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A new simplified low temperature deposition method to manufacture flexible transparent conductive electrodes (FTCE) based on conductive polymer composite filled with silver nanowires (AgNWs) was investigated. Polyurethane/AgNWs composite was deposed on a poly(ethylene terephthalate) substrate as a conductive paint in a thin layer lower than 2 μm. The high aspect ratio nanowires influence on the electrical behavior is followed with surface resistivity and optical transparency experiments. The best compromise was obtained with a conductive layer filled with 2.84 vol.% of AgNWs; it exhibits a surface resistivity of 143 Ω/sq with 73% in transmittance. These transparent conductive composites processing in one step with good touching manipulation resistance demonstrate the real interest for this kind of FTCEs technology without indium tin oxide. [ABSTRACT FROM AUTHOR]

The aim of this work is to study electrically conductive composites from an epoxy matrix loaded with silver nanowires (AgNWs). Dynamic mechanical analysis (DMA) and dynamic dielectric spectroscopy (DDS) were used to study the molecular mobility of the epoxy matrix and its epoxy/AgNWs composites. The influence of the epoxy/amine ratio on the macroscopic properties was analyzed. The loss modulus of the epoxy matrix highlights two major relaxations, β and α. The β relaxation is due to the localized mobility initiated by hydroxyl groups. The α trelaxation is the anelastic effect liberated at the glass transition. The introduction of a small amount of AgNWs (<8 vol%) has practically no influence on the mechanical properties of the glassy state. For the rubbery state, AgNWs cause an increase in the storage modulus as a function of the filler content. The loss modulus profile is modified: The ω relaxation due to heterogeneities of the 3D network is observed independently from the hydration level of composites. The magnitude of the α mode is increased due to the stick–slip phenomenon. Moreover, it is shifted toward lower temperatures upon the introduction of AgNWs. In other words, the activation enthalpy decreases for both modes. Electrical study through DDS and conductivity measurement of epoxy/AgNWs composites shows the consequence of a lower relative degree of conversion caused by the insertion of AgNWs. Epoxy/AgNWs composites allow us to obtain one of the highest values of the electrical conductivity for polymer‐based composites without any drastic evolution of mechanical properties. [ABSTRACT FROM AUTHOR]

Electrospun scaffolds can find numerous applications, including biomedical; for example, tissue engineering. Poly‐L‐lactic acid is considered suitable for these applications, but its low‐thermal stability and its poor mechanical properties limit this polymer use. The aim of this work is to obtain a modulation of the final scaffolds characteristics such as fibers dimension, wettability, elasticity, and resistance to rupture through the choice of the polymers to be electrospun. Different electrospun scaffolds containing gelatin, Poly‐DL‐lactic acid, different percentages of cellulose nanocrystals and an elastin peptide have been produced. Thermal stability, physical structure, and its mechanical behavior have been studied. Results suggest that the electrospun scaffolds show better thermal and mechanical properties than bulk materials; that is, the scaffolds with the best hydrophilic and thermomechanical properties are the samples containing 3% (wt/wt) of CNCs and elastin peptide. [ABSTRACT FROM AUTHOR]

Polymer-based magnetoelectric composites are processed with an intrinsic piezoelectric poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) matrix and high-aspect-ratio magnetic nickel–decorated silver nanowires. These core/ shell wires are obtained by the polyol reduction of Ni2+ ions on high-aspect-ratio silver nanowires. Scanning electron microscopy and transmission electron microscopy analyses show a homogeneous and well-crystallized nickel layer. Magnetic properties of the intrinsic particles and their composites are measured and show a strong enhancement of the coercive field compared to spherical Ni nanopowders. They also show the existence of strong magnetic anisotropy in the composites. The composites processed with a small amount of metallic particles (0.3 vol%) allow the maintaining of the P(VDF-TrFE) crystalline phase and the ability of a macroscopic polarization. The latter is conducted under a 80 MV m−1 field, leading to a significant d33 (3.2 pC N−1). Thus, the magnetoelectric properties are analyzed and an important coupling coefficient αME equal to 1.8 V m−1 Oe−1 is measured. [ABSTRACT FROM AUTHOR]

