Electrical, mechanical and adhesive properties of ethylene-vinylacetate copolymer (EVA) filled with wollastonite fibers coated by silver

Relationship between Viscosity, Microstructure and Electrical Conductivity in Copolyamide Hot Melt Adhesives Containing Carbon Nanotubes

The polymeric adhesive used for the bonding of thermoplastic and thermoset composites forms an insulating layer which causes a real problem for lightning strike protection. In order to make that interlayer electrically conductive, we studied a new group of electrically conductive adhesives based on hot melt copolyamides and multi-walled carbon nanotubes fabricated by the extrusion method. The purpose of this work was to test four types of hot melts to determine the effect of their viscosity on the dispersion of 7 wt % multi-walled carbon nanotubes and electrical conductivity. It was found that the dispersion of multi-walled carbon nanotubes, understood as the amount of the agglomerates in the copolyamide matrix, is not dependent on the level of the viscosity of the polymer. However, the electrical conductivity, analyzed by four-probe method and dielectric spectroscopy, increases when the number of carbon nanotube agglomerates decreases, with the highest value achieved being 0.67 S/m. The inclusion of 7 wt % multi-walled carbon nanotubes into each copolyamide improved their thermal stability and changed their melting points by only a few degrees. The addition of carbon nanotubes makes the adhesive's surface more hydrophilic or hydrophobic depending on the type of copolyamide used.

Solvent-free electrically conductive Ag/ethylene vinyl acetate (EVA) composites for paper-based printable electronics

Solvent-free electrically conductive composites have been applied to flexible electronics to obtain high electrical conductivity. However, some of the proposed composites have low electrical conductivities and are unable to meet the requirements of commercial printable electronics. In this study, solvent-free electrically conductive Ag/EVA (ethylene vinyl acetate) composites for paper-based printable electronics were prepared by a thermal melting method. The properties of these electrically conductive Ag/EVA composites, including particle sizes, morphologies and phase purities of the flake silver flake powders, were investigated using a particle size analyzer, scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The results showed that nanometer-thick flake silver flake powders with smooth and flat surfaces were made by the nanofilm transition technique. These obtained powders were able to form smooth face-to-face contacts, which facilitated the formation of an excellent conductive network in the conductive system. Dynamic mechanical analysis (DMA) was conducted to investigate the mechanical properties of EVA and Ag/EVA composites. A Fourier transformation infra-red (FTIR) spectrometer, laser micro-Raman spectrometer and thermogravimetric analyzer were used to analyze the organic functional groups, glass transition temperatures and thermal weight losses of the EVA resin and solvent-free electrically conductive composites. The solvent-free electrically conductive Ag/EVA composite, which contained 55 wt% of the as-prepared flake silver flake powders, was found to have an extremely low volume resistivity of 1.23 × 10-4 Ω cm as well as excellent bending performance and adhesion. These features indicate the great potential of these composites for application in printed electronics.

Resistivity optimization and properties of silver nanoparticles-filled alcohol-soluble conductive coating based on acrylic resin

An alcohol-soluble acrylic resin used to improve the dispersity of modified silver nanoparticles (AgNPs) was successfully synthesized. The structure of acrylic resin was designated according to the elements and groups on the surface of modified AgNPs. The content of γ-(2,3-epoxypropoxy)propytrimethoxysilane (KH-560) and conductive filler, temperature, mechanical properties, anticorrosion, and so on were investigated in order to optimize the electrical conductivity and dispersion of modified AgNPs in coating. Surface chemical structure of modified AgNPs was characterized by X-ray photoelectron spectroscopy. Morphology of conductive coating was characterized by scanning electron microscopy. Groups in modified AgNPs and acrylic resin were characterized by Fourier transform infrared spectroscopy. And surface resistivity of conductive coating was characterized by digital multimeter techniques. The optimum surface resistivity of the acquired AgNPs conductive coating could be up to 0.01 ohm/sq, reaching the level of electromagnetic interference shielding. Moreover, the conductive coating possesses good property of anti-chemical and weather corrosion resistance.

Effect of rare Earth ions on the properties of composites composed of ethylene vinyl acetate copolymer and layered double hydroxides

Background

The study on the rare earth (RE)-doped layered double hydroxides (LDHs) has received considerable attention due to their potential applications in catalysts. However, the use of RE-doped LDHs as polymer halogen-free flame retardants was seldom investigated. Furthermore, the effect of rare earth elements on the hydrophobicity of LDHs materials and the compatibility of LDHs/polymer composite has seldom been reported.

Methodology/Principal Findings

The stearate sodium surface modified Ni-containing LDHs and RE-doped Ni-containing LDHs were rapidly synthesized by a coprecipitation method coupled with the microwave hydrothermal treatment. The influences of trace amounts of rare earth ions La, Ce and Nd on the amount of water molecules, the crystallinity, the morphology, the hydrophobicity of modified Ni-containing LDHs and the adsorption of modifier in the surface of LDHs were investigated by TGA, XRD, TEM, contact angle and IR, respectively. Moreover, the effects of the rare earth ions on the interfacial compatibility, the flame retardancy and the mechanical properties of ethylene vinyl acetate copolymer (EVA)/LDHs composites were also explored in detail.

Conclusions/Significance

S-Ni_0.1MgAl-La displayed more uniform dispersion and better interfacial compatibility in EVA matrix compared with other LDHs. Furthermore, the S-Ni_0.1MgAl-La/EVA composite showed the best fire retardancy and mechanical properties in all composites.