelopment,theyareundesirableinpulpingandpapermaking.CelluloseCelluloseistheprincipalcomponentofplantfibresusedinpulping.Itformsthebasicstructuralmaterialofcellwallsinallhigherterrestrialplantsbeinglargelyresponsibleforthestrengthoftheplantcells.Cellulosealwayshasthesameprimarystructure,itisα-1,4linkedpolymerofD-glucans.Itoccursintheformoflong,linear,ribbon-likechains,whichareaggregatedintostructuralfibrils.Eachfibrilcontainsfrom30toseveralhundredpolymericchainsthatrunparallelwiththelaterallyexposedhydroxylgroups.Thehydroxylgroupstakepartinhydrogenbonding,withlinkagesbothwithinthepolymericmoleculesandbetweenthem.Thisarrangementofthehydroxylgroupsincellulosemakesthemrelativelyunavailabletosolvents,suchaswater,andgivescelluloseitsunusualresistancetochemicalattack,aswellasitshightensilestrength.Thefirstlayerofcelluloseareformedintheprimarycellwallsduringtheextensionstageofthecell,butmostcelluloseisdepositedinthesecondarywalls.Theproportionofcelluloseinprimarycellwallsis20to30%ofDMandinsecondarycellwalls45to90%.Thecellulosecontentofaplantdependsonthecellwallcontent,whichcanvarybetweenplantspeciesandvarieties.Theageoftheplantandplantpartalsoaffectthecellulosecontent.Annualplantsgenerallyhaveaboutthesamecellulosecontentaswoodyspecies,buttheirhighercontentofhemicelluloseincreasesthelevelofpulpyieldmorethantheexpectedlevelonthebasisofcellulosecontentalone.Thecelluloseandalpha-cellulosecontentscanbecorrelatedwiththeyieldsofunbleachedandbleachedpulps,respectively.HemicelluloseHemicelluloseconsistofaheterogeneousgroupofbranchedpolysaccharides.Thespecificconstitutionofthehemicellulosepolymerdependsontheparticularplantspeciesandonthetissue.Glucose,xyloseandmannoseoftenpredominateinthestructureofthehemicelluloses,andaregenerallytermedglucans,xylans,xyloglucansandmannans.Xylansarethemostabundantnon-cellulosepolysaccharidesinthemajorityofangiosperms,wheretheyaccountfor20to30%ofthedryweightofwoodytissues.Theyaremainlysecondarycellwallcomponents,butinmonocotyledonstheyarefoundalsointheprimarycellwalls,representingabout20%ofboththeprimaryandsecondarywalls.Indicotstheyamountto20%ofthesecondarywalls,buttoonly5%oftheprimarycellwalls.Xlansarealsodifferentinmonocotsandindicots.Ingymnosperms,wheregalactoglucomannansandglucomannansrepresentthemajorhemicelluloses,xylansarelessabundant(8%).Thehemicellulosesinsecondarycellwallsareassociatedwiththearomaticpolymer,lignin.PectinsPectins,i.e.pecticpolysaccharides,arethepolymersofthemiddlelamellaandprimarycellwallofdicotyledons,wheretheymayconstituteupto50%ofthecellwall.Inmonocotyledons,theproportionofpecticpolysaccharidesinnormallylessthanthisandinsecondarywallstheproportionofhemicellulosepolysaccharidesgreatlyexceedstheamountsofpecticpolysaccharides.ThepecticsubstancesarecharacterisedbytheirhighcontentofD-galacturonicacidandmethylgalacturonicacidresidues.Pectinsaremoreimportantingrowingthaninnon-growingcellwalls,andthustheyarenotasignificantconstituentincommercialfibresexceptinflaxfibre,wherepectinsarefoundinlamellaebetweenthefibresandaccountfor1.8%ofdryweight.LigninLigninisthemostabundantorganicsubstanceinplantcellwallsafterpolysaccharides.Ligninsarehighlybranchedphenolicpolymersandconstituteanintegralcellwallcomponentofallvascularplants.Thestructureandbiosynthesisofligninhasbeenwidelystudied.Thereasonforthegreatinterestistheabundanceoflignininnature,aswellasitseconomicalimportanceformankind.Forpapermaking,ligninischemicallydissolvedbecauseoftheseparationofthefibresintherawmaterial.Incattlefeeds,ligninmarkedlylowersthedigestibility.Ligninsaretraditionallyconsideredtobepolymers,whichareformedfrommonolignols:p-coumarylalcohol,coniferylalcohol,andsinapylalcohol.Eachoftheprecursorsmayformseveraltypesofbondswithotherprecursorsinconstructingtheligninpolymer.Agreatvariationinligninstructureandamountexistsamongthemajorplantgroupsandamongspecies.Greatvariationinligninstructureandamountexistsalsoamongcelltypesofdifferentagewithinasingleplantandevenbetweendifferentpartsofthewallofasinglecell.Gymnospermlignincontainsguaiacylunits(G-units),whicharepolymerizedfromconiferylalcohol,andasmallproportionofp-hydroxylphenylunits(H-units)formedfromp-coumarylalcohol.Angiospermligninsareformedfrombothsyringylunits(S-units),polymerizedfromsinapylalcohol,andG-unitswithasmallproportionofH-units.Syringylligninincreasesinproportionrelativetoguaiacylandp-hydroxylphenylligninduringmaturationofsomegrasses.Ingrassspeciesthetotallignincontentvariesfrom15to26%.ForreedcanarygrassBurritetallfoundonly1.2%.ingrassesandlegumesligninsarepredominantlyformedfromconiferylandsinapylalcoholswithonlysmallamountsofp-coumarylalcohol.Ligninsareconsideredtocontributetothecompressivestrengthofplanttissueandwaterimpermeabilityofthecellwall.Ligninsaidcellsinresistancetomicrobialattack,buttheydonotinfluencethetensilepropertiesofthecellwall.Monolignolscanalsoformbondswithothercellwallpolymersinadditiontolignin.Cross-linkingwithpolysaccharidesandproteinsusuallyresultsinaverycomplexthree-dimensionalnetwork.Thiscloseconnectionbetweenphenolicpolymersandplantcellwallcarbohydratesmakestheeffectiveseparationandutilizationofthefibresmorecomplicated.Inwoodyplantsrelativelyfewcovalentbondsexistbetweencarbohydratesandlignincomparedwiththoseinforagelegumesandgrasseswherethelignincomponentisalsocovalentlylinkedtophenolicacids,notably4-hydroxycinnamicacids,p-coumaricacidandferulicacid.Ligninandhemicellulosesfillthespacesbetweenthecellulosechainsinthecellwallandbetweenthecellsthemselves.Thiscombinedstructuregivestheplantcellwallandthebulktissueitselfstructuralstrength,andimprovesstiffnessandtoughnessproperties.MineralsThereare19mineralsthatareessentialorusefulforplantgrowthanddevelopment.Themacronutrients,suchasN,P,S,K(Potassium),MgandCaareintegraltoorganicsubstancessuchasproteinsandnucleicacidsandmaintainosmoticpressure.Theirconcentrationsinplantsvaryfrom0.1to1.5%ofDM.Themicronutrients,suchasFe,Mn,Zn,Cu,B,Mo(molybdenum),Cl,andNi,contributemainlytoenzymeproductionoractivationandtheirconcentrationsinplantsarelow.Silicon(Si)isessentialonlyinsomeplantspecies.Theamountofsiliconuptakesbyplantsisdescribedbysilica(SiO2)concentration.Thehighestsilicaconcentrations(10-5%)arefoundinEquisetum()-speciesandingrassplantsgrowinginwater,suchasrice.Othermonocotyledons,includingcereals,foragegrassesandsugarcanecontainSiO2at1-3%ofDM.Siinepidermiscellsisassumedtoprotecttheplantagainstherbivoresandinxylemwalls,tostrengthentheplantaslignin.Theconcentrationofaparticularmineralsubstanceinaplantvariesdependingonplantageorastageofdevelopment,plantspeciesandtheconcentrationofothermineralsaswellastheplantpart.Inthepulpingprocessthemineralsoftherawmaterialsareconsideredtobeimpuritiesandshouldberemovedduringpulpingorbleaching.Thesameelementsarefoundbothinnon-woodyandinwoodyspecies,buttheconcentrationsarelowerinwoodyplants.Siisthemostdeleteriouselementintherawmaterialforpulping,becauseitcomplicatestherecoveryofchemicalsandenergyinpulpmills.Siwearsouttheinstallationsofpaperfactoriesandcanlowerthepaperquality.OtherharmfulelementsforthepulpingprocessincludeK,Cl,Al,Fe,Mn,Mg,Na,S,CaandN.Choosingasuitableplantspeciesastherawmaterialforpulpingcanminimisetheamountofundesirablemineralsinprocess.Moreover,usingonlytheplantpartsthatcontainlowamountsofmineralssuchasSirepresentsanimprovement.Readingmaterial:biosynthesisoftheligninpolymer：Lignification,inanalogywithotherpolymerizationprocesses,isthemeansbywhichligninmacromoleculesgrow.Thustheprimaryreactionsofconcernarethoseinwhichthemacromoleculeisextendedbythecouplingofanewmonomertothegrowingpolymer.Branchingreactionsarealsoimportant.Theycanoccurwhentwosequentialreactionsarepossibleatthegrowingend,i.e.thephenolicend,ofthepolymer.Theprimarymonomersforlignificationarethethreep-hydroxycinnamylalcohols:p-coumarylalcohol,coniferylalcohol,andsinapylalcohol.Thesemonolignolsdifferintheirdegreeofmethoxylation.Intheligninpolymer,thesemonolignolsproducep-hydroxyphenyl,guaiacyl,andsyringylunits.Duetothecapabilityofelectron-delocalizedradicalstocoupleatvarioussites,avarietyofstructuralunitsarefoundintheresultingpolymer.Erdtmanwasthefirsttorecognizethatmajorligninstructuralfeatureswereconsistentwithaprocessofradicalcouplingofphenols.Simplechemicaldehydrodimerizationreactionsofconiferylalcohol,usingeithertheperoxidase-H2O2systemthatisimplicatedinvivo,orotherchemicalsingle-electronoxidantsincludingvariousFe,Mn,Cu,andAgsalts,producethreedehydrodimericcouplingproductsincomparableamounts.Mostreviewsandtextsalsoincludeothercouplingmodesforthemonolignols,buttheseareinfactnotobserved;5–5-and4–O–5-coupledstructuresinligninsdonotarisefrommonolignol-monolignolcouplingreactions.Theproductsinvolveatleastoneofthemonolignolscouplingatitsfavoredβ-position.Evidenceforfurthercouplingreactionsbetweenthemonolignolandtheinitiallyformeddimmerbecameavailablefromwell-characterizedoligomers.Thenotionthatlignificationwasaprocessinvolving“uncontrolled”radicalcouplingreactionswasthereforeborn,althoughErdtmansuspectedthatlignificationmightbefoundtobemorehighlycontrolled.Syntheticlignins,so-calleddehydrogenationpolymers(DHPs),canbepreparedinvitrofrommonolignolsoxidizedbyperoxidase-H2O2.Suchsyntheticligninsarevaluableforexploringandunderstandingcouplingandpost-couplingreactions,andasmodelsforspectroscopicandreactivitystudies.However,theydifferfromnativeorisolatedlignins;inparticulartheyhavealowerβ–O–4-ethercontent.Theprimaryreasonisthatdehydrodimerizationreactionsareover-represented.Dehydrodimerizationofconiferylalcoholyieldsthreeprimaryproducts,whereassinapylalcoholyieldstwo.Couplingattheβ-positionisfavoredforconiferylandevenmorestronglyforsinapylalcohol;thecouplingproductsalwaysresultfromcouplingofatleastoneofthemonolignolsatitsβ-position.Incouplingreactions