Presentation on theme: "Anionic Synthesis of Liquid Polydienes and Their Applications"— Presentation transcript:
1 Anionic Synthesis of Liquid Polydienes and Their Applications Taejun Yoo* and Steven HenningOctober 14, 2009
2 Contents Anionic synthesis of liquid polydienes MicrostructureMacrostructureFunctionalizationStructure and propertiesApplications
3 Additives for rubber products Liquid polydieneLow molecular weight homopolymers or copolymers containing unsaturated carbon-carbon double bondsCuring by sulfur or peroxidesLiquid polydieneElastomerMolecular weight1,000-10,000100,000-1,000,000Physical stateViscous liquidSolidProcessingLow shearHigh shearPolymerization typeBatch or semi batchBatch or continuousModificationEasyRelatively harderCatalyst cost on productCriticalNegligibleApplicationAdditives for rubber productsMain rubber products
4 Why anionic polymerization? A variety of different liquid polymers ! MicrostructurePolymer composition (styrene, butadiene, isoprene)Mode of addition (1,4- and 1,2- vinyl or 3,4-vinyl)Monomer sequence distribution (random, tapered or block)Cyclic structure (batch vs. semi batch)MacrostructureMolecular weight and distributionMolecular geometry (linear and branched)FunctionalizationIn chainChain end: mono and difunctional (telechelic)A variety of different liquid polymers !
8 Counter ion and initiator concentration effect Lithium catalystsoluble in hydrocarbon solventsthe lowest 1,2-vinyl contentgood low temperature propertiesCatalystCis-1,4Trans-1,41,2Lithium355213Sodium102565Potassium154045Rubidium73162Cesium659Initiator Concentration (M)1.4-Cis (%)1,4-Trans (%)3,4-Vinyl (%)*PI6.12x10-2741881.0x10-3781751.0x10-484110.8x10-5973PB5x10-153475x10-290105x10-3937* 1,2-vinyl for polybutadiene
9 Polar additive and Temperature effect Free ionsaggregatedContact ion pairPolar solventPresence of Lewis base (alkali metal alkoxides) in HC solventMonodendate vs. BidendateTemperatureT.A. Antkowiak, A.E. Oberster, A.F. Halasa, and D.P. Tate JPS, Part A-1 Vol. 10, 1319 (1972)Polybutadiene with the highest 1,2-vinyl can be prepared in polar solvent at lower reaction temperature
10 Comonomer effect (random copolymerization) Adding polar additivesMaintaining the concentration of comonomer with a lower monomerreactivity ratio high during the copolymerization.Effect of styrene content on 1,2-vinyl formation in styrene-butadiene copolymerizationThe presence of styrene in copolymerization results in less 1,2-vinyl content than BD homopolymerization due to steric effect between allylic chain end and styrene unit.
11 Cyclization of polybutadiene High 1,2-vinylLewis baseReaction temperatureMonomer starving conditionBatch vs. ContinuousMonomer feed rateG. Quack and L. J. Fetters, Macromolecules, 11, 369 (1978).Cyclization is favorable in monomer starved reaction conditionCyclization consumes 1,2-vinyl
12 Cyclization of polybutadiene (continuous system) Cyclization reaction increases aspolar additive amount increases (higher 1,2-vinyl)reaction temperature increases (Ea cyclization>Ea propagation)
13 Cyclization of polybutadiene Total 1,2-vinylCyclic vinyl7618267729Stiff structure increases TgLogh ~ (T-Tg)-1Cyclic vinyl has more impact on the physical properties than 1,2-vinyl
14 Macrostructure Molecular weight (gram of monomer/moles of initiator) Molecular weight distribution (Ki >Kp, Xw/Xn=1+1/Xn)Branched structure (linking reaction and transmetallation)
15 Chain transfer reaction Ea chain transfer > Ea propagationthermodynamic controlkinetic controlNot applicable for functionalized polymerCost reduction of liquid polymer production
16 Chain transfer reaction Mn calculated: 6,830Mn measured : 6,120 PI: 1.57Mn calculated: 17,750Mn measured : 1,830 PI: 3.54Chain transfer reaction in lithium initiated anionic polymerization increases assize of counter ion increases (Li < Na <K )polar additive amount increases (Li)reaction temperature increases (Ea chain transfer >Ea propagation)monomer feed rate decreasesandchain transfer reaction is maximized in pure toluene
17 Branched polymer [h]b < [h]l # of branchLength of branchMW of backboneType of branch (star, graft and hyper branched)Reduction in melt and solution viscositiesProcessing benefits, applications
18 Branched polymers by linking reactions ChlorosilaneSiCl4 + 4 PLi SiP4 + 4LiClDivinylbenzeneDVB core*** = reactive chain end+Epoxy and silanol compoundsPLi +P-OHOHOHOHOHOHOHOHQuirk and Zhou US patent 7,235,615
19 Functionalization Chain end functionalization Post polymerization modification(Functional groups are randomly distributed on polymer backbone)
