An Introduction to Dynamic Mechanical Analysis · 13-06-2019 · 6/13/2019 1 An Introduction to...
Transcript of An Introduction to Dynamic Mechanical Analysis · 13-06-2019 · 6/13/2019 1 An Introduction to...
6/13/2019
1
An Introduction to Dynamic Mechanical Analysis
Jeffrey A. Jansen
June 13, 2019
Introduction to DMAJeffrey A. Jansen
The Madison Group
608‐231‐[email protected] 1
Goals
• Become familiar with how DMA can be used to identify the temperature dependency of polymeric materials.
• Gain insight into the use of DMA to evaluate and project the effects of time on polymeric materials.
• Understand how DMA can be used to assess the suitability of a material in the application.
Introduction to DMA Jeffrey A. Jansen The Madison Group
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Outline
• Fundamental Principle
• DMA Method
• Temperature‐related Property Evaluation
• Time‐related Property Evaluation
Introduction to DMAJeffrey A. Jansen
The Madison Group
608‐231‐[email protected] 3
FUNDAMENTALS
Introduction to DMA Jeffrey A. Jansen The Madison Group
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Viscoelasticity
• Because of the molecular structure of the molecules, thermoplastic materials have different properties compared to other materials, like metals.
Introduction to DMA Jeffrey A. Jansen The Madison Group
Jeffrey A. [email protected]
The polymer molecules consist of very long chains – high molecular weight.
The individual polymer chains are entangled in each other.
The polymer chains are mobile and can slide past each other because they do not share chemical bonds with the other chains around them.
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• Viscoelasticity is the property of materials that exhibit
both viscous and elastic characteristics when
undergoing deformation.
• Viscous materials, like honey, resist shear flow and
strain linearly with time when a stress is applied.
• Elastic materials, like a rubber band steel rod, strain
when stressed and quickly return to their original state
once the stress is removed.
• Viscoelastic materials have elements of both of these
properties and, as such, exhibit time‐dependent strain.
Introduction to DMA Jeffrey A. Jansen The Madison Group
Viscoelasticity
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Viscoelasticity
• There are three main factors that will affect the viscoelasticity of a plastic part:
Temperature, Time, and Strain Rate
• As the temperature is increased, the polymer chains are further apart, there is more free volume and kinetic energy, and they can slide past one another and disentangle more easily.
• As the strain rate is increased, the polymer chains do not have enough time to undergo yielding and they will disentangle.
• Over time, there is mobility between the polymer chains.
Introduction to DMA Jeffrey A. Jansen The Madison Group
Jeffrey A. [email protected] 7
Viscoelasticity
Elastic Response
• Typical in classical solid materials
• Stress Proportional deformation / strain
• σ = ε ∙ Ε (stress = strain x modulus)
• Response to applied stress: system stores the energy and can return it completely when the stress is removed
Introduction to DMAJeffrey A. Jansen
The Madison Group
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Viscoelasticity
Elastic Response
Introduction to DMAJeffrey A. Jansen
The Madison Group
ε
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Viscoelasticity
Viscous Response
• Typical in classical fluids
• Stress strain increases proportionally
• τ = γ ∙ η (stress = strain rate x viscosity)
• Response to applied stress: energy is lost to the system, strain is not recoverable
Introduction to DMAJeffrey A. Jansen
The Madison Group
•
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Viscoelasticity
Viscous Response
Introduction to DMAJeffrey A. Jansen
The Madison Group
ε
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Viscoelasticity
Viscoelastic Response
• Thermoplastic materials
• Stress proportional
• Response to applied stress: system stores energy and returns part of it when the stress is removed ‐ remaining energy is lost to the system, and is not recoverable
Introduction to DMAJeffrey A. Jansen
The Madison Group
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Viscoelasticity
Viscoelastic Response
Introduction to DMAJeffrey A. Jansen
The Madison Group
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• Viscoelastic materials have elements of both of these properties and, as such, exhibit time‐dependent behavior
Introduction to DMA Jeffrey A. Jansen The Madison Group
Viscoelasticity
Spring and dashpot model
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DMA
DMA
• Technique in which a small deformation is applied to a sample in a cyclic manner. This allows the material’s response to stress, temperature, frequency and other values to be studied.
