Lecture2 - Polymeric Materials Structure-Property Behavior...

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Unformatted text preview: Polymeric Materials Structure-Property Behavior Dr. Anthony Brennan University of Florida Department of Materials Science & Department Engineering Engineering EMA 6165 Polymer Physics – AB Brennan EMA 1 Agenda • • • • • • Overview of Plastics General Classifications Structure/Property Relationships Plastics Processing Plastics Industry Experimenting with Plastics EMA 6165 Polymer Physics – AB Brennan EMA 2 Polymer Structure -Property Behavior • chain chain thermodynamics thermodynamics • chain dimensions • chain environment • chain topography • mechanical mechanical behavior behavior EMA 6165 Polymer Physics – AB Brennan EMA 3 (A.U.) Stress (A.U.) Stress - Strain Response D B C A Strain • A: Modulus-chain A: entanglements, bond rotation rotation • B: Yielding-chain B: disentanglement, volume expansion volume • C: Strain HardeningC: chain viscous motion, chain alignment chain • D: Failure-chain bond D: breakage, reduction in molar mass molar EMA 6165 Polymer Physics – AB Brennan EMA 4 Stress - Strain Response (A.U.) Stress (A.U.) • • A B • C • D A: High frequency (τ << t), Low temperature (T<<Tg,Tm), high crystallinity crystallinity B: Decreasing frequency, (τ ~t) (T~Tg, T<Tm) ~t) C: Decreasing frequency C: (τ >t), decreasing crystallinity, (T>Tg, T<Tm) crystallinity, D: Low frequency (τ >>t), high temperature (T>>Tg, T~Tm), low crystallinity T~Tm), Strain EMA 6165 Polymer Physics – AB Brennan EMA 5 Stress Strain Behavior - Comparison • Note Scales • Note Differences σ = ETensile ε E = 2 (1 + υ ) G E = 3 (1 − 2υ ) B σ yield = 0.028 ETensile dapted from Polymer Processing, TA Osswald, Hanser, 1998. EMA 6165 Polymer Physics – AB Brennan EMA 6 Stress Strain Behavior - Elastomers • NR _ Natural NR Rubber Rubber • SBR- Styrene SBRButadiene Rubber Rubber dapted from Polymer Processing, TA Osswald, Hanser, 1998. EMA 6165 Polymer Physics – AB Brennan EMA 7 Exp’l vs Theoretical Stress Strain (Rubber) (Rubber) Exp’l Ecomposite = ∑ ϕ i Ei ROM dapted from Polymer Processing, TA Osswald, Hanser, 1998. EMA 6165 Polymer Physics – AB Brennan EMA 8 Chain Energy (Thermodynamics) HEAT H - bonding COOL ∆ G = ∆Η − Τ∆ S ∆Η EMA 6165 Polymer Physics – AB Brennan EMA 9 Chain Thermodynamics Order of Thermodynamic Transitions Chain Dimensions Characterization Methods EMA 6165 Polymer Physics – AB Brennan EMA 10 Polymer Structure -Property Behavior Thermodynamics • Glass transition (Tg) – solid to liquid – second order second transition transition – modulus decreases modulus by 2 to 3 orders of magnitude magnitude – elongation increases – volume expansion volume rate increases (CTE) rate – ~2/3 Tm • Melting transition Melting (Tm) (Tm) – – – solid to liquid first order transition modulus decreases modulus by 2 to 3 orders of magnitude magnitude – volume expansion volume discontinuous discontinuous EMA 6165 Polymer Physics – AB Brennan EMA 11 Polymer Structure -Property Behavior Chain Dimensions • conformation – spatial arrangement – changes with rotation around bonds • configuration – bonding arrangement – changes only through bond breakage • aspect ratio (L/D) for PE (100kg/mol) – 60,000 EMA 6165 Polymer Physics – AB Brennan EMA 12 Polymer Structure -Property Behavior Chain Dimensions • Dependent upon – composition – configuration – molar mass – temperature – pressure • Controls – viscosity – Tg – modulus – elongation – solubility – processability – stability EMA 6165 Polymer Physics – AB Brennan EMA 13 Polymer Structure -Property Behavior Chain Dimensions - Measurement • Absolute Methods – Mw • Solution light Solution scattering scattering – Mn • Membrane Membrane Osmometry Osmometry • Freezing Pt Freezing depression depression • Boiling Pt. elevation • Vapor phase Vapor osmometry, Ebulliometry, Cryosocopy Cryosocopy – Mz • ultracentrifugation • Relative Methods – – – GPC Viscosity Fractionation End group analysis EMA 6165 Polymer Physics – AB Brennan EMA 14 Polymer Structure -Property Behavior Chain Dimensions • Viscosity (solution) – hydrodynamic hydrodynamic volume volume – relative – inherent – intrinsic (Mv) – Mark-Houwink • Viscosity (melt) – similar • Gel Permeation Gel Chromatography (GPC) (GPC) – hydrodynamic hydrodynamic volume volume – size exclusion – universal calibration – Mn (number average) – Mw (weight average) – Mz (z-average) EMA 6165 Polymer Physics – AB Brennan EMA 15 Polymer Structure -Property Behavior Chain Dimensions – Gel Permeation Chromatography Σc ΣNM Mn = = Σc/M ΣN Σ cM ΣNM2 Mw = = Σc ΣNM 2 3 Σ cM ΣNM MZ = = 2 Σ cM ΣNM EMA 6165 Polymer Physics – AB Brennan EMA detector 16 Viscosity • Viscosity Viscosity (solution) (solution) η−η0 – hydrodynamic [η]=lim c →0 hydrodynamic cη 0 volume volume a – relative 0 V – inherent η = KM – intrinsic (Mv) – Mark-Houwink M N < MV < MW < M Z EMA 6165 Polymer Physics – AB Brennan EMA 17 Polymer Structure -Property Behavior Chain Dimensions • Polydispersity – Mechanical Mechanical Properties Properties – Processing – Stability Mw PDI = Mn σ = Mn EMA 6165 Polymer Physics – AB Brennan EMA Mw −1 Mn 18 Polymer Structure -Property Behavior Chain Environment • Temperature – size increases with increasing temperature – viscosity decreases with increasing viscosity temperature temperature – governed by WLF equation η (T1, t ) − 17.4 (T − Tg ) ∝ η (T2 , t ) 51.6 + (T − Tg ) EMA 6165 Polymer Physics – AB Brennan EMA 19 Polymer Structure -Property Behavior Degree of Polymerization SchultzFlory 1 1 1 − ni = Xi Xi i −1 Lower case x refers to mole fraction, upper case X is DP Schultz 2 1 + ni = 2 ( xn − 1) ( xn − 1) 4i EMA 6165 Polymer Physics – AB Brennan EMA −i 20 Polymer Structure -Property Behavior Chain Environment -Plasticization • Low Molar Mass Molecules – decreases Tg – decreases viscosity – governed by Flory-Huggins governed Relationship Relationship – “like dissolves like” – requires a negative ∆ H requires – reduces melting point – eg. PVC • vinyl siding versus raincoats EMA 6165 Polymer Physics – AB Brennan EMA 21 Thermal Transitions EMA 6165 Polymer Physics – AB Brennan EMA 22 Dynamic DSC of PET – Perkin Elmer Dynamic DSC 7 DSC EMA 6165 Polymer Physics – AB Brennan EMA 23 DSC/Complex Viscosity – Influence of Cooling DSC/Complex Rate Rate http://scholar.lib.vt.edu/theses/available/etd-0898-145634/unrestricted/CH5.PDF Hydroxybenzoic Acid-Terephthalic Acid-Hydroquinone EMA 6165 Polymer Physics – AB Brennan EMA 24 Summary • Thermodynamics govern the properties Thermodynamics of polymers of • Composition and topography Composition determine structure and thus properties such as Tg, Tm, Modulus, Viscosity, etc. Viscosity, • Properties vary logarithmically with Properties time and linearly with temperature EMA 6165 Polymer Physics – AB Brennan EMA 25 References • Fundamental Principles of Polymeric Materials, 2nd Fundamental Edition, Stephen L. Rosen, Wiley Interscience (1993) ISBN 0-471-57525-9 ISBN • Introduction to Physical Polymer Science, 4th Edition, Lesley H. Sperling, Wiley Interscience (2006) ISBN 13 978-0-471-70606-9 ISBN • Polymer Science and Technology, Joel R. Fried, Polymer Prentice Hall PTR (1995) ISBN Prentice EMA 6165 Polymer Physics – AB Brennan EMA 26 ...
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This note was uploaded on 07/20/2011 for the course EMA 6165 taught by Professor Brennan during the Spring '08 term at University of Florida.

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