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Composites piézoélectriques et diélectriques à base de polymères fluorés

Sara DALLE VACCHE Laboratoire de Technologie des Composites et Polymères (LTC)

Ecole Polytechnique Fédérale de Lausanne (EPFL) CH-1015 Lausanne, Switzerland

PLASTICS UPDATE, 12 novembre 2015

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LTC  

Created: 1990

Director: Prof. J.-A. Månson

Direction: P.-E. Bourban, Y. Leterrier, V. Michaud, C. Plummer

Staff: 20 members (postdocs, PhDs, engineers)

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LTC creates the scientific base for the next generation of materials and processes in the fast-growing fields of polymers and composites: •  incorporating unique additional functionality •  developing new routes to cost-effective materials and manufacturing •  scaling up to an industrial context (aerospace, automotive, building, medical,

electronics, sports…)  

Research domains •  Advanced Thermoset Composite Processing •  Thermoplastic Composite Manufacturing •  Smart Composites •  Nanostructured materials •  Biocomposites •  Multilayer films •  Cost and implementation strategies Main industrial sponsors •  DaimlerChrysler, Ford, VW, Renault, USCAR •  Johnson Controls, Vetrotex, ABB, Bekaert, KB •  DuPont, Dow, EMS Chemie, Firmenich, Konarka, Solvay •  Essilor, Tetra Pak, Alinghi, Solar Impulse, Swatch Group

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Outline

• Why dielectric and piezoelectric polymer composites • Process – structure – property analyses •  Solvent based and melt processing

•  Morphology and crystallinity

•  Thermomechanical properties

•  Barrier properties

•  Dielectric and piezoelectric properties

• Application case •  Self-sensing high pressure H2 storage vessel

• Conclusions and outlook

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Why dielectric and piezoelectric composites

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Dielectric and piezoelectric composites: applications

Hydrophone (<40 kHz)

Sonar (40 kHz - 10 MHz)

Underwater applications

Imran Patel (2011) www.intechopen.com

Materials Systems Inc. http://www.matsysinc.com

Dielectric elastomer actuators

AIST (www.aist.go.jp)

Energy harvesting and vibration control

Advanced Cerametrics www.advancedcerametrics.com

APC International, Ltd. www.americanpiezo.com

APC International, Ltd. www.americanpiezo.com

…and more…

http://www.vermon.com

Biomedical imaging and Non Destructive Testing (NDT)

Vermon SA http://www.vermon.com

Vermon SA http://www.vermon.com

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Relative permittivity Dielectric loss tangent Breakdown strength Emax

Dielectricity and piezoelectricity

Ep

After poling Before poling

+  

_  

F [N]

Q[pC]

d33 pC N!" #$=Q pC!" #$F N!" #$

εr f( )tanδ f( )

+  -­‐  

+  -­‐  

+  -­‐  

+  -­‐  +  

-­‐  

+  -­‐  

+  -­‐  

+  -­‐  

+  -­‐  +  

-­‐  

+  -­‐  

+  -­‐  

E +

_  

+  +  +  +  +  ++  

-­‐  -­‐  -­‐  -­‐  -­‐    

+  -­‐  

+  -­‐  

+  -­‐  

+  -­‐  

+  -­‐  

Dielectric material

Piezoelectric material

Coercive field Ec (Ep > Ec)

Piezoelectric coefficient

Poled  piezoelectric  material  

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(Fluoro)polymers Perovskite ceramics Relative permittivity ~10 Breakdown strength > 1000 kV/cm Dielectric loss tang. < 0.01 Piezoelectric coefficient ~-30 pC/N High coercive field 500 kV/cm Ease of processing Flexibility and compliance Low density

Why dielectric and piezoelectric composites

Relative permittivity >1000 Breakdown strength < 100 kV/mm Piezoelectric coefficient >100 pC/N Difficult processing and shaping Brittleness and high stiffness High density

High energy density capacitors: Energy harvesters: High breakdown strength High piezoelectric coefficient High relative permittivity Compliance

Transducers: High piezoelectric coefficient Low dielectric losses Compliance

✗  ✔  

✔  ✗  

D. Tan and P. Irwin (2011)

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(Fluoro)polymers Perovskite ceramics Relative permittivity ~10 Breakdown strength > 1000 kV/cm Dielectric loss tang. < 0.01 Piezoelectric coefficient ~-30 pC/N High coercive field 500 kV/cm Ease of processing Flexibility and compliance Low density

Why dielectric and piezoelectric composites

Relative permittivity >1000 Breakdown strength < 100 kV/mm Piezoelectric coefficient >100 pC/N Difficult processing and shaping Brittleness and high stiffness High density

High energy density capacitors: Energy harvesters: High breakdown strength High piezoelectric coefficient High relative permittivity Compliance

