TY  - JOUR
A1  - Stoyanov, Hristiyan
A1  - Mc Carthy, Denis N.
A1  - Kollosche, Matthias
A1  - Kofod, Guggi
T1  - Dielectric properties and electric breakdown strength of a subpercolative composite of carbon black in thermoplastic copolymer
N2  - We investigate the dielectric properties and electric breakdown strength of subpercolative composites of conductive carbon black particles in a rubber insulating matrix. A significant increase in the permittivity in the vicinity of the insulator to conductor transition was observed, with relatively low increases in dielectric loss; however, a rapid decrease in electric breakdown strength was inevitable. A steplike feature was ascribed to agglomeration effects. The low ultimate values of the electric field strength of such composites appear to prohibit practical use.
Y1  - 2009
UR  - http://apl.aip.org/
U6  - https://doi.org/10.1063/1.3154553
SN  - 0003-6951
ER  - 
TY  - JOUR
A1  - Mc Carthy, Denis N.
A1  - Risse, Stefan
A1  - Katekomol, Phisan
A1  - Kofod, Guggi
T1  - The effect of dispersion on the increased relative permittivity of TiO2/SEBS composites
N2  - Polymer composites are currently suggested for use as improved dielectric materials in many applications. Here, the effect of particle size and dispersion on the electrical properties of composites of rutile TiO2 and poly(styrene- ethylene-butadiene-styrene) (SEBS) are investigated. Both 15 and 300 nm particles are mixed with SEBS, with amounts of sorbitan monopalmitate surfactant from 0 to 3.3 vol%, and their dielectric and mechanical properties are measured. Composites with the 300 nm TiO2 particles result in increases of 170% in relative permittivity over the pure polymer, far above those predicted by standard theories, such as Bruggeman (140%) and Yamada (114%), and improving dispersion with surfactant has little effect. The composites with 15 nm particles showed surprisingly large relative permittivity increases (350%), but improving the dispersion by the addition of any surfactant causes the relative permittivity to decrease to 240% of the pure polymer value. We suggest that the increase is due to the formation of a highly conductive layer in the polymer around the TiO2 particles.
Y1  - 2009
UR  - http://iopscience.iop.org/0022-3727/
U6  - https://doi.org/10.1088/0022-3727/42/14/145406
SN  - 0022-3727
ER  - 
TY  - JOUR
A1  - Kofod, Guggi
A1  - Mc Carthy, Denis N.
A1  - Krissler, Jan
A1  - Lang, Günter
A1  - Jordan, Grace
T1  - Electroelastic optical fiber positioning with submicrometer accuracy : model and experiment
N2  - We present accurate electromechanical measurements on a balanced push-pull dielectric elastomer actuator, demonstrating submicrometer accurate position control. An analytical model based on a simplified pure-shear dielectric elastomer film with prestretch is found to capture the voltage-displacement behavior, with reduced output due to the boundary conditions. Two complementary experiments show that actuation coefficients of 0.5-1 nm/V-2 are obtainable with the demonstrated device, enabling motion control with submicrometer accuracy in a voltage range below 200 V.
Y1  - 2009
UR  - http://apl.aip.org/
U6  - https://doi.org/10.1063/1.3134002
SN  - 0003-6951
ER  -