湘大高分子专业英语Charpter-5-2

Charpter5-25.2.SyntheticRubbersandElastomers5.2.1IntroductionSyntheticrubber,invariablyapolymer,isanytypeofartificialelastomermainlysynthesizedfrompetroleumbyproducts.Anelastomerisamaterialwiththemechanical(ormaterial)propertythatitcanundergomuchmoreelasticdeformationunderstressthanmostmaterialsandstillreturntoitsprevioussizewithoutpermanentdeformation.About15billionkilogramsofrubbersareproducedannually,andofthatamounttwothirdsissynthetic.5.2.合成橡胶和弹性体5.2.1介绍合成橡胶，不约而同的聚合物，是任何类型的人造弹性体主要是由石油副产品合成。弹性体与机械（或材料）的属性，它可以在压力下进行更elasticdeformation比大多数的材料，仍然恢复到原来的大小不会产生永久变形的材料。大约15十亿kilograms橡胶每年生产，而该款额的三分之二是合成的。Syntheticrubberismadebythepolymerizationofavarietyofpetroleum-basedprecursorscalledmonomers.Themostprevalentsyntheticrubbersarestyrene-butadienerubbers(SBR)derivedfromthecopolymerizationofstyreneand1,3-butadiene.Othersyntheticrubbersarepreparedfromisoprene(2-methyl-1,3-butadiene),chloroprene(2-chloro-1,3-butadiene),andisobutylene(methylpropene)withasmallpercentageofisopreneforcross-linking.Theseandothermonomerscanbemixedinvariousproportionstobecopolymerizedtoproduceproductswitharangeofphysical,mechanical,andchemicalproperties.Themonomerscanbeproducedpureandtheadditionofimpuritiesoradditivescanbecontrolledbydesigntogiveoptimalproperties.Polymerizationofpuremonomerscanbebettercontrolledtogiveadesiredproportionofcisandtransdoublebonds.合成橡胶的各种石油基前体称为单体聚合而制成。最普遍的合成橡胶是由苯乙烯和1,3的共聚得到的苯乙烯-丁二烯橡胶（SBR）-丁二烯。其他合成橡胶是由异戊二烯制备的（2-甲基-1，3-丁二烯），氯丁二烯（2-氯-1,3-丁二烯）和异丁烯（甲基丙烯）与异戊二烯的用于交联的小百分比。这些和其它的单体可以混以各种比例进行共聚，生产出的产品具有广泛的物理，机械和化学性能。这些单体可以制备纯和除杂质或添加剂，可以通过设计加以控制，以提供最佳性能。纯单体的聚合反应可以得到更好的控制，以得到所希望的比例的顺式和反式双键。5.2.2Polymersfrom1,4-DienesTherearethreecommerciallyimportantmonomeric1,4-dienes.Twoareprimarilyproducedusingsteroregulatingcatalystsystems.Thesemonomerspossessaconjugatedpibondsequenceof-CC-CC-thatreadilyformspolymerswithanaverageenergyreleaseofabout20kcal/mol(80kJ/mol)withtheconversionofoneofthedoublebondsintolower(potentialenergywise;generallymorestable)energysinglebonds.Foralloftheseproducts,crosslinkingandgraftingsitesareavailablethroughtheremainingdoublebond.1,4-Butadienecanformthreerepeatunitsasdescribedin(7.25),the1,2;cis-1,4;andtrans-1,4.Commercialpolybutadieneismainlycomposedofthe1,4-cisisomerandisknownasbutadienerubber,BR.5.2.2从1,4-二烯烃聚合物有三种商业上重要的单体的1,4-二烯。二是使用steroregulating催化剂体系，主要生产的。这些单体具有的-CC-CC-，一个共轭pibond序列容易形成的聚合物具有约20kcal/mol(80kJ/mol)，该双键中的一个转化成低级（势能明智的平均能量释放;一般比较稳定）能源单键。对于所有这些产品，交联和接枝点都可以通过剩余的双键。1,4-丁二烯可形成3个重复单元中（7.25）所描述的，1,2;顺式-1，4;和反式-1，4。商业聚丁二烯主要由1,4-顺式异构体和被称为丁二烯橡胶，BR。Asnotedbefore,polybutadieneismadefromtheuseofstereoregulatingcatalysts.Thecompositionoftheresultingpolybutadieneisquitedependentonthenatureofthecatalystsuchthatalmosttotaltrans-1,4units,orcis-1,4units,or1,2unitscanbeformedaswellasalmostanycombinationoftheseunits.Themostimportantsingleapplicationofpolybutadienepolymersisitsuseinautomotivetireswhereover107tonsareusedyearlyintheUSmanufactureofautomobiletires.BRisusuallyblendedwithnaturalrubber,NR,orstyrene-butadienerubber,SBR,toimprovetiretreadperformance,particularlywearresistance.AseconduseisinthemanufactureofABScopolymerswherethestereogeometryisalsoimportant.Apolybutadienecompositionofabout60%trans-1,4;20%cis-1,4;and20%1,2configurationisgenerallyemployedintheproductionofABS.ThegoodlowtemperatureimpactstrengthisachievedinpartbecauseofthelowTgvaluesforthecompositions.Forinstance,theTgfortrans-1,4-polybutadieneisabout-14oCwhiletheTgforcis-1,4-polybutadieneisabout-108oC.MostoftheABSrubberismadeemployinganemulsionprocesswherethebutadieneisinitiallypolymerizedformingsubmicronparticles.Thestyrene–acrylonitrilecopolymeristhengraftedontotheoutsideoftheBRrubberparticles.ABSrubbersaregenerallytougherthanHIPSrubbersbutaremoredifficulttoprocess.ABSrubbersareusedinanumberofappliancesincludingluggage,powertoolhousings,vacuumcleanerhousings,toys,householdpiping,andautomotivecomponentssuchasinteriortrim.如之前所指出的，聚丁二烯，从使用立体调节催化剂的制造。所得到的聚丁二烯的组合物是相当依赖于催化剂的性质，使得几乎总反式-1，4个单位，或顺式-1，4单元，或1,2单元可以被形成，以及其中，几乎任何组合单位。聚丁二烯聚合物的最重要的一个应用是其在超过10汽车轮胎用7吨逐年被用在美国制造的汽车轮胎。BR是通常混合有天然橡胶，天然橡胶，或苯乙烯-丁二烯橡胶，丁苯橡胶，以提高轮胎胎面性能，特别是耐磨损性。第二个用途是在ABS共聚物，其中stereogeometry也是很重要的用途。约60％的反式-1，4聚丁二烯的组合物，20％的顺式1,4;和20％的1,2结构，一般采用在生产ABS。良好的低温冲击强度，这部分是因为该组合物的低Tg值的实现。举例来说，Tg的为反式-1,4-聚丁二烯是大约-14oC，同时的Tg为顺式1,4-聚丁二烯为约-108oC。大多数ABS橡胶的是由采用的乳液方法，其中丁二烯先聚合形成的亚微米颗粒。苯乙烯-丙烯腈共聚物，然后接枝到的BR的橡胶颗粒的外部。ABS橡胶通常比HIPS橡胶强硬但更难以处理。ABS橡胶用于许多设备，包括行李，电动工具外壳，吸尘器外壳，玩具，家用管道，以及汽车部件，如内饰。Anothermajoruseofbutadienepolymerisinthemanufactureofhighimpactpolystyrene,HIPS.MostHIPShasabout4to12%polybutadieneinitsothatHIPSismainlyapolystyreneintensematerial.Herethepolybutadienepolymerisdissolvedinaliquidalongwithstyrenemonomer.Thepolymerizationprocessisunusualinthatbothamatrixcompositionofpolystyreneandpolybutadieneisisformedaswellasagraftbetweenthegrowingpolystyreneontothepolybutadienebeingformed.Thegraftingprovidestheneededcompatibilitybetweenthematrixphaseandtherubberphase.Thegraftingisalsoimportantindeterminingthestructureandsizeofrubberparticlesthatareformed.丁二烯聚合物的另一个重要用途是在高冲击性聚苯乙烯，高抗冲聚苯乙烯的用途。最HIP