Transducers: High piezoelectric coefficient Low dielectric losses Compliance

✗  

✗  

✔  

✔  

D. Tan and P. Irwin (2011)

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(Fluoro)polymers Perovskite ceramics Relative permittivity ~10 Breakdown strength > 1000 kV/cm Dielectric loss tang. < 0.01 Piezoelectric coefficient ~-30 pC/N High coercive field 500 kV/cm Ease of processing Flexibility and compliance Low density

Why dielectric and piezoelectric composites

Relative permittivity >1000 Breakdown strength < 100 kV/mm Piezoelectric coefficient >100 pC/N Difficult processing and shaping Brittleness and high stiffness High density

High energy density capacitors: Energy harvesters: High breakdown strength High piezoelectric coefficient High relative permittivity Compliance

Transducers: High piezoelectric coefficient Low dielectric losses Compliance

D. Tan and P. Irwin (2011)

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Types of composites

Commercial applications are mainly based on 2-2 and 1-3 composites Ø Fabrication and shaping may be

complex (e.g. dice & fill) 0-3 composites allow a cost effective polymer-like processing and shaping

R.E. Newnham (1978)

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Fabrication of fluoropolymer based composites with high inorganic particles volume fractions and/or high aspect ratios: •  great surface energy difference between matrix and filler •  complex morphology due to coexistence of several phases

Polymer Ceramic particles, agglomerates and aggregates

(Solvent) Micro and macro porosity

The challenge of 0-3 composites

P(VDF-TrFe)/BaTiO3 composite (Φ=0.6)

Interface

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Fluoropolymer composites : process – structure – property analyses

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PVDF based polymers

Relative permittivity εr = 10 d33 = – 30 pC/N Ec = 500 kV/cm TC = 126 °C

H

C#

H

F#

C#

F#

F#

C#

F#

H

C#

F#n" m"

P(VDF-TrFE)

H

C#

H

F#

C#

F#

F#

C#

F#

H

C#

F#n" m"

PVDF H

α β

F

C

T  >  TC    β  è  α  

Paraelectric Piezoelectric

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Layered  silicates  (clay)  Cloisite  15A  (organically  modified  montmorillonite)                        Gas  barrier  enhancement:          

Functional (nano)particles

Barium Titanate (BT) Spherical particles, d = 200 nm Lead-free perovskite

A = Ba B = Ti

Relative permittivity εr= 2000 d33 = 100 – 350 pC/N TC = 120 °C 1Takahashi H et al. (2008)

a high-performance carbonaceous-silicate char, whichbuilds up on the surface during burning. This insulatesthe underlying material and slows the mass loss rate ofdecomposition products.

In a recent study, Zhu et al. [98] reported the fireretardant properties of PS/MMT nanocomposites,which were prepared using three different types ofnew organically modified MMT (see Fig. 25). Theyinitially used phosphonium salt for the modification ofclay, and then examined the differences betweenorgano ammonium and phosphonium salt treatmentsof clay fillers in nanocomposites towards thermalstability. The peak HRR for PS and the threenanocomposites is also shown graphically in Fig. 96.As mentioned above, the suggested mechanism bywhich clay nanocomposites function involves theformation of a char that serves as a barrier to bothmass and energy transport [17]. As the fraction of clayincreases, the amount of char that can be formedincreases, and the rate at which heat is releaseddecreases. One of these nanocomposites, OH-16, ismostly intercalated. This yields a slight reduction inthe rate of heat release compared with the other twosystems, which contain a significant exfoliatedfraction. This observation again supports the sugges-tion that an intercalated material is more effective thanan exfoliated material in fire retardance [433].

In contrast, the decrease in the rate of heat releasecorresponds to (1) a decrease in mass loss rate and theamount of energy released by the time PS has ceased

burning, and (2) a modest increase in the time atwhich the peak heat release is reached. The pro-duction of a char barrier must serve to retain some ofthe PS, and thus both the energy released and the massloss rate decrease. The amount of smoke evolved andspecific extinction area also decrease with theformation of the nanocomposites. There is somevariability in the smoke production. Although it isobserved that the formation of the nanocompositesreduces smoke production, the presence of additionalclay does not continue this smoke reduction.

4.5. Gas barrier properties

Clays are believed to increase the barrier propertiesby creating a maze or ‘tortuous path’ (see Fig. 97) thatretards the progress of the gas molecules through thematrix resin. The direct benefit of the formation ofsuch a path is clearly observed in polyimide/claynanocomposites by dramatically improved barrierproperties, with a simultaneous decrease in thethermal expansion coefficient [11,255,257]. Thepolyimide/layered silicate nanocomposites with asmall fraction of OMLS exhibited reduction in thepermeability of small gases, e.g. O2, H2O, He, CO2,and ethylacetate vapors [11]. For example, at 2 wt%clay loading, the permeability coefficient of watervapor was decreased ten-fold with synthetic micarelative to pristine polyimide. By comparing nano-composites made with layered silicates of variousaspect ratios, the permeability was seen to decreasewith increasing aspect ratio.

