Ultralight Microcellular Polymer–Graphene Nanoplatelet Foams with Enhanced Dielectric Performance

Abstract

Dielectric polymer nanocomposites with high dielectric constant (ε') and low dielectric loss (tan δ) are extremely desirable in the electronics industry. Percolative polymer-graphene nanoplatelet (GnP) composites have shown great promise as dielectric materials for high-performance capacitors. Herein, an industrially-viable technique for manufacturing a new class of ultralight polymer composite foams using commercial GnPs with excellent dielectric performance is presented. Using this method, the high-density polyethylene (HDPE)-GnPs composites with a microcellular structure were fabricated by melt-mixing. This was followed by supercritical fluid (SCF) treatment and physical foaming in an extrusion process, which added an extra layer of design flexibility. The SCF treatment effectively in situ exfoliated the GnPs in the polymer matrix. Moreover, the generation of a microcellular structure produced numerous parallel-plate nanocapacitors consisting of GnP pairs as electrodes with insulating polymer as nanodielectrics. This significantly increased the real permittivity and decreased the dielectric loss. The ultralight extruded HDPE-1.08 vol % GnP composite foams, with a 0.15 g·cm density, had an excellent combination of dielectric properties (ε' = 77.5, tan δ = 0.003 at 1 × 10 Hz), which were superior to their compression-molded counterparts (ε' = 19.9, tan δ = 0.15 and density of = 1.2 g·cm) and to those reported in the literature. This dramatic improvement resulted from in situ GnP's exfoliation and dispersion, as well as a unique GnP parallel-plate arrangement around the cells. Thus, this facile method provides a scalable method to produce ultralight dielectric polymer nanocomposites, with a microscopically tailored microstructure for use in electronic devices.

Thermal‐Insulation, Electrical, and Mechanical Properties of Highly‐Expanded PMMA/MWCNT Nanocomposite Foams Fabricated by Supercritical CO2 Foaming

“…Similar high electrical conductivity of conductive polymer composite foams was also found in some other published literatures . Moreover, it is reported that there is an optimal expansion ratio to allow the nanocomposite foams with a fixed MWCNT content to achieve the highest electrical conductivity . However, the optimal expansion ratio is very low, usually less than fivefold.…”

A reduced graphene oxide–borate compound-loaded melamine sponge/silicone rubber composite with ultra-high dielectric constant

“…This was due to an increase in the number of "micro-capacitors" and the increased interface between rGB and SR; this resulted in higher interfacial polarization density and dielectric constant. 11 Therefore, the sample obtained using the rGO volume fraction of 0.81 vol% at the frequency of 1 kHz had the ultrahigh dielectric constant of up to 2.71 Â 10 4 , which was four orders of magnitude higher than that of the MS/SR composite. In particular, note that both MS/rGO/SR and MS/borate/SR have signicantly lower dielectric constants than the MGS composite; this shows that a synergistic effect exists between rGO and borates with an increase in dielectric constants.…”

“…10 Polymer-based conductive ller composites have the advantages of lightweightness, low cost, high exibility, high corrosion resistance, excellent processability, and adjustable dielectric constant and dielectric loss. 11 To a certain extent, these advantages overcome the limitations of polymerbased ceramic ller composites and can help in the achievement of higher dielectric constants at ultralow ller concentrations; 6,12,13 therefore, these composites have broad application prospects in health monitoring, wearable electronic devices, motion sensors and electromagnetic shielding. [14][15][16] The conductive network formed by conductive llers can usually improve the electrical properties of composites.…”

Supercritical Fluid‐Facilitated Exfoliation and Processing of 2D Materials

“…After rapid pressure reduction, CO 2 solubility in a composite decreases, causing nucleation and growth of oversaturated CO 2 to generate bubbles. [125] The GNP had nominal dimensions of 50 µm in diameter and 20 nm in thickness. Such porous structures encompass closed cell pores, open-cell pores (interconnected cells), macropores, and mesopores.…”

“…As a result, 2D nanosheets coated with a porous polymer network are formed. [125] This foaming action resulted in a positive synergistic effect to produce parallel GNPs that were very polarizable in applied fields. Foam inner morphology relies on SCF saturation level that is associated with several parameters such as SCF pressure and temperature, dynamics of nucleation and bubble growth (due to pressure drop and interfacial stabilization by nanosheets [126] ), and SCF pressure reduction rate.…”