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《六級(jí)新題型段落閱讀專項(xiàng)練習(xí)》由會(huì)員上傳分享，免費(fèi)在線閱讀，更多相關(guān)內(nèi)容在工程資料-天天文庫(kù)。
1、Paper—orethanMeetstheEyeA)Wearesur^roundedbysomuchpaperandcardtha/titiseasytcforgetjusthowcomp!exitis.Therearemanyvarietiesandgradesofpapermaterials,andwhilstitisfairlyeasytospotthevarieties，itisfarmoreclifficulttospotthegrades.B)丄tneedstobeuridorstoodthatrnostpaper*andcardismanufacturedforaspeci
2、ficpurpose,sotha/twhilstthecom—f*lakepacketmay1ooksmart,itisclearlynetsomethingdestinedfortheaarchives?JLtismacletolookgood,butonlyneedsalimitedlifespan?Itisalsomuchcheapertomanufacturethanhi曲gradoca±*d.C)Papercanbemadefromanalmostend!essv<±rietyofcel1ulose-basedma/terialwhichwi11includemanywoods
3、,cottonsandgrassesorwhichpapyrusisanexampleandfromwherewegettheword^paper^.Manyoftheseai'everyspecialized,buttheprepondo上ancoo￡papermakinghasbeen￡romso￡twoodaridcottonorrags,withthebulkbeingwood—based.PaperfromWoodD)Inordertomakewoodintopaperitneedstobebrokenclownintofinestrands.Firstlybypowerful
4、machineryandthenboiledwithstrongalkaliossuchascausticsoda,unti1afinopulpofcellulosefibersisproduced.Ttisfromthispulpthatthefinalproductismade,relyingonthebondingtogetherof*thecel1uloseintolayers.That,inaverysmallnutshell,istheessenceofpapermakingfromwood.However,therealityisrathermorecomp1icated.
5、Inordertogiveusourwhitopaperandcard,themakerswilladdbleach<±nclctherma/terialssuchaschinaclayandadditionalchemicals.E)Afurtherproblemwithwoodisthatitcontainsamaterialthatisnotcellulose.Somethingcalledlignin.Thisisessentialforthetreesinceitho1dsthece1lulosoFibrestogether,butifitisincoY'poratedinto
6、themanufacturedpaperitpresentsarch1vistswithaproblem.Lignineventual1ybreaksdownandreleasesacidproductsintothepaper.Thiswillweakenthebondbetweenthecellulosefibersandthepaperwillbecomebrittleand1ookratherbrownandcareworn.Wohavea11seenthisinoldnewsp<±persandcheappaperbackbooks?Tthasbeenestimatedthat
7、mostpaperbackbookswi11haveallfeofnotgreaterthanfiftyyeaars?Notwha/tweneedforourarchives.F)Sincethelignincanboromovodfromthopapoi'pulpduringrnanufacturo,thoobviousquestionis"whyisit1eftinthop<±per?zzTheanswer1iesinthefa