Oxygen gas permeability has been measured fornear to exfoliated PLA/synthetic mica nanocompo-sites prepared by Sinha Ray et al. [383]. The relativepermeability coefficient value, i.e. PPLACN=PPLA

where PPLACN and PPLA are the nanocomposite andpure PLA permeability coefficient, respectively, isplotted as a function of the wt% of OMLS inFig. 98. The data are analyzed with the Nielsentheoretical expression [436], allowing prediction of

Fig. 96. Peak HRRs for PS and the three nanocomposites [98].Reproduced from Zhu, Morgan, Lamelas and Wilkei by permission

of American Chemical Society, USA. Fig. 97. Formation of tortuous path in PLS nanocomposites.

S. Sinha Ray, M. Okamoto / Prog. Polym. Sci. 28 (2003) 1539–16411608

 CaEon  :  2M2HT  

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Melt process

Process

Solvent based

Casting, drying and annealing

Compounding in twin screw extruder

Injection or compression molding

DSM microextruder

Dispersing and homogenizing in solution

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P(VDF-TrFE) /BaTiO3 composites (ϕp= 60%): morphology

P(VDF-TrFE)+BT-A ϕv = 16% P(VDF-TrFE)+BT ϕv = 25%

Scanning electron microscopy of freeze fractured surfaces Porosity ϕv estimated gravimetrically

P(VDF-TrFE)+BT ϕv = 15% P(VDF-TrFE)+BT-TF ϕv = 9% P(VDF-TrFE)+BT-A ϕv = 11%

Process optimization

Interface modification

Interface modification

Aminosilane

Fluorosilane

H2O

H2O

Silane coupling agents:

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Differential Scanning Calorimetry ΔHf scales with BaTiO3 wt%: the degree of crystallinity of the polymer does not change with addition of BaTiO3

Crystallinity and Thermomechanical properties

Dynamic mechanical analysis

BT  

H    I  N  –  H            F        H        F        F  

       I            I          I          I  –  C  –  C  –  C  –  C  –          I          I            I          I            F        H        F        H    

Melting enthalpy of P(VDF-TrFE)/BaTiO3 composites

Hydrogen bonding between the aminosilane and P(VDF-TrFE) enhances thermomechanical stability

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Dielectric and piezoelectric properties

6  mm  

Composite  with    gold  electrodes    

RelaEve  permiRvity  and  loss  factor  of  P(VDF-­‐TrFE)/BaTiO3  composites  

d33  of  composites  poled  with  Ep  =  100  kV/cm    

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P(VDF-TrFE)/BaTiO3 composites

Piezoelectric composites with 60 vol% well dispersed submicron sized ceramic particles: •  Storage modulus: 7x increase with respect to P(VDF-TrFE)

•  Relative permittivity: 8x increase with respect to P(VDF-TrFE)

•  Piezoelectric coefficient: 5x increase with respect to P(VDF-TrFE) with poling field of 100 kV/cm

•  Particle surface modification increased thermomechanical stability and decreased dielectric loss factor at low frequency

Research is ongoing to further increase dielectric and piezoelectric properties for practical applications

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Morphology of P(VDF-TrFE)/clay composites 0.5 vol% clay:

exfoliation

4 vol% clay non-exfoliation

Images of P(VDF-TrFE)/clay films

0.5  vol%  Clay  

1.0  vol%  Clay   4.0  vol%  Clay  

0  vol%  Clay  

Non  exfoliated  clay   Exfoliated  clay  

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Differential Scanning Calorimetry The degree of crystallinity has a maximum for ϕclay = 0.5

Annealing increases β phase

Crystalline structure of (PVDF-TrFE )/clay composites

Melting enthalpy of P(VDF-TrFE)/Clay composites

X-Ray diffraction

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0h0.5%1%2%4%CM-20A-0.5%

10 20 30 40 500

100

200

300

400

500

600

0 %

10 20 30 40 50

2h4h16h40h

T (°C)

P (1

06 .cm

3 .cm

/cm

2 .s.P

a)

T (°C)

not annealed annealed

Gas barrier and piezoelectric properties

ϕclay = 0.5 %

O2 permeability of P(VDF-TrFe)/clay composites Piezoelectric coefficient of P(VDF-TrFe)/clay composites

annealed

Gas barrier and piezoelectric properties can be enhanced optimizing annealing time and clay concentration

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Self-sensing high pressure H2 storage vessel

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-­‐ High  barrier  properEes  -­‐>    Low  permeability  material    

 

-­‐ Health  monitoring  and  sensing  (safety)    -­‐>    “smart  structure”    

 

