Plastics General Survey writted by michigen molecular insitute英文版.pdf

2012 Wiley-VCH Verlag GmbH&Co.KGaA,WeinheimArticle No:a20_543Plastics,General SurveyHANS-GEORGELIAS,MichiganMolecular Institute,Midland,MI 48 640,United States1.Introduction.361.1.Polymers.371.1.1.Fundamental Terms.371.1.2.Nomenclature.371.2.Plastics.381.2.1.Fundamental Terms.381.2.2.Designations.401.3.History of Plastics.451.4.Economic Importance.472.Molecular Structure of Polymers.482.1.Constitution.482.1.1.Homopolymers.482.1.2.Copolymers.512.1.3.Branched Polymers.512.1.4.Ordered Chain Assemblies.532.1.5.Unordered Networks.542.2.Molar Masses and Molar MassDistributions.552.2.1.Molar Mass Average.552.2.2.Determination of Molar Mass.552.2.3.Molar Mass Distributions.572.2.4.Determination of Molar Mass Distributions.592.3.Configurations.592.4.Conformations.612.4.1.Microconformations.612.4.2.Conformations in Ideal Polymer Crystals.622.4.3.Conformations in Polymer Solutions.632.4.4.Unperturbed Coils.642.4.5.Perturbed Coils.652.4.6.Wormlike Chains.653.Polymer Manufacture.653.1.Raw Materials.653.1.1.Wood.653.1.2.Coal.663.1.3.Natural Gas.663.1.4.Petroleum.663.1.5.Other Natural Raw Materials.663.2.Polymer Syntheses:Overview.673.2.1.Classifications.673.2.2.Functionality.693.2.3.Cyclopolymerizations.693.3.Chain Polymerizations andPolyeliminations.703.3.1.Thermodynamics.703.3.2.Free-Radical Polymerizations.713.3.3.Anionic Polymerizations.753.3.4.Cationic Polymerizations.753.3.5.Ziegler Natta Polymerizations.763.3.6.Copolymerizations.773.4.Polycondensations and Polyadditions.793.4.1.Bifunctional Polycondensations.793.4.2.Multifunctional Polycondensations.803.4.3.Polyaddition.823.5.Polymer Reactions.823.5.1.Polymer Transformations.823.5.2.Block and Graft Formations.833.5.3.Cross-Linking Reactions.833.5.4.Degradation Reactions.834.Plastics Manufacture.844.1.Homogenization and Compounding.844.2.Additives.844.2.1.Overview.844.2.2.Chemofunctional Additives.854.2.3.Processing Aids.864.2.4.Extending and Reinforcing Fillers.864.2.5.Plasticizers.874.2.6.Colorants.874.2.7.Blowing Agents.884.3.Processing.885.Supermolecular Structures.895.1.Noncrystalline States.895.1.1.Structure.895.1.2.Orientation.895.2.Polymer Crystals.905.2.1.Introduction.905.2.2.Crystal Structures.915.2.3.Crystallinity.925.2.4.Morphology.925.3.Mesophases.945.3.1.Introduction.945.3.2.Types of Liquid Crystals.955.3.3.Mesogens.965.3.4.Lyotropic Liquid Crystalline Polymers.985.3.5.Thermotropic Liquid Crystal Polymers.995.3.6.Block Copolymers.995.3.7.Ionomers.1015.4.Gels.1025.5.Polymer Surfaces.1025.5.1.Structure.1025.5.2.Interfacial Tension.1025.5.3.Adsorption.1036.Thermal Properties.103DOI:10.1002/14356007.a20_5436.1.Molecular Motion.1036.1.1.Thermal Expansion.1036.1.2.Heat Capacity.1046.1.3.Heat Conductivity.1046.2.Thermal Transitions and Relaxations.1046.2.1.Overview.1046.2.2.Crystallization.1066.2.3.Melting.1076.2.4.Liquid Crystal Transitions.1086.2.5.Glass Transitions.1096.2.6.Other Transitions and Relaxations.1106.2.7.Technical Methods.1106.3.Transport.1106.3.1.Self-Diffusion.1106.3.2.Permeation1117.Rheological Properties.1137.1.Introduction.1137.2.Shear Viscosities at Rest.1137.2.1.Fundamentals.1137.2.2.Molar Mass Dependence.1137.2.3.Concentrated Solutions.1147.3.Non-Newtonian Shear Viscosities.1147.3.1.Overview.1147.3.2.Flow Curves.1157.3.3.Melt Viscosities.1167.4.Extensional Viscosities.1177.4.1.Fundamentals.1177.4.2.Melts.1187.4.3.Solutions.1188.Mechanical Properties.1188.1.Introduction.1188.1.1.Deformation of Polymers.1188.1.2.Tensile Tests.1198.1.3.Moduli and Poisson Ratios.1218.2.Energy Elasticity.1218.2.1.Theoretical Moduli.1218.2.2.Real Moduli.1228.2.3.Temperature Dependence.1238.3.Entropy Elasticity.1248.4.Viscoelasticity.1248.4.1.Fundamentals.1248.4.2.Time Temperature