Electrospun composite nanofibers of poly (vinylidene fluoride‐trifluoroethylene)/polyaniline‐polystyrene sulfonic acid

Nanofibers of poly(vinylidene fluoride‐trifluoroethylene)/polyaniline‐polystyrene sulfonic acid (PVDF‐TrFE/PANi‐PSSA) were fabricated in air at room temperature using electrospinning, with the thinnest fiber having a diameter of ～ 6 nm. This is a cheap, fast, and reliable process for generating PVDF‐TrFE/PANi‐PSSA composite nanofibers. The presence of conducting PANi‐PSSA increased the charge density of the solution and assisted in the fabrication of PVDF‐TrFE nanofibers at low polymer concentrations in dimethylformamide without the beading effect. Ultraviolet and visible spectroscopy showed that PANi‐PSSA was well incorporated into the PVDF‐TrFE solution with no polymer segregation or degradation. A scanning electron microscope was used for morphological characterization of the fibers and a profilometer used to determine the fiber diameter. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly(lactic acid)/poly(3‐hexylthiophene) composite nanofiber fabrication for electronic applications

Fibers of the biopolymer poly(lactic acid) (PLA) and the p‐type semiconducting polymer poly(3‐hexylthiophene) (P3HT) were fabricated using the electrospinning technique at low PLA concentration (5 wt%) in CHCl₃. The fibers were several millimeters long and had diameters in the range 100 nm–4 µm. Nanofibers containing 63%/37% of PLA/P3HT were electroactive, and therefore were used to construct p–n diodes whose ideality parameter was 2.4 and rectification (on/off) ratio was 400 at ±1 V. These diodes were also able to sense UV radiation and remain operable with an increase in the on/off ratio and a lowering of the turn‐on voltage. By fabricating reusable and low‐cost multifunctional diodes from PLA/P3HT, the applications of PLA as a biocompatible and biodegradable polyester are expanded to include electronic device fabrication with low environmental impact. © 2016 Society of Chemical Industry     

Electrochemical behaviour of PANi/polyurethane antifouling coating in salt water studied by electrochemical impedance spectroscopy

Electrochemical behaviour of polyaniline–polyurethane (PANi–PU) antifouling coating in 3.5 wt% NaCl is studied by electrochemical impedance spectroscopy (EIS). A thick coating (∼1 mm) of 10, 15 and 20% PANi in marine grade PU, is cast over corrosion resistant aluminium alloy 2024 and its impedance characteristics are measured by EIS and compared with neat PU. On addition of 10% PANi, the impedance of the coating drastically comes down from 10⁹ to 10⁷ Ω. 20% is the maximum processable amount of PANi for the selected PU system. The coatings are exposed to 3.5 wt% NaCl and its impedance characteristics are monitored as a function of time. Changes in the impedance characteristics of the systems were found to occur as a function of the exposure time in all cases, though their evolution with time showed marked differences with PANi content. Water sorption and break down frequency are derived from the experimental results and analysed.     

Preparation of polyaniline nanofibers and their use as a cathode of aqueous rechargeable batteries

Normal pulse voltammetric method was used to synthesize nanofibers of polyaniline (PANi) in HCl solution on a platinum electrode. The influences of the synthesis parameters, such as potential increment, pulse duration and monomer concentration on the electrochemical properties of the PANi films were investigated. Scanning electron microscopic micrographs clearly revealed the formation a nanofiber structure with average diameter in range 70-100 nm under optimum experimental conditions. The electrochemical properties of PANi films were studied with the impedance analysis, cyclic voltammetry and charge/discharge capacities. FT-IR results revealed that the PANi nanofibers were in emeraldine salt form. The film was employed as a positive electrode (cathode) for a PANi-Zn secondary battery containing 1.0 M ZnCl₂ and 0.5 M NH₄Cl as electrolyte. The cells were charged and discharged under a pulse current of 0.31 mA cm⁻². It was found that the maximum capacity of the PANi-Zn battery is 235.60 Ah kg⁻¹ with a columbic efficiency of 97-100% over a wide range of current density of 0.3-5.6 mA cm⁻². The specific energy was 287.43 Wh kg⁻¹ and the PANi cathode exhibited good recycleability.     

