Structure-induced high dielectric constant and low loss of CNF/PVDF composites with heterogeneous CNF distribution

Abstract

The enhancement of dielectric constant in a polymer while maintaining low loss through composite methods has been challenging. In this paper, we report that through designing multi-layered structures with carbon nanofiber (CNF)/poly(vinylidene fluoride) (PVDF) composites intercalated by a pure PVDF layer, enhanced dielectric constant and low loss were achieved. The dielectric loss was similar to that of pure PVDF at high frequencies and even lower than pure PVDF at low frequencies. The results were achieved by designing special multi-layered structures including CNF/PVDF composite layers. The multi-layered sandwich-like or laminate structure composites with transversely heterogeneous CNF distributions were prepared using a simple two-step processing including solution casting and compression molding methods. The dielectric constant obtained from the sandwich structure containing 5, 7 and 15 wt% CNF/PVDF composite layers is even more independent of the frequency in a wide range from 10(2) to 10(6) Hz. Furthermore, the effects of the heterogeneous CNF distribution on the dielectric properties were studied by designing different multi-layered composite structures with varying architecture while maintaining the same CNF concentration level. It is shown that varying this stack-up architecture of different CNF distributions plays an important role in the enhancement level of the dielectric constant while having negligible effect on the dielectric loss of the nanocomposite, which is determined mainly by the CNF loading content.

Modeling large permittivity of poly(vinylidenefluoride-co-trifluoroethylene) and nanospring single-walled carbon nanotube-polyvinylpyrrolidone nanocomposites

“…6,7 CNTs having high electron density in the ferroelectric polymer formed many local capacitors, which in turn increased the dielectric constant of the composites. 8 According to Lee et al, 1 when NS-CNTs were incorporated in a piezoelectric P(VDF-TrFE) polymer matrix with up to 15 wt.% of nanofiller, the dielectric constant (K) of the nanocomposite at 1 kHz was greatly enhanced from 12.7 (pristine) to 62.5 with 11 wt.% NS-CNTs, corresponding to a 492% increase while retaining a dielectric loss tangent (D) as small as tan θ=0.1. Thus, it is key to understand how the dielectric constant of these composite materials can be greatly increased by mixing uniquely shaped NS-CNTs nanofillers made of multiple piled layers with an empty interior.…”

Enhanced dielectric and mechanical properties in chlorine-doped continuous CNT sheet reinforced sandwich polyvinylidene fluoride film

“…Ag [12], Zn [13]), carbon-based materials (e.g. carbon nano fiber [14], graphene [15], reduced graphene oxide [16]), and semiconductor fillers (e.g. SiC [17], Bi 2 S 3 [18]) into an insulating polymer matrix.…”

Enhancing the dielectric properties of highly compatible new polyimide/γ-ray irradiated MWCNT nanocomposites

“…Polymer-based composites were explored as dielectric materials to solve the problems associated with other conventional dielectrics 24,25 . Considering high mechanical strength, good solvent resistance, excellent thermal stability, and low dielectric loss, PIs gained preference over other polymeric dielectrics [36][37][38][39][40][41][42] . Among these polymers, polyvinylidene fluoride (PVDF) and its copolymers are most widely explored materials due to high dielectric constants originating from their high dipole density 1, 27,29 .…”

“…Considering high mechanical strength, good solvent resistance, excellent thermal stability, and low dielectric loss, PIs gained preference over other polymeric dielectrics [36][37][38][39][40][41][42] . Various researchers reported the dispersion of CNTs in poly(methyl methacrylate) 35 , PVDF 29,37,[48][49][50] , cyanate ester [51][52][53][54] , and polyurethane 34,55 . The applicability of PIs as dielectric material can be enhanced by substantially increasing their dielectric constant while retaining their high tensile strength, thermal stability, and chemical resistance.…”