Low percolation threshold conductive device derived from a five-component polymer blend

In this work we report on the preparation of a solid, 3D, low percolation threshold conductive device prepared through the control of multiple encapsulation and multiple percolation effects in a 5 component polymer blend system through melt processing. Conductive polyaniline (PANI) is situated in the core of the 5 component continuous system comprised of high-density polyethylene (HDPE), polystyrene (PS), poly(methyl methacrylate)(PMMA) and poly(vinylidene fluoride)(PVDF). In this fashion, its percolation threshold can be reduced to below 5 vol%. The approach used here is thermodynamically controlled and is described by Harkins spreading theory. In this work the detailed morphology and continuity diagrams of binary, ternary, quaternary and finally quinary systems are progressively studied in order to systematically demonstrate the concentration regimes resulting in the formation of these novel multiple-encapsulated morphological structures. Initially, onion-type dispersed phase structures are prepared and it is shown that through the control of the composition of the inner and outer layers the morphology can be transformed to a hierarchical-self-assembled, multi-percolated structure. The influence of a copolymer on selected pairs in the encapsulated structure is also examined. The conductivity of the quinary blend system can be increased from 10⁻¹⁵ S cm⁻¹ (pure HDPE) to 10⁻⁵ S cm⁻¹ at 5 vol% PANI and up to 10⁻³ S cm⁻¹ for 10 vol% PANI. These are the highest conductivity values ever reported for these PANI concentrations in melt processed systems.     

Electrically conductive self-healing polymer composite coatings

The goal of the research described herein is the fabrication and assessment of electrically conductive partially-cured epoxy coatings which, upon cracking, autonomously restore barrier, mechanical and electrical properties via a microcapsule based healing mechanism. Upon cracking, microcapsules in the crack path release the ‘healing’ solvent ethyl phenyl acetate (EPA), which locally swells the matrix, promoting crack closure and enabling the diffusion and subsequent reaction of the residual hardener in the vicinity of the crack. Two different self-healing coatings and two controls based on an electrically conductive epoxy resin with approximately 20% carbon nanotubes (CNTs) were fabricated. Electrochemical impedance spectroscopy was employed to evaluate the potential of the CNT and non-CNT containing encapsulated systems to restore relatively large cracks and thus restore the barrier function. An in situ electro-tensile test in a microscope revealed that electrical conductivity and mechanical properties were restored to 64% (±23) and 81% (±39) respectively, which correlated to crack closure. Under appropriate testing conditions the system showed successive damage-heal events in terms of electrical conductivity.     

A three-dimensional Monte Carlo model for electrically conductive polymer matrix composites filled with curved fibers

A three-dimensional (3-D) Monte Carlo model is developed for predicting electrical conductivity of polymer matrix composites filled with conductive curved fibers. The conductive fillers are modeled as a 3-D network of finite sites that are randomly positioned. The percolation behavior of the network is studied using the Monte Carlo method, which leads to the determination of the critical fiber volume fraction (or the percolation threshold). The effect of fiber curliness on the percolation behavior is incorporated in the current model by using 3-D arm-shaped fibers, each of which needs five independent geometrical parameters (i.e., three coordinates for its vertex and two orientation angles) for its identification. There are three controlling parameters for such fibers, namely the fiber arm length, the fiber aspect ratio, and the fiber arm angle. The new model also considers the sample size and scaling effects. The simulation results reveal an exponential relationship between the fiber aspect ratio and the percolation threshold: the higher the aspect ratio, the lower the threshold. It is also found that the curliness largely influences the percolation threshold: the more curved the fiber, the higher the threshold. However, the effect of curliness diminishes with the increase of the fiber aspect ratio. With the percolation threshold obtained from the Monte Carlo model, the effective electrical conductivity of the composite is then determined by applying the theory of percolation. The numerical results indicate that the composite conductivity decreases as the fibers become more curved and as the fiber aspect ratio decreases. These predicted trends of the percolation threshold and composite conductivity are in good agreement with existing experimental and simulation results.     

Enhanced Electrically Conductive Polypropylene/Nano Carbon Black Composite

In this work, a porous polypropylene (PP)/nano carbon black (CB) composite was facilely fabricated via immiscible co-continuous polymer blend and subsequent dissolution process. The porous structure was generated from co-continuous polymer blend, which was exploited as the substrate for depositing nano CB. The interconnected micro pores of the co-continuous polymer blend and nano pores derived from agglomerated CB resulted in a significant enhancement of conductivity. Comparing with the conventional carbon composite obtained through dual-percolation method, the electrical conductivity of PP/CB composite increased 10 orders of magnitude with CB loading ranged from 1 wt% to 5 wt%. Moreover, it was found that the percolation threshold of PP/CB composite decreased nearly 80% compared with that of as-mixed sample. The enhanced conductivity and much lower percolation make this novel method a potential way for fabricating porous conductive materials for advanced application.     