,includinginabiomimeticperoxidase-H2O2system,theβ-etherdimmeristypicallyproducedinlessthanonethirdoftheyieldintheconiferylalcoholcase,andatonlyaboutthe9%levelforsinapylalcohol.Monolignolradicalspreferentiallycouplewithlikemonolignolradicals(whenavailable)ratherthancross-couplewithdimmersorhigheroligomers.Dehydrodimerizationreactionsarethereforeover-representedinsyntheticligninsevenwhenattemptsaremadetointroducethemonolignolslowly.Consequently,theβ-etherfrequencyislow,considerablylowerthanintypicallignins.Limitingthediffusionrates(andthereforemonolignolradicalconcentrations)tofavorcross-couplingreactionsrevealsthatβ-ethersarestronglyfavoredincrosscouplingreactions.Ligninmonomersdonothaveanyopticalactivity–unliketheproteinandpolysaccharidemonomers,theypossessnochiralcenters.Opticalcentersarehowevercreatedineachcouplingreactioninvolvingthesidechainβ-position,twoperevent.Theresultisthatthenumberofisomersofany“randomly”formedligninstructureincreaseswithitsdegreeofpolymerization,quicklybecomingastronomical.Thusaβ-etherdimer,forexample,has4opticalisomersandhalfthatnumber(i.e.2of“real”chemicallydistinctisomers.Aβ-ethertrimerhas8chemicallydistinctisomers,thatcanberesolvedinhigh-resolutionprotonNMRspectra.Aβ-ethertetramerhas32isomers.Andsoitprogressesgeometrically.Apurerandomβ-ether110-merwasnotedtohaveaboutthesamenumberofisomersasthereareatomsinourgalaxy.Lesson3PulpandpaperpropertiesandtestingAlargenumberofpulptestingmethodsareincommontocharacterizepulpswithrespecttoquality,processability,andsuitabilityforvariousenduses.Themost“fundamental”measurementsprovidethemeanstopredictbehaviorwhile“functional”testsaredesignedtomeasurespecificproperties.Thekappanumbertestisusedinmillcontrolworktoindicatethedegreeofdelignificationoccurringduringcookingandthechemicalrequirementforbleaching.Agoodindicationofcellulosedegreeofpolymerization(DP)canbeobtainedbymeasuringviscosityofacellulosesolutionofknownconcentrationusingcupriathylenediaminehydroxide(CED)asasolvent.Pulpdrainabilityisanimportantpropertywithrespecttopulpprocessingandpapermaking.Measurementofpulpdrainageareknownasfreeness,slowness,wetness,ordraintimeaccordingtotheinstrumentormethodused.Freenessandslownessscaleshaveaninverserelationship.TheCanadianStandardFreeness(CSF)andtheSchopper-Riegler(°SR)slownesstesteraretwoprincipaldrainagetestingdevicesusedrespectivelyforthesetwopropertiesinNorthAmericaandEurope.Tosimulatethetypeofdrainagewithmicroturbulenceandorientedshear,theBrittdynamicdrainagejar(DDJ)wasdevelopedforstudyingstockdrainagephenomenonunderconditionsmorecloselyapproachingthoseofthepapermachine.Thewidediversityofpapergradeswithdifferentfunctionalpropertiesnecessitiesamultiplicityofpapertestmethods.Somebasicpropertiesareimportantforallgradessuchasbasisweightorgrammageandcaliper.Othersarespecificallydevelopedtoassesstheperformanceattributesofspecialityproductsandtheirapplication.Sincepaperisahygroscopicmaterialandwillseekequilibriummoisturewiththesurroundingair,papersamplesmustbeconditionedinastandardizedenvironmenttoobtainreproducibleresults.Duetothe“two-sidedness”,thewireandtop-side’spropertiesmustbetakenintoaccountforcertainenduses.Paperhasadefinite“grain”causedbythegreaterorientationoffibersinthemachinedirectionandbythestress/strainimposedduringpressinganddrying.Thedirectionalityofpapermustbealsotakenintoaccountinmeasuringphysicalproperties.Thephysicaltestsonpapercanbeconvenientlydividedintofourgroups:mechanicalandstrengthproperties(tensile,burst,tear,foldingstrength,stiffness,softness,etc);surfaceproperties(roughness,pickstrength);opticalproperties(brightness,opacity,gloss,color);andpermeabilitytofluids(sizingdegree,oilresistance,airresistance,andwatervaporpermeability).Paperchemicalpropertiesareimportantforcertaingradesofpapersuchasphotographicpapers,reproductionpapers,anti-tarnishpapers,safetypapers,electricalpapers,food-wrappingpapers,andanypaperrequiringahighdegreeofperformance.Wordsandexpressionskappanumber卡伯值degreeofpolymerization聚合度cupriathylenediaminehydroxide铜乙氢氧二铵Canadianstandardfreeness加拿大标准游离度schopper-rieglerslowness打浆度basisweight定量grammage克重two-sidedness两面性tensile抗张强度burst耐破度tear撕裂度foldingstrength耐折度stiffness挺度softness柔软度roughness粗糙度pickstrength拉毛强度brightness白度，亮度opacity不透明度gloss光泽度color色度，色值，涂料sizingdegree施胶度oilresistance抗油性airresistance透气阻力watervaporpermeability水蒸气渗透性photographicpaperreproductionpaper复印纸anti-tarnishpaper防锈纸safetypaper防伪纸electricalpaper电气用纸food-wrappingpaper食品包装纸Lesson4PulpingprocessandpulpendusesPulpconsistsofwoodorotherlignocellulosicmaterialsthathavebeenbrokendownphysicallyand/orchemicallysothatdiscretefibersareliberatedandcanbedispersedinwaterandreformedintoaweb.Pulpingreferstoanyprocessesbywhichwood(orotherfibrousrawmaterial)isreducedtofibrousmass.Basically,itisthemeansbywhichthebondsaresystematicallyrupturedwithinthewoodstructure.Thetaskcanbeaccomplishedmechanically,thermally,chemically,orbycombinationofthesetreatments.Existingcommercialprocessesarebroadlyclassifiedas:chemical,semi-chemical,semi-mechanicalandmechanicalpulping.Theseareinorderofincreasingmechanicalenergyrequiredtoseparatefibersanddecreasingrelianceonchemicalaction.Asaresult,chemicalmethodsrelyontheeffectofchemicalstoseparatefibers,whereasmechanicalpulpingmethodsrelycompletelyonphysicalaction.Themorethatchemicalsareinvolved,thelowertheyieldandlignincontentsincechemicaldegradesandsolublizescomponentsofthewood,especiallyligninandhemicelluloses.Ontheotherhand,chemicalpulpingyieldsindividualfibersthatisnotcutandgivesstrongpaperssincethelignin,whichinterfereswithhydrogenbondingoffibers,islargelyremoved.Thetypicalpulpingprocessesareclassifiedasfollows:Mechanicalpulping:stonegroundwoodforlogs;RMPandTMPforchips.Chemi-mechanicalpulping:chemigroundwood,coldsoda,CTMP.Semichemicalpuling:NSSC,highyieldsulfite,highyieldkraft.Chemicalpulping:kraft,sodaandsoda–AQ,sulfite(acidandbisulfite).Allchemicalpulpsmustbemechanicallyworkedtodevelopoptimumpapermakingpropertiesforvariousapplications.Softwoodkraftpulpsproducedthestrongestpapersandarepreferentiallyutilizedwherestrengthisrequired.Typicalapplicationsareforwrapping,sack,andbox-linerpapers.Bleachedkraftfibersareaddedtonewsprintandmagazinegradestoprovidethesheetwithsufficientstrengthtorunonhighspeedprintingprocess.Bleachedgradesarealsousedfortowelingandfoodboards.Sulfitepulpsfindamajormarketinbond,writing,andreproducingpaperswheregoodformationandmoderatestrengtharerequired.Kraftorsodahardwoodisusuallyaddedforimprovedformationandopaci