Superposition.1258.5.Dynamic Behavior.1268.5.1.Fundamentals.1268.5.2.Molecular Interpretations.1268.6.Fracture.1288.6.1.Overview.1288.6.2.Theoretical Fracture Strength.1288.6.3.Real Fracture Strength.1298.6.4.Impact Resistance.1318.6.5.Stress Cracking.1318.6.6.Fatigue.1318.7.Surface Mechanics.1328.7.1.Hardness.1328.7.2.Friction.1328.7.3.Abrasion and Wear.1329.Electric Properties.1339.1.Dielectric Properties.1339.1.1.Relative Permittivity.1339.1.2.Dielectric Loss.1339.1.3.Dielectric Strength and Tracking Resistance 1349.1.4.Electrostatic Charging.1359.2.Electrical Conductivity.1359.3.Photoconductivity.13610.Optical Properties.13711.Polymer Composites.13811.1.Introduction.13811.1.1.Overview.13811.1.2.Mixture Rules.13911.2.Filled Polymers.14111.2.1.Microcomposites.14111.2.2.Molecular Composites.14311.2.3.Macrocomposites.14311.3.Homogeneous Blends.14411.3.1.Thermodynamics.14411.3.2.Plastification.14511.3.3.Rubber Blends.14611.3.4.Plastic Blends.14711.4.Heterogeneous Blends.14711.4.1.Compatible Polymers.14711.4.2.Blend Formation.14711.4.3.Toughened Plastics.14811.4.4.Thermoplastic Elastomers.14811.5.Expanded Plastics.15012.Waste Disposal.151References.1531.IntroductionPlastics are commercially used materials thatare based on polymers or prepolymers.Thename plastics refers to their easy processibilityand shaping(Greek:plastein to form,toshape).Plasticsandpolymersarenotsynonyms.Poly-mersorprepolymersarerawmaterialsforplastics;they become plastics only after physical com-pounding and/or chemical hardening.The samepolymersmaybeusednotasplasticsbutasfibers,inpaints,orinotherapplications.Otherpolymersmay be utilized as fibers,elastomers,thickeners,ion-exchange resins,etc.,but not as plastics.36Plastics,General SurveyVol.281.1.Polymers1.1.1.Fundamental Terms 15,814Polymers are chemical substances(chemicalcompounds)composed of polymer molecules.The term polymer refers to molecules composedof many units(Greek:poly many,meros parts).Polymer molecules may thus consist ofmanyatoms,usuallyathousandormore,therebyhavinghighmolarmasses(molecularweights).Benzene can,for example,be poly-merized from three acetylene molecules andwas originally called a polymer.What is nowcalled a polymer consists of molecules withhundreds and thousands of such units;it wastherefore termed high polymer in the olderliterature.The term polymer carries with it the connota-tion of molecules composed of many equalmers,such as the ethylene units in polyethyl-ene,R0(CH2CH2)nR00.The number n of mers in apolymer molecule is called the degree of poly-merizationX.Thereare,however,manypolymermolecules(especially biopolymer molecules)with very different types of mers per molecule,such as protein molecules H(NH CHR CO)nOH with up to 16 different R substituentsin irregular sequence.A less constraining andmore general term for polymer molecule is thusmacromolecule.No sharp dividing line withrespect to the number of units per moleculeexists,however,between macromolecules andlow molar mass compounds(micromolecules).Macromolecules constitute the simplest indi-vidual chemical constituents of a polymer.Amacromolecule may exist as an individual entity(in linear and branched polymers)or may bethought of as the primary molecule before chem-ical cross-linking.Macromoleculesexistinnature;examplesarenucleic acids,proteins,polysaccharides,poly-prenes,and lignins.Some of these naturallyoccurring polymers are used by man withoutfurther chemical transformation(e.g.,cellulosefor paper and cardboard).The chemical transfor-mationofnaturalpolymerswithretentionoftheirchainstructuresleadstosemisyntheticmaterials,for example,cellulose acetates from cellulose.Chainsofothernaturalpolymersarecross-linkedbefore commercial use.Examples are the hard-ening of casein(a protein)by