20 Chain end functionalization Functional agentProtected functional initiator or agenta- or w-functionalized polymer by deprotectionDifunctional initiator(HTPB)(CTPB)
21 Post polymerization modification Hydrogenation (thermal stability and copolymer)EpoxidationMaleinization1,2 > 1,41,4 > 1,21,4 > 1,2EsterificationAddition of acryl groupImidization
23 Molecular weight effect Properties that depend on chain endsProperties that depend on entanglementEntanglementIntermolecular interaction Number of end groupsMwMnMelt viscosityh=KMwaIzod impact resistanceTensile strengthFlexural modulusTg and Tm
24 J. T. Gruver and G. Kraus, J. Polym. Sci. Part A, 2, 797 (1964) ViscosityMacrostructural (MW) effectMcrh0=KMwPP=1P=3.4Newtonian RegionLow MWHigh MWLog shear rate ()Log ha123.Broad MWDShear thinningJ. T. Gruver and G. Kraus, J. Polym. Sci. Part A, 2, 797 (1964)Random coilsOriented coilsMcrPolybutadiene: 6,000Polyisoprene: 10,000
25 Viscosity Microstructural effect Zero shear viscosity data (Brookfield) as a function of both molecular weight and microstructure using a series of commercially available liquid polydiene grades ( low vinyl polybutadiene, high vinyl polybutadiene, poly(butadiene-co-styrene).Viscosity of liquid polydiene is dependant on MW as well as microstructure:high vinyl polybutadienes > SBR copolymers > low vinyl polybutadienes
26 ViscosityFunctional group effect on chain end functionalized PB
27 Glass transition temperature Tg = Tg() - (A/Mn)Tg as a function of vinyl content and molecular weight for a series of commercially available liquid polybutadienes.Tg as a function of comonomer content for a series of butadiene-isoprene copolymers.
28 Glass transition temperature Functional group effectTg as a function of oxiran content for a series epoxidized liquid polybutadienes.
29 Molecular weight dependency of crosslinking rate of polyisoprene Microstructure (1,2- vs. 1,4)MacrostructureSulfur crosslinkingMolecular weight dependency of crosslinking rate of polyisopreneMc of diene elastomers: ~ 12,000 g/molLiquid polydienes do not form elastically effective crosslinksMizuho Maeda, RubberChem 2006
30 Applications Functional additives Low viscosity (processing) Similar chemical properties of elastomers (vulcanization)Outstanding properties (High thermal stability, good moisture and chemical resistance, good adhesive characteristics and excellent electrical properties)
31 Unfunctionalized liquid polydienes Processing aidsLow viscosity, non-toxic, low volatility and no bleeding (miscible with rubbers and non-extractable)Coagents1,2-polybutadiene for peroxide cure of elastomersWire and cable applications (better heat aging, fluid resistance and electrical properties)Engineering rubber products (belts, hoses, gaskets and rollers)Coating and potting agentsAutoxidation with baking or metallic driers (high level of unsaturation)Tire applicationHVPB and SBR: wet tractionLVPB: wear, low temperature properties
33 SummaryThe microstructure and macrostructure affect the Tg and bulk viscosity of final diene resin products.Lithium-based anionic polymerization provides liquid polydienes with a variety of microstructure and macrostructure including functionalization.The unique characteristics of liquid polydiene products has led to their utility in a wide variety of markets and applications such as functional additives for rubber and other thermosets, modification of thermoplastics, adhesives, and coatings.
35 Adhesion Potential - Metal 5 phr coagentLVPB-MAHVPB-MAEPDM, Peroxide curePB-MA adhesion promoters increase adhesive bond strength
36 Thermoplastic polyurethanes HTPB / Diisocyanate / Diol chain extenderPU harddomainselastomericsoft segmentMelt FlowT < TsofteningT > TsofteningVulcanizateAdhering a Urethane component to a Rubber Compound substrateDiene-segments interpenetrate and co-cure with rubber compoundUrethane segments bond to similar structure in PUFunctional Additive to a traditional Rubber Compoundvaried loading increases impact on physical propertiesimpart modulus while minimizing hysteresis (vs. TPE)realize advantages from phase structure at higher loading
37 Intercalated nanocomposite Exfoliated nanocomposite PolymerLayered clay+Intercalated nanocompositeExfoliated nanocompositeAn organophilic clay can be produced from a normally hydrophilic clay by ion exchange with an organic cation such as an alkylammonium ion. For example, in montmorillonite, the sodium ions in the clay can be exchanged for an amino acid such as 12-aminododecanoic acid (ADA):Na+-CLAY + HO2C-R-NH3+Cl- .HO2C-R-NH3+-CLAY + NaClMechanical and thermal propertiesPermeabilityFlame retardanceUV resistance