new elastomer applications - tut · nbr. examples from ongoing research ... 150 nm incorporated in...
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Amit Das1,2, Minna Poikelispää1, Alexandra Shakun1, Jyrki Vuorinen1
1Department of Materials Science, Technical University of Tampere, Finland2Leibniz-Institut für Polymerforschung Dresden e.V., Germany
New Elastomer Applications
Exploitation of rubber formulations
• A crosslinked polymer (high molecular weight) Rubber
StretchedRelaxed
• Peroxide• Organic peroxide
• Co-agent• Antioxidant• Antiozonant
• Processing aid• Mastication agent
• Fillers• Dispersing agent
• Sulphur• Organic accelerator
• Sulphur• --• --• --• --• --
Mainly two different ways ofcrosslinking
2
3
Examples from ongoing research
Artificial Muscles by DielectricElastomers
Sensor Materials fromElectrically Conducting Rubbers
Self-healing Rubber Materials
4
Artificial Muscles by DielectricElastomers
Sensor Materials fromElectrically Conducting Rubbers
Self-healing Rubber Materials
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Voltage off Voltage on
Weight lifting by Maxwell stress, source: JAppl Phy 112, 041101 (2012)
Dielectric elastomer actuator (DEA) can have more promising future in the application of artificialmuscles due to its physical nature like human muscle and various adjustable properties whichcan be tailored according to the demand.
Dielectric elastomer for artificial muscles
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Dielectric materials:
• High polarity
• Low modulus, Y
• High relative dielectric permittivity, ε’
• Low dielectric losses, ε’’
Electrodes:
• Compliant
• Durable
• High electric conductivity
• Easy fabrication• Design freedom• Cost efficiency• Reasonable life-time• High performance (low
energy loss)
State of the art
Most of the actuator materials based oncommercial silicone rubber or ACM tape from 3M 7
DEAs usually require high operating electricfields E (up to 100 kV/mm)
Modification of general purpose rubbers
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Actuation behaviour
Commercial ACM tape
• Well-studied
• Used in large number of articles
Reference samples
• Compounded and fabricated atTUT
75% prestrain
0
1
2
3
4
5
6
1 3 5 7 9St
ress
,kPa
Electric field, kV/mm
3M tape NBR3330
Reference sample ACM NBR
Dielectric permittivity 6.6 18.3
Modulus 0.97 MPa 1.66 MPa
ε’/Y ratio 6.8 11.0
3M adhesive tape VHB4910
Dielectric permittivity 6.4
Modulus 0.88 MPa
ε’/Y ratio 7.3
00.20.40.60.8
11.21.41.61.8
1 2 3 4 5 6 7 8
Stre
ss,k
Pa
Electric field, kV/mm
3M ACM 75% prestrain
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Actuation performance of general purpose rubbers
02468
10121416
1 3 5 7
Stre
ss,k
Pa
Electric field, kV/mm
neatLNBR5F5DOA5
0
0.4
0.8
0 5 10Actu
atio
nst
ress
,kPa
Electric field, kV/mm
ACM (pure)
ACM + Dielectric Filler
4
8
12
16
1.00E-01 1.00E+02 1.00E+05
Rela
tive
perm
ittiv
ity,-
Frequency, Hz
0
0.4
0.8
1.2
1.6
2
0 5 10
Actu
atio
nst
ress
,kPa
Electric field, kV/mm
NBR 3330
NBR 3945
XNBR
ACM(dual)
CO
NR
Dielectric transformeroil, Fomblin (F)Liquid nitrile rubber(LNBR)Dioctyl adipate (DOA)
BaTi
O3
Tailor-madeproperties General purpose rubber can be formulated according to the desire way can be utilised
as dielectric actuator materials. The use of dielectric filler the permittivity of the acrylicrubber increases and enhances the actuation performance.
10
NBR
Examples from ongoing research
Artificial Muscle by DielectricElastomers
Sensor Materials fromElectrically Conducting Rubbers
Self-healing Rubber Materials
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Elastomeric Sensor Materials
R [ ]WR [ ]W
R [ ]WR [ ]W
e
1 10 100
200
400
600
800
1000
Rel
.res
ista
nce
(%)
Strain e [%]
Rubber-based Piezoresistive Strain Sensors or Conductors
Schematic illustration of piezorestistive strain sensing in rubber filledwith electrical conductive carbon nanotubes
Dependence of the electrical resistance on strainof a piezorestistive rubber material
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conductors
sensors
Elastomeric sensors
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0 10 20 30 40 50 600
200
400
600
800
1000
Res
ista
nce
kOhm
Strain (%)
3 CNT 3.5 CNT 4 CNT 5 CNT
Strain, pressure sensors and body movement monitoring based on conducting elastomers
10 10010-2
10-1
100
101
102
103
104
DR
/R0
% Strain
MWCNT 2.75 phr MWCNT 3 phr MWCNT 4 phr
0 100 200 300 400 50010-2
10-1
100
101
102
Time (sec.)
