Preferred structuring of filler particles in a polymer matrix by using dielectrophoretic assembly process can enhance anisotropic dielectric properties. For this purpose, precipitated silica (SiO2) was structured in silicone rubber using an alternating electric field. This filler structure was stabilized by vulcanizing rubber during electric field application. Filler particle orientation and resulted anisotropy was verified by equilibrium swelling. Structuring filler in the rubber matrix led to increased dielectric permittivity and loss in the thickness direction. Filler surface modification by (vinyl-tris-(2- diethoxy/methoxy) silane) improved structure formation and anisotropic properties. It was shown that applying silane modifier and orientation of silica particles by dielectrophoretic assembly process increased dielectric permittivity of silicone rubber in the thickness direction while dielectric loss had either minor changes or increased less than permittivity in this direction. Although elastic modulus of composite, which was measured by dynamic-mechanical analysis, increased to some extent, enhancement in dielectric permittivity was much higher. This introduced the structured composite as a potential for dielectric elastomeric actuator with higher efficiency than the original silicone rubber with no filler addition.
Formation of controlled morphology of fillers in polymeric composites may be difficult to achieve by conventional
methods such as mechanical shear or chemical methods. Tunable structure of filler and anisotropic properties in
composites can be obtained by exploiting dielectrophoretic assembly of fillers in a polymer composite by using electric
fields. In this study, different concentrations of Titanium Dioxide (TiO2) particles in silicone rubber matrix were
assembled in a chain-like structure by using an alternating electric field. Silicone rubber matrix was vulcanized to
transform the liquid to solid and maintain the filler structure in the desired direction. Generation of chain structure of
filler was verified by Scanning Electron Microscopy (SEM) and equilibrium swelling. It was shown that dielectric
permittivity of the oriented composite is higher whereas its dielectric loss factor is lower in the orientation (thickness)
direction than those for the composites with random distribution of filler. This phenomenon was in agreement with
results of dynamic-mechanical loss factor for these composites, and can be utilized in more efficient dielectric elastomer
actuators. Elastic modulus is higher for the structured samples, but presence of titania filler induced a softening effect at
higher strains where the actuators are practically being pre-stretched. A critical concentration of filler was distinguished
as the percolation point at which the change in dielectric behavior is amplified. Using a simple blocking-force
measurement, potential advantages of structured composites over the ones with randomly-distributed filler was explained
for potential dielectric elastomer actuator applications.
Dielectric elastomer composites are widely used electromechanical actuators. Compounding of dielectric elastomers
with electroceramics helps to decrease the required electric field. In this work, silicone rubber was compounded with
Lead- Zirconate-Titanate (PZT) electroceramic powder by the help of a silane coupling agent for better compatibility
between organic ceramic and inorganic polymer. Modified PZT was added to silicone rubber with variable amount to
study the effect of ceramic concentration on composites properties. Morphology of the composites was characterized by
scanning electron microscopy, mechanical properties of the samples were studied by uniaxial tension, and their dielectric
properties were compared through dielectric measurements. The results showed that at about 10 wt% of PZT loading
dielectric permittivity is higher for this composite compared to those for composites with lower or even higher loading of PZT.
Dielectric elastomers are light weight, low-cost, and highly deformable smart materials widely in used as sensors and
actuators. Compounding of silicone rubber with various fillers can enhance efficiency of smart materials. Effect of
organically modified Montmorillonite (OMMT) nanoclay on improvement of dielectric properties and actuation stress
was considered in this study. Room Temperature Vulcanized (RTV) silicone rubber was compound with 2% and 5% of
OMMT by solution method and a composite film was cast. Dielectric measurements show enhancement of both
dielectric permittivity and dielectric loss in these composites. Actuation stress for different composites was measured by
using an in-house actuation set-up, which showed that actuation stress for a given electric field intensity is higher for
composites than that for pristine silicone rubber. Furthermore, time dependent actuation response of the samples was
evaluated. Dielectric properties of the composites were measured under AC electric fields, and results were compared
with the reference silicone rubbers with no filler. Results shows increase in both storage and loss dielectric constants of
base silicone rubber when it is compounded with OMMT.
Conference Committee Involvement (11)
Electroactive Polymer Actuators and Devices (EAPAD) XXII
27 April 2020 | Online Only, California, United States
Electroactive Polymer Actuators and Devices (EAPAD) XXI
4 March 2019 | Denver, Colorado, United States
Electroactive Polymer Actuators and Devices (EAPAD) XX
5 March 2018 | Denver, Colorado, United States
Electroactive Polymer Actuators and Devices (EAPAD) XIX
26 March 2017 | Portland, Oregon, United States
Electroactive Polymer Actuators and Devices (EAPAD) XVIII
21 March 2016 | Las Vegas, Nevada, United States
Electroactive Polymer Actuators and Devices (EAPAD) XVII
9 March 2015 | San Diego, California, United States
Electroactive Polymer Actuators and Devices (EAPAD) XVI
10 March 2014 | San Diego, California, United States
Electroactive Polymer Actuators and Devices (EAPAD) XV
11 March 2013 | San Diego, California, United States
Electroactive Polymer Actuators and Devices (EAPAD) XIV
12 March 2012 | San Diego, California, United States
Electroactive Polymer Actuators and Devices (EAPAD) XIII
7 March 2011 | San Diego, California, United States
Electroactive Polymer Actuators and Devices (EAPAD) XII
8 March 2010 | San Diego, California, United States
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