An Introduction to Dynamic Mechanical Analysis · 13-06-2019 · 6/13/2019 1 An Introduction to Dynamic Mechanical Analysis Jeffrey A. Jansen June 13, 2019 Introduction to DMA

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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


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FUNDAMENTALS



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Viscoelasticity

• Because of the molecular structure of the molecules, thermoplastic materials have different properties compared to other materials, like metals.


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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.


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.


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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


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Viscoelasticity

Elastic Response


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ε


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


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Viscoelasticity

Viscous Response


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ε


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


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Viscoelasticity

Viscoelastic Response


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• Viscoelastic materials have elements of both of these properties and, as such, exhibit time‐dependent behavior


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


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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.


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DMA


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Elastic System Viscous System


DMA

DMA applies an oscillatory load to a sample to evaluate the strain response to stress.


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DMA


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Viscoelastic System


DMA


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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


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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


DMA


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TEMPERATURE DEPENDENCY



DMA Methodology

Temperature Sweep

• ASTM D4065– Step Method

– Continuous Heating Method

• Shear– Uncured Crosslinkable Materials

– Adhesives

– Pastes

• Flex / Tensile ‐ Consistency– Solid‐state Performance


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DMA Methodology


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DMA Methodology


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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


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Modulus

• Modulus over a temperature range


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25.00°C2479MPa

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1000

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3000

Sto

rag

e M

od

ulu

s (M

Pa

)

-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


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100.00°C1912MPa

25.00°C2479MPa

0.00°C2574MPa

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500

1000

1500

2000

2500

3000

Sto

rag

e M

od

ulu

s (M

Pa

)

-50 0 50 100 150

Temperature (°C)




Modulus



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100.00°C1912MPa

25.00°C2479MPa

0.00°C2574MPa

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500

1000

1500

2000

2500

3000

Sto

rag

e M

od

ulu

s (M

Pa

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-50 0 50 100 150

Temperature (°C)




Modulus


• Superior to tensile testing


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0.00°C9133MPa

25.00°C6611MPa

100.00°C3728MPa

2000

4000

6000

8000

10000

12000

14000

Sto

rag

e M

od

ulu

s (M

Pa

)

-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


Modulus



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0.00°C9133MPa

25.00°C6611MPa

100.00°C3728MPa

2000

4000

6000

8000

10000

12000

14000

Sto

rag

e M

od

ulu

s (M

Pa

)

-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


Modulus


• Superior to tensile testing


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Modulus

• Comparison of two materials

• Modulus cross‐over


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10

100

1000

10000

Sto

rag

e M

od

ulu

s (M

Pa

)

-50 0 50 100 150

Temperature (°C)

PC––––––– PC / PBT Blend–––––––



Molecular Structure


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• Structural information


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Molecular Structure


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Molecular Structure


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Amorphous

Semi‐crystalline

Crosslinked

Tg

Tg


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Molecular Structure

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Sto

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Mod

ulu

s (M

Pa

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Temperature (°C)

Polycarbonate––––––– Nylon 6–––––––



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• Amorphous vs. Semi‐crystalline –structural

Amorphous

Semi‐crystalline

TgTg


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


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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


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Glass Transition

0.5

1.0

1.5

2.0

Tan

De

lta

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300

400

Loss

Mod

ulu

s (M

Pa)

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500

1000

1500

2000

2500

3000

Sto

rage

Mod

ulu

s (M

Pa

)

-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



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Glass Transition

0.5

1.0

1.5

2.0

Tan

De

lta

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200

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400

Loss

Mod

ulu

s (M

Pa)

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500

1000

1500

2000

2500

3000S

tora

ge M

odu

lus

(MP

a)

-50 -25 0 25 50 75 100 125

Temperature (°C)





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Glass Transition

0.5

1.0

1.5

2.0

Tan

De

lta

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100

200

300

400

Loss

Mod

ulu

s (M

Pa)

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1000

1500

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2500

3000

Sto

rage

Mod

ulu

s (M

Pa

)

-50 -25 0 25 50 75 100 125

Temperature (°C)





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Rapid rise in E’’ indicates an increase in polymer structural mobility – motion within the molecules ‐ relaxation


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Glass Transition

0.5

1.0

1.5

2.0

Tan

De

lta

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100

200

300

400

Loss

Mod

ulu

s (M

Pa)

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500

1000

1500

2000

2500

3000S

tora

ge M

odu

lus

(MP

a)

-50 -25 0 25 50 75 100 125

Temperature (°C)





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During the glass transition non‐crystalline and non‐crosslinked polymer segments attain high level of freedom – flow or movement under stress


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


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• Polycarbonate

• Determining the glass transition temperature (Tg)

138.86°C

146.62°C152.84°C

0.5

1.0

1.5

2.0

Ta

n D

elta

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Lo

ss M

odu

lus

(MP

a)

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Sto

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e M

od

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s (M

Pa

)

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






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96.28°C

104.60°C

113.36°C

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1.0

1.5

2.0

Ta

n D

elta

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Lo

ss M

odu

lus

(MP

a)

