Conductive composites of UHMWPE and ceramics based on the segregated network concept

Bouchet, J. B.; Carrot, Christian; Guillet, Jacques; Boiteux, Gisèle; Seytre, Gérard; Pinéri, M.

doi:10.1002/pen.11137

Cited by 52 publications

(52 citation statements)

References 14 publications

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“…If the drying temperature is above the minimum film formation temperature of the polymer, these particles will inter-diffuse (i.e., coalesce) to form a coherent film. [19] In the presence of SWNTs, a ªsegregated networkº [20,21] evolves due to the inability of the nanotubes to penetrate the polymer particles. This restricted organization of the conductive filler results in the low percolation threshold seen in Figure 2.…”

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Water‐Based Single‐Walled‐Nanotube‐Filled Polymer Composite with an Exceptionally Low Percolation Threshold

Grunlan¹,

et al. 2004

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Polymer composites containing carbon-based filler (e.g., carbon black or carbon nanotubes) are becoming increasingly useful due to their unique combination of metallic conductivity and polymer flexibility. These materials are being investigated for use as electromagnetic interference (EMI) shielding, [1] heat dissipation films, [2] chemical sensors, [3] actuators, [4] photoconductors, [5] and impedance adapters for organic lightemitting diodes (OLEDs).[6] Despite these advantages, carbon black concentrations of more than 25 wt.-% are often required to achieve sufficient electrical conductivity in typical solution or melt-based systems. [7,8] High filler loadings can lead to processing difficulties and loss of polymer-like mechanical behavior. The critical filler concentration needed to achieve true electrical conductivity, known as the percolation threshold, [9] can be reduced in a number of ways. For carbon-black-filled composites, percolation thresholds below 5 wt.-% have been achieved by using a polymer emulsion (or latex) binder, [10] while solution-based systems have exhibited thresholds below 1 wt.-% by replacing carbon black with carbon nanotubes.[6]In the present work, these two concepts have been combined to achieve a percolation threshold below 0.1 wt.-%. Single-walled carbon nanotubes (SWNTs) produced via the high pressure carbon monoxide (HiPco) process [11] are extremely hydrophobic and require the use of a stabilizer to achieve a stable aqueous suspension. Gum Arabic (GA), known to be an effective stabilizing agent for SWNTs in water, [12] was used for this purpose. The quality of nanotube stabilization is evidenced by transmission electron micrographs (TEMs) shown in Figure 1. These are images of dried suspensions that originally contained 2 wt.-% GA and 0.4 wt.-% SWNTs in water. At relatively low magnification (Fig. 1a), most of the SWNTs can be seen as aggregated threads. In the higher magnification image (Fig. 1b) it is clear that these clusters are comprised of 20±30 nanotubes, assuming the individual tubes have an average diameter of 1.2 nm.[11] The dark particles in this image are impurities such as metal catalyst and carbonaceous soot attached to the SWNT bundles. Once stabilized, the SWNTs were combined with a poly(vinyl acetate) (PVAc) emulsion to create an aqueous pre-composite mixture that was dried to create electrically conductive composite films. Figure 2 shows how conductivity increases with SWNT concentration. The solid curve is the fit to the experimental data using the classical percolation power law: [13,14] where r is the composite conductivity in S cm ±1 , r 0 is a scaling factor related to the intrinsic conductivity of the filler, s is the power law exponent (typically 1.6±2.0 for random systems), [15] and V c is the volume fraction of filler at the percolation threshold. The values for r 0 , V c , and s are shown in Figure 2. V c is reported as weight fraction in this case due to the uncertainty of the SWNT density, although it is likely that weight fraction is very similar t...

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Water‐Based Single‐Walled‐Nanotube‐Filled Polymer Composite with an Exceptionally Low Percolation Threshold

Grunlan¹,

et al. 2004

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“…13,14 The electrical properties and the percolation threshold can also be affected by the processing parameters, such as the mixing method used, the processing pressure and the temperature. Although the effects of the processing conditions on the electrical properties of conductive PMCs have been previously reported, 8,15 the influence of processing conditions have not yet been fully investigated or optimized yet. It is still difficult to determine under what conditions, the best properties can be obtained due to the fact that the combined effect of temperature, pressure, thickness and filler content provide a complex problem that requires detailed studies of a specific series of specimens to clarify.…”

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confidence: 99%

Fabrication and simulation of semi-transparent and flexible PMMA/ATO conductive nanocomposites obtained by compression molding at different temperatures and pressures

Jin

Gerhardt

2017

AIP Advances

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This paper investigated the effect of temperature and pressure on the microstructure and electrical behavior of compression molded and mechanically blended polymer composites. Poly (methyl methacrylate) (PMMA) and antimony tin oxide (ATO) were used as the matrix and conductive filler respectively and the composition was varied from 0 to 1.75 ATO vol %. Mixtures of the two precursor materials were compression molded at temperatures ranging from 150 to 190 °C and pressures ranging from 12 to 50 MPa. It was found that a segregated network microstructure was formed in all cases but that the distribution of the conductive ATO fillers varied as a function of the compression molding temperature and pressure used. The thickness of the specimens, determined by the amount of precursor materials and pressure used during compression molding, was also found to affect the resulting microstructure and concomitant properties. The electrical conductivity of these polymer matrix composites can be increased by up to 2 orders of magnitude by decreasing the processing temperature, while maintaining the processing pressure and the filler concentration constant. On the other hand, the flexibility of PMCs can be improved by increasing the processing temperature. For the compositions evaluated, the maximum electrical conductivity obtained was 5 x 10-3 S/m (about three orders of magnitude lower than the conductivity of the filler). Finite element simulations were used to model this microstructure-driven phase segregated percolation behavior. COMSOL Multiphysics® was used to calculate the electric potential and current density distribution in a 3D geometry. There was good agreement between the experimental and simulation results.

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“…This structure allows us to obtain very low values of the percolation threshold [21][22]. After sintering, the segregated distribution of CB phase can be further preserved because the extremely high viscosity of PTFE at its melt state will minimize the migration of carbon particles into the polymer matrix and deformation of the polymer particles during processing.…”

Section: Resultsmentioning

confidence: 99%

Positive temperature coefficient effects of carbon blackfilled polytetrafluoroethylene composites

2009

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Carbon black (CB)-filled polytetrafluoroethylene (PTFE) composites were prepared by compact molding of a dry-mixture of CB and polymer powders followed by a sintering technology. The composites show a very low percolation threshold about 5 vol. %, which can be attributed to the segregated distribution of CB in the interfacial regions of PTFE particles. The PTFE/CB composites exhibit a high PTC transition temperature (>300 0 C), high PTC intensity (3.5) and no NTC effects. The absence of NTC effect of the composites was attributed to the extremely high viscosity of PTFE at temperatures above its melting point, which restricts the migration of CB particles and prevents the formation of new conductive networks.

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Conductive composites of UHMWPE and ceramics based on the segregated network concept

Cited by 52 publications

References 14 publications

Water‐Based Single‐Walled‐Nanotube‐Filled Polymer Composite with an Exceptionally Low Percolation Threshold

Water‐Based Single‐Walled‐Nanotube‐Filled Polymer Composite with an Exceptionally Low Percolation Threshold

Fabrication and simulation of semi-transparent and flexible PMMA/ATO conductive nanocomposites obtained by compression molding at different temperatures and pressures

Positive temperature coefficient effects of carbon blackfilled polytetrafluoroethylene composites

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