• Assesses the proportion of elastic and viscous components in a polymer
• Determines the factors that change this balance
• How will a material perform in a given application environment
Introduction to DMAJeffrey A. Jansen
The Madison Group
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DMA
DMA
Applies a sinusoidal deformation to a sample of known
geometry. The sample can be subjected by a controlled stress or a controlled strain. For a known stress, the sample will then deform a certain amount. How much it deforms is related to its stiffness (modulus). A force motor is used to generate the sinusoidal wave and this is transmitted to the sample via a drive shaft.
Introduction to DMAJeffrey A. Jansen
The Madison Group
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DMA
Introduction to DMAJeffrey A. Jansen
The Madison Group
Elastic System Viscous System
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DMA
DMA applies an oscillatory load to a sample to evaluate the strain response to stress.
Introduction to DMAJeffrey A. Jansen
The Madison Group
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DMA
Introduction to DMAJeffrey A. Jansen
The Madison Group
Viscoelastic System
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DMA
Introduction to DMAJeffrey A. Jansen
The Madison Group
For a viscoelastic material, the stress and strain will be out of phase by some quantity known as the phase angle – common referred to as delta (δ).
Small phase angle – highly elasticLarge phase angle – highly viscous
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DMA
Introduction to DMAJeffrey A. Jansen
The Madison Group
Complex response of the material is resolved into:
E’ elastic or storage modulus (tensile)The ability of the material to store energy.
E’’ viscous or loss modulus (tensile)
The ability of the material to dissipate energy.
Tan δ E’’ / E’Measure of material damping
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DMA
Introduction to DMAJeffrey A. Jansen
The Madison Group
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TEMPERATURE DEPENDENCY
Introduction to DMA Jeffrey A. Jansen The Madison Group
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DMA Methodology
Temperature Sweep
• ASTM D4065– Step Method
– Continuous Heating Method
• Shear– Uncured Crosslinkable Materials
– Adhesives
– Pastes
• Flex / Tensile ‐ Consistency– Solid‐state Performance
Introduction to DMAJeffrey A. Jansen
The Madison Group
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DMA Methodology
Introduction to DMAJeffrey A. Jansen
The Madison Group
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DMA Methodology
Introduction to DMAJeffrey A. Jansen
The Madison Group
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Temperature Sweep
Storage Modulus
• Contribution of the elastic component in the polymer – store energy under conditions of stress
• Stiffness of the material – resistance to strain
Introduction to DMAJeffrey A. Jansen
The Madison Group
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Modulus
• Modulus over a temperature range
Introduction to DMAJeffrey A. Jansen
The Madison Group
25.00°C2479MPa
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Sto
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Temperature (°C)
Sample: PolycarbonateSize: 35.0000 x 12.9100 x 3.3100 mmMethod: temp ramp -60 to 175 C at 2c/mi
DMARun Date: 06-Feb-2015 11:32Instrument: DMA Q800 V21.1 Build 51
Universal V4.7A TA Instruments
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100.00°C1912MPa
25.00°C2479MPa
0.00°C2574MPa
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s (M
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Temperature (°C)
Sample: PolycarbonateSize: 35.0000 x 12.9100 x 3.3100 mmMethod: temp ramp -60 to 175 C at 2c/mi
DMARun Date: 06-Feb-2015 11:32Instrument: DMA Q800 V21.1 Build 51
Universal V4.7A TA Instruments
Modulus
• Modulus over a temperature range
Introduction to DMAJeffrey A. Jansen
The Madison Group
608‐231‐[email protected]
100.00°C1912MPa
25.00°C2479MPa
0.00°C2574MPa
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s (M
Pa
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-50 0 50 100 150
Temperature (°C)
Sample: PolycarbonateSize: 35.0000 x 12.9100 x 3.3100 mmMethod: temp ramp -60 to 175 C at 2c/mi
DMARun Date: 06-Feb-2015 11:32Instrument: DMA Q800 V21.1 Build 51
Universal V4.7A TA Instruments
Modulus
• Modulus over a temperature range
• Superior to tensile testing
Introduction to DMAJeffrey A. Jansen
The Madison Group
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0.00°C9133MPa
25.00°C6611MPa
100.00°C3728MPa
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10000
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Sto
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od
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s (M
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-50 0 50 100 150
Temperature (°C)
Sample: Nylon 6 - 30% GFSize: 35.0000 x 12.0600 x 3.0500 mmMethod: temp Ramp -40 to 175 C at 2c/mi
