材料科学与工程基础第四章

材料科学与工程基础第四章第1页，课件共53页，创作于2023年2月WhyStudyPolymerStructures?Chemicalandstructuralcharacteristicsaffectthepropertiesandbehaviorsofpolymericmaterials.2.Degreeofcrosslinking—onthestiffnessofrubber-likematerials1.Degreeofcrystallinityofsemicrystallinepolymers—ondensity,stiffness,strength,andductility.密度、硬度、强度、塑性交联第2页，课件共53页，创作于2023年2月4.1INTRODUCTIONNaturalpolymersplantsanimalswood,rubber,cotton,wool,leather,silk.proteins,enzymes,starches,andcelluloseOthernaturalpolymersbiologicalandphysiologicalManyofourusefulplastics,rubbers,andfibermaterialsaresyntheticpolymers.Thischapterexploresmolecularandcrystalstructuresofpolymers;蛋白质、酶、淀粉、纤维素第3页，课件共53页，创作于2023年2月4.2HydrocarbonMoleculesHydrocarbons:manyorganicmaterialsarehydrocarbons;thatis,theyarecomposedofhydrogenandcarbon.烃methane(CH4).甲烷EthyleneC2H4乙烯H|H—C—H|H

acetylene,C2H2乙炔H-CC-HHH||C=C||HH第4页，课件共53页，创作于2023年2月Unsaturated：

Atermdescribingcarbonatomsthatparticipateindoubleortriplecovalentbondsand,therefore,donotbondtoamaximumoffourotheratoms.Saturated：Atermdescribingacarbonatomthatparticipatesinonlysinglecovalentbondswithfourotheratoms.Someofthesimplehydrocarbonsbelongtotheparaffinfamily;thechainlikeparaffinmoleculesincludemethane(CH4),ethane(C2H6),propane(C3H8),andbutane(C4H10).石蜡Thecovalentbondsineachmoleculearestrong,butonlyweakhydrogenandvanderWaalsbondsexistbetweenmolecules,不饱和的饱和的甲、乙、丙、丁烷第5页，课件共53页，创作于2023年2月第6页，课件共53页，创作于2023年2月Isomerism：Thephenomenonwherebytwoormorepolymermoleculesormerunitshavethesamecompositionbutdifferentstructuralarrangementsandproperties.同质异构Forexamples:butaneisobutane异丁烷丁烷normalbutane-0.5oCisobutane-12.3oCtheboilingtemperatures链节第7页，课件共53页，创作于2023年2月whereRandR’

representorganicradicals羟基羧基羟基醇醚酸醛芳香烃甲醇乙醚乙酸甲醛苯酚第8页，课件共53页，创作于2023年2月4.3PolymerMoleculesMacromolecule:

Ahugemoleculemadeupofthousandsofatoms.Withineachmolecule,theatomsareboundtogetherbycovalentinteratomicbonds.formoflongandflexiblechainsMer.Thegroupofatomsthatconstitutesapolymerchainrepeatunit.Polymer.Asolid,nonmetallic(normallyorganic)compoundofhighmolecularweightthestructureofwhichiscomposedofsmallrepeat(ormer)units.Monomer.Amoleculeconsistingofasinglemer.高分子链节聚合体单体第9页，课件共53页，创作于2023年2月4.4TheChemistryofPolymerMoleculesethylene(C2H4),gasatambienttemperatureandpressure,appropriateconditionsoftemperatureandpressurepolyethylene(PE),solidpolymericmaterial.第10页，课件共53页，创作于2023年2月(4.1)catalystspecies(R·)unpairedelectron(4.2)and(b)aperspectiveofthemolecule,indicatingthezigzagbackbonestructure.FIGURE4.1Forpolyethylene,(a)aSchematicrepresentationofmerandchainstructures,109o0.154nm.催化剂种类第11页，课件共53页，创作于2023年2月FIGURE4.2Merandchainstructuresfor(a)polytetrafluoroethylene,(b)polyvinylchloride,and(c)polypropylene.聚四氟乙烯(PTFE)聚氯乙烯(PVC)聚丙烯(PP).第12页，课件共53页，创作于2023年2月聚乙烯聚氯乙烯聚四氟乙烯聚丙烯第13页，课件共53页，创作于2023年2月聚苯乙烯聚甲基丙烯酸甲酯酚醛树脂(电木)第14页，课件共53页，创作于2023年2月尼龙聚碳酸酯聚乙烯对苯二酸酯

