Influence of particle arrangement on the permittivity of an elastomeric composite

Abstract

Elastomers are used as dielectric layers contained between the parallel conductive plates of capacitors. The introduction of filler particles into an elastomer changes its permittivity ε. When particle organization in a composite is intentionally varied, this alters its capacitance. Using numerical simulations, we examine how conductive particle chains introduced into polydimethylsiloxane (PDMS) alter ε. The effects of filler volume fraction ψ, interparticle d and interchain spacing a, zigzag angle θ between adjacent particles and overall chain orientation, particle size r, and clearance h between particles and the conductive plates are characterized. When filler particles are organized into chainlike structures rather than being just randomly distributed in the elastomer matrix, ε increases by as much as 85%. When particles are organized into chainlike forms, ε increases with increasing ψ and a, but decreases with increasing d and θ. A composite containing smaller particles has a higher ε when ψ<9% while larger particles provide greater enhancement when ψ is larger than that value. To enhance ε, adjacent particles must be interconnected and the overall chain direction should be oriented perpendicular to the conductive plates. These results are useful for additive manufacturing on electrical applications of elastomeric composites.

Magnetodielectric Response of Soft Magnetoactive Elastomers: Effects of Filler Concentration and Measurement Frequency

“…In the absence of magnetic field, the increase of the effective permittivity in comparison to the pure elastomer can be attributed to the presence of the conducting phase; the remarkable enhancement of the effective permittivity comes into play with the applied magnetic field. Tsai et al [16] calculated that if filler particles are organized into chainlike structures rather than just randomly distributed in the elastomer matrix, the DC effective permittivity may increase by 85%, which is approximately two times smaller than the effect observed at low (1–200 kHz) frequencies in our experiments. The electric-field-induced anisotropy of particle distribution established during the polymer curing has been studied theoretically in the closely related group of electro-active polymer materials [17,18].…”

“…Interactions of polarized magnetic particles cause their alignment into chain-like or columnar structures along the filed direction, which can simply be observed by optical microscopy [23,24]. Enhancement of the material permittivity with initial isotropic filler distribution due to a chain-like ordering of filler particles was demonstrated by numerical modeling in [16]. It should be noted that in our samples, the filling degree is rather high, so that the magnetic particles may form percolated structures within the polymer matrix [23,24].…”

Influence of the Porosity of Polymer Foams on the Performances of Capacitive Flexible Pressure Sensors

“…The porosity f of the fabricated foams is calculated from the density of the PDMS foam ( ρ foam ) and the bulk PDMS density ( ρ bulk ) using Equation (2): f=1−ρfoamρbulk, where ρ foam is determined from the ratio of the mass to the volume of the fabricated foam, and where ρ bulk = 1100 kg/m 3 [19]. The relative permittivity of the PDMS foam ( ε r ) is a combination of the relative permittivity of PDMS ( ε PDMS = 2.69 [20]) and the relative permittivity of air ( ε air = 1). The resulting foam relative permittivity can be theoretically estimated using [17]:εr=εairf+false(1−ffalse)εPDMS, where f is the foam porosity.…”

Simulation of Magnetodielectric Effect in Magnetorheological Elastomers

“…Kramarenko et al studied hysteresis characteristics of MDE in magnetoactive materials [26]. In [27], Tsai et al studied influence of conductive particles chains on permittivity of elastomer. They showed that organizing particles into chain-like structures may increase permittivity of material by 85% compared to random distribution of filler particles.…”