Nanostructured polymer blend formed from poly(N-vinylpyrrolidone) and end-functional polystyrene

Phase structures of blends of poly(N-vinylpyrrolidone) (PVP) with SO₃H terminated polystyrene (PSS) were investigated. The PVP-PSS blends were macroscopically homogeneous, although the blends of PVP with polystyrene (PS) showed macroscopic phase separation. The PVP-PSS blends, however, showed two glass transitions indicating existence of two phases. Small-angle X-ray scattering measurements revealed the PVP-PSS blends formed mesomorphically ordered morphologies which change with variation of blend composition. The nano-organized phase separation in the PVP-PSS blends was caused due to hydrogen bonding of the PVP with the terminal SO₃H group of the PSS and repulsive interaction between PVP and main chain of the PSS.     

One-step elaboration of flexible transparent conductive electrodes from silver nanowires/polymer nanocomposites

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.     

Effect of imidazole based polymer blend electrolytes for dye-sensitized solar cells in energy harvesting window glass applications

The exploration of polymer electrolyte in the field of dye sensitized solar cell (DSSC) can contribute to increase the invention of renewable energy applications. In the present work, the influence of imidazole on the poly (vinylidene fluoride) (PVDF)-poly (methyl methacrylate) (PMMA)-Ethylene carbonate (EC)-KI-I₂ polymer blend electrolytes has been evaluated. The different weight percentages of imidazole added into polymer blend electrolytes have been prepared by solution casting. The prepared films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), UV-visible spectra, photoluminescence spectra and impedance spectroscopy. The surface roughness texture of the film was analyzed by atomic force microscopy (AFM). The ionic conductivity of the optimized polymer blend electrolyte was determined by impedance measurement, which is 1.95×10^-3 S·cm^-1 at room temperature. The polymer electrolyte containing 40 wt% of imidazole content exhibits the highest photo-conversion efficiency of 3.04% under the illumination of 100 mW·cm^-2. Moreover, a considerable enhancement in the stability of the DSSC device was demonstrated.     

Numerical and experimental approach to testing the adhesive properties of modified polymer blend based on EVA/PMMA as coatings for optical fibers

The adhesive properties of polymer blends based on poly(ethylene-co-vinyl acetate) (EVA) and poly(methyl methacrylate) (PMMA) were studied. Two samples were prepared, whereby one kind was a physically mixed blend of commercial polymers in a solution of toluene and the other was a blend with EVA-g-PMMA polymer in a toluene solution, produced via in situ free radical polymerization using redox system initiators. A scanning electron microscopy (SEM) revealed the improved microstructure that was achieved blending with graft polymer that could also be seen by FTIR spectral analysis. Optical fibers were glued together using both of the solutions and subjected to a micro mechanical testing machine. The adhesion test showed that the graft copolymer had enhanced mechanical properties as an adhesive than the physical polymer blend. Optical microscopy of the samples after the adhesion test enabled the determination of the type of adhesive failure. Image analysis of the SEM micrographs was used to determine an area of the contact surface, and characterization microstructure. These results were then implemented in a numerical simulation that demonstrated the influence of microstructure on the adhesive properties showing the stress distribution for both samples. The main aim of obtaining an adhesive with uniform structure, great miscibility of the polymers, and good mechanical and adhesive properties was achieved and a numerical model was established that can be used in selecting the adhesive.     

Characterisation of [(1−x)PMMA-xPVdF] polymer blend electrolyte with Li ion

The possible use of polymeric materials in thin-film solid electrolytes for battery systems, fuel cells, sensors and other electrochemical applications has stimulated worldwide interest in metal salt solvating macromolecules. Polymer electrolyte membranes comprising of poly(methyl methacrylate) (PMMA), poly(vinylidene fluoride) (PVdF) and lithium perchlorate are prepared using a solvent casting technique. Polymer blends have been characterised by FTIR and XRD studies to determine the molecular environment for the conducting ions. The role of interaction between polymer hosts on conductivity is discussed using the results of ac impedance studies. The ionic conductivity is presented as a function of temperature and PVdF content. Room temperature conductivity of 3.14×10⁻⁵ S cm⁻¹ has been obtained for the [0.25PMMA/0.75PVdF]-LiClO₄ polymer complex.     