Field emission of MWCNTs/PANi nanocomposites prepared by ex‐situ and in‐situ polymerization methods

The present work describes the field‐emission properties of multiwalled carbon nanotubes (MWCNTs) coated with conducting polymer polyaniline (PANi). MWCNTs/PANi nanocomposites have been prepared by ex‐ situ polymerization methods and inex‐ situ chemical polymerization and are analyzed by SEM and Raman spectroscopy. It is fairly clear from SEM images that PANi is coated on the surface of MWCNT. SEM image of PANi powder also shows that the powder obtained is PANi nanofibers. It is also observed from SEM images that the shell diameter of MWCNTs depends on PANi content in thenanocomposites. The average outer diameter of MWCNTs increases from 7–15 to 50–80 nm upon PANi coating. Field‐emission study shows that although there is decrease in the value of turnex‐on field E_to and increase in the value field enhancement factor β of the nanocomposites as we go from direct solid‐state mixing method to inex‐ situ chemical polymerization method, the parameters obtained by inex‐ situ polymerization chemical method shows superior field emission. The turn‐on field of the nanocomposites are between 2.5 and 4.5 V/μm and the field enhancement factors are significantly high, between 1.2 × 10³ and 9.2 × 10³ while. PANi nanofibers does not show any field emission. POLYM. COMPOS. 34:1298–1305, 2013. © 2013 Society of Plastics Engineers     

Fabrication and characterization of new bulky layer mixed metal oxide ceramic nanofibers through two nozzle electrospinning method

New bulky layers of metal mixed ceramic nanofibers were fabricated through two-nozzle electrospinning method followed by calcination. Solutions of PAN in DMF with various concentrations were prepared as: 11, 12, 13, 14, and 15 wt% to which the constant amounts of 2.1 g of Aluminum acetate, 0.3 g of Copper acetate and 0.3 g of Boehmite nanoparticles were added. A stepwise calcination process was utilized to obtain the ceramic nanofibers. The nanofibers were characterized by FTIR spectroscopy, TG-DTA, XRD, SEM and EDS techniques. The formulation with 12 wt% of PAN in DMF was proved to be the optimum spinable sample. The average diameter of as spun nanofibers was detected as 568 nm, which decreased to 181 nm after calcination and thermal degradation. Ceramic nanofibers were composed of CuO, Al₂O₃ and Cu₂Al₄O₇ phases. The average density of the sample was about 0.090 (g/cm³) and the porosity of the mat was 94.5% and thus, production of a 3D structure may be claimed. The ceramic nanofibers performed well as catalyst in the C-C coupling reaction (Suzuki reaction) by facilitating the synthesis of biaryl compound from aryl iodide in 20 min with isolated yield of 89% only by using 15 mg of ceramic nanofibers as the nano catalyst.     

Balancing crystalline and amorphous domains in PLA through star-structured polylactides with dual plasticizer/nucleating agent functionality

The development of the first star-structured poly(l-lactides) (s-PLLAs) with dual functionality as both nucleating agent and plasticizer in polylactide (PLA) blends is described. Mechanisms controlling this functionality are deduced. Blends of PLA containing s-PLLAs show significant improvements in thermal and mechanical properties. The s-PLLAs are made by using appropriate saccharides, e.g., methyl-α-d-glucopyranoside and β-cyclodextrin, as star-shaped core macroinitiators for l-lactide polymerization. Varying the l-lactide mole ratio gives control of the degree of polymerization (DP_n) of PLLA branches from 5 to 30. Blending ≈1 wt% of the new s-PLLAs with PLA resins produces a drastic decrease in the glass transition temperature (T_g) (from 57 °C to 22 °C), and an increase in the elongation at break (30–40%) confirms significant increases in chain mobility and plasticity. A concomitant reduction of crystallization temperature (from 127 °C to 81 °C) as well as a higher crystallization rate (a factor of four increase) implies rapid nucleation of crystalline domains. With only 1 wt% of s-PLLA in the blend of PLA film, the elongation at break of PLA increases eightfold. In addition to the dual functionality, the PLLA branches also provide miscibility with PLA in the blend (as confirmed by a single T_g, combined with estimates from the Fox equation and solubility parameters).     