第15页，课件共53页，创作于2023年2月Homopolymer.Apolymerhavingachainstructureinwhichallmerunitsareofthesametype.Bifunctional.Designatingmonomerunitsthathavetwoactivebondingpositions.formingthetwo-dimensionalchainlikemolecularstructure.Trifunctionalmer.Designatingmerunitsthathavethreeactivebondingpositions.Forexamples,phenol-formaldehyde.athree-dimensionalmolecularnetworkstructureresults.Copolymer.Apolymerthatconsistsoftwoormoredissimilarmerunitsincombinationalongitsmolecularchains.均聚物共聚物二功能的三功能的酚醛树脂第16页，课件共53页，创作于2023年2月4.5MolecularWeightnotallpolymerchainswillgrowtothesamelength;thisresultsinadistributionofchainlengthsormolecularweights.definitionofaveragemolecularweight:1).Thenumber-averagemolecularweight(4.3a)Mi

:themean(middle)molecularweightofsizerangei,xi:

thefractionofthetotalnumberofchainswithinthecorrespondingsizerange.FIGURE4.3Hypotheticalpolymer-moleculesizedistributionsonthebasisofnumberfractionsofmolecules第17页，课件共53页，创作于2023年2月2).weight-averagemolecularweight(4.3b)Mi

:molecularweightwithinasizerange,wi:denotestheweightfractionofmoleculeswithinthesamesizeinterval.FIGURE4.3Hypotheticalpolymer-moleculesizedistributionsonthebasisofweightfractionsofmolecules.Degreeofpolymerization(n):theaveragenumberofmerunitsperpolymerchainmolecule.number-average(nn)weight-average(nw)(4.4a)(4.4b)聚合度第18页，课件共53页，创作于2023年2月misthemermolecularweight.Foracopolymer:(4.5)fj

:thechainfractionofmerj.mj:molecularweightofmerj.EXAMPLEPROBLEM4.1polyvinylchlorideinFigure4.3.compute

(a)thenumber-averagemolecularweight;(b)thenumber-averagedegreeofpolymerization;

(c)theweight-averagemolecularweight.第19页，课件共53页，创作于2023年2月SOLUTION(a)FromFigure4.3aandbyMn=

21,150Table4.4aDataUsedforNumber-AverageMolecularWeightComputationsinExampleProblem4.1第20页，课件共53页，创作于2023年2月(b)forPVC:theatomicweightsofC,H,andClare,respectively,12.01,1.01,and35.45g/mol.m=

2(12.01g/mol)+

3(1.01g/mol)+

35.45g/mol=62.50g/moland(c)FromFigure4.3bandbyMw=

23,200g/mol第21页，课件共53页，创作于2023年2月Table4.4bDataUsedforWeight-AverageMolecularWeightComputationsinExampleProblem4.1第22页，课件共53页，创作于2023年2月FIGURE4.4Distributionofmolecularweightsforatypicalpolymer.第23页，课件共53页，创作于2023年2月themolecularweightaffectpolymercharacteristicsmeltingtemperature