For electromagnetic shielding in space environment, the metallization of carbon fiber reinforced polymer (CFRP) is required. A specific attention is paid due to the thermal expansion coefficient difference between substrate and metal coating. A surface metallization of a CFRP has been elaborated by electrodeposition. This study presents an original process based on an electrically conductive polymer coating elaborated from a polyurethane matrix filled with a low content of silver nanowires (<10%vol). A continuous and adherent deposit is obtained by an optimization of the electroplating parameters. A minimal volume fraction was determined at 3%vol associated with an applied current density estimated near 0.1 A/dm2. The growth speed is 7 μm/h at 0.1 A/dm2. The adhesion was checked in severe environmental conditions (−196 to 165°C). The effectiveness shielding obtained with this solution reaches an attenuation value higher than 90 dB between 1 and 26 GHz necessary for space communication applications. [ABSTRACT FROM AUTHOR]

In this work, three phase magnetoelectric nanocomposites are successfully prepared by solvent casting from α-PVDF. The extrinsic piezoelectric effect is insured by 20 vol% of NaNbO 3 ferroelectric nanoparticles prepared by the hydrothermal process. Nickel is chosen as the magnetic phase. In order to maintain insulation, electrical percolation is avoided by using nickel contents lower than the percolation threshold. Two different morphologies are employed: spherical nanoparticles (NiNPs) and nanochains (NNCs) with an aspect ratio of 80. NNCs are obtained by a polyol process under a magnetic field. Thin films of nanocomposites are processed by hot pressing. The real part of the dielectric permittivity (ε') of composites is governed by Maxwell-Wagner-Sillars polarization at the PVDF/Ni interfaces. An important increase of ε' at low frequency is observed for PVDF/NaNbO 3 /NNCs composites; it favors the magnetoelectric coupling. Piezoelectric properties of composites are dependent upon mechanical modulus so that the most higher d 33 is obtained for PVDF / NaNbO 3 / NiNPs. Magnetoelectric coupling coefficient (α ME) is determined from magnetoelectric intensity. PVDF / NaNbO 3 / NiNPs composites exhibit enhanced magnetoelectric coupling. The a ME coupling coefficient reaches 4.2V/(mOe). The magnetic properties are significantly improved by the NiNPs [ABSTRACT FROM AUTHOR]

A new kind of high electrical conductive epoxy coating with low filler rate was investigated for lightning strike protection (LSP) of carbon fiber reinforced polymer (CFRP). The coating without CFRP substrate was firstly studied. The influence of silver submicronic wires (AgSWs) with a high aspect ratio on the electrical behavior is observed; that is, the electrical resistivity evolution, the current density value, and the electrical conduction mechanisms as function of temperature. The preponderant electrical conduction mechanism is an Ohmic behavior. The higher level of conductivity obtained is 5.5 × 105 S m−1 for 9% vol of AgSWs. Lightning strike tests were carried out on an epoxy/AgSWs coating filled with 8% in volume (74 gsm) and deposited on a CFRP. The ultrasonic testing after lightning strike on coated CFRP shows no structural delamination and demonstrates the interest of this new route for an efficient LSP. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48700. [ABSTRACT FROM AUTHOR]

ABSTRACT: High performance thermoplastic poly(ether ketone ketone) (PEKK) polymers with various meta phenyl links ratio were investigated by dynamical mechanical analysis. Analyses were carried out in a wide range of temperature from solid state (torsion rectangular mode) to the melt state (torsion parallel plates mode) as function of thermal history and environmental conditions. In the solid state, this study was focused on the secondary relaxations in the vitreous state. A complementary investigation conducted with different poly(aryl ether ketones) allowed us to propose a molecular interpretation of PEKK sub‐vitreous relaxations. In the molten state, storage modulus (G′), loss modulus (G″), storage viscosity (η′), and loss viscosity (η″) were studied to determine zero shear‐rate viscosity (η0) and thermal activation energy Ea. Master curves were built and the shift factor aT was determined. Thermal activation energies were extracted from an Arrhenius model on the shift factor temperature's dependency. Finally, Ea and η0 were determined thanks to the dynamic viscosity fit with Cross model and Cole–Cole representation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46456. [ABSTRACT FROM AUTHOR]