Mechanical properties of poly lactic acid composite films reinforced with wet milled jute nanofibers

In the present study, waste jute fibers generated in textile industries, were wet pulverized to the scale of nanofibers of 50 nm diameter using high energy planetary ball milling for 3 h. The presence of water during wet pulverization found to reduce the rising temperature of mill, which prevented sticking of nanofibers on the mill wall and resulted in unimodal size distribution. In the subsequent stage, 1, 5, and 10 wt% of jute nanofibers were incorporated in poly(lactic acid) (PLA) matrix to prepare nanocomposite films by solvent casting. The reinforcement of nanofibers was investigated from the improvements in mechanical properties based on tensile tests, dynamic mechanical analysis, and differential scanning calorimetry. The maximum improvement was observed in case of 5 wt% nanocomposite film where initial modulus and tensile strength increased by 217.30% and 170.59%, respectively as compared to neat PLA film. These improvements are attributed to the increased interaction between nanofibers and matrix as well as to the increased crystallinity of PLA in composites. The improvements in load bearing capacity of nanocomposite films were significant at 60°C than 35°C, which showed ability of jute nanofibers to improve the softening temperature of PLA matrix. In the end, experimental results of Young's modulus were compared with predicted modulus of mechanical models. A good level of agreement was observed up to 5 wt% loading of jute nanofibers. POLYM. COMPOS., 34:2133–2141, 2013. © 2013 Society of Plastics Engineers     

Extruded PLA/clay nanocomposite foams blown with supercritical CO2

The effects of nanoclay (Cloisite 30B) on the foamability of polylactide (PLA) were investigated in continuous extrusion foaming using supercritical CO₂ as the blowing agent. PLA samples containing 0–5 wt% of nanoclay were prepared. The X-ray diffraction and transmission electron microscopy images showed a high degree of exfoliation of clay nanoparticles within PLA. A single-screw tandem extruder was used to produce foams with 5 wt% and 9 wt% supercritical CO₂. The crystallization behavior of the samples was analyzed using regular and high-pressure differential scanning calorimeters and using a rotational rheometer under small amplitude oscillatory shearing. In the presence of dissolved CO₂, clay, and shear action, the PLA crystallization kinetics was significantly enhanced. The foamed results showed that both the cell density and the expansion ratio were greatly promoted with increased clay content and the dissolved CO₂, as well as by the possibly nucleated crystals. By further use of Cloisite 20A nanoclay particles with poor disperse-ability in PLA, we also proved that a high degree of dispersion significantly promoted the cell density and the expansion ratio of the PLA nanocomposites. Further, by varying the temperature profile within second extruder of the tandem-line, it was confirmed that the more rapid crystallization along the second extruder was responsible for the enhanced cell density and expansion ratio. The final crystallinity of the foamed samples was also enhanced at higher expansion ratios due to the strain induced crystallization.     

Preparation and Xylene‐Sensing Properties of Co3O4 Nanofibers

Co₃O₄ nanofibers were prepared by an electrospinning method and characterized by differential thermal and thermal gravimetric analyzer (DTA‐TGA), X‐ray diffraction (XRD), Fourier Transform Infrared Spectrometer (FT‐IR), and scanning electron microscopy (SEM). Xylene‐sensing properties of the as‐prepared nanofibers were also investigated in detail. The results showed that the morphology of the as‐prepared fibers was largely influenced by the calcination temperature. The Co₃O₄ nanofibers calcined at 500°C exhibited the highest response to xylene in a wide concentration range. Moreover, Co₃O₄ nanofibers calcined at 500°C also exhibited good selectivity, fast response (15 s) and recovery (22 s) rate at a low operating temperatures of 255°C. These properties make the fabricated nanofibers good candidates for xylene detection.     

Preparation and characterization of poly(lactic acid)/poly(ethylene oxide) blend film: effects of poly(ethylene oxide) and poly(ethylene glycol) on the properties

Poly(lactic acid) (PLA) film plasticized with poly(ethylene oxide) (PEO) at various weight percentages (1–5 wt%) was prepared to improve the elongation, thus overcoming the inherent brittleness of the material. After optimization of the amount of PEO (4 wt%) through mechanical analysis, poly(ethylene glycol) (PEG), a well‐established plasticizer of PLA, was added (0.5–1.5 wt%) without hampering the transparency and tensile strength much, and again its amount was optimized (1 wