Melt blending of carbon nanotubes/polyaniline/polypropylene compounds and their melt spinning to conductive fibres

Blends of polypropylene with polyaniline and multi-walled carbon nanotubes have been prepared and melt spun to fibre filaments. The resulted filaments have been characterised regarding conductivity, morphology, thermal and mechanical properties. DSC suggests that carbon nanotubes act as nucleating sites for PP/polyaniline blend. Electrical conductivity has been measured for blends with extruded rod shape, as-spun fibre filaments and fibres made under draw ratio of four. Polypropylene containing 20 wt% polyaniline polymer modified with 7.5 wt% carbon nanotubes shows the maximum conductivity among all the samples, about 0.16 S/cm.     

Recombination studies in a polyfluorene copolymer for photovoltaic applications

We present detailed continuous wave (cw) and transient photoinduced absorption (PA) measurements in thin films of a novel alternating polyfluorene copolymer, poly[2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3-benzo-thiadiazole)] (DiO-PFDTBT), and its blends with the soluble fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in weight ratios of 1:0, 4:1 and 1:4. We measure the frequency, intensity and temperature dependence of the PA signal in the frequency domain, and compare with the results obtained from the transient PA decay measurements in the time domain. In all blends, the PA spectrum shows a broad high energy PA band ranging from ∼1 eV to 2 eV as well as a low energy band peaking at ∼0.35 eV. We attribute the low energy band to the P₁ transition of polarons and part of the high energy band to the correlated P₂ transition of polarons. Both frequency and time domain measurements show that the high energy band has two decay components, a faster component in the microsecond time regime and a slower component in the millisecond time regime. The slow component is strongly dispersive, whereas the fast component is practically non-dispersive.     

Electronic conduction mechanism in chitin–polyaniline blend

The electrical conductivity of chitin–polyaniline blend doped with HCl has been studied in the temperature range 323–373 K for various blend compositions. Conductivity of blends increases from less than ≈10^?7 S/cm to 2.15 × 10^?5 S/cm, depending on the percentage of polyaniline in the blend due to self-doping of LiCl. When these blends are doped with HCl conductivity raises to ≈9.68 × 10^?2 S/cm. Current–voltage data is analyzed using various models available. The results suggest Schottky–Richardson and one-dimensional variable range hopping mechanisms for undoped blend and one-dimensional variable range hopping mechanism in the case of doped blend.     

Splat morphology of plasma sprayed aluminum oxide reinforced with carbon nanotubes: A comparison between experiments and simulation

This study elucidates the effect of carbon nanotube (CNT) addition on the splat formation in plasma sprayed aluminum oxide (Al₂O₃) composite coating using experimental and computational methods. CNT content was varied as 0, 4 and 8 wt.% in Al₂O₃ matrix. With an increasing CNT content, splat morphology became more circular and disk-shaped. The average diameter of disk-shaped splats increased from 28.6 ± 1.4 μm for Al₂O₃ to 43.2 ± 1.3 μm for Al₂O₃–8 wt.% CNT. The population density of splats with fingers, fragments, and voids was the lowest for the highest (8 wt.%) CNT content. The addition of CNTs resulted in two simultaneously competing phenomena viz. increased thermal capacity and increased viscosity of the melt. Increased thermal capacity delayed the localized solidification resulting in higher splat diameter while agglomeration of CNTs at the periphery of the splat results in higher viscosity of the melt which suppresses the splat fragmentation that leads to increased population density of disk shaped splats. Splat morphology of three compositions was also simulated using SIMDROP software, which showed a good agreement with the experimentally collected splats.     

White light emission from two blue emitters of an equimolar (1:1) blend in single-layer device

A white light emission was observed from a single-layer emitting system consisting of an equimolar blend of two blue emitters of a bipolar oligomer, 9,9-spirobifluorene-centered bioxadiazole (303) and polyvinylcarbazole (PVK), featuring a single broad emission (ranging in 400–800 nm), which is distinctly different from those of large PVK-fraction blends (λ_em ≈ 490 nm) and that of pristine 303 (λ_em ≈ 555 nm) as well.     