ABSTRACT Poly ether ketone ketone (PEKK) with different proportion of meta phenyl links were investigated by combining differential scanning calorimetry and dynamic mechanical analysis. The influence of the Terephthalyl/Isophthalyl isomers (T/I) ratio on the vitreous phase is mild, the shift of the glass transition is limited to a few degrees and the vitreous G′ is only sensitive to the content of the crystalline phase. Contrarily, the increase of meta isomers is responsible for a significant decrease of the melting temperature (Tm) by 60 °C, which considerably facilitates processing. The modification of interchain interactions in the crystalline phase might be implied. A series of thermal protocols evidenced that the difference of crystallization behavior is also dependent upon the T/I isomer ratio. A time and temperature dependence of annealing on the double melting behavior of PEKK was observed. Regarding the mechanical behavior, the observed reinforcing effect due to the crystalline phase was more prominent in the rubbery state than in the glassy state. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43396. [ABSTRACT FROM AUTHOR]

Abstract: High-performance conductive thermoplastic composites poly(ether ketone ketone) (PEKK)/silver nanowires were elaborated by melt blending. Silver nanowires (AgNWs) with high aspect ratio (ξ~220) were elaborated through the polyol process in presence of poly(vinyl pyrrolidone) (PVP) and ethylene glycol. Scanning electron microscopy observations of nanowires were performed after an adapted cleaning process. The dispersion of NWs in the polymeric matrix was evaluated. A very low percolation threshold of 0.6vol% was obtained. Electrical conductivity values obtained above the percolation threshold were among the highest measured for low-filled conductive polymer composites. The influence of AgNWs on the PEKK matrix has been investigated by differential scanning calorimetry and dynamic mechanical analyses. It is important to note that thermal and dynamic mechanical performances of the polymeric matrix were preserved in composites. [Copyright &y& Elsevier]

Abstract: Nickel nanowires with high aspect ratio (250) were elaborated and incorporated into poly(vinylidene difluoride-trifluoroethylene) up to 30vol% via solvent mixing way. These nanocomposites are characterized by a conductive behavior with a high electrical conductivity value (102 S m−1) above a very low percolation threshold (0.75vol% of metallic nanowires). The introduction of nanowires strongly depressed the matrix crystallinity. Static and dynamic mechanical analysis have been realized at low nanowire volume fraction (<10vol%). Below 5vol% of nanowires, nanocomposites remain ductile. The dynamic mechanical properties are related to the volume fraction of nanowires. A strong increase of the viscoelastic contribution related to the increase of the percentage of amorphous phase is observed. The major effect is the increase of the rubbery modulus. The highest increase of 300% is obtained for only 5vol% of nanowires; it represents an original mechanical result for low filled composites. The dependence versus nanowire content has been described by adapting the Halpin–Tsai model to high aspect ratio filler. Metallic nanowires create additional entanglements that are randomly distributed in the rubbery polymeric matrix. With their low percolation threshold, metallic nanowires based nanocomposites constitute a new class of multifunctional materials with a high conductivity associated with a ductile polymer matrix characterized by a high rubbery modulus. [Copyright &y& Elsevier]

The aim of this work is to enhance the electrical conductivity of PAEK/continuous carbon fiber (CF) composites while maintaining their mechanical properties. A conductive sizing was elaborated by mixing polyetherimide (PEI) with silver nanoplates (AgNpts) in suspension in dichloromethane. An aqueous PEI formulation was used as insulating sizing reference. The presence of AgNpts into the sizing enhances electrical conductivity up to 0.2 S.m−1 for a silver content ∼ 0.2 vol % without any modification of mechanical properties. The influence of conductive sizing on PAEK–AgNWs/CF was observed. For low AgNWs content lower (<1 vol %); the conductive sizing increases the electrical conductivity of the composite by one decade. This result shows that both types of Ag particles participate to the conductive path. For higher AgNWs content, electrical conductivity (200 S.m−1) is independent from the AgNpts content: the conductive path is only constituted by AgNWs. Mechanical properties of such composites show that the value of the conservative modulus is almost the same, while the dissipative modulus slightly increases. The global mechanical properties of the composite are preserved despite the addition of the CF, AgNWs, and AgNpts. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47872. [ABSTRACT FROM AUTHOR]

