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Bimodal condensation silicone elastomers as dielectric elastomers
Yu, Liyun; Madsen, Frederikke Bahrt; Skov, Anne Ladegaard
Publication date:
2016
Document Version
Accepted author manuscript
Link to publication
Citation (APA):
Yu, L., Madsen, F. B., & Skov, A. L. (2016). Bimodal condensation silicone elastomers as dielectric elastomers.
Poster session presented at 6th International Conference on Electromechanically Active Polymer (EAP)
Transducers & Artificial Muscles, Helsingør, Denmark.
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EuroEAP 2016
International conference on Electromechanically Active
Polymer (EAP) transducers & artificial muscles
Helsingør (Copenhagen), 14-15 June 2016
Poster ID:
2.3.5
Bimodal condensation silicone elastomers as dielectric elastomers
Liyun Yu, Frederikke Bahrt Madsen, Anne Ladegaard Skov*
Contact e-mail:
[email protected]
Technical University of Denmark, Department of Chemical and Biochemical Engineering, The Danish Polymer Centre, Lyngby, Denmark
Abstract
Lately, dielectric elastomers (DEs) which consist of an elastomer sandwiched between electrodes on both sides, have gained interest as materials for actuators, generators, and sensors. An ideal elastomer for DE uses
is characterized by high extensibility, flexibility and good mechanical fatigue as well as high electrical and mechanical breakdown strengths. [1] Most model elastomers are prepared by an end-linking process using a
crosslinker with a certain functionality f and a linear polymer with functional groups in both ends, and the resulting networks are so-called unimodal networks where unimodal refers to that there is one polymer only
in the system. As an alternative to unimodal networks there are the bimodal networks where two polymers with significantly different molecular weights are mixed with one crosslinker. [2]
Silicone rubber can be divided into condensation type and addition type according to the curing reaction. The advantages of condensation silicones compared to addition are the relatively low cost, the curing rate
largely being independent of temperature, the excellent adhesion, and the catalyst being nontoxic. [3]
In this work, a series of bimodal condensation silicone elastomers were prepared by mixing different mass ratios between long polydimethylsiloxane (PDMS) chains and short PDMS chains. The resulting elastomers
were investigated with respect to their rheology, dielectric properties, tensile strength, electrical breakdown, thermal stability, as well as hydrophobicity and morphology.
Keywords: bimodal, condensation silicone, dielectric properties, tensile sterngth, electrical breakdown
Results
Unimodal network
Short chain
Long chain
Bimodal network
Condensation
curing
Long chain : Short chain = 10:0, 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 0:10 (mass ratio), @23oC & 50% RH
Long chain : Short chain = 7:3 (mass ratio), @23oC
@ 90%, 70%, 50%, 30%, 10% RH
Viscoelasticity
90%
70%
BD
(V/µm)
80
76
Tensile strength
(MPa)
1.59
1.45
Strain @ Break
(%)
197
211
Y @5% strain
(MPa)
1.51
1.35
50%
71
1.33
190
1.20
30%
10%
69
64
1.15
0.93
179
157
1.03
0.90
Composition
70% FD6 +
30% cSt40
RH
Breakdown
Tensile strength
Long chain : Short chain = 7:3 (mass ratio), @23oC & 50% RH
Composition
Bottom surface
Top surface
Pure FD6
90% FD6 + 10% cSt40
80% FD6 + 20% cSt40
70% FD6 + 30% cSt40
60% FD6 + 40% cSt40
50% FD6 + 50% cSt40
40% FD6 + 60% cSt40
Pure cSt40
G’ @0.01Hz
(MPa)
0.54
0.50
0.46
0.38
0.80
0.85
0.94
1.91
Tanδ @0.01Hz
0.020
0.013
0.019
0.047
0.050
0.074
0.113
0.077
Tensile strength Strain @ Break (%) Y @5%strain
(MPa)
(MPa)
0.68
60
1.54
0.92
115
1.47
0.97
133
1.42
1.33
190
1.20
1.26
155
1.39
0.66
45
2.18
0.59
19
2.36
-
BD
(V/μm)
53
70
73
71
63
51
25
-
Dielectric properties
Conclusions
A series of bimodal condensation silicone elastomers were prepared by mixing different mass
ratios (10:0, 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 0:10) between long PDMS chains and short PDMS
chains. The bimodal elastomers reinforce themselves at large strain and the high electrical
breakdown strength is obtained due both to the low extensibility of the short chains that attach
strongly the long chains and to the extensibility of the last ones that retards the rupture process.
Moreover, a series of elastomers with the same mass ratio (7:3) between long and short PDMS
chains were made at different humidity (90%, 70%, 50%, 30%, 10%) at 23oC. The dielectric and
mechincal properties of the resulting elastomers were shown to depend strongly on the
atmospheric humidity level.
In addition, the top and bottom surfaces of the elastomer (7:3) prepared at 23oC and 50%
humidity were tested by water contact angle and optical microscope. The results show the
bimodal condensation elastomer possesses structural heterogeneity, which may lead to
favourable properties for DE applications.
Acknowledgments
The authors gratefully acknowledge the financial support of InnovationsFonden.
Thermal stability
Composition
Pure FD6
90% FD6 + 10% cSt40
80% FD6 + 20% cSt40
70% FD6 + 30% cSt40
60% FD6 + 40% cSt40
50% FD6 + 50% cSt40
40% FD6 + 60% cSt40
Pure cSt40
References
1. F.B. Madsen, A.E. Daugaard, S. Hvilsted, A.L. Skov. The current state of silicone-based dielectric elastomer transducers. Macromolecular Rapid Communications 2016, 37, 378.
2. A.G. Bejenariu, L. Yu, A.L. Skov. Low moduli elastomers with low viscous dissipation. Soft Matter 2012, 8, 3917.
3. A.R. Hannas, L.T.A. Poletto, E.L. Souza, J.F.B.G. Giovannini. Quantification of the condensation silicone curing contraction. Journal of Dental Research 2002, 81, B173.
εr
@0.1Hz
3.26
3.50
3.77
3.84
3.61
3.56
3.92
4.16
Loss Tanδ
@0.1Hz
0.055
0.023
0.053
0.238
0.277
0.783
0.895
1.02
σ @0.1Hz
(S/cm)
1.26E-13
1.39E-13
1.49E-13
1.55E-13
1.66E-13
2.28E-13
2.36E-13
2.95E-13
Td2%
(oC)
302
303
306
309
310
314
318
326