Electro-conductive composite fibers by melt spinning of polypropylene/polyamide/carbon nanotubes

In this study, the blends of polypropylene/polyamide with carbon nanotubes (CNTs) have been prepared and melt spun to as-spun and drawn fibers. Thermal analysis showed that increasing the polyamide content, decreased the degree of crystallinity in the blends. Characterization of fibers showed that both conductivity and tensile strength have been improved by increasing the amount of polyamide in the blends as well as the melt blending temperature; furthermore, the morphology, electrical and mechanical properties of the blends were significantly influenced by adding 1 phr compatibilizer to the blend. The comparison between as-spun fibers and drawn fibers proved that although mechanical properties were improved after drawing, the electrical conductivity was decreased from the order of E?02 to E?06 (S/cm), due to applied draw-ratio of three.     

Dielectric and morphological properties of PAni-DBSA blended with polystyrene sulfonic acid

Polyaniline (PAni) doped with organic protonic and polymeric acids shows better solubility and processability by conventional methods. In this work, we report the results of polyaniline doped with dodecylbenzenesulfonic acid (PAni-DBSA) and reprocessing with polystyrene sulfonic acid (PSS) in an internal mixer, to obtain a conductive polymer blend (PAni-DBSA/PSS).Impedance spectroscopy, scanning electron microscopy and infrared spectroscopy of the samples were evaluated. Significantly different morphologies were observed for PAni-DBSA and PAni-DBSA/PSS complexes. The effect of different degrees of doping with DBSA and the influence of PSS on the dielectric properties of PAni were investigated by impedance spectroscopy in frequency range 10 Hz–30 MHz. The different complexes present two dielectric relaxation processes suggesting two types of chain structure.We show that DBSA improves the doping range of the PAni/PSS complexes and the homogeneity of the blends.     

Dendrites and pillars in spin cast blends of polyaniline or its oligomeric analogue

In the present work morphological structures were examined which are formed spontaneously during the spin-casting of polymer blends. Mixtures of polyaniline (PANI) (doped with camphorsulfonic acid, CSA) or its oligomeric counterpart (N,N′-diphenyl-p-phenylenediimine, DPI) and a conventional polymer (polystyrene, PS or poly(methyl methacrylate), PMMA) were studied. The samples were manufactured in controlled humidity conditions (relative humidity, RH = 10%, 60% or 95%). In case of PANI(CSA)/PS (or PMMA) blends, hierarchic structures arise. They are built of large (>10 μm) PS-rich (or PMMA-rich) dendrites and sub-micron PANI-rich pillars in the pores of PS (PMMA) host. In analogous PS/DPI films, DPI dendrites embedded in the PS film are observed. This microstructure formation route, based on solution blend processing, is an alternative to chemical synthesis of fibres and columns. Film structures were determined with microscopic (optical, Atomic Force Microscopy) and spectroscopic techniques (dynamic Secondary Ion Mass Spectroscopy and X-ray Photoelectron Spectroscopy). Structure formation models are presented. Diffusion-Limited Aggregation is postulated for solution droplets agglomerating as PS-rich fractals (with low attachment probability P) and for crystallizing DPI dendrites (with higher P value and hence larger and less compact fractals, as observed).     

Warm die compaction and sintering of titanium and titanium alloy powders

A study has been made of the effect of non-lubricated warm die (200 °C) compaction on the densification of hydride–dehydride (HDH) Ti powder, pre-alloyed (PA) Ti-6Al-4V and Ti-10V-2Fe-3Al powders, and HDH Ti and V-Fe-Al master alloy powder blends, compared to cold die compaction. Depending on the compaction pressure, which was varied from 200 to 1000 MPa, non-lubricated warm die (200 °C) compaction was very effective for −100 mesh HDH Ti powder, increasing the green density by 5.0–9.4% theoretical density (TD). Die wall lubrication with stearic acid showed no influence on the green density when compacted at 800 MPa. With warm die (200 °C) compaction, achieving a green density of greater than 90%TD was straightforward for HDH Ti powder when compacted at ≥750 MPa. Accordingly, near pore-free (≥99.5%TD) Ti microstructures were obtained after sintering at 1300 °C for 120 min in vacuum when compacted at 1000 MPa. The resulting increment in the sintered density was between 2.0%TD and 4.4%TD. Warm die (200 °C) compaction showed no effect on PA Ti-10V-2Fe-3Al powder and only a small effect on PA Ti-6Al-4V powder when compacted at 1000 MPa. However, it was still virtually effective for Ti-10V-2Fe-3Al powder blends made of HDH Ti powder and V-Fe-Al master alloy powder. The observations were compared with literature data and discussed in accordance with the yield strength of Ti, Ti-6Al-4V, Ti-10V-2Fe-3Al and Al₃V as a function of temperature.     

White organic light-emitting diodes via mixing exciplex and electroplex emissions

The authors report the fabrication of white organic light-emitting devices and discuss their electroluminescence (EL) properties. The device structure is ITO/TPD (50 nm)/BCP (8 nm)/Rubrene (0.5 nm)/BCP (10 nm)/Alq₃ (20 nm)/LiF (1 nm)/Al. In the EL spectra of this device, two new emissions peaking at 590 and 630 nm have been observed. These two emissions should be attributed to triplet exciplex and electroplex occurring at TPD/BCP interface. White emission was obtained based on this device under 12 V driving voltage, the Commission Internationale de l’Eclairage (CIE) coordinates arrives to (0.31, 0.33).     

Surface modification of cellulose by PCL grafts

Two cellulosic substrates (microcrystalline cellulose, MCC, and bleached kraft softwood pulps, BSK) were grafted by polycaprolactone (PCL) chains with different molecular weights, following a three-step procedure using non-swelling conditions in order to limit the reaction to their surface. First, one of the two OH PCL ends was blocked by phenyl isocyanate and the reaction product (adduct 1) was subsequently reacted with 2,4-toluene diisocyanate (adduct 2) to provide it with an NCO function, capable of reacting with cellulose. The ensuing PCL-grafted cellulosic materials were characterized by weight gain, elemental analysis, contact angle measurements, attenuated total reflexion–Fourier transform infrared (ATR–FTIR), X-ray photoelectron spectroscopy (XPS) and biodegradation tests. The modification was proven to occur by the presence of nitrogen atoms in the elemental analysis tests and XPS spectra of modified and soxhlet-extracted cellulose. The contact angle measurements have also shown that the surface became as hydrophobic as PCL itself. The polar component of the surface energy of cellulosic substrates before treatment was found to be about 32 and 10 mJ m^?2, for MCC and BSK, respectively. This value vanished to practically zero after grafting with different PCLs. The strategy proposed in the present work is original since, to the best of our knowledge, this paper reports for the first time the chemical “grafting onto” of the cellulose surface by PCL macromolecular structures, with the aim of obtaining fibre–matrix co-continuous fully sustainable and biodegradable composite materials.     

Conducting blends of polyaniline and aromatic main-chain liquid crystalline polymer,XYDAR SRT-900

Conductive polyaniline/fully aromatic main-chain liquid crystalline polymer, XYDAR SRT-900 films have been prepared by solution blend of polyaniline (PANI) emeraldine salt and the liquid crystalline polymer. The polymer blends exhibit excellent mechanical properties and good conductivity at moderate PANI concentration. Moreover, polymer films have optical transparent property at concentration lower than 10 wt.%. The morphology of the blends has been investigated using scanning electronic microscopy and X-ray scattering.     

Influence of the scan rate on the morphology of polyaniline grown on conducting fabrics. Centipede-like morphology

We report the apparition of different polyaniline (PANI) morphologies when different scan rates were employed in the electrochemical deposition of PANI on conducting fabrics. The most impressive structure obtained was the centipede-like morphology. PANI was deposited on conducting textiles of polyester covered with polypyrrole (PPy)/anthraquinone sulphonic acid (AQSA) by means of cyclic voltammetry. With the scan rates of 50 mV s^?1 and 5 mV s^?1 PANI with centipede-like morphology was obtained in the first scans. Globular PANI gained importance for higher number of scans due to the formation of new nucleation sites. When a scan rate of 1 mV s^?1 was employed a variety of different morphologies were observed, such as: fibrillar, stalagmite-like, coral-like and plain irregular forms. Such variety of morphologies is due to the slow growth that allowed different types of morphologies.     

Structural properties of carbon prepared from aligned polyacetylene thin films

Aligned polyacetylene (PA) thin films consisting of fibrils of about 100 nm in diameter were carbonized at 1000 °C in a vacuum or in an argon gas. Structures and morphologies of the carbons prepared from the aligned PA thin films were investigated using Raman spectroscopy, X-ray measurements, and scanning and transmission electron microscopes. The carbonization gave rise to a char of amount of 20% in weight of the PA film. The char was found to contain nanorods of about 10 nm in width. Morphology of the carbon nanorod reflected that of the aligned PA thin film. Subsequently, the char was graphitized by further heating at 2600 °C.     

Chromium carbide–CNT nanocomposites with enhanced mechanical properties

Chromium carbide is widely used as a tribological coating material in high-temperature applications requiring high wear resistance and hardness. Herein, an attempt has been made to further enhance the mechanical and wear properties of chromium carbide coatings by reinforcing carbon nanotubes (CNTs) as a potential replacement of soft binder matrix using plasma spraying. The microstructures of the sprayed CNT-reinforced Cr₃C₂ coatings were characterized using transmission electron microscopy and scanning electron microscopy. The mechanical properties were assessed using micro-Vickers hardness, nanoindentation and wear measurements. CNT reinforcement improved the hardness of the coating by 40% and decreased the wear rate of the coating by almost 45–50%. Cr₃C₂ reinforced with 2 wt.% CNT had an elastic modulus 304.5 ± 29.2 GPa, hardness of 1175 ± 60 VH_0.300 and a coefficient of friction of 0.654. It was concluded that the CNT reinforcement increased the wear resistance by forming intersplat bridges while the improvement in the hardness was attributed to the deformation resistance of CNTs under indentation.     

A new organic/inorganic electroluminescent material with a silsesquioxane core

This paper describes a new polyhedral oligomeric silsesquioxane (POSS)-based blue-light electroluminescent nanoparticle, octakis[N-(9-ethyl-9H-carbazol-3-yl)undecanamide-11-dimethylsiloxy]silsesquioxane (POSS-C11-Cz), which contains eight carbazole chromophore arms, synthesized through the hydrosilation reaction of octakis(dimethylsiloxy)silsesquioxane with the terminal olefin Cz-C11ene. POSS-C11-Cz exhibits good thermal and electrochemical stabilities and good film-forming properties. The optical and photoluminescence spectra of POSS-C11-Cz in solution and in the solid state indicate a reduction in the degrees of aggregation and excimer formation because inter-chain interactions were prohibited by the bulky POSS core. Moreover, photoluminescence spectra of a POSS-C11-Cz (3 wt.%)/polyfluorene (97 wt.%) blend revealed that the color was stable after heating the sample at 200 °C for 5 h; in contrast, the pure polyfluorene exhibited a significant green emission at 530 nm. A triple-layer device based on this blend exhibited higher maximum brightness and luminance efficiencies relative to those of the pure polyfluorene. Thus, the organic/inorganic POSS-C11-Cz/polyfluorene blend has potential for use in polymeric light-emitting diodes because of its improved thermal and optoelectronic characteristics.     

Thermal decomposition kinetics of in situ reinforcing composite based on polypropylene and liquid crystalline polymer

A thermotropic liquid crystalline polymer (TLCP), a copolyester with a 80/20 molar ratio of p-hydroxy benzoic acid (HBA) and poly(ethylene terephthalate (PET), known as Rodrun LC5000, was melt blended with polypropylene (PP) using a twin-screw extruder. The thermal degradation of the blends containing various TLCP contents was investigated using thermogravimetry (TG). In nitrogen and in air, the TG profiles of PP revealed a single weight-loss step, whereas TLCP showed two and three major weight-loss steps in nitrogen and in air, respectively. In air, more complex TG curves were observed for the blends with TLCP loading. Simultaneous DSC thermograms revealed that the degradation processes for all neat polymers and the blends were endothermic in nitrogen and exothermic in air. The kinetic parameters (E_a, ln A, and n) calculated using isoconversional method indicated that the thermal stability of PP was significantly improved by in situ reinforcing with TLCP. Addition of SEBS-g-MA compatibilizer slightly enhanced the thermal resistance of blend.     

Investigation of bulk metallic glass structure by means of electron irradiation

The sensitivity of radiation effects on structural features in metallic glasses (MG) provides a way of investigating the structure and structural defects of MG through the studies of accumulation and relaxation processes of radiation damages in the glasses. In particular, it is a way to verify the validity of models proposed for the MG structure. Currently, there are two theoretical structural models of MG, based on completely different concepts. On the one hand, the model of random closely packed spheres + free volume approach is based on the idea of “the ultimate disorder”. On the other hand, in the polycluster model the idea of altering and distorted short-range order is used. Each of the models implies fairly different kinds of primary radiation damages, relaxation kinetics, and other properties. We have studied the accumulation and recovery kinetics of radiation defects in ZrTiCuNiBe and ZrTiCuNiAl bulk metallic glasses irradiated with 2.5 MeV electrons at T ～ 80 K. Electrical resistance measurements of the irradiated samples were performed. Dose dependences at ～80 K and the recovery spectrum of irradiation-induced electrical resistance in the 85–300 K temperature range were obtained. The data suggest that the point defects are stable in the metallic glasses, and the defect mobility is a thermally activated process. The results obtained are evidently in accord with the polycluster model of the MG structure.     

The use of cross-linkable interlayers to improve device performances in blue polymer light-emitting diodes

High efficiency blue PLEDs were fabricated by adding a thin interlayer between PEDT:PSS and emitting polymer layers. Two different cross-linkable alkoxysilane-based interlayer materials, X-NPB and X-PDA, were synthesized based on N,N′-bis(4-methylphenyl)-N,N′-diphenyl-1,4-phenylenediamine (PDA) and N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1-biphenyl-4,4-diamine (NPB) which are well-known OLED HTLs. The devices, with configuration of indium tin oxide (ITO)/PEDT:PSS (65 nm)/interlayer (10–20 nm)/emitting polymer layer (70 nm)/BaF₂ (2 nm)/Ca (50 nm)/Al (300 nm), were fabricated by spin coating and thermal evaporation. In this device structure, the cross-linked X-NPB or X-PDA interlayers are more adherent and mechanically robust as well as impervious to spin coating of next emitting polymer layer. In addition, the devices with these interlayers exhibit a higher luminescence and current efficiency than those without interlayers because interlayers have two functions which are blocking electrons and preventing from severe quenching by PEDT:PSS.     

Elastic properties of metastable Mo1 − xSix alloy thin films: A Brillouin light scattering study

Elastic properties of Mo_1 ? xSi_x alloy films with 0 ≤ x ≤ 1 have been investigated by the Brillouin light scattering technique thanks to the analysis of the surface acoustic waves in the film on substrate: the so-called Rayleigh surface wave and the Sezawa waves. A transition from crystalline to amorphous state is observed for a Si content, x = 0.19. This transition is accompanied by different modifications of the elastic constants, namely, C₁₁, C₃₃, C₁₃ and C₄₄ that are necessary with C₁₂ to define the effective hexagonal symmetry for the textured <110> polycrystalline alloys. A pronounced softening of the shear elastic C₄₄ constant is observed, from 110 to 60 GPa when x varies from 0 to the critical threshold composition x = 0.19. The longitudinal C₃₃ constant estimated in this work from the BLS measurements shows also a softening from 425 to 315 GPa. An intrinsic consequence of the high supersaturation of MoSi alloys is the development of an important lattice instability. In the amorphous state, the evolution of the elastic properties, that can be defined by the two independent constants C₁₁ and C₄₄ = (C₁₁ ? C₁₂)/2, exhibits two distinct behaviors depending on the electronic properties and the interatomic bonding of the amorphous alloys.