-­‐  High  pressure  to  reduce  volume    -­‐>    High  strength  without  embriblement  

Nanocomposite  of  PVDF-­‐TrFE  (poly-­‐vinylidene  fluoride  trifluoroethylene  copolymer)  with  surface  modified  clay  platelet  parGcles  

+  High  strength  carbon  fiber    reinforced  composite  

piezosensor)and)hydrogen)barrier)membrane)(PVDF))

carbon)fiber)reinforced)polymer)composite)shell)

polyamide)liner)aluminium)connec=on)

4  kg  H2  needed  to  drive  a  fuel  cell  car  400  km  (45  m3  at  ambient    -­‐>    0.11  m3  at  400  bar)  Schlapbach,  L.  Zübel,  A.  Hydrogen-­‐storage  materials  for  mobile  applicaEons,  Nature,  414  (2001)  

Self-sensing high pressure H2 storage vessel

Commercial  H2  storage  vessels  (thick  polymer  liner  +  metal  +  carbon  fiber  composites)  are  expensive  and  present  a  risk  of  H2  embriblement    

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Collaboration EPFL-CSEM on process-structure-property relations in piezoelectric polymer materials

•  The Greenpower project combines for the first time a self-sensing liner with a cost-effective composite production process

•  Proportion of piezoelectric β-phase in modified P(VDF-TrFE): 95%

•  30% increase in piezoelectric coefficient

•  10x reduction of gas permeation

Copyright 2012 CSEM | XRD Application LAB | Page 5

Figure 5. 3D isolines-view of the patterns obtained during the heating.

0 8 16 24 32 40 48

10°C30°C

50°C40°C

Annealing time [h]

0

100

200

300

400

500

600

0 10 20 30 40 50

0h2h4h16h24h48h

Temperature [°C]

P [1

016 c

m3 c

m c

m-2

s-1

Pa-1

]

0

20

40

60

80

0 20 40 60

A B

Oxygen permeability of modified P(VDF-TrFE)

In-situ XRD analysis of P(VDF-TrFE)

Self-sensing high pressure H2 storage vessel

Oliveira F, et al. (2014)

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Silver  electrode  

Composite  shell  piezo  sensor  

PA12  Liner  

1  liter,  100  bars  demonstrator  

Self-sensing high pressure H2 storage vessel

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Conclusions and outlook

• Fluoropolymer based 0-3 composites offer a unique combination of properties and design flexibility for sensing and actuating applications

• Their structure and properties are highly dependent on processing conditions

Practical applications have now become possible… …and research is still ongoing to improve their properties and scale up processes

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Acknowledgements

LTC – EPFL Ceramics Laboratory – EPFL

Dr. Y. Leterrier Prof. V. Michaud Prof. D. Damjanovic

Dr. F. Oliveira Mr. Robert Tween

Olha Sereda - CSEM

Undergraduate  students:  S.  Poitel,  V.  Magnin,  F.  Lindstroem  A.  Aebersold,  D.  Chevret,  E.  Stutz,  M.  Hausmann,  R.  Thierrin  …    Interdisciplinary  Centre  for  Electron  Microscopy  (CIME-­‐EPFL)        

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Thank you!

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References •  Dalle Vacche S, et al. The effect of processing conditions on the morphology, thermomechanical,

dielectric, and piezoelectric properties of P(VDF-TrFE)/BaTiO3 composites. Journal of Materials Science. 2012;47(11):4763-4774.

•  Dalle Vacche S, et al. Effect of silane coupling agent on the morphology, structure, and properties of poly(vinylidene fluoride–trifluoroethylene)/BaTiO3 composites. Journal of Materials Science. 2014;49(13):4552-4564.

•  Dalle Vacche S, et al. Effect of interfacial interactions on the electromechanical response of poly(vinylidene fluoride-trifluoroethylene)/BaTiO3 composites and its time dependence after poling. Composites Science and Technology. 2015;114:103-109.

•  Oliveira F, et al. Process Influences on the Structure, Piezoelectric, and Gas-Barrier Properties of PVDF-TrFE Copolymer. Journal of Polymer Science Part B-Polymer Physics. 2014;52(7):496-506.

•  Newnham RE, et al. Connectivity and piezoelectric-pyroelectric composites. Mater Res Bull. 1978;13(5):525-536.

•  Daniel Tan and Patricia Irwin (2011). Polymer Based Nanodielectric Composites, Advances in Ceramics -Electric and Magnetic Ceramics, Bioceramics, Ceramics and Environment, Prof. Costas Sikalidis (Ed.), ISBN:978-953-307-350-7, InTech

•  Takahashi H, et al. . Considerations for BaTiO3 Ceramics with High Piezoelectric Properties Fabricated by Microwave Sintering Method. Japanese Journal of Applied Physics. 2008;47(11):8468-8471.