Abstract
Ternary composites of flexible thermoplastic polyurethane (TPU), lead zirconate titanate (PZT), and multiwalled carbon nanotubes (MWCNTs) with very high dielectric permittivity (εr) and low dielectric loss (tan δ) are reported. To assess the evolution of dielectric properties with the interactions between conductive and dielectric fillers, composites were designed with a range of content for PZT (0–30 vol%) and MWCNT (0–1 vol%). The microstructure was composed of PZT-rich and segregated MWCNT-rich regions, which could effectively prevent the formation of macroscopic MWCNT conductive networks and thus reduce the high ohmic loss. Therefore, εr increased by a maximum of tenfold, reaching up to 166 by the addition of up to 1 vol% MWCNT to TPU/PZT. More importantly, tan δ remained relatively unchanged at 0.06–0.08, a similar range to that of pure TPU. εr/tan δ ratio reached 2870 at TPU/30 vol% PZT/0.5 vol% MWCNT, exceeding most of the reported values. This work demonstrates the potential of three-phase polymer/conductive filler/dielectric filler composites for efficient charge storage applications.
Highlights
With the continuous demand for enhanced materials in diverse areas of applications, research has progressed toward multi-phase materials with complementary properties, which are not obtainable using the constituents individually
For a 30 vol% ceramic filler content, the establishment of electrical connectivity of the multiwalled carbon nanotubes (MWCNTs) was studied, but the results showed no huge enhancements in the dielectric properties [42]
In thermoplastic polyurethane (TPU)/PZT/MWCNT composites, a smaller number and size of MWCNT agglomerates were observed, which is due the fact that the micro-sized PZT filler disentangled some of the larger nanotube aggregates during mixing and interconnected the networks of MWCNTs and helped achieve a more uniform dispersion of the fillers
Summary
With the continuous demand for enhanced materials in diverse areas of applications, research has progressed toward multi-phase materials with complementary properties, which are not obtainable using the constituents individually. Dielectric materials with high dielectric permittivity are widely required for applications such as energy storage in batteries and supercapacitors [6,7,8,9], actuators [10,11,12,13,14], electromagnetic interface (EMI) shielding [4,15,16,17], and static charge dissipation [18,19] Ceramics such as barium titanate (εr = 1700 [20]) and lead zirconate titanate (εr = 3400 [21]) exhibit very high relative permittivity, but they are brittle and heavy with low dielectric strength [22] and difficult fabrication processes. This, in turn, results in a composite with poor mechanical properties, poor processability, and poor adhesive strength
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