Rel
.Res
ista
nce
0
50
100
150
200
250
300
Strain
(%)
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Specialdispersiontechnique
Dynamic Piezoresistive Sensor Materials
• Stress, strain and relative resistance responses of in 5 sec window
• In accordance to the strain, there is a proportionate response for stress and resistance
DMA – equipped with electricalresistivity measurement
top: dynamic mechanical measurement (force / strain)bottom: dynamic resistivity / conductivity measurement
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0 1 2 3 4 5
-40
-20
0
20
40 Strain [%] Stress [MPa] Rel. resistance [%]
Time [s]
-1
0
1
-100
0
100
Response of the electrical resistance ondynamic mechanical stress / strain
Dynamic Piezoresistive Sensor Materials
s id ew al l
p iezo -res is tivesenso r
s id ew al l
p iezo -res is tivesenso r
Possible application:• Piezoresistive sensors in tires for
information on running conditions, oscillationfrequencies of the tire, acceleration signals,temperature, deflation, rolling resistance,roughness of the road surface, tire wear, orfatigue of the tire
• structural health monitoring of elastomermaterials, as sealing gaskets, bearings …
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Elastic Conductors: Hybrid fillers:
Special Carbon BlackDBP number : 350 - 410 ml/100gSurface Area: 1002 m2/gPrimary particle size: 35nm
Special silica(Sidistar)Surface Area: 20 m2/gPrimary particle size: 150 nm
Incorporated in S-SBR together
• Very high structure carbon black with very large surface area• Non reinforcing microsize silica particles (Sidistar) with very low surface
area
Special Rubber Composites
Synergisticeffect!!!
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Development of highly electrical conducting elastomers
40 50 60 70 80 90 10010-3
10-2
10-1
elec
tric
alvo
l.co
nduc
tivity
(S.c
m-1
)
Amount of Sidistar
with Sidistar
without Sidistar (20 phr CB)
Eshwaran et al. Manuscript under preparation 17
0 100 200 3000
10
20
30
40
Time (s)
Res
ista
nce
(MO
hm)
Stra
in(%
)
0
50
100
150
200
0 100 200 300 400 5000
200
400
600
800
1000
Time (s)
Res
ista
nce
(kO
hm)
Stra
in(%
)
0
4
8
12
16
20
Examples from ongoing research
Artificial Muscle by DielectricElastomers
Sensor Materials fromElectrically Conducting Rubbers
Self-healing Rubber Materials
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Example of Self-healing and literature!
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• Viscous liquids
• Raw rubbers
• Thermoplastics
Water has also a self-healing character!
Intrinsic nature of aviscous polymer!
Macromol. Chem. Phys. 2012, 213, 234−242
Self-healing materials are smart materials that can intrinsically repair damageleading to longer lifetimes, reduce inefficiency caused by degradation.
An un-crosslinkedrubber has always
a self-healing tendency
This rubber cap is alsocapable to self-
healing!
Butyl and bromobutyl rubber application
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• Very low gas permeability• Chemicaly inert• High tensile strength• Heat and weathering resistant• High damping
-150 -100 -50 0 50 100
0.0
0.5
1.0
1.5
tand
Temperature °C
Natural Rubber
Butyl Rubber
Typical dynamic mechanical pattern of Butyl Rubber
bromination
Bromine modifiedPoly-isobutylene-
isoprene co-polymer(BIIR)
Modification of the BIIR
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ΔT
0 5 10 15 20 25 300
5
10
15
20
25
30
35
BIIR and butyl imidazole at 85°C
Torq
ue(N
m)
Time (min)
pure BIIR at 85°C
0 5 10 15 20 25 300
5
10
15
20
25
Torq
ue(N
m)
Time (min)
pure BIIR at 40°C
BIIR and Butyl imidazole at 40°C
Modification of the bromobutyl rubber by imidazole (polyisobutylene-isoprene copolymer)
Torque time curves for the mixing of BIIR and butyl imidazole obtainedfrom an internal mixer (Thermo Hakke Rheocord Polylab), capacity of 75
ml and the rotor speed was 60 rpm
Network formation by ionicassociation
Self-healing nature of modified BIIR
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Modified rubber strip was cut into two pieces and allowed to mend for 24 hrs and finally tested!
Direct Self-healing Test
Healing was carried out at room temperature after keeping the damaged samples for 1h to 192 h(black); some samples were kept at 100 °C for the first 10 min of the total healing time (red) 23
Test of self-healing
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Acknowledgement
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Phd studentsEshwaranSankarDebdiptaAladdin….