formaldehyde togalalith(plastic)or the vulcanization of cis-1,4-polyisoprene(natural rubber)to an elastomer.Most polymers are,however,synthesizedchemically from molecules with low molarmasses,the so-called monomers.Examples arethe preparations of polyethylene from ethylene,poly(vinylchloride)fromvinyl chloride,nylon 6frome-caprolactam,ornylon66fromadipicacidand hexamethylenediamine.Some industrialpolymers result from the chemical conversionof other synthetic polymers,for example,poly(vinyl alcohol)from poly(vinyl acetate).1.1.2.Nomenclature 1,5,15The nomenclature of individual polymers andplastics is as confusing as their classification ac-cording to properties.Various systems of nomen-clatureareusedsimultaneously,oftenbythesameauthor.Abbreviations and acronyms abound,sometimes with different meanings for the sameletter combinations and other times without ex-planation.In addition,about 25 000 trade namesare used worldwide for plastics,fibers,and elas-tomers.Furthermore,a polymer from a certaincompany may come in many different gradesdepending on the processibility and application,sometimes up to 100 per polymer type.Some ofthese grades may even bear different trade namesfor various applications.On the other hand,thesame trade name is occasionally used for plasticsbased on very different polymer types.An exam-ple is Bexloy of Du Pont,which may be anamorphous polyamide(Bexloy C),a high-impactpolyester(BexloyJ),anionomer(BexloyW),orathermoplastic elastomer(Bexloy V).The following nomenclature systems arecommonly used for polymers:Long-Known Natural Polymers Often haveTrivial Names.Examples are cellulose,thepolymeric sugar(-ose)of the plant cell;casein,the most important protein of milk and cheese(Latin:caseus cheese);nucleic acids,theacids found in the cell nucleus;catalase,a cata-lyzing enzyme.Synthetic Polymers are Often Named afterTheir Monomers.Polymers of ethylene thuslead to polyethylene,those of styrene to polysty-rene,those of vinyl chloride to poly(vinyl chlo-Vol.28Plastics,General Survey37ride),and those of a lactam to a polylactam.Thispolymonomernomenclaturehasthedisadvan-tage that the constitution of monomeric units ofthe polymer molecules is not identical with theconstitution of the monomers themselves.Forexample,thepolymerizationofethylene,CH2CH2,leadsto?(CH2 CH2)n?,asaturat-ed compound and thus a polyalkane,not anunsaturatedeneasthenamepolyethylenemaysuggest.The polymerization of lactams(cyclicamides)does not give macromolecules with in-tact lactam rings in the polymer chains but givesopen-chain polyamides,etc.This polymonomerscheme is also ambiguous if a monomer can leadtomorethan onecharacteristicunitinapolymer.An example is acrolein,CH2CH(CHO),whichcan polymerize via the ethylenic double bond togive?CH2 CH(CHO)n?,via the aldehydegroup to?O CH(CHCH2)n,or via both togive six-membered rings in polymer chains.For trade purposes,certain polymer namesmay denote not only homopolymers but alsocopolymers,contrary to what the chemicalnames imply.For example,the copolymers ofethylene with up to 10%butene-1,hexene-1,oroctene-1 are known as linear low-density poly-ethylenes(LLDPEs).Thecommonlyusedchem-ical names of plastics thus often do not indicatethe true chemical structure of the monomericunits of the polymers on which they are based.Polymers are Often Named after Character-istic Groups in Their Repeating Units.Polya-mides are thus polymers with amide groups NHCO in their repeating units;for example?NHCO(CH2)5n?polyamide6 nylon6 poly(e-caprolactam).Other examples arepolyesters with ester groups COO or poly-urethanes with urethane groups NH CO O in the chains.A disadvantage is that thisnaming scheme is identical with that of organicchemistry where a polyisocyanate denotes a lowmolar mass compound with more than one iso-cyanate group per molecule e.g.,C6H3(NCO)3.Amacromolecularpolyisocyanatewouldthusbea polymer with many intact isocyanate groupsper chain,for example,poly(vinyl isocyanate)?CH2 CH(NCO)n?.The poly(isocyanate)sof polymer chemistry,on the other hand,possesspolymerized isocyanate groups as,for example,in?