A 1. The Polymer Parameters. Webinar on Accelerated Testing of Adhesives and Polymers- Part One. Strain Energy Total. Time Domain Experiments

Transcription

1 A Webinar on Accelerated estin of Adhesives and Polymers- Part One Sponsored by ASC Presented by Dr. homas C. Ward Virinia ech A he Polymer Parameters Chemical Composition Molecular Weiht Distribution Stereochemistry opoloy Morpholoy Additives All are heteroeneous, and have temperature and rate sensitive behavior A 2 he Frequency and ime Domains Dampin Dampin or Modulus or Modulus ime Domain Eperiments ransient ests est Geometry What Chanes Representation Stress-Strain ensile/ Shear Everythin Modulus Stress Relaation ensile / Shear Stress E / G Creep ensile / Shear Strain D / J A 3 A 4 Viscoelastic Effects in Stress-Strain ests Strain Enery otal Enery / Volume Rate of Deformation A 5 A 6

2 A 2 Relaation ime Concept Which Viscoelastic Element is affected by strain rate?? E η ime Domain Eperiments ransient ests est Geometry What Chanes Representation Stress-Strain ensile/ Shear Everythin Modulus η Pa s τ s E Pa Stress Relaation ensile / Shear Stress E / G Creep ensile / Shear Strain D / J A 7 A 8 Stress Relaation Eperiment Stress Relaation Eperiments F ( t / A0 σ ( t E ( t l / l ε 0 0 A 9 A.V. obolsky, Properties and Structure of Polymers, Wiley, 960 A 0 S-R Master Curves at 75 C Generic Shape S-R Master Curves A A 2

3 A 3 ime Domain Eperiments ensile Creep Eperiment ransient ests est Geometry What Chanes Representation Stress-Strain ensile/ Shear Everythin Modulus Stress Relaation ensile / Shear Stress E / G Creep ensile / Shear Strain D / J A 0 A 0 D (t A 3 A 4 Creep and Creep Recovery Oriinal Data, Shear Creep Isotherms for PI Newtonian (nonrecoverable flow time D(t Creep recovery time A 5 A 6 Creep Master Curve for 00 C he Frequency and ime Domains Dampin Dampin or Modulus or Modulus A 7 A 8

4 A 4 DMA Fitures for Mechanical estin Viscoelastic Response in DMA Mechanical Oscillations Storae Modulus E Loss Modulus E an δ E / E f(,ω A 9 A 20 Storae and Loss Modulus PMMA A 2 σ stress field E electric field A 22 Shear Loss Modulus of PMMA Frequency Effects in DMA What happens when the frequency increases? A 23 A 24

5 A 5 he Relaations Uniformly Shift to Hiher emperatures Frequency Shiftin of an δ ω i * A 25 A 26 Dampin Lo ω Rate - emperature Relationships for Polymers β α ω 3 ω 2 Arrhenius β ma, β ma,2 α ma, α ma,2 wo Relaation Mechanisms in Frequency/ime Space A 27 ω ω Ln ω WLF.. Voel. 2 H R 2 A 28 Viscous Flow Activation Eneries Polymer Activation Enery kj / mol Evaluation of Dependence of Characteristic Viscoelastic imes, Polyethylene Cis polybutadiene Polystyrene Poly (α-methyl Styrene ~ Mechanism i From rheoloy eperiments at different temperatures A 29 A 30

6 A 6 Generic Shapes - DMA Master Curves Rane of Shear Rates for Full Melt Characterization Master Where do these Master Curves come from?? A 3 A 32 Full Rane of Viscoelastic Const. Linear, Hih MW, Amorphous Polymer Relaation ime Concept Which Viscoelastic Element is affected by & strain rate?? E η η Pa s τ s E Pa How does shift this response A 33 A 34 Viscosity and (- Oriin of WLF Equation Lo η (Poise Doolittle viscosity equation η ( Lo Lo η ( η ( A ep B f ( τ ( Lo a τ ( B f ( f ( f ( f ( + α ( A 35 η Pa s τ s E Pa A 36

7 A 7 ime and emperature Connection Lo a Lo a C C + 2 ( ( WLF equation o C ( r o C 2 + ( r Lo a Constants in the WLF Equation C ( C + ( 2 C C ( ref + ( * * * ω τ η 2 2 * * * ω 2 τ η L o a L o L o L o C (B / 2.303f( 7, C 2 (f( / α 52, B ~ So α , f( ref A 37 A 38 WLF Plot with R Master Curve Questions Where does time-temperature superposition come from? What are reduced variables? When can we believe the predictions? What are the limits to this scheme? A 39 A 40 Master Curve Construction Short time rane eperiments epanded to many decades Narrow frequency data rane epanded from ~static to iahertz vibrations Isothermal and other intensive variable scalin factors (shift factors PC S-R Isotherms A 4 A 42

8 A 8 PC S-R Master Curve at ref Shift Factors of PC Master Curve A 43 A 44 Master Curve Construction Shift Factor Empirical Plot Master Curve at ref A 45 A 46 Calculatin Master Curve Relocation Shift Factor for New emperature Horizonal Shifts are Applied to Each Point to Move from ref Master Curve at 298 K A 47 A 48

9 A 9 Shiftin Master Curve away from ref Relocated Master Curve at New emperature Master Curve at 230 K ref ref A 49 A 50 Creep of PC / Graphite 2 Ply Composite Shift Factors PC / Graphite 48 C 00 C Encyclopedia of Polymer Sci, McGraw Hill, Creep A 5 Creep in out- of- plane bendin eometry A 52 Storae Modulus Master Curve for Epoy Shift Factors for E (ω of Epoy A 53 A 54

10 A 0 Master Curve Checklist VE Shift Factors are Shared within a Mechanism Overlap of the slopes of the individual isovariable curves Quality of the shift factor plots One underlyin mechanism over the rane of the intensive variable acceleratin the process A 55 A 56 Master Curves of Shear Storae Modulus of wo Epoies Master Curves of Yield Stress of wo Epoies Untouhened ouhened Huan,Y and Kinloch, A.J., J. Adhesion, 4, 5-22,(993 A 57 Kinloch A 58 Common Shift Factors for DMA and Yieldin, wo Epoies Spectrum of Relaation imes Derived from S-R Data k j i Huan,Y and Kinloch, A.J., J. Adhesion, 4, 5-22,(993 A 59 A 60

11 A Carbon/Epoy 2 Ply Laminate Master Curve Carbon/Epoy 2 Ply Laminate Master Curve A 6 A 62 Carbon/Epoy 2 Ply Laminate Shift Factor Plot Webinar Part wo opics Brief review What is the rane of linear viscoelastic and adhesive properties covered by accelerated testin. Can ultimate properties like lap shear strenths of bonds be accelerated? Are there other variables that may be used to drive acceleration of property chanes? What are doubly reduced variables? A 63 A 64 Question and Answer Session A 65