molecularweightforMuptoabout100,000g/mol.polymerswithveryshortroomtemperature,asliquidsorgases.havingmolecularweightsontheorderof100g/molwithmolecularweightsofapproximately1000g/molwaxysolidsandsoftresins.highpolymersSolidpolymersmolecularweightsbetween10,000andseveralmilliong/mol.柔软固体和软树脂第24页，课件共53页，创作于2023年2月4.6MolecularShapeFIGURE4.5Schematicrepresentationsofhowpolymerchainshapeisinfluencedbythepositioningofbackbonecarbonatoms(solidcircles).For(a),therightmostatommaylieanywhereonthedashedcircleandstillsubtenda109oanglewiththebondbetweentheothertwoatoms.Straightandtwistedchainsegmentsaregeneratedwhenthebackboneatomsaresituatedasin(b)and(c),respectively.第25页，课件共53页，创作于2023年2月FIGURE4.6Schematicrepresentationofasinglepolymerchainmoleculethathasnumerousrandomkinksandcoilsproducedbychainbondrotations.havingamultitudeofbends,twists,andkinks.r<<totalchainlengthPolymerslargenumbersofmolecularchains,Eachofwhichmaybend,coil,andkinkextensiveintertwiningandentanglementofneighboringchainmolecules弯曲扭曲缠结盘绕纠缠第26页，课件共53页，创作于2023年2月TheserandomcoilsandentanglementsimportantcharacteristicsincludethelargeelasticextensionsofrubbermaterialsthemechanicalandthermalcharacteristicsofpolymersFunction(responsetostressesorthermalvibrations)RotationalflexibilitydependentonmerstructureandchemistryForexample,polystyrenemolecules,whichhaveaphenylsidegroup,aremoreresistanttorotationalmotionthanarepolyethylenechains.旋转柔性聚苯乙烯第27页，课件共53页，创作于2023年2月4.7MolecularStructurephysicalcharacteristicsofapolymerdependonmolecularweightandshapethestructureofthemolecularchains.LINEARPOLYMERSApolymerinwhicheachmoleculeconsistsofbifunctionalmerunitsjoinedendtoendinasinglechain.FIGURE4.7(a)Schematicrepresentationsoflinearpolyethylene,polyvinylchloride,polystyrene,polymethylmethacrylate,nylon,fluorocarbons.聚乙烯聚氯乙烯聚苯乙烯聚甲基丙烯酸甲酯尼龙碳氟化合物longchainsareflexible线型双功能链节第28页，课件共53页，创作于2023年2月BRANCHEDPOLYMERS支链型Apolymerhavingamolecularstructureofsecondarychainsthatextendfromtheprimarymainchains.FIGURE4.7(b)Schematicrepresentationsofbranched,branches,consideredtobepartofthemain-chainmolecule,resultsinaloweringofthepolymerdensity.Thosepolymersthatformlinearstructuresmayalsobebranched.第29页，课件共53页，创作于2023年2月CROSSLINKEDPOLYMERS交联型Apolymerinwhichadjacentlinearmolecularchainsarejoinedatvariouspositionsbycovalentbonds.FIGURE4.7(c)SchematicrepresentationsofcrosslinkedTheprocessofcrosslinkingeitherduringsynthesisorbyanonreversiblechemicalreactionatanelevatedtemperature.Manyoftherubberarecrosslinkedcalledvulcanization,硫化高温不可逆的第30页，课件共53页，创作于2023年2月NETWORKPOLYMERS网络型Apolymercomposedoftrifunctionalmerunitsthatformthree-dimensionalmolecules.Trifunctionalmerunits,FIGURE4.7(d)SchematicrepresentationsofnetworkThesematerialshavedistinctivemechanicalandthermalproperties.Epoxiesandphenol-formaldehydebelongtothisgroup.环氧的苯甲醛三功能链节第31页，课件共53页，创作于2023年2月FIGURE4.8Classificationschemeforthecharacteristicsofpolymermolecules.同质异构立体异构几何异构全同立构间同立构不同立构独立体贯穿结构第32页，课件共53页，创作于2023年2月4.9ThermoplasticandThermosettingPolymersThermoplasts