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Sto

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e M

od

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s (M

Pa

)

-50 -25 0 25 50 75 100 125

Temperature (°C)




• ABS

• Determining the glass transition temperature (Tg)


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Alloy or Blend

• PPO / PS Resin Blend


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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

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Tan

Del

ta

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Loss

Mod

ulus

(kP

SI)

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Sto

rage

Mod

ulus

(kP

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


Tg 215°C

Tg 100°C

Resin Alloy: Single Tg 144 °C

Resin Blend: Two Tg


Impact Resistance

• Secondary transition –short range molecular mobility

• Energy absorption – impact properties


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-4.26°C

2.39°C

0.01

0.02

0.03

0.04

Tan

Del

ta

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s M

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Mo

dulu

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Pa)

-50 -25 0 25 50 75 100

Temperature (°C)





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Impact Resistance


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Impact Modifier Effectiveness


Impact Resistance


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1 0 0

2 0 0

3 0 0

4 0 0

5 0 0

Los

s M

odu

lus

(MP

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.


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Plastic TodayThe Materials Analyst, Part 114: The challenge of bonding plastic components in medical devicesBy Michael SepePublished: February 17th, 2010


TIME DEPENDENCY



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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.



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



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Creep


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


Creep


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Graph from Smithers RAPRAhttp://www.rapra.net


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Creep


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0 0

Metal Plastic

Initial Placement

Stress Stress


Creep


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300 45

Metal Plastic

Initial Placement

Initial Deformation

Day 1Stress Stress


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Creep


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300 45

Metal Plastic

Initial Placement

Initial Deformation

Day 10Stress Stress


Creep


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300 45

Metal Plastic

Initial Placement

Initial Deformation

Day 100Stress Stress


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Creep


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Metal Plastic

0 0



Creep


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0 0

Metal Plastic

Initial Placement

Initial Deformation

Stress Stress


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Creep Rupture


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300 45

Metal Plastic

Initial Placement

Initial Deformation



Creep Rupture


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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.



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.



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Time and Temperature


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Time and Temperature have the same effect

on Plastics


0.5

1.0

1.5

2.0

Tan

Del

ta

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300

400

Loss

Mod

ulus

(M

Pa)

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1500

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2500

Sto

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Mo

dulu

s (M

Pa)

-50 0 50 100 150Tem perature (°C ) Universal V4.7A TA Instrum ents



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0.5

1.0

1.5

2.0

Tan

Del

ta

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Loss

Mod

ulus

(M

Pa)

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Sto

rage

Mo

dulu

s (M

Pa)

-50 0 50 100 150Tem perature (°C ) Universal V4.7A TA Instrum ents



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TIME – Scale Unknown


DMA‐TTS


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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


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


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DMA‐TTS


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• Plots of modulus versus decay time for each temperature

• Select temperature of interest


DMA‐TTS


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• Build master curve by shifting individual plots

• Extends time


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DMA‐TTS


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• Build master curve by shifting individual plots

• Extends time


DMA‐TTS


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• Master curve represents apparent modulus over time


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Creep Projection


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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


Creep Projection


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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


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Creep Projection


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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)


Creep at 25 °C

• Master curve as semi‐log plot


Creep Projection


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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


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Creep Projection


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‐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)


Creep Projection


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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


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Creep Projection


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


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



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)


Creep at 25 °C



1000 MPa

11,000 hours


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


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


Introduction to DMA

• Glass oriented relatively randomly• Glass well bonded to polymer matrix


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Introduction to DMA

• Similar fracture features on all parts examined• Fractography indicative of creep rupture failure


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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


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


The Madison Group89

0 5000 10000 15000psi

Anticipated Safety Margin

Stress


The Madison Group90

89

90

6/13/2019

46

0 5000 10000 15000psi

Actual Safety Margin – Time Zero

Stress


The Madison Group91

0 5000 10000 15000psi

Reduction of Apparent Strength over Time

Stress

Time


The Madison Group92

91

92

6/13/2019

47

Proposed Material Substitution

• Replacement of 30% glass fiber reinforced nylon 6/6 with

30% glass fiber reinforced polyarylamide (PARA)


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


The Madison Group94

93

94

6/13/2019

48

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


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


The Madison Group96

95

96

6/13/2019

49

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


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


The Madison Group98

97

98

6/13/2019

50

Additional Testing

• Additional temperatures ‐ above ambient most critical

• Glass fiber orientation – longitudinal and transverse

• Knit lines

• Moisture content – dry‐as‐molded and conditioned


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.


The Madison Group100

99

100

6/13/2019

51

Questions?


The Madison Group

Jeffrey A. JansenThe Madison Group608‐231‐[email protected]

THANK YOU

101

101

Documents

An Introduction to Dynamic Mechanical Analysis · 13-06-2019 · 6/13/2019 1 An Introduction to Dynamic Mechanical Analysis Jeffrey A. Jansen June 13, 2019 Introduction to DMA