DMARun Date: 31-Dec-2013 10:46Instrument: DMA Q800 V20.9 Build 27
Universal V4.7A TA Instruments
Modulus
• Modulus over a temperature range
Introduction to DMAJeffrey A. Jansen
The Madison Group
608‐231‐[email protected]
0.00°C9133MPa
25.00°C6611MPa
100.00°C3728MPa
2000
4000
6000
8000
10000
12000
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Sto
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e M
od
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s (M
Pa
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-50 0 50 100 150
Temperature (°C)
Sample: Nylon 6 - 30% GFSize: 35.0000 x 12.0600 x 3.0500 mmMethod: temp Ramp -40 to 175 C at 2c/mi
DMARun Date: 31-Dec-2013 10:46Instrument: DMA Q800 V20.9 Build 27
Universal V4.7A TA Instruments
Modulus
• Modulus over a temperature range
• Superior to tensile testing
Introduction to DMAJeffrey A. Jansen
The Madison Group
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Modulus
• Comparison of two materials
• Modulus cross‐over
Introduction to DMAJeffrey A. Jansen
The Madison Group
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Temperature (°C)
PC––––––– PC / PBT Blend–––––––
Universal V4.7A TA Instruments
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Molecular Structure
Introduction to DMAJeffrey A. Jansen
The Madison Group
• Structural information
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Molecular Structure
Introduction to DMAJeffrey A. Jansen
The Madison Group
• Structural information
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Molecular Structure
Introduction to DMAJeffrey A. Jansen
The Madison Group
• Structural information
Amorphous
Semi‐crystalline
Crosslinked
Tg
Tg
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Molecular Structure
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Temperature (°C)
Polycarbonate––––––– Nylon 6–––––––
Universal V4.7A TA Instruments
Introduction to DMAJeffrey A. Jansen
The Madison Group
• Amorphous vs. Semi‐crystalline –structural
Amorphous
Semi‐crystalline
TgTg
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Viscous Properties
Loss Modulus
• Contribution of the viscous component in the polymer – flow under conditions of stress
• Creep / cold flow or stress relaxation
• Not the derivative of the storage modulus
Introduction to DMAJeffrey A. Jansen
The Madison Group
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Viscous Properties
Tan Delta
• Comparison of polymers where storage and loss moduli are subject to change because of alterations on composition, geometry, or processing conditions
• Index of viscoelasticity
• Unitless / dimensionless
Introduction to DMAJeffrey A. Jansen
The Madison Group
608‐231‐[email protected]
Glass Transition
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Pa)
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Sto
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-50 -25 0 25 50 75 100 125
Temperature (°C)
Sample: ABSSize: 35.0000 x 9.9400 x 3.7000 mmMethod: temp Ramp to 120 C at 2c/min
DMARun Date: 06-Sep-2011 13:52Instrument: DMA Q800 V20.9 Build 27
Universal V4.7A TA Instruments
Introduction to DMAJeffrey A. Jansen
The Madison Group
608‐231‐[email protected]
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Glass Transition
0.5
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Tan
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s (M
Pa)
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tora
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odu
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a)
-50 -25 0 25 50 75 100 125
Temperature (°C)
Sample: ABSSize: 35.0000 x 9.9400 x 3.7000 mmMethod: temp Ramp to 120 C at 2c/min
DMARun Date: 06-Sep-2011 13:52Instrument: DMA Q800 V20.9 Build 27
Universal V4.7A TA Instruments
Introduction to DMAJeffrey A. Jansen
The Madison Group
608‐231‐[email protected]
Glass Transition
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s (M
Pa)
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s (M
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-50 -25 0 25 50 75 100 125
Temperature (°C)
Sample: ABSSize: 35.0000 x 9.9400 x 3.7000 mmMethod: temp Ramp to 120 C at 2c/min
DMARun Date: 06-Sep-2011 13:52Instrument: DMA Q800 V20.9 Build 27
Universal V4.7A TA Instruments
Introduction to DMAJeffrey A. Jansen
The Madison Group
Rapid rise in E’’ indicates an increase in polymer structural mobility – motion within the molecules ‐ relaxation
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Glass Transition
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Loss
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s (M
Pa)
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tora
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odu
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a)
-50 -25 0 25 50 75 100 125
Temperature (°C)
Sample: ABSSize: 35.0000 x 9.9400 x 3.7000 mmMethod: temp Ramp to 120 C at 2c/min
