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Dynamic mechanical analysis(DMA)

Manar Alfhad, profile picture
Manar Alfhad

Dynamic Mechanical Analysis (DMA) allows relating a material's molecular structure, processing conditions, and product properties by applying an oscillating force to a material and measuring its response. DMA can measure storage and loss moduli and viscosity to characterize glass transitions, relaxations, and other molecular motions as a function of temperature, time, or frequency. Multiple sample geometries enable testing materials in various forms under tension, compression, flexure, and shear modes.

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Dynamic Mechanical Analysis (DMA) Basics and Beyond Dr. Lin Li Thermal Analysis PerkinElmer Inc. April 2000 ε∗ ω= Σ(Δεβ/1+ιωτβ)
molecular structure processing conditions product properties Material Behavior The DMA lets you relate:
Force Motor Temperature Enclosure LVDT Core Rod Interchangeable Furnace Heat Sink/Cooling System Measuring System How the DMA works: DMA Structure in general Coil Magnet  Constant inputs and outputs function as in the TMA  A sine wave current is added to the force coil  The resultant sine wave voltage of the LVDT is compared to the sine wave force  The amplitude of the LVDT is related to the storage modulus, E' via the spring constant, k.  The phase lag, δ, is related to the E" via the damping constant, D.
Outstanding Flexibility 1: Multiple Geometries Extension Compressive Shear Flexure Parallel Plate Cup & Plate Tray & Plate Sintered Plates 3 pt. Bending 4 pt. Bending ASTM Flexure Dual Cantilever Single Cantilever Extension Shear Sandwich Coaxial Cylinder Paper FoldCup & Plate
Why? 3 4 5 6 7 8 9 10 11 12 LogE’ 1 mm 20 mm 20 mm 5 mm
Stress Causes Strain... Lo L Cauchy or Engineering Strain L-Lo = ΔL Henchy or True Strain εεεε = ln (ΔL/Lo) εεεε = ΔL/Lo Kinetic Theory of Rubber Strain εεεε = 1/3{L/Lo-(Lo/L)2} Kirchhoff Strain Murnaghan Strain εεεε = 1/2{ (L/Lo)2-1} εεεε = 1/2{1-(Lo/L)2} The different definitions of tensile strain become equivalent at very small deformations.
The Elastic Limit: Hooke’s Law = Strain increases with increasing Stress σσσσ εεεε slope = k
Real vs... Hookean Stress- Strain Curves 4.0 8.0 12.0 16.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Thu Apr 14 16:34:38 1994 Slope 359171.32 Pa/% Stress(Pax107) KPMStrain (%) Slope 1642965.02 Pa/% Curve 1: DMACreep Recoveryin Parallel Plate File info: Drssr90R.2Thu Apr 14 15:16:52 1994 Sample Height:3.359 mmCreep Stress: 2600.0mN Recovery Stress: 1.0mN Dresser 90 Durameter PERKIN-ELMER 7 Series ThermalAnalysis System TEMP1: 20.0 C TIME1: 5.3 min Limiting Modulus Real behavior Hookean Behavior σσσσ εεεε
The Viscous Limit: Newtonian Behavior σσσσ γγγγ .The speed at whichthe fluidflows throughthe holes(the strainrate) increases with stress!!! slope = η
Viscosity Effects • Newtonian behavior is linear and the viscosity is independent of rate. • Pseudoplastic fluids get thinner as shear increases. • Dilatant Fluids increase their viscosity as shear rates increase. • Plastic Fluids have a yield point with pseudoplastic behavior. • Thixotrophic and rheopectic fluids show viscosity-time nonlinear behavior. For example, the former shear thin and then reform its gel structure. γγγγ ττττ .
Polymers are Non-Newtonian Fluids!!! • At low shear rates, the viscosity is controlled by MW. The material shows Newtonian behavior • Viscosity shows a linear dependence on rate above the ηo region. • At high rates, the material can no longer shear thin and a second plateau is reached. ηηηη γγγγ . Zero Shear Plateau ~ ηηηηo Infinite Shear Plateau ~ ηηηη ∞ Linear Dependence on Rate Log Log
Analyzing a Stress-Strain Curve σσσσ εεεε linear region nonlinear region failure (εΒ, σΒ) yield point (εy, σy) Young’s modulus (E) E d d L L = = σ ε σ ε The area under the curve to this line is the energy needed to break the material
Under Continuos Loads: Creep Recovery • Applying a constant load for long times and removing it from a sample. • Allows one to see the distortion under constant load and also how well it recovers.
Creep is a fundamental engineering test. • Creep is used as a basic test for design. • By looking at both the creep and recovery parts of the curve, we can begin to examine how polymers relax. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 -250.0 0.0 250.0 500.0 750.0 1000.0 1250.0 1500.0 1750.0 2000.0 2250.0 2500.0 Thu Apr 28 20:32:20 1994 Strain(%) DMA7 APPLICATIONS LABTime (minutes) # 1PTFE - CREEP/RELAXATION AT -5C:cr_ptfe-5 Strain (%) Curve 1: DMACreep Recoveryin 3 Point Bending File info: cr_ptfe-5 Wed Jun 29 15:31:18 1988 Sample Height:3.300mmCreep Stress: 1.50e+06Pa Recovery Stress: 6.25e+02Pa PTFE - CREEP/RELAXATION PERKIN-ELMER 7 Series ThermalAnalysis System TEMP1: -15.0 C TIME1: 7.0 min Force(mN) # 2 Force (mN)
Dynamic Stress F (static) Force Time Force (dynamic) Phase angle = δ= δ= δ= δ Stress Time material response Strain =yo/y Amplitude = k Stress =FA
Why? Let’s bounce a ball. E” ~ energy loss in internal motion E’ ~ elastic response
All this is calculated from δδδδ and k: • From k, we calculate E’ (storage modulus) • From δ, we calculate E’’ (loss modulus) • then: Tan δ = E”/E’ E* = E’ + iE” = SQRT(E’2 + E”2) G* = E*/2(1+ν) η = 3G*/ω
To apply this to materials... σσσσοοοο εεεε οοοο Dynamic Stress Scan Since each part of the ramp has a sine wave stress associated with it, we get: tan δ E*, E’, E” η for each data point!! εεεεσσσσ
For example, DSS Curves 0.2 0.4 0.6 0.8 1.0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Thu Apr 28 20:28:00 1994 Viscosity(Pasx107) KPMStrain (%) # 1 Dresser 70 Durameter:Drssr70Dss Complex Viscosity (Pas x 10 7 ) Curve 1: DMAAC Stress Scanin Parallel Plate File info: Drssr70DssThu Apr 14 16:44:41 1994 Frequency: 1.00 Hz Stress Rate: 250.0mN/min Tension: 110.000%Dresser 70 Durameter PERKIN-ELMER 7 Series ThermalAnalysis System TEMP1: 10.5 C TIME1: -1.2 min # 2 Dresser 90 Durameter:Drssr90dss Complex Viscosity (Pa s x 10 7 ) 0.2 0.4 0.6 0.8 1.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Thu Apr 14 16:59:58 1994 DynamicStress(Pax106) KPMStrain (%) Slope 1274361.04 Pa/% Curve 1: DMAAC Stress Scanin Parallel Plate File info: Drssr70DssThu Apr 14 16:44:41 1994 Frequency: 1.00 Hz Stress Rate: 250.0mN/min Tension: 110.000%Dresser 70 Durameter PERKIN-ELMER 7 Series ThermalAnalysis System TEMP1: 10.5 C TIME1: -1.2 min Slope 6297938.16 Pa/%
Now, let’s induce temperature as a variable. • We can heat the material under minimal load at a calibrated rate. • This allows the material to change with temperature. • These changes can be described in terms of free volume or relaxation times. FreeVolume
Thermomechanical Analysis as a starting Point. 50.0 75.0 100.0 125.0 150.0 175.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 Sun Nov 26 20:10:47 1995 Penetration(mm) Temperature (C) # 1 Tg by flex:Tgflex Penetration (mm) Onset 106.92 C Curve 1: TMAin Penetration File info: Tgflex Tue Oct 10 16:21:08 1995 DC Force: 100.0 mNSample Height:4.180 mm Tg by flex PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: 30.0 C TIME1: 0.0 min RATE1: 10.0 C/min TEMP2: 150.0 C
TMA - It’s all free volume. 70.0 80.0 90.0 100.0 110.0 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.05 2.10 Sun Nov 26 20:08:09 1995 Expansion(mm) Temperature ( C) # 1 cte :cte Expansion (mm) Onset 105.53 C Cx 2.948 x 10 -5 / C Cx 2.195 x 10 -2 / C Curve 1: TMA in Expansion File info: cte Tue Oct 10 16:46:51 1995 DC Force: 10.0 mNSample Height: 1.742 mm cte PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: 30.0 C TIME1: 0.0 min RATE1: 10.0 C/min TEMP2: 150.0 C Tg Free Volume Occupied Volume
And it’s not just Tg. 0.0 50.0 100.0 150.0 200.0 250.0 11.98 12.00 12.02 12.04 12.06 12.08 12.10 12.12 12.14 12.16 12.18 12.20 Tue Feb 21 12:29:39 1995 Extension(mm) He/20psi/H/Chiller Tech.Support Lab/K.MenardTemperature ( C) # 1 FIBER E:menard005 Extension (mm) Curve 1: TMA in Extension File info: menard005 Tue Feb 21 12:28:20 1995 DC Force: 0.0 mNSample Height: 12.017 mm FIBER E PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: 30.0 C TIME1: 0.0 min RATE1: 5.0 C/min TEMP2: 250.0 C (the traditional way to do heat set)
Time Temperature Scans at a Fixed Frequency • hold frequency constant and vary temperature or time at temperature • allows detection of transitions in material • allows one to study cures • most sensitive method for finding Tg • can also get changes in dimension (TMA) while collecting DMA data • Best probe of polymer relaxations as function of temperature
Idealized Multi-Event DMA Scan E’ Temperature Tm - melting (1) Rubbery Plateau (2) Tg - glass transition (3) αααα Β (4)Β (4)Β (4)Β (4) (6)(6)(6)(6) (5)(5)(5)(5) (4)(4)(4)(4) (3)(3)(3)(3) (2)(2)(2)(2) (1)(1)(1)(1) local bend side gradual large chain motions and groups main scale slippage stretch chain chain γ (5)γ (5)γ (5)γ (5)(6)(6)(6)(6)
In more detail... 5 6 7 8 9 10 Glassy Rubbery Cross-linked Temperature A B C D E Deformation Molecular Motion Unstrained State Strained State E D C B A Hookean Behavior Second Transition Primary Transition Highly Visco Elastic Flow (rubbery)(gamma) (beta) (alpha) Bend & Stretch Bonds Side Groups Main Chain Gradual Main Chain Large Scale Mobility Chain Slipping Increasing F F Secondary Dispersion Localized Motion R. Seymour, 1971 (melt) 3 4 11 LogModulus(Pa) Crystal-crystal slip Crystalline Polymer
Common changes show as: E’ tan δδδδ MW MWD Crosslink Density Crystallinity
Tg are easily seen, as in PET Film 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 -100.0 0.0 100.0 200.0 300.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Sun Nov 26 21:02:11 1995 Modulus(Pax10 9 ) # 2 Storage Modulus (Pa x 10 9 ) Onset 83.29 C tan Temperature ( C) # 1 pet film:demofilm tan Onset 107.82 C Onset 79.35 C Curve 1: DMA Temp/Time Scan in Extension File info: demofilm Wed Oct 11 17:06:48 1995 Frequency: 1.00 Hz Amplitude: 21.949u Tension: 110.000%pet film PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -100.0 C TIME1: 0.0 min RATE1: 10.0 C/min TEMP2: 250.0 C
or in PP fishing line. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 -100.0 -50.0 0.0 50.0 100.0 150.0 200.0 0.0 0.5 1.0 1.5 2.0 2.5 Sun Nov 26 21:24:35 1995 Modulus(Pax10 9 ) # 2 Storage Modulus (Pa x 10 9 ) tan(x10 -1 ) Temperature ( C) # 1 fishing line:1116942 tan (x 10 -1 ) Curve 1: DMA Temp/Time Scan in Extension File info: 1116942 Wed Nov 16 13:20:39 1994 Frequency: 1.00 Hz Dynamic Stress: 200.0mN Static Stress: 300.0mNfishing line PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -130.0 C TIME1: 0.0 min RATE1: 10.0 C/min TEMP2: 270.0 C Sample prep can be minimal if only temperatures are needed.
Transitions are clearly seen in highly crosslinked samples 0.0 50.0 100.0 150.0 200.0 250.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Thu Jun 23 13:45:10 1994 Modulus(Pax10 9 ) heavy xlink kmTemperature ( C) # 1 epoxyresin:afriedli.1 Storage Modulus (Pa x 10 9 ) Curve 1: DMA Temp/Time Scan in 3 Point Bending File info: afriedli.1 Thu Feb 17 12:14:11 1994 Frequency: 1.00 Hz Dynamic Stress: 800.0mN Static Stress: 1000.0mNepoxyresin PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: 30.0 C TIME1: 0.0 min RATE1: 10.0 C/min TEMP2: 250.0 C tan # 2 tan This Tg is undetectable in the DSC !!!!!!
as well as in blends. -150.0 -100.0 -50.0 0.0 50.0 100.0 150.0 200.0 10 6 10 7 10 8 10 9 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Sun Nov 26 20:54:43 1995 Modulus(Pa) K66:22T914 APPLICATION LABORATORYTemperature ( C) # 1 STYRENE BUTADIENE RUBBER:sbr14 Storage Modulus (Pa) L Curve 1: DMA Temp/Time Scan in 3 Point Bending File info: sbr14 Thu Feb 15 10:45:19 1990 Frequency: 1.00 Hz Dynamic Stress: 2.00e+05Pa Tension: 110.000%STYRENE BUTADIENE RUBBE PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -180.0 C TIME1: 0.0 min RATE1: 5.0 C/min TEMP2: 250.0 C tan # 2 tan
It’s not always so simple: For example, crystal-crystals slips can cause α∗ transitions -150.0 -100.0 -50.0 0.0 50.0 100.0 0.5 1.0 1.5 2.0 2.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Sun Nov 26 20:58:36 1995 Modulus(Pax10 9 ) AMP Flame Retardant Polypropylene KPMTemperature ( C) # 1 LeBrun samples:AMPfrPP.1 Storage Modulus (Pa x 10 9 ) Curve 1: DMA Temp/Time Scan in 3 Point Bending File info: AMPfrPP.1 Wed Oct 27 13:49:06 1993 Frequency: 1.00 Hz Dynamic Stress: 950.0mN Static Stress: 1000.0mNLeBrun samples PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -160.0 C TIME1: 0.0 min RATE1: 5.0 C/min TEMP2: 300.0 C tan(x10 -1 ) # 2 tan (x 10 -1 ) Tg or Alpha Tα *
Higher Order Transitions affect toughness 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 -150.0 -100.0 -50.0 0.0 50.0 100.0 150.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Sat Oct 15 14:32:54 1994 LeBrun samples tan(x10 -1 ) Modulus(Pax10 9 ) AMP good part 20% glass filled Nylon 6/6 KPMTemperature ( C) Curve 1: DMA Temp/Time Scan in 3 Point Bending File info: AMP66gp.1 Tue Oct 26 16:05:29 1993 Frequency: 1.00 Hz Dynamic Stress: 190.0mN Static Stress: 200.0mNLeBrun samples PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -160.0 C TIME1: 0.0 min RATE1: 5.0 C/min TEMP2: 300.0 C β Transitions Tg Good Impact Strength Poor Impact was good if Tg/Tβ was 3 or less.
...and also define operating range. -100.0 0.0 100.0 200.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Sun Nov 26 20:13:53 1995 Modulus(Pax10 10 ) PE DMA7 R&D LABTemperature ( C) # 1 EPOXY PC BOARD AT 7 Hz:gamma_1 Storage Modulus (Pa x 10 10 ) Curve 1: DMA Temp/Time Scan in 3 Point Bending File info: gamma_1 Thu Jun 30 02:17:24 1988 Frequency: 7.00 Hz Dynamic Stress: 1.86e+06Pa Static Stress: 1.86e+06PaEPOXY PC BOARD AT 7 Hz PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -180.0 C TIME1: 0.0 min RATE1: 10.0 C/min TEMP2: 300.0 C tan(x10 -1 ) -> # 2 tan (x 10 -1 ) Beta Tg Operating range
It can get complex... -200.0 -150.0 -100.0 -50.0 0.0 50.0 100.0 150.0 200.0 5 6 7 8 9 10 9 2 3 4 5 6 7 8 9 10 10 2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Sun Nov 26 20:59:14 1995 Modulus(Pa) iNITIAL RUN B.CasselTemperature ( C) # 1 NYLON MONOFILAMENT:T2n4ptg Storage Modulus (Pa) L Curve 1: DMA Temp/Time Scan in Extension File info: T2n4ptg Fri Jan 18 18:14:51 1991 Frequency: 1.00 Hz Dynamic Stress: 1.00e+07Pa Static Stress: 1.05e+07PaNYLON MONOFILAMENT PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -180.0 C TIME1: 0.0 min RATE1: 4.0 C/min TEMP2: 0.0 C TIME2: 0.0 min RATE2: 2.0 C/min TEMP3: 150.0 C tan(x10 -1 ) # 2 tan (x 10 -1 ) Tg or Tα Stress ReliefTβ Tγ
Curing of Thermosets • can be studied at constant temperature or by a temperature ramp • can get minimum viscosity, gelation point (time), vitrification point, and activation energies from DMA curve • can adapt instrument to do simultaneous DEA- DMA to follow cure to completion • cure studies are not limited to polymeric systems but include food products like cakes and cookies
Analysis of a Cure by DMA 50.0 70.0 90.0 110.0 130.0 150.0 100 101 102 103 104 105 106 107 108 E’ E” Modulus Τ η∗ E’-E” Crossover ~ gelation point vitrification point Minimum Viscosity (time, length, temperature ) 106 Pa ~ Solidity Melting Curing
QC can often be done by simply fingerprinting the resin. 25.0 50.0 75.0 100.0 125.0 150.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 η∗ note the different slopes and the different curve shapes good bad
Postcure studies allow process optimization: Property Postcure time vs... Tg and E’ 0 20 40 60 80 100 120 140 160 180 200 0 2 4 6 8 TIME IN HOURS E'@50 (E9 PA ) E' ONSET TAN D PE A K TAN D ONSET tanδδδδ Temperature 1.0 0.5 0.0 0 hours 1 hour 2 hours 3 - 8 hours 150 200175
Frequency Scans • hold temperature constant and vary frequency • allows one to look at trends in material • can estimate changes in MW and MWD • looks at both tack-like and peel-like behavior • can use data for Time Temperature Superposition to extend frequency range or predict age life.
Frequency determines the type of response 10 -2 10 -1 10 0 10 1 10 3 10 4 10 5 10 6 10 7 10 3 10 4 10 5 10 6 10 7 Modulus(Pa) Frequency (Hz) Viscosity(Pa s) More Liquid like More solid like Flow dominates Elastic dominates
For example, two hot melt adhesives... Τ 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 -4 10 -3 10 -2 10 -1 100 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 η∗ E’’ show affect of rate (peel vs.... tack) good bad
Creep can look at distortion under load, 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 -250.0 0.0 250.0 500.0 750.0 1000.0 1250.0 1500.0 1750.0 2000.0 2250.0 2500.0 Thu Apr 28 20:32:20 1994 Strain(%) DMA7 APPLICATIONS LABTime (minutes) # 1 PTFE - CREEP/RELAXATION AT -5C:cr_ptfe-5 Strain (%) Curve 1: DMA Creep Recovery in 3 Point Bending File info: cr_ptfe-5 Wed Jun 29 15:31:18 1988 Sample Height: 3.300 mm Creep Stress: 1.50e+06Pa Recovery Stress: 6.25e+02Pa PTFE - CREEP/RELAXATION PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -15.0 C TIME1: 7.0 min Force(mN) # 2 Force (mN)
cyclic application of loads, 6.0 Time in minutes %Strain 0.0 1.0 2.0 3.0 4.0 5.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 Good Bad Differences can be seen in good and bad samples and get more apparent with several cycles. Here the bad material is not flowing enough to fill the pores and form a mechanical bond.
and with varying temperatures. 0.0 25.0 50.0 75.0 100.0 125.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 -250.0 0.0 250.0 500.0 750.0 1000.0 1250.0 1500.0 1750.0 2000.0 2250.0 2500.0 2750.0 Sun Nov 26 20:41:31 1995 Strain(%) KPMTime (minutes) # 1 Dresser 90 D:DR90D2.1 Strain (%) Curve 1: DMA Creep Recovery in Parallel Plate File info: DR90D2.1 Fri Jul 23 12:23:50 1993 Sample Height: 2.836 mm Creep Stress: 2600.0mN Recovery Stress: 1.0mN Dresser 90 D PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -50.0 C TIME1: 11.0 min RATE1: 10.0 C/min TEMP2: 0.0 C TIME2: 15.0 min RATE2: 10.0 C/min TEMP3: 50.0 C TIME3: 15.0 min RATE3: 10.0 C/min TEMP4: 100.0 C TIME4: 75.0 min # 3 T P ( C) Force(mN) # 2 Force (mN)
And you can tabulate this stuff graphically... • The time to 1/e percent recovery is the relaxation. • This is a measure of how quickly a material recovers. (There is a lot more to this subject.)1/T ττττ
Stress Relaxation • By exploiting the special controls of the DMA-7e, we can run stress relaxation experiments. • These look at how the force change for a sample kept at a set distortion as a function of time or temperature. Time Position Experiment Starts σσσσ Sample would be distorted to y length and held.
Don’t forget the DMA-7e also does Stress Scans • can do either static or dynamic ramps • static scans calculate Young’s modulus and stress-strain curves • dynamic scans give material response to increasing oscillatory forces: – get complex viscosity and modulus for each data point – can look at changes in elasticity (E’) and lag (phase angle) with increasing stress • Both methods are fast tests for QC applications after the material has been fully characterized by other DMA modes.
Specialized Testing is Possible... The design of the DMA-7e makes it possible to do: Time-Temperature Superposition (TTS) DEA/DMA Tests in Solution Microscopic DMA Photo DMA DMA-?
PP fibers in solvent 20.0 40.0 60.0 80.0 100.0 0.0 25.0 50.0 75.0 100.0 125.0 150.0 175.0 200.0 ForceinmN Temperature in C xylene iso-octane air water
To Review, DMA ties together... molecular structure processing conditions product properties Molecular weight MW Distribution Chain Branching Cross linking Entanglements Phases Crystallinity Free Volume Localized motion Relaxation Mechanisms Stress Strain Temperature Heat History Frequency Pressure Heat set Material Behavior Dimensional Stability Impact properties Long term behavior Environmental resistance Temperature performance Adhesion Tack Peel
Conclusions • DMA allows you to preform a wide range of tests from sensitive probes of molecular structure to model studies. • the DMA-7e allows operation as six different instruments to maximize flexibility. • Data can be overlayed with DSC, TGA, TMA, and DTA for easier analysis.
References: Books • Menard, DMA: Introduction to the Technique, Its Applications and Theory, CRC Press, 1999. • Brostow et a., Failure of Plastics, Hanser, 1986. • Ferry, Viscoelastic Properties of Polymers, Wiley, 1980. • Gordon et al., Computer Programs for Rheologists, Hanser, 1995. • Gol'dman, Prediction of Deformation Properties of Polymeric and Composite Materials,, ACS, 1994. • Mascosko, Rheology, VCH, 1993. • Matsouka, Relaxation Phenomena in Polymers, Hanser, 1993. • McCrum et al, Anelastic and Dielectric Properties of Polymeric Solids, Dover, 1992 (reprint of 1967 edition). • Nielsen et al., Mechanical Properties of Polymers and Composites, Dekker, 1994. • Sperling, Introduction to Physical Polymer Science, Academic Press, 1994. • Ward et al., Introduction to Mechanical Properties of Solid Polymers, Wiley, 1993.

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Dynamic mechanical analysis(DMA)

  • 1. Dynamic Mechanical Analysis (DMA) Basics and Beyond Dr. Lin Li Thermal Analysis PerkinElmer Inc. April 2000 ε∗ ω= Σ(Δεβ/1+ιωτβ)
  • 2. molecular structure processing conditions product properties Material Behavior The DMA lets you relate:
  • 3. Force Motor Temperature Enclosure LVDT Core Rod Interchangeable Furnace Heat Sink/Cooling System Measuring System How the DMA works: DMA Structure in general Coil Magnet  Constant inputs and outputs function as in the TMA  A sine wave current is added to the force coil  The resultant sine wave voltage of the LVDT is compared to the sine wave force  The amplitude of the LVDT is related to the storage modulus, E' via the spring constant, k.  The phase lag, δ, is related to the E" via the damping constant, D.
  • 4. Outstanding Flexibility 1: Multiple Geometries Extension Compressive Shear Flexure Parallel Plate Cup & Plate Tray & Plate Sintered Plates 3 pt. Bending 4 pt. Bending ASTM Flexure Dual Cantilever Single Cantilever Extension Shear Sandwich Coaxial Cylinder Paper FoldCup & Plate
  • 6. Stress Causes Strain... Lo L Cauchy or Engineering Strain L-Lo = ΔL Henchy or True Strain εεεε = ln (ΔL/Lo) εεεε = ΔL/Lo Kinetic Theory of Rubber Strain εεεε = 1/3{L/Lo-(Lo/L)2} Kirchhoff Strain Murnaghan Strain εεεε = 1/2{ (L/Lo)2-1} εεεε = 1/2{1-(Lo/L)2} The different definitions of tensile strain become equivalent at very small deformations.
  • 7. The Elastic Limit: Hooke’s Law = Strain increases with increasing Stress σσσσ εεεε slope = k
  • 8. Real vs... Hookean Stress- Strain Curves 4.0 8.0 12.0 16.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Thu Apr 14 16:34:38 1994 Slope 359171.32 Pa/% Stress(Pax107) KPMStrain (%) Slope 1642965.02 Pa/% Curve 1: DMACreep Recoveryin Parallel Plate File info: Drssr90R.2Thu Apr 14 15:16:52 1994 Sample Height:3.359 mmCreep Stress: 2600.0mN Recovery Stress: 1.0mN Dresser 90 Durameter PERKIN-ELMER 7 Series ThermalAnalysis System TEMP1: 20.0 C TIME1: 5.3 min Limiting Modulus Real behavior Hookean Behavior σσσσ εεεε
  • 9. The Viscous Limit: Newtonian Behavior σσσσ γγγγ .The speed at whichthe fluidflows throughthe holes(the strainrate) increases with stress!!! slope = η
  • 10. Viscosity Effects • Newtonian behavior is linear and the viscosity is independent of rate. • Pseudoplastic fluids get thinner as shear increases. • Dilatant Fluids increase their viscosity as shear rates increase. • Plastic Fluids have a yield point with pseudoplastic behavior. • Thixotrophic and rheopectic fluids show viscosity-time nonlinear behavior. For example, the former shear thin and then reform its gel structure. γγγγ ττττ .
  • 11. Polymers are Non-Newtonian Fluids!!! • At low shear rates, the viscosity is controlled by MW. The material shows Newtonian behavior • Viscosity shows a linear dependence on rate above the ηo region. • At high rates, the material can no longer shear thin and a second plateau is reached. ηηηη γγγγ . Zero Shear Plateau ~ ηηηηo Infinite Shear Plateau ~ ηηηη ∞ Linear Dependence on Rate Log Log
  • 12. Analyzing a Stress-Strain Curve σσσσ εεεε linear region nonlinear region failure (εΒ, σΒ) yield point (εy, σy) Young’s modulus (E) E d d L L = = σ ε σ ε The area under the curve to this line is the energy needed to break the material
  • 13. Under Continuos Loads: Creep Recovery • Applying a constant load for long times and removing it from a sample. • Allows one to see the distortion under constant load and also how well it recovers.
  • 14. Creep is a fundamental engineering test. • Creep is used as a basic test for design. • By looking at both the creep and recovery parts of the curve, we can begin to examine how polymers relax. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 -250.0 0.0 250.0 500.0 750.0 1000.0 1250.0 1500.0 1750.0 2000.0 2250.0 2500.0 Thu Apr 28 20:32:20 1994 Strain(%) DMA7 APPLICATIONS LABTime (minutes) # 1PTFE - CREEP/RELAXATION AT -5C:cr_ptfe-5 Strain (%) Curve 1: DMACreep Recoveryin 3 Point Bending File info: cr_ptfe-5 Wed Jun 29 15:31:18 1988 Sample Height:3.300mmCreep Stress: 1.50e+06Pa Recovery Stress: 6.25e+02Pa PTFE - CREEP/RELAXATION PERKIN-ELMER 7 Series ThermalAnalysis System TEMP1: -15.0 C TIME1: 7.0 min Force(mN) # 2 Force (mN)
  • 15. Dynamic Stress F (static) Force Time Force (dynamic) Phase angle = δ= δ= δ= δ Stress Time material response Strain =yo/y Amplitude = k Stress =FA
  • 16. Why? Let’s bounce a ball. E” ~ energy loss in internal motion E’ ~ elastic response
  • 17. All this is calculated from δδδδ and k: • From k, we calculate E’ (storage modulus) • From δ, we calculate E’’ (loss modulus) • then: Tan δ = E”/E’ E* = E’ + iE” = SQRT(E’2 + E”2) G* = E*/2(1+ν) η = 3G*/ω
  • 18. To apply this to materials... σσσσοοοο εεεε οοοο Dynamic Stress Scan Since each part of the ramp has a sine wave stress associated with it, we get: tan δ E*, E’, E” η for each data point!! εεεεσσσσ
  • 19. For example, DSS Curves 0.2 0.4 0.6 0.8 1.0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Thu Apr 28 20:28:00 1994 Viscosity(Pasx107) KPMStrain (%) # 1 Dresser 70 Durameter:Drssr70Dss Complex Viscosity (Pas x 10 7 ) Curve 1: DMAAC Stress Scanin Parallel Plate File info: Drssr70DssThu Apr 14 16:44:41 1994 Frequency: 1.00 Hz Stress Rate: 250.0mN/min Tension: 110.000%Dresser 70 Durameter PERKIN-ELMER 7 Series ThermalAnalysis System TEMP1: 10.5 C TIME1: -1.2 min # 2 Dresser 90 Durameter:Drssr90dss Complex Viscosity (Pa s x 10 7 ) 0.2 0.4 0.6 0.8 1.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Thu Apr 14 16:59:58 1994 DynamicStress(Pax106) KPMStrain (%) Slope 1274361.04 Pa/% Curve 1: DMAAC Stress Scanin Parallel Plate File info: Drssr70DssThu Apr 14 16:44:41 1994 Frequency: 1.00 Hz Stress Rate: 250.0mN/min Tension: 110.000%Dresser 70 Durameter PERKIN-ELMER 7 Series ThermalAnalysis System TEMP1: 10.5 C TIME1: -1.2 min Slope 6297938.16 Pa/%
  • 20. Now, let’s induce temperature as a variable. • We can heat the material under minimal load at a calibrated rate. • This allows the material to change with temperature. • These changes can be described in terms of free volume or relaxation times. FreeVolume
  • 21. Thermomechanical Analysis as a starting Point. 50.0 75.0 100.0 125.0 150.0 175.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 Sun Nov 26 20:10:47 1995 Penetration(mm) Temperature (C) # 1 Tg by flex:Tgflex Penetration (mm) Onset 106.92 C Curve 1: TMAin Penetration File info: Tgflex Tue Oct 10 16:21:08 1995 DC Force: 100.0 mNSample Height:4.180 mm Tg by flex PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: 30.0 C TIME1: 0.0 min RATE1: 10.0 C/min TEMP2: 150.0 C
  • 22. TMA - It’s all free volume. 70.0 80.0 90.0 100.0 110.0 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.05 2.10 Sun Nov 26 20:08:09 1995 Expansion(mm) Temperature ( C) # 1 cte :cte Expansion (mm) Onset 105.53 C Cx 2.948 x 10 -5 / C Cx 2.195 x 10 -2 / C Curve 1: TMA in Expansion File info: cte Tue Oct 10 16:46:51 1995 DC Force: 10.0 mNSample Height: 1.742 mm cte PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: 30.0 C TIME1: 0.0 min RATE1: 10.0 C/min TEMP2: 150.0 C Tg Free Volume Occupied Volume
  • 23. And it’s not just Tg. 0.0 50.0 100.0 150.0 200.0 250.0 11.98 12.00 12.02 12.04 12.06 12.08 12.10 12.12 12.14 12.16 12.18 12.20 Tue Feb 21 12:29:39 1995 Extension(mm) He/20psi/H/Chiller Tech.Support Lab/K.MenardTemperature ( C) # 1 FIBER E:menard005 Extension (mm) Curve 1: TMA in Extension File info: menard005 Tue Feb 21 12:28:20 1995 DC Force: 0.0 mNSample Height: 12.017 mm FIBER E PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: 30.0 C TIME1: 0.0 min RATE1: 5.0 C/min TEMP2: 250.0 C (the traditional way to do heat set)
  • 24. Time Temperature Scans at a Fixed Frequency • hold frequency constant and vary temperature or time at temperature • allows detection of transitions in material • allows one to study cures • most sensitive method for finding Tg • can also get changes in dimension (TMA) while collecting DMA data • Best probe of polymer relaxations as function of temperature
  • 25. Idealized Multi-Event DMA Scan E’ Temperature Tm - melting (1) Rubbery Plateau (2) Tg - glass transition (3) αααα Β (4)Β (4)Β (4)Β (4) (6)(6)(6)(6) (5)(5)(5)(5) (4)(4)(4)(4) (3)(3)(3)(3) (2)(2)(2)(2) (1)(1)(1)(1) local bend side gradual large chain motions and groups main scale slippage stretch chain chain γ (5)γ (5)γ (5)γ (5)(6)(6)(6)(6)
  • 26. In more detail... 5 6 7 8 9 10 Glassy Rubbery Cross-linked Temperature A B C D E Deformation Molecular Motion Unstrained State Strained State E D C B A Hookean Behavior Second Transition Primary Transition Highly Visco Elastic Flow (rubbery)(gamma) (beta) (alpha) Bend & Stretch Bonds Side Groups Main Chain Gradual Main Chain Large Scale Mobility Chain Slipping Increasing F F Secondary Dispersion Localized Motion R. Seymour, 1971 (melt) 3 4 11 LogModulus(Pa) Crystal-crystal slip Crystalline Polymer
  • 27. Common changes show as: E’ tan δδδδ MW MWD Crosslink Density Crystallinity
  • 28. Tg are easily seen, as in PET Film 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 -100.0 0.0 100.0 200.0 300.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Sun Nov 26 21:02:11 1995 Modulus(Pax10 9 ) # 2 Storage Modulus (Pa x 10 9 ) Onset 83.29 C tan Temperature ( C) # 1 pet film:demofilm tan Onset 107.82 C Onset 79.35 C Curve 1: DMA Temp/Time Scan in Extension File info: demofilm Wed Oct 11 17:06:48 1995 Frequency: 1.00 Hz Amplitude: 21.949u Tension: 110.000%pet film PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -100.0 C TIME1: 0.0 min RATE1: 10.0 C/min TEMP2: 250.0 C
  • 29. or in PP fishing line. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 -100.0 -50.0 0.0 50.0 100.0 150.0 200.0 0.0 0.5 1.0 1.5 2.0 2.5 Sun Nov 26 21:24:35 1995 Modulus(Pax10 9 ) # 2 Storage Modulus (Pa x 10 9 ) tan(x10 -1 ) Temperature ( C) # 1 fishing line:1116942 tan (x 10 -1 ) Curve 1: DMA Temp/Time Scan in Extension File info: 1116942 Wed Nov 16 13:20:39 1994 Frequency: 1.00 Hz Dynamic Stress: 200.0mN Static Stress: 300.0mNfishing line PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -130.0 C TIME1: 0.0 min RATE1: 10.0 C/min TEMP2: 270.0 C Sample prep can be minimal if only temperatures are needed.
  • 30. Transitions are clearly seen in highly crosslinked samples 0.0 50.0 100.0 150.0 200.0 250.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Thu Jun 23 13:45:10 1994 Modulus(Pax10 9 ) heavy xlink kmTemperature ( C) # 1 epoxyresin:afriedli.1 Storage Modulus (Pa x 10 9 ) Curve 1: DMA Temp/Time Scan in 3 Point Bending File info: afriedli.1 Thu Feb 17 12:14:11 1994 Frequency: 1.00 Hz Dynamic Stress: 800.0mN Static Stress: 1000.0mNepoxyresin PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: 30.0 C TIME1: 0.0 min RATE1: 10.0 C/min TEMP2: 250.0 C tan # 2 tan This Tg is undetectable in the DSC !!!!!!
  • 31. as well as in blends. -150.0 -100.0 -50.0 0.0 50.0 100.0 150.0 200.0 10 6 10 7 10 8 10 9 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Sun Nov 26 20:54:43 1995 Modulus(Pa) K66:22T914 APPLICATION LABORATORYTemperature ( C) # 1 STYRENE BUTADIENE RUBBER:sbr14 Storage Modulus (Pa) L Curve 1: DMA Temp/Time Scan in 3 Point Bending File info: sbr14 Thu Feb 15 10:45:19 1990 Frequency: 1.00 Hz Dynamic Stress: 2.00e+05Pa Tension: 110.000%STYRENE BUTADIENE RUBBE PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -180.0 C TIME1: 0.0 min RATE1: 5.0 C/min TEMP2: 250.0 C tan # 2 tan
  • 32. It’s not always so simple: For example, crystal-crystals slips can cause α∗ transitions -150.0 -100.0 -50.0 0.0 50.0 100.0 0.5 1.0 1.5 2.0 2.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Sun Nov 26 20:58:36 1995 Modulus(Pax10 9 ) AMP Flame Retardant Polypropylene KPMTemperature ( C) # 1 LeBrun samples:AMPfrPP.1 Storage Modulus (Pa x 10 9 ) Curve 1: DMA Temp/Time Scan in 3 Point Bending File info: AMPfrPP.1 Wed Oct 27 13:49:06 1993 Frequency: 1.00 Hz Dynamic Stress: 950.0mN Static Stress: 1000.0mNLeBrun samples PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -160.0 C TIME1: 0.0 min RATE1: 5.0 C/min TEMP2: 300.0 C tan(x10 -1 ) # 2 tan (x 10 -1 ) Tg or Alpha Tα *
  • 33. Higher Order Transitions affect toughness 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 -150.0 -100.0 -50.0 0.0 50.0 100.0 150.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Sat Oct 15 14:32:54 1994 LeBrun samples tan(x10 -1 ) Modulus(Pax10 9 ) AMP good part 20% glass filled Nylon 6/6 KPMTemperature ( C) Curve 1: DMA Temp/Time Scan in 3 Point Bending File info: AMP66gp.1 Tue Oct 26 16:05:29 1993 Frequency: 1.00 Hz Dynamic Stress: 190.0mN Static Stress: 200.0mNLeBrun samples PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -160.0 C TIME1: 0.0 min RATE1: 5.0 C/min TEMP2: 300.0 C β Transitions Tg Good Impact Strength Poor Impact was good if Tg/Tβ was 3 or less.
  • 34. ...and also define operating range. -100.0 0.0 100.0 200.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Sun Nov 26 20:13:53 1995 Modulus(Pax10 10 ) PE DMA7 R&D LABTemperature ( C) # 1 EPOXY PC BOARD AT 7 Hz:gamma_1 Storage Modulus (Pa x 10 10 ) Curve 1: DMA Temp/Time Scan in 3 Point Bending File info: gamma_1 Thu Jun 30 02:17:24 1988 Frequency: 7.00 Hz Dynamic Stress: 1.86e+06Pa Static Stress: 1.86e+06PaEPOXY PC BOARD AT 7 Hz PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -180.0 C TIME1: 0.0 min RATE1: 10.0 C/min TEMP2: 300.0 C tan(x10 -1 ) -> # 2 tan (x 10 -1 ) Beta Tg Operating range
  • 35. It can get complex... -200.0 -150.0 -100.0 -50.0 0.0 50.0 100.0 150.0 200.0 5 6 7 8 9 10 9 2 3 4 5 6 7 8 9 10 10 2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Sun Nov 26 20:59:14 1995 Modulus(Pa) iNITIAL RUN B.CasselTemperature ( C) # 1 NYLON MONOFILAMENT:T2n4ptg Storage Modulus (Pa) L Curve 1: DMA Temp/Time Scan in Extension File info: T2n4ptg Fri Jan 18 18:14:51 1991 Frequency: 1.00 Hz Dynamic Stress: 1.00e+07Pa Static Stress: 1.05e+07PaNYLON MONOFILAMENT PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -180.0 C TIME1: 0.0 min RATE1: 4.0 C/min TEMP2: 0.0 C TIME2: 0.0 min RATE2: 2.0 C/min TEMP3: 150.0 C tan(x10 -1 ) # 2 tan (x 10 -1 ) Tg or Tα Stress ReliefTβ Tγ
  • 36. Curing of Thermosets • can be studied at constant temperature or by a temperature ramp • can get minimum viscosity, gelation point (time), vitrification point, and activation energies from DMA curve • can adapt instrument to do simultaneous DEA- DMA to follow cure to completion • cure studies are not limited to polymeric systems but include food products like cakes and cookies
  • 37. Analysis of a Cure by DMA 50.0 70.0 90.0 110.0 130.0 150.0 100 101 102 103 104 105 106 107 108 E’ E” Modulus Τ η∗ E’-E” Crossover ~ gelation point vitrification point Minimum Viscosity (time, length, temperature ) 106 Pa ~ Solidity Melting Curing
  • 38. QC can often be done by simply fingerprinting the resin. 25.0 50.0 75.0 100.0 125.0 150.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 η∗ note the different slopes and the different curve shapes good bad
  • 39. Postcure studies allow process optimization: Property Postcure time vs... Tg and E’ 0 20 40 60 80 100 120 140 160 180 200 0 2 4 6 8 TIME IN HOURS E'@50 (E9 PA ) E' ONSET TAN D PE A K TAN D ONSET tanδδδδ Temperature 1.0 0.5 0.0 0 hours 1 hour 2 hours 3 - 8 hours 150 200175
  • 40. Frequency Scans • hold temperature constant and vary frequency • allows one to look at trends in material • can estimate changes in MW and MWD • looks at both tack-like and peel-like behavior • can use data for Time Temperature Superposition to extend frequency range or predict age life.
  • 41. Frequency determines the type of response 10 -2 10 -1 10 0 10 1 10 3 10 4 10 5 10 6 10 7 10 3 10 4 10 5 10 6 10 7 Modulus(Pa) Frequency (Hz) Viscosity(Pa s) More Liquid like More solid like Flow dominates Elastic dominates
  • 42. For example, two hot melt adhesives... Τ 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 -4 10 -3 10 -2 10 -1 100 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 η∗ E’’ show affect of rate (peel vs.... tack) good bad
  • 43. Creep can look at distortion under load, 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 -250.0 0.0 250.0 500.0 750.0 1000.0 1250.0 1500.0 1750.0 2000.0 2250.0 2500.0 Thu Apr 28 20:32:20 1994 Strain(%) DMA7 APPLICATIONS LABTime (minutes) # 1 PTFE - CREEP/RELAXATION AT -5C:cr_ptfe-5 Strain (%) Curve 1: DMA Creep Recovery in 3 Point Bending File info: cr_ptfe-5 Wed Jun 29 15:31:18 1988 Sample Height: 3.300 mm Creep Stress: 1.50e+06Pa Recovery Stress: 6.25e+02Pa PTFE - CREEP/RELAXATION PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -15.0 C TIME1: 7.0 min Force(mN) # 2 Force (mN)
  • 44. cyclic application of loads, 6.0 Time in minutes %Strain 0.0 1.0 2.0 3.0 4.0 5.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 Good Bad Differences can be seen in good and bad samples and get more apparent with several cycles. Here the bad material is not flowing enough to fill the pores and form a mechanical bond.
  • 45. and with varying temperatures. 0.0 25.0 50.0 75.0 100.0 125.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 -250.0 0.0 250.0 500.0 750.0 1000.0 1250.0 1500.0 1750.0 2000.0 2250.0 2500.0 2750.0 Sun Nov 26 20:41:31 1995 Strain(%) KPMTime (minutes) # 1 Dresser 90 D:DR90D2.1 Strain (%) Curve 1: DMA Creep Recovery in Parallel Plate File info: DR90D2.1 Fri Jul 23 12:23:50 1993 Sample Height: 2.836 mm Creep Stress: 2600.0mN Recovery Stress: 1.0mN Dresser 90 D PERKIN-ELMER 7 Series Thermal Analysis System TEMP1: -50.0 C TIME1: 11.0 min RATE1: 10.0 C/min TEMP2: 0.0 C TIME2: 15.0 min RATE2: 10.0 C/min TEMP3: 50.0 C TIME3: 15.0 min RATE3: 10.0 C/min TEMP4: 100.0 C TIME4: 75.0 min # 3 T P ( C) Force(mN) # 2 Force (mN)
  • 46. And you can tabulate this stuff graphically... • The time to 1/e percent recovery is the relaxation. • This is a measure of how quickly a material recovers. (There is a lot more to this subject.)1/T ττττ
  • 47. Stress Relaxation • By exploiting the special controls of the DMA-7e, we can run stress relaxation experiments. • These look at how the force change for a sample kept at a set distortion as a function of time or temperature. Time Position Experiment Starts σσσσ Sample would be distorted to y length and held.
  • 48. Don’t forget the DMA-7e also does Stress Scans • can do either static or dynamic ramps • static scans calculate Young’s modulus and stress-strain curves • dynamic scans give material response to increasing oscillatory forces: – get complex viscosity and modulus for each data point – can look at changes in elasticity (E’) and lag (phase angle) with increasing stress • Both methods are fast tests for QC applications after the material has been fully characterized by other DMA modes.
  • 49. Specialized Testing is Possible... The design of the DMA-7e makes it possible to do: Time-Temperature Superposition (TTS) DEA/DMA Tests in Solution Microscopic DMA Photo DMA DMA-?
  • 50. PP fibers in solvent 20.0 40.0 60.0 80.0 100.0 0.0 25.0 50.0 75.0 100.0 125.0 150.0 175.0 200.0 ForceinmN Temperature in C xylene iso-octane air water
  • 51. To Review, DMA ties together... molecular structure processing conditions product properties Molecular weight MW Distribution Chain Branching Cross linking Entanglements Phases Crystallinity Free Volume Localized motion Relaxation Mechanisms Stress Strain Temperature Heat History Frequency Pressure Heat set Material Behavior Dimensional Stability Impact properties Long term behavior Environmental resistance Temperature performance Adhesion Tack Peel
  • 52. Conclusions • DMA allows you to preform a wide range of tests from sensitive probes of molecular structure to model studies. • the DMA-7e allows operation as six different instruments to maximize flexibility. • Data can be overlayed with DSC, TGA, TMA, and DTA for easier analysis.
  • 53. References: Books • Menard, DMA: Introduction to the Technique, Its Applications and Theory, CRC Press, 1999. • Brostow et a., Failure of Plastics, Hanser, 1986. • Ferry, Viscoelastic Properties of Polymers, Wiley, 1980. • Gordon et al., Computer Programs for Rheologists, Hanser, 1995. • Gol'dman, Prediction of Deformation Properties of Polymeric and Composite Materials,, ACS, 1994. • Mascosko, Rheology, VCH, 1993. • Matsouka, Relaxation Phenomena in Polymers, Hanser, 1993. • McCrum et al, Anelastic and Dielectric Properties of Polymeric Solids, Dover, 1992 (reprint of 1967 edition). • Nielsen et al., Mechanical Properties of Polymers and Composites, Dekker, 1994. • Sperling, Introduction to Physical Polymer Science, Academic Press, 1994. • Ward et al., Introduction to Mechanical Properties of Solid Polymers, Wiley, 1993.