(NR CO)n?.Such compounds are unfor-tunately also often called polyisocyanates.IUPACNames.IUPACrecommendstheuseof constitutive names,similar to those used ininorganic and organic chemistry.The nomencla-ture of low and high molar mass inorganicmolecules follows the additivity principle;thoseof low molar mass organic molecules the substi-tution principle.The nomenclature of organicmacromolecules is a hybrid of both principles:the smallest repeating units are thought of asbiradicalsaccordingtothesubstitutionprinciple;then their names are added according to theadditivity principle,put in parentheses,and pre-fixed with poly.Names of repeating units arewrittenwithoutspacesbetweenwords.Thepoly-mer?O CH2n?fromformaldehyde,H2CO,is thus called poly(oxymethylene).Thepolycondensation of ethylene glycol HO CH2 CH2 OHwithterephthalicacidHOOC (p-C6H4)COOH leads to a polymer?O CH2CH2 O OC(p-C6H4)COn?withthe systematic name poly(oxyethyleneoxyter-ephthaloyl).The trivial names of this polymerare polyethyleneterephthalate,and poly(ethyleneglycol terephthalate),poly(ethylene terephthal-ate).It is also known as saturated polyester(although it is only one of the many possiblesaturated polyesters),as PET(an acronym)orPETP(an abbreviation)in the plastics literature,by the acronym PES in the fiber literature,and asPETE for recycling purposes.IUPAC names are rarely used in the plasticsliterature.They are however important for sys-tematicsearchesinChemicalAbstractsandotherliterature services.1.2.Plastics1.2.1.Fundamental Terms 1639,4153Early plastics resembled natural resins.Thesenatural resins are organic solids that break with aconchoidal fracture in contrast to the planarsurfaces created upon the fracture of crystallinematerials or the drawn-out zones formed uponthe breaking of gums and waxes.Natural resinrefers mainly to oleoresins from tree sap but isalso used for shellac,insect exudations,andmineral hydrocarbons(!Resins,Natural).Early plastics were thus sometimes calledsynthetic resins.The word resin is today occa-sionally used for any organic chemical com-38Plastics,General SurveyVol.28pound with medium to high molar mass thatserves as a raw material for plastics(for a defini-tion of the term resin according to current standards,see!Resins,Synthetic).Resin is not tobe confused with rosin,which refers to mixturesof C20fused-ring monocarboxylic acids such aspineoil,talloil,andkauriresin.Rosinisthemaincomponent of naval stores(!Resins,Natural).Plastics are usually divided into two groupsaccording to their hardening processes.Thosethat yield solid materials by simple cooling of apolymer melt(a physical process)and softenwhile being heated are called thermoplastics.Thermosets,on the other hand,harden throughchemical cross-linking reactions between poly-mer molecules;when heated,they do not softenbutdecomposechemically(!Thermosets).Theshaping of a thermoplastic is thus a reversibleprocess:the same material can be melted andprocessedagain.Athermosetcannotberemeltedand reshaped;its formation is irreversible.Thermoplasticsare normally composed offairly high molar mass molecules because manyphysical properties effectively become molarmass independent only above a certain molarmass.Examples are melting temperatures andthe moduli of elasticity.Other properties,how-ever,increase with increasing molar mass(e.g.,melt viscosities).Thermosetsare usually generated from fair-ly low molar mass polymers,called oligomers