DMARun Date: 06-Sep-2011 13:52Instrument: DMA Q800 V20.9 Build 27
Universal V4.7A TA Instruments
Introduction to DMAJeffrey A. Jansen
The Madison Group
During the glass transition non‐crystalline and non‐crosslinked polymer segments attain high level of freedom – flow or movement under stress
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Glass Transition Temperature
• DMA provides best measurement technique – direct assessment of molecular changes within the material
• Onset of sharp reduction in storage modulus –practical effect of temperature on load‐bearing capabilities
• Loss modulus peak temperature – corresponds well with other thermal analysis techniques, ASTM D 4065
• Tan Delta peak temperature ‐ material has highest ratio of flow to storage – the point of highest realtiveviscous contribution
Introduction to DMAJeffrey A. Jansen
The Madison Group
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Glass Transition Temperature
Introduction to DMAJeffrey A. Jansen
The Madison Group
• Polycarbonate
• Determining the glass transition temperature (Tg)
138.86°C
146.62°C152.84°C
0.5
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a)
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s (M
Pa
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50 100 150
Temperature (°C)
Sample: PCSize: 35.0000 x 12.9100 x 3.3100 mmMethod: temp ramp -60 to 175 C at 2c/mi
DMARun Date: 06-Feb-2015 11:32Instrument: DMA Q800 V21.1 Build 51
Universal V4.7A TA Instruments
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Glass Transition Temperature
Introduction to DMAJeffrey A. Jansen
The Madison Group
96.28°C
104.60°C
113.36°C
0.5
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elta
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a)
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s (M
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)
-50 -25 0 25 50 75 100 125
Temperature (°C)
Sample: ABSSize: 35.0000 x 9.9400 x 3.7000 mmMethod: temp Ramp to 120 C at 2c/min
DMARun Date: 06-Sep-2011 13:52Instrument: DMA Q800 V20.9 Build 27
Universal V4.7A TA Instruments
• ABS
• Determining the glass transition temperature (Tg)
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Alloy or Blend
• PPO / PS Resin Blend
Introduction to DMAJeffrey A. Jansen
The Madison Group
22.00°C330.3kPSI
144.20°C
temperature rampheat 2°C/min from 15°C to 150°C40 um at 1 Hzdual cantilever
0.2
0.4
0.6
0.8
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Tan
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ta
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Loss
Mod
ulus
(kP
SI)
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Mod
ulus
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SI)
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Temperature (°C)
Sample: Noryl 731 tensile barSize: 35.0000 x 12.4700 x 3.0700 mm DMA
File: T:\_DMA\2012\ENB013385P.405Operator: MKKInstrument: DMA Q800 V20.9 Build 27
Universal V4.5A TA Instruments
Tg 215°C
Tg 100°C
Resin Alloy: Single Tg 144 °C
Resin Blend: Two Tg
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Impact Resistance
• Secondary transition –short range molecular mobility
• Energy absorption – impact properties
Introduction to DMAJeffrey A. Jansen
The Madison Group
-4.26°C
2.39°C
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0.03
0.04
Tan
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s M
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a)
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s (M
Pa)
-50 -25 0 25 50 75 100
Temperature (°C)
Sample: ABSSize: 35.0000 x 9.9400 x 3.7000 mmMethod: temp Ramp to 120 C at 2c/min
DMARun Date: 06-Sep-2011 13:52Instrument: DMA Q800 V20.9 Build 27
Universal V4.7A TA Instruments
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Impact Resistance
Introduction to DMAJeffrey A. Jansen
The Madison Group
Impact Modifier Effectiveness
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Impact Resistance
Introduction to DMAJeffrey A. Jansen
The Madison Group
1 0 0
2 0 0
3 0 0
4 0 0
5 0 0
Los
s M
odu
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a)
-5 0 0 5 0 1 0 0 1 5 0 2 0 0T e m p e ra tu re (° C )
G o o d Im p a c t P ro p e r tie s - 2 0 0 6– – – – – – – P o o r Im p a c t P ro p e rtie s - 2 0 1 5– – – – – – –
U n iv e r s a l V 4 .7 A T A In s t ru m en ts
Use Temperature 55 °C
Aromatic Nylon Resin
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Solvent‐induced Rearrangement
• Figure 4: As‐molded PC – typical results. Rom Modulus at 25 °C ‐ 340 kpsi.
• Figure 5: Altered behavior after the PC has been exposed to cyclohexanone – major ingredient in adhesive bonding agent. Modulus at 25 °C reduced to 315 kpsi. More importantly, the presence of a preliminary relaxation that occurs between 40°C and 80°C with a peak near 60°C. The elastic modulus reduction associated with this transition represents a 40% decline and is associated with a greater degree of molecular mobility within the polymer matrix as a result of contact with the cyclohexanone.