Magnetic nickel nanoparticles (NPs) and nanochains (NNCs) are grown in a polyol medium under a static field as an alternative to template electrodeposition and strong reducers. Scanning electron microscopy (SEM) images and their statistical analysis show an important aspect ratio of 75 for NNCs. These NNCs present enhanced magnetic properties in terms of coercive field (HC = 163 Oe) and saturation magnetization (MS = 10.8 emu g−1). Nanocomposites of NNCs/PVDF are fabricated with 2 %vol. NNCs and present better properties than NPs/PVDF with higher filler content. The longitudinal and transverse magnetic properties of the composite are measured showing that higher properties are recorded in the longitudinal direction. Electrical conductivity of composite is plotted as a function of NNCs volume content to determine the electrical percolation threshold. The corresponding value of the apparent aspect ratio (ξ = 70) confirms that the processing of composite does not modify the particles morphology. Thus, it explains the enhancement of the magnetic properties due to the NNCs anisotropy. [ABSTRACT FROM AUTHOR]

Thermal and electrical behaviors of a poly(epoxy) coating with high electrical conductivity used for aeronautic applications are investigated. The poly(epoxy) used is designed for resin transfer molding (RTM) applications, it have a low viscosity at room temperature (around 1 Pa s) and a high Tg (>160 °C). This study details the influence of silver nanowires with a high aspect ratio, on the thermal behavior such as the relative degree of reaction α and the kinetics parameters thanks to dynamic and isothermal differential scanning calorimetry. Conductivity measurements of surface and volume have permitted to determine a very low percolation threshold at around 0.7% in volume. The value of electrical conductivity above the percolation threshold is upper than 102 S m−1 and the lowest surface resistivity was measured around 13 mΩ sq−1 both for 8% in volume of AgNWs. This kind of coating has a great interest for lightning strike protection of aircraft parts due to the high electrical conductivity obtained with a low overweight. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46829. [ABSTRACT FROM AUTHOR]

The thermal conductivity accurate measurement of polymer based composites is a challenge: it would allow us to understand the mechanisms of thermal transport in such materials. Silver nanoparticles were introduced in Polyetheretherketone matrix and their influence on thermal properties was studied. Thermal conductivity and specific heat capacity of composites were determined by Modulated-Temperature Differential Scanning Calorimetry and analysed as a function of particles volume content and temperature. The specific heat capacity of the composites decreases with increasing silver particles content below the electrical percolation threshold. Above the electrical percolation threshold the specific heat capacity decreases more slowly and converge toward the specific heat capacity of compressed silver nanoparticles. The evolution of the thermal conductivity with filler content exhibits a non-linear profile. Experimental data are coherent with the Maxwell model suggesting continuity of the polymer matrix and a contribution of the silver particles to the effective thermal conductivity greater than volume effect. The temperature dependence of the composites thermal conductivity is characteristic of amorphous phase, while a transition from vitreous-like to crystalline-like behaviour of the specific heat capacity is observed with the introduction of metallic particles. [ABSTRACT FROM AUTHOR]

High conductive composites were elaborated by incorporating high aspect ratio (250) silver nanowires in polyimide matrix via solvent mixing way. Silver nanowires were synthesized in solution by polyol synthesis. The composite conductivity reaches the value of 102 S·m−1 above a very low percolation threshold (0.48vol.% of silver nanowires). SEM-FEG images showed that metallic nanowires are well dispersed in PI matrix. They do not influence the physical structure of the polymer. Below the percolation threshold, γ, β and α relaxation modes were detected. γ relaxation mode was fitted to determinate the activation energy value (32.7kJ·mol−1) and the relaxation time (1.5×10−16 s). The mobility associated with the γ relaxation is considered to be localized and non-cooperative. According to the Mott theory, studies on composites below the percolation threshold showed that the conduction mechanism is ruled by tunneling at low temperatures. The transport mechanism led by hopping is activated at −50°C. [ABSTRACT FROM AUTHOR]

Abstract: Raman spectroscopy is used to access the dispersion state of DWNTs in a PEEK polymer matrix. The interaction of the outer tube with the matrix can be determined from the line shape of the Raman G band. This allows us to distinguish regions where the nanotubes are well dispersed and regions where the nanotubes are agglomerated. The percolation threshold of the electrical conductivity of the double wall carbon nanotubes (DWNTs)/PEEK nanocomposites is found to be at 0.2–0.3wt%. We find a maximum electrical conductivity of 3×10−2 Scm−1 at 2wt% loading. We detect nanotube weight concentrations as low as 0.16wt% by Raman spectroscopy using a yellow excitation wavelength. We compare the Raman images with transmission electron microscopy images and electrical conductivity measurements. A statistical method is used to find a quantitative measure of the DWNTs dispersion in the polymer matrix from the Raman images. [Copyright &y& Elsevier]