Tuning the Network Structure in Poly(vinylidene fluoride)/Carbon Nanotube Nanocomposites Using Carbon Black: Toward Improvements of Conductivity and Piezoresistive Sensitivity

Abstract

Piezoresistive poly(vinylidene fluoride) (PVDF) nanocomposites are very intriguing for strain sensor applications in structural health monitoring (SHM) systems. In general, high piezoresistive sensitivity combined with broad measurable strain ranges are greatly favored in those sensors. Here, a facile strategy, i.e. constructing strain susceptible conductive networks using hybrid filler systems consisting of carbon nanotubes (CNTs, 0.5-1 wt %) and carbon black (CB, 0.5-4 wt %), was introduced to tune both electrical conductivity and piezoresistive sensitivity of melt mixed PVDF nanocomposites. At the same filler content CNTs, due to their larger aspect ratio, contribute more to electrical conductivity improvements of nanocomposites than CB, while contacts between CB particles are more sensitive to tensile strain. With retained ductility of PVDF, tunable electrical conductivity and ΔR/R0-strain sensitivity can be achieved by combining the advantages of CNTs and CB by adjusting the conductive network structure. Conductivity improvement is more remarkable if the mass ratio of CNTs to CB (mCNTs/mCB), varied between 1:1 and 1:4, is higher in hybrid filler compositions. Lower mCNTs/mCB ratios result in higher ΔR/R0 values in PVDF nanocomposites whether they have the same content of total filler or similar/the same initial electrical resistivity. At 10% tensile strain, the highest ΔR/R0 of 0.65 was obtained for the nanocomposite filled with 0.5 wt % CNTs and 0.5 wt % CB, while that for the counterpart containing 1 wt % CNTs is 0.35 at the same strain. The concept of using hybrid fillers provides a low-cost and effective way to fabricate piezoresistive polymer nanocomposites toward SHM applications.

Dielectric behavior and electrical conductivity of PVDF filled with functionalized single-walled carbon nanotubes

“…Probably, carbon nanotubes (CNTs) are among the most studied reinforcements due to their intrinsic characteristics including high aspect ratio, outstanding electrical and mechanical properties, and versatility for surface functionalization. The CNT/PVDF composites enable new applications in different sectors, including membranes for ultrafiltration [3], superhydrophobic surfaces [4] fuel cell electrodes, charge transport layers in sensor systems [5], high energy storage systems [6,7], infrared detectors [8], electromagnetic interference shielding and radar absorbing coatings for military energy systems [9], electrodes for electrocardiograms [10], actuators and pressure sensors [11,12], in-vitro muscle cell growth [13], and structural health monitoring systems [14]. A comprehensive description of the applications of CNT-based PVDF composites can be found in several reviews [15,16].…”

Comprehensive Analysis of Mechanical Properties of CB/SiO2/PVDF Composites

“…In the beginning of this paper, we reviewed the vital importance of fillers in terms of the mechanical and electrical properties of PVDF matrix composites. The study of Ke et al [21] showed that, when the filler content of CB in the PVDF/CB system was 1.81 wt.%, the volume resistivity approached 10 13 , and, when the filler was increased to 4 wt.%, the volume resistivity decreased to about 10 3 . Huang et al [22] found that, with the increase in CB load, the electrical conductivity of composites increased obviously.…”

1-D polymer ternary composites: Understanding materials interaction, percolation behaviors and mechanism toward ultra-high stretchable and super-sensitive strain sensors

“…The dosage and proportion of hybrid conductive fillers are important to the tensile strain response of strain sensors [19,21]. The relation curves of CNTs/FLG dosage changes on the responsive sensitivity and tensile strain of SCGFs under 50% min −1 tensile rate are shown in Fig.…”

“…In addition, the deterioration of mechanical properties for strain sensors could be dramatically avoided due to low percolation threshold caused by the synergistic effect of hybrid conductive fillers. Ke et al [21] manufactured a sensor based on PVDF/CB/CNTs composite, in which the higher the CB amount used, the higher the response sensitivity of sensors and the lower electroosmotic flow threshold. In this scenario, Liu et al [22] fabricated flexible strain sensors based on PU/CNTs/FLG conductive composites.…”