Introduction to DMAJeffrey A. Jansen
The Madison Group
Plastic TodayThe Materials Analyst, Part 114: The challenge of bonding plastic components in medical devicesBy Michael SepePublished: February 17th, 2010
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TIME DEPENDENCY
Introduction to DMA Jeffrey A. Jansen The Madison Group
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Creep
Creep is…..
the tendency of a solid material to deform permanently under the influence of constant stress (tensile, compressive, shear, or flexural). It occurs as a function of time through extended exposure to levels of stress that are below the yield strength of the material.
Introduction to DMA Jeffrey A. Jansen The Madison Group
608‐231‐[email protected]
Creep
• Low to moderate forces exerted over an extended me → lower duc lity. Can result in bri le fracture
in normally ductile plastics
• Inherent viscoelastic nature of polymers leads to time dependency
• Prolonged static stresses lead to a decay in apparent modulus through localized molecular reorganization of polymer chains
• At stresses below the yield point molecular reorganization includes disentanglement as there is no opportunity for yielding
Introduction to DMA Jeffrey A. Jansen The Madison Group
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Creep
Introduction to DMA Jeffrey A. Jansen The Madison Group
Time
Stress
1,000 psi
5,000 psi
7,500 psi
2,500 psi
9,000 psi
10,000 psiDuctile Failure
Brittle Failure
Yield Point
Source: “Understanding the Consequence of Ductile-to-Brittle Transitions in a Plastics Materials Failure”, Published and Presented at ANTEC, 2008
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Creep
Introduction to DMAJeffrey A. Jansen
The Madison Group
Graph from Smithers RAPRAhttp://www.rapra.net
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Creep
Introduction to DMAJeffrey A. Jansen
The Madison Group
0 0
Metal Plastic
Initial Placement
Stress Stress
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Creep
Introduction to DMAJeffrey A. Jansen
The Madison Group
300 45
Metal Plastic
Initial Placement
Initial Deformation
Day 1Stress Stress
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Creep
Introduction to DMAJeffrey A. Jansen
The Madison Group
300 45
Metal Plastic
Initial Placement
Initial Deformation
Day 10Stress Stress
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Creep
Introduction to DMAJeffrey A. Jansen
The Madison Group
300 45
Metal Plastic
Initial Placement
Initial Deformation
Day 100Stress Stress
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Creep
Introduction to DMAJeffrey A. Jansen
The Madison Group
Metal Plastic
0 0
Day 100Stress Stress
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Creep
Introduction to DMAJeffrey A. Jansen
The Madison Group
0 0
Metal Plastic
Initial Placement
Initial Deformation
Stress Stress
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Creep Rupture
Introduction to DMAJeffrey A. Jansen
The Madison Group
300 45
Metal Plastic
Initial Placement
Initial Deformation
Day 100Stress Stress
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Creep Rupture
Introduction to DMAJeffrey A. Jansen
The Madison Group
300 45
Metal Plastic
Initial Placement
Initial Deformation
Day 1000 ??Stress Stress
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Viscoelasticity
• If a polymeric material is under constant stress or strain, a continual change in the apparent modulus is observed.
• The modulus (tangent modulus or Young’s modulus) of a material is expressed as the applied stress divided by the resulting strain.
• The modulus value is the slope of the stress/strain curve in the linear region of the curve.
• Under constant stress this is observed in the form of an increasing level of strain, known as creep.
• Under constant strain this is observed in the form of an decreasing level of apparent stress, known as stress relaxation.
Introduction to DMA Jeffrey A. Jansen The Madison Group
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Viscoelasticity
• When a material is placed under a constant stress or strain, the response observed initially will be a function of the modulus of the material.
• If stress is continuously applied, strain will continually increase. Therefore, the calculated modulus at a point later in time will appear to have decreased. However, the stiffness of the material is not actually decreasing.
• Apparent modulus is the apparent stiffness of the material and is a mathematical artifact for describing the effect of a constant stress on the manner and the corresponding increase in strain over time.