Preparation,morphology, and conductivity of waterborne,nanostructured, cationic polyurethane/polypyrrole conductive coatings

To endow cellulose fiber papers with good conductivity and simultaneously retain the mechanical strength of the conductive paper, a kind of waterborne, nanostructured, cationic polyurethane (CPU)/polypyrrole (PPy) conductive coatings were developed to modify the paper surface. Fourier transform infrared spectroscopy, atomic force microscopy, and thermogravimetry–differential thermogravimetry demonstrated that the peak associated with hydrogen bonding between ? NH and C?O of CPU was shifted, and chemical bonds between CPU and PPy were formed. Good compatibility between CPU and PPy was simultaneously established. Transmission electron microscopy and atomic force microscopy also suggested that PPy was encased and embedded in the CPU colloidal particles in a uniform style, and the surface of the CPU/PPy film was covered with a smooth, coherent conductive layer. With increasing pyrrole (Py) content from 5 to 20 wt %, the particle size increased from 55.08 to 74.59 nm, and the dispersity index (DPI) decreased. In addition, the conductivity of CPU/PPy increased from 0.1 to 5.0 S/cm. When the Py content was greater than 20 wt %, apparent increases in the particle size and DPI were detected as was particle coagulation; this resulted in decreased conductivity. Compared with the uncoated paper, the paper coated with CPU/PPy dispersions displayed different surface morphologies. The surface of the paper was completely enwrapped by the CPU/PPy conductive films when the coating amount was 45.42 g/m². With increasing coating amounts from 10.35 to 67.86 g/m², the conductivity of the conductive coated paper increased from 2.78 × 10^?3 to 2.16 S/cm, the tensile strength increased from 35.3 to 60.4 N m/g, and the conductive coated paper displayed good conductivity stability. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41445.     

Optical,thermal and electrical characterization of PEO/CMC incorporated with ZnO/TiO2 NPs for advanced flexible optoelectronic technologies

The optical, thermal, and electrical properties of a blend of polyethylene oxide (PEO) and carboxymethyl cellulose (CMC) are examined in the current work in relation to the effects of zinc oxide (ZnO) and titanium dioxide (TiO₂) nanoparticles. To create hybrid ZnO/TiO₂ NPs nanocomposites with a PEO/CMC matrix, the solution casting method was utilized. The XRD study results demonstrate that the nanocomposite films' crystallinity decreases with increasing ZnO/TiO₂ NP concentrations. FT-IR spectra reveal the interaction between metal oxide NPs and the PEO/CMC composite. UV/Vis analytical spectroscopy was used to calculate the optical properties, such as the energy gap (Eg), refractive index (n), and the number of carbon atoms (M). The inclusion of 7 wt%ZnO/TiO₂ NPs decreased the polymer matrix's allowed direct energy gap from 3.68 to 2.81 eV. The AC conductivity results show that the ${\sigma }_{dc}$ of the nanocomposite samples decreases with increasing ZnO/TiO₂ NPs concentrations. The ${\sigma }_{dc}$ of the final sample (PEO/CMC@7 wt% ZnO/TiO₂) was 5.18 × 10⁻⁷Scm⁻¹. According to exponential factor (S) results, the dominates conduction mechanism is correlated barrier hopping (CBH) with non-Debye relaxation processes. Space charge polarization was demonstrated by large ε′ values in the low-frequency dielectric properties, whereas an increase in energy loss may be related with a larger εʹ' value in the composite samples. These results prove that these nanocomposites can be used in a variety of energy-related devices, such as flexible capacitors, and energy storage systems.     

Development of new ionomer blend membranes,their characterization,and their application in the perstractive separation of alkenes from alkene–alkane mixtures. I. Polymer modification,ionomer blend membrane preparation,and characterization

In this contribution, the synthesis and characterization of novel ion‐exchange blend membranes which contain the SO₃Ag group for the application in the perstractive separation of alkene–alkane mixtures, where the Ag⁺ ion serves as facilitated transport site for the alkene via formation of a pi complex with the alkene double bond, is presented. In this part of the article, the synthesis and characterization of following blend membrane types are described: (1) acid–base blend membranes of ortho‐sulfone‐sulfonated polysulfone (PSU) with ortho‐sulfone‐diaminated PSU; (2) blend membranes of ortho‐sulfone‐sulfonated PSU with unmodified PSU; (3) blend membranes of ortho‐sulfone‐sulfonated PSU with ortho‐sulfone disilylated PSU. The differently modified PSU types were characterized via ¹H nuclear magnetic resonance (¹H‐NMR). The acid–base blend membranes were characterized via Fourier transfer infrared (FTIR) spectroscopy. It could be indirectly proved that formation of PSU–SO₃ ⁺H₃N–PSU ionic crosslinks takes place. Transmission electron microscopy (TEM) investigations of (1) and (2) yielded the results that these blends are inhomogeneous at the microscopic scale. Mechanical stabilization of these blends is accomplished by physical entanglement of the different macromolecules. The blends (3) were macroscopically inhomogeneous due to the strong difference in hydrophilicity of the blend components. Only the blend 90% PSU–SO₃H 10% PSU[Si(CH₃)₃]₂ formed a blended membrane. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 428–438, 1999     