(orthermoplasticpolymers):Apolymericmaterialthatsoftenswhenheatedandhardensuponcooling.Whileinthesoftenedstate,articlesmaybeformedbymoldingorextrusion.processesarereversibleandmayberepeated.Mostlinearpolymersandthosehavingsomebranchedstructureswithflexiblechainsarethermoplastic.热塑性和热固性聚合物可逆的第33页，课件共53页，创作于2023年2月thermosets(orthermosettingpolymers)Apolymericmaterialthat,oncehavingcured(orhardened)byachemicalreaction,willnotsoftenormeltwhensubsequentlyheated.热固性塑料Thermosetpolymersaregenerallyharderandstrongerthanthermoplastics,andhavebetterdimensionalstability.Mostofthecrosslinkedandnetworkpolymers,arethermosetting.whichincludevulcanizedrubbers,epoxies,andphenolicandsomepolyesterresins,硫化橡胶环氧类酚类聚酯树脂第34页，课件共53页，创作于2023年2月4.10CopolymersCopolymer：Apolymerthatconsistsoftwoormoredissimilarmerunitsincombinationalongitsmolecularchains.FIGURE4.9Schematicrepresentationsof(a)random,(b)alternating,(c)block,and(d)graftcopolymers.Thetwodifferentmertypesaredesignatedbyblackandcoloredcircles.共聚物第35页，课件共53页，创作于2023年2月Randomcopolymer.Apolymerinwhichtwodifferentmerunitsarerandomlydistributedalongthemolecularchain.Alternatingcopolymer.Acopolymerinwhichtwodifferentmerunitsalternatepositionsalongthemolecularchain.随机共聚物交替共聚物第36页，课件共53页，创作于2023年2月Blockcopolymer.Alinearcopolymerinwhichidenticalmerunitsareclusteredinblocksalongthemolecularchain.Graftcopolymer.Acopolymerwhereinhomopolymersidebranchesofonemertypearegraftedtohomopolymermainchainsofadifferentmer.块交替共聚物接枝共聚物均聚物第37页，课件共53页，创作于2023年2月Table4.5ChemicalRepeatUnitsThatAreEmployedinCopolymerRubbers丙烯腈苯乙烯丁二烯氯丁二烯独立橡胶异丁烯二甲基硅氧烷第38页，课件共53页，创作于2023年2月4.11PolymerCrystallinityThecrystallinestatemayexistinpolymericmaterials.theatomicarrangementswillbemorecomplex.PolymerCrystallinity:Forpolymers,thestatewhereinaperiodicandrepeatingatomicarrangementisachievedbymolecularchainalignment.Crystalstructuresmaybespecifiedintermsofunitcells,quitecomplex.第39页，课件共53页，创作于2023年2月FIGURE4.10Arrangementofmolecularchainsinaunitcellforpolyethylene.unitcell:polyethylenethechainmoleculesalsoextendbeyondtheunitcell第40页，课件共53页，创作于2023年2月polymermoleculespartiallycrystalline(orsemicrystalline)Astheirsizeandoftencomplexitycrystallineregionsdispersedwithintheremainingamorphousmaterial.polymerdegreeofcrystallinityFromcompletelyamorphoustoalmostentirelycrystalline(95%)metalAlmostalwaysentirelycrystallineceramicseithertotallycrystallineortotallynoncrystalline.第41页，课件共53页，创作于2023年2月degreeofcrystallinity结晶度(4.10)wheres

isthedensityofaspecimenforwhichthepercentcrystallinityistobedetermined,a

isthedensityofthetotallyamorphouspolymer,andc

isthedensityoftheperfectlycrystallinepolymer.Thevaluesofa

andc

mustbemeasuredbyotherexperimentalmeans.degreeofcrystallinitydependsonrateofcoolingandchainconfigurationmeltingtemperaturehighlyrandomandentangledintheviscousliquid,sufficienttimeforchainstomoveandalignthemselves.第42页，课件共53页，创作于2023年2月Themolecularchemistryaswellaschainconfigurationinfluencecrystallizecomplexmerstructuresisnotfavoredcrystallizationisnoteasilypreventedinchemicallysimplepolymersevenforveryrapidcoolingrates.linearpolymers,crystallizationiseasilyaccomplishedbranchedpolymersneverarehighlycrystalline;Mostnetworkandcrosslinkedpolymersarealmosttotallyamorphous第43页，课件共53页，创作于2023年2月themoreirregularandrandomthemerarrangementsthegreateristhetendencyforthedevelopmentofnoncrystallinity.thedegreeofcrystallinityinfluencethephysicalpropertiesofpolymeric

Crystallinepolymersstrongerandmoreresistanttodissolutionandsofteningbyheatafewcrosslinkedpolymersarepartiallycrystalline.Withregardtostereoisomers,atacticpolymersaredifficulttocrystallize;however,isotacticandsyndiotacticpolymerscrystallizemuchmoreeasily*不同立构全同和间同立构第44页，课件共53页，创作于2023年2月4.12PolymerCrystalsbrieflydiscusssomeofthemodelsofmolecularchainsinpolymercrystals.FIGURE4.11Fringed-micellemodelofasemicrystallinepolymershowingbothcrystallineandamorphousregions.fringed-micellemodelasemicrystallinepolymerconsistsofsmallcrystal