Introduction to DMA Jeffrey A. Jansen The Madison Group
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Time and Temperature
Introduction to DMAJeffrey A. Jansen
The Madison Group
Time and Temperature have the same effect
on Plastics
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0.5
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ulus
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Pa)
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s (M
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-50 0 50 100 150Tem perature (°C ) Universal V4.7A TA Instrum ents
Time and Temperature
Introduction to DMAJeffrey A. Jansen
The Madison Group
608‐231‐[email protected]
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0.5
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Tan
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100
200
300
400
Loss
Mod
ulus
(M
Pa)
0
500
1000
1500
2000
2500
Sto
rage
Mo
dulu
s (M
Pa)
-50 0 50 100 150Tem perature (°C ) Universal V4.7A TA Instrum ents
Time and Temperature
Introduction to DMAJeffrey A. Jansen
The Madison Group
TIME – Scale Unknown
608‐231‐[email protected]
DMA‐TTS
Introduction to DMAJeffrey A. Jansen
The Madison Group
0
500
1000
1500
2000
2500
3000
Fle
xura
l Mo
du
lus
(MP
a)
0 20 40 60 80 100 120 140 160
Temperature (°C)
Sample: PolyacetalSize: 35.0000 x 12.4800 x 3.1200 mmMethod: Creep TTS
DMARun Date: 18-Aug-2015 15:15Instrument: DMA Q800 V21.1 Build 51
Universal V4.7A TA Instruments
Time‐Temperature Superposition
• Multiple fifteen‐minute determinations for at isothermal conditions
• From 10 to 145°C increments of 5°C
• Evaluations conducted using a dual cantilever configuration
• Stress of 1.9 MPa
608‐231‐[email protected]
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DMA‐TTS
Introduction to DMAJeffrey A. Jansen
The Madison Group
• Plots of modulus versus decay time for each temperature
• Select temperature of interest
608‐231‐[email protected]
DMA‐TTS
Introduction to DMAJeffrey A. Jansen
The Madison Group
• Build master curve by shifting individual plots
• Extends time
608‐231‐[email protected]
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DMA‐TTS
Introduction to DMAJeffrey A. Jansen
The Madison Group
• Build master curve by shifting individual plots
• Extends time
608‐231‐[email protected]
DMA‐TTS
Introduction to DMAJeffrey A. Jansen
The Madison Group
• Master curve represents apparent modulus over time
608‐231‐[email protected]
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Creep Projection
Introduction to DMAJeffrey A. Jansen
The Madison Group
100
1000
10000
0.001 0.01 0.1 1 10 100 1000 10000 100000
Apparent Modulus (M
Pa)
Time (hours)
Apparent Modulus v. TimePolyacetal
Creep at 25 °C
• Master curve represents apparent modulus over time
• Log / log plot
608‐231‐[email protected]
Creep Projection
Introduction to DMAJeffrey A. Jansen
The Madison Group
10 0
1 00 0
1 0 00 0
Sto
rag
e M
odul
us (
MP
a)
2 5 5 0 7 5 1 00 12 5 1 5 0Te m pe ra ture (°C )
S a m p le : P o lya c e ta lS ize : 3 5 .0 0 0 0 x 1 2 .4 8 0 0 x 3 .1 2 0 0 m mM e th o d : te m p ra m p -4 0 to 1 6 5 C a t 2 c /m i
D M AR u n D a te : 1 8 -A u g -2 0 1 5 1 0 :1 3In s tru m e n t: D M A Q 8 0 0 V 2 1 .1 B u ild 5 1
U n ivers a l V 4 .7A T A In s tru m en ts
• DMA temperature sweep matches well with master curve
608‐231‐[email protected]
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Creep Projection
Introduction to DMAJeffrey A. Jansen
The Madison Group
0
500
1000
1500
2000
2500
0.001 0.01 0.1 1 10 100 1000 10000 100000
Apparen
t Modulus (M
Pa)
Time (hours)
Apparent Modulus v. TimePolyacetal
Creep at 25 °C
• Master curve as semi‐log plot
608‐231‐[email protected]
Creep Projection
Introduction to DMAJeffrey A. Jansen