Novel water-soluble polymer coatings control NPK release rate,improve soil quality and maize productivity

We investigated different combinations of polymers (5% each) (i) starch, gelatin (polymer coating; PC-1), (ii) polyvinyl alcohol (PVA), gum Arabica (PC-2), (iii) PVA, gelatin (PC-3), (iv) starch, gum Arabica (PC-4), (v) gelatin, gum Arabica (PC-5), (vi) starch, PVA (PC-6), for coating NPK (17, 17:17) in a fluidized bed granulator. Morphological characterization indicated a uniform coating of all formulations on NPK granules. A slow release of N (PC-3), P (PC-6), and K (PC-3) was observed in water. In soil, high mineral N (63%), plant-available P (72%), and K (24%) were observed in PC-3, PC-5, and PC-6, respectively than uncoated fertilizer. Microbial biomass NPK was also higher in these treatment. This resulted in higher maize yield (66%), N (114%), P (164%), and K (137%) uptakes and apparent N (267%), P (196%), and K (358%) recoveries from applied fertilizer in these treatments. Among these, PC-3 resulted in an increase of 115% shoot N, 169% P and 138% K uptakes and 268% apparent N, 206% P and 361% K recoveries than uncoated fertilizer. Hence, coating of NPK with this biodegradable polymer combination controlled N, P, and K release and synchronized these nutrients availabilities with maize nutrients demand therefore resulted in higher maize crop yield and nutrient utilization efficiencies.     

Advances in the science and technology of paints, inks and related coatings: 2005

Summary  This review summarises the developments in adhesion, VOC emissions, coatings, transparent conductive coatings, hybrid organic-inorganic coatings, UV curing, biocidal coatings, paints, weathering, wood coatings, surface treatment of concrete, metal corrosion, pigments, film formation, printing, modelling fluid flow in printing, dot gain and inkjet printing reported inSurface Coatings International Part B: Coatings Transactions,88, 2005.     

Development of new ionomer blend membranes,their characterization,and their application in the perstractive separation of alkenes from alkene–alkane mixtures. II. Electrical and facilitated transport properties

In this contribution, the synthesis and characterization of novel ion‐exchange blend membranes which contain the SO₃Ag group for the application in the perstractive separation of alkene–alkane mixtures, where the Ag⁺ ion serves as facilitated transport site for the alkene via formation of a pi complex with the alkene double bond, is presented. In this part of the article, the transport properties of the following blend membrane types are described: (1) acid–base blend membranes of ortho‐sulfone‐sulfonated polysulfone (PSU) with ortho‐sulfone‐diaminated PSU; (2) blend membranes of ortho‐sulfone‐sulfonated PSU with unmodified PSU; (3) blend membranes of ortho‐sulfone‐sulfonated PSU with ortho‐sulfone disilylated PSU. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 422–427, 1999     

Structural,electrical and optical properties of pure and NaLaF<Subscript>4</Subscript> doped PEO polymer electrolyte films

A Sodium ion conducting polymer electrolyte based on Polyethylene oxide (PEO) complexed with Sodium lanthanum tetra fluoride (NaLaF₄) was prepared using solution cast technique. The complexation of the salt with PEO was confirmed by X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopic (FTIR) studies. Differential Scanning Calorimetry (DSC) is carried out to determine the melting temperature of these electrolyte films. Electrical conductivity was measured in the temperature range 300–370 K as a function of dopant concentration as well as temperature. Optical absorption studies were made in the wavelength range 200–600 nm on pure and NaLaF₄ doped PEO film. The absorption edge was observed at 4.62 eV for undoped PEO while it ranged from 3.16 to 3.5 eV for NaLaF₄ doped films. The direct band gaps for undoped and NaLaF₄ doped PEO films were found to be, respectively, 4.54 and 3.44, 3.24 and 3.12 eV while the indirect band gaps were 4.43 and 3.25, 3.05 and 2.9 eV, respectively. It was found that the energy gaps and band edge values shifted to lower energies on doping with NaLaF₄ salt.