The Madison Group
0
10
20
30
40
50
60
70
80
90
100
0.0 2.0 4.0 6.0 8.0 10.0
Stress (psi)
Stress (MPa)
Strain (%)
PolyacetalTensile Stress ‐ Strain at 25 °C
Stress / Strain
Modulus
Yield
ProportionalLimit
• Tensile properties to establish modeling parameters
608‐231‐[email protected]
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Creep Projection
Introduction to DMAJeffrey A. Jansen
The Madison Group
‐0.500
0.500
1.500
2.500
3.500
4.500
5.500
6.500
7.500
8.500
0.001 0.01 0.1 1 10 100 1000 10000 100000
Strain (%)
Time (hours)
Polyacetal‐ Strain v. TimeCreep at 25 °C15 MPa
20 MPa
• Use stress to determine strain over time
• Project time to cracking
Projected time to cracking:15 MPa: >200,000 hours (22.8 years)20 MPa: 45,700 hours (5.2 years)
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Creep Projection
Introduction to DMAJeffrey A. Jansen
The Madison Group
TimeMax Working
Stresshours Mpa0.003 500.1 450.2 440.5 431 422 405 3910 3720 3650 34100 32200 31500 291000 272000 265000 2410000 2220000 2150000 19100000 18200000 17
608‐231‐[email protected]
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Creep Projection
Introduction to DMAJeffrey A. Jansen
The Madison Group
0
500
1000
1500
2000
2500
0.001 0.01 0.1 1 10 100 1000 10000 100000
Apparen
t Modulus (M
Pa)
Time (hours)
Apparent Modulus v. TimePolyacetal 25
6070
• Able to model and compare multiple temperatures
608‐231‐[email protected]
0
1000
2000
3000
Sto
rag
e M
odu
lus
(MP
a)
25 50 75 100 125 150Tem perature (°C )
S am ple: P o lyace ta lS ize: 35 .0000 x 12.4800 x 3 .1200 m mM ethod: tem p ram p -40 to 165 C a t 2c /m i
D M AR un D ate: 18-A ug-2015 10 :13Ins trum ent: D M A Q 800 V21.1 B u ild 51
U niversal V 4.7A TA Instrum ents
Time and Temperature
Introduction to DMA Jeffrey A. Jansen The Madison Group
1000 MPa
100 °C
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0
500
1000
1500
2000
2500
0.001 0.01 0.1 1 10 100 1000 10000 100000
Apparen
t Modulus (M
Pa)
Time (hours)
Apparent Modulus v. TimePolyacetal
Creep at 25 °C
Time and Temperature
Introduction to DMA Jeffrey A. Jansen The Madison Group
1000 MPa
11,000 hours
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Failure Example
• Failure of automotive aftermarket component
• Cracking observed in some parts after approx. 2 years, some longer
• Nylon 6/6 – 30% glass fiber reinforced
• Load bearing – predicted at 60 MPa, constant load application
• Not an under‐hood application
Introduction to DMAJeffrey A. Jansen
The Madison Group84
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Failure Example – Part 1
Introduction to DMA
• Partial cracking at design corner – adequate radius
Jeffrey A. Jansen The Madison Group
85
Failure Example – Part 2
Introduction to DMA
• Glass oriented relatively randomly• Glass well bonded to polymer matrix
Jeffrey A. Jansen The Madison Group
86
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Failure Example – Part 3
Introduction to DMA
• Similar fracture features on all parts examined• Fractography indicative of creep rupture failure
Jeffrey A. Jansen The Madison Group
87
Creep Rupture Failure
• Consistent failure mechanism across all parts.• The cracking lacked significant macro and micro ductility. However,
substantial ductility was present within the laboratory fracture and at isolated locations outside of the crack origins. Indicated that the material was not inherently brittle. Ductile‐to‐brittle transition.
• Multiple individual cracks formed within the component at a design corner – adequate radius. The cracks subsequently coalesced and propagated.
• The fracture characteristics were indicative of stresses that exceeded the long‐term strength of the material through a creep rupture mechanism.
• Material analysis as expected ‐ 30% glass fiber reinforced nylon 6/6– No molecular degradation– No contamination– Good crystallinity– Proper glass content
Introduction to DMAJeffrey A. Jansen
The Madison Group88
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DMA‐Creep Experiment
•Tensile strength: 172 MPa
•Predicted stress: 60 MPa
0
20
40
60
80
100
120
140
160
180
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Stress (psi)
Stress (MPa)
Strain (%)
Tensile Stress ‐ Strain at 23 °CNylon 6/6 30% Glass Fiber
Stress /Strain
Introduction to DMAJeffrey A. Jansen
The Madison Group89
0 5000 10000 15000psi
Anticipated Safety Margin
Stress
Introduction to DMAJeffrey A. Jansen
The Madison Group90
89
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0 5000 10000 15000psi
Actual Safety Margin – Time Zero
Stress
Introduction to DMAJeffrey A. Jansen
The Madison Group91
0 5000 10000 15000psi
Reduction of Apparent Strength over Time
Stress
Time
Introduction to DMAJeffrey A. Jansen
The Madison Group92
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Proposed Material Substitution
• Replacement of 30% glass fiber reinforced nylon 6/6 with
30% glass fiber reinforced polyarylamide (PARA)
Introduction to DMAJeffrey A. Jansen
The Madison Group93
DMA‐Nylon 6/6 30% Glass Fiber
• Modulus as expected
• Tg: 67 °C
• Looming loss of modulus
25.00°C8889MPa
66.83°C
0.02
0.04
0.06
0.08
Ta
n D
elta
0
200
400
600
Loss
Mo
dul
us
(MP
a)
2000
4000
6000
8000
10000
Sto
rag
e M
od
ulu
s (M
Pa)
-50 0 50 100 150 200 250Temperature (°C) Universal V4.7A TA Instrum ents
Introduction to DMAJeffrey A. Jansen
The Madison Group94
93
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DMA‐Polyarylamide 30% Glass Fiber
25.00°C11842M Pa
79.11°C
0.02
0.04
0.06
0.08
0.10
Ta
n D
elta
0
200
400
600
800
1000
1200
Lo
ss M
od
ulu
s (M
Pa
)
2000
4000
6000
8000
10000
12000
14000
Sto
rag
e M
od
ulu
s (M
Pa
)
-50 0 50 100 150 200 250Tem perature (°C ) Universal V4.7A TA Instrum ents
• Modulus as expected
• Tg: 79 °C (higher)
• Looming loss of modulus
Introduction to DMAJeffrey A. Jansen
The Madison Group95
DMA‐Comparison of Temperature Effects
25.00°C8889M Pa
25.00°C11842M Pa
0
2000
4000
6000
8000
10000
12000
14000
Sto
rage
Mod
ulus
(M
Pa
)
-50 0 50 100 150 200 250Tem perature (°C )
N ylon 6 /6 30% G lass F iber––––––– Polyarylam ide 30% G lass F iber–––––––
U niversa l V4.7A TA Instrum ents
• Higher initial modulus ‐structure
• Higher Tg ‐structure
Introduction to DMAJeffrey A. Jansen
The Madison Group96
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DMA‐Creep Experiments
• Master curves of apparent modulus vs. time show differences
• Consistent with relative temperature sweeps
0
2000
4000
6000
8000
10000
12000
0.001 0.01 0.1 1 10 100 1000 10000 100000
Apparen
t Modulus (M
Pa)
Time (hours)
Apparent Modulus v. TimeCreep at 25 °C
Polyarylamide30% Glass Fiber
Nylon 6/6 30% Glass Fiber
Introduction to DMAJeffrey A. Jansen
The Madison Group97
DMA‐Creep Experiments
• Strain vs. time at 60MPa
• Cracking in nylon 6/6 projected for 25,000 hours (2.85 years)
• No cracking projected for polyarylamidein 200,000 hours (20+ years)
0.000
0.500
1.000
1.500
2.000
2.500
0.001 0.01 0.1 1 10 100 1000 10000 100000
Strain (%)
Time (hours)
Strain v. TimeCreep at 25 °C
Nylon 6/6 30% Glass Fiber
Polyarylamide 30% Glass Fiber
Introduction to DMAJeffrey A. Jansen
The Madison Group98
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Additional Testing
• Additional temperatures ‐ above ambient most critical
• Glass fiber orientation – longitudinal and transverse
• Knit lines
• Moisture content – dry‐as‐molded and conditioned
Introduction to DMAJeffrey A. Jansen
The Madison Group99
Limitations
• Testing performed on “ideal” samples. Factors that decrease material strength will reduce the predicted time or stress to produce failure:– Molecular degradation from service or molding ‐ oxidative or
ultraviolet (UV) radiation – Environmental stress cracking– Transverse glass orientation– Inadequate molecular fusion from knit lines
• Models time to crack initiation. The actual time to catastrophic failure under the temperature and stress conditions modeled may be somewhat greater than those predicted by the model. for resins that exhibit an ultimate strain limit that is much greater than the yield strain.
Introduction to DMAJeffrey A. Jansen
The Madison Group100
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Questions?
Introduction to DMAJeffrey A. Jansen
The Madison Group
Jeffrey A. JansenThe Madison Group608‐231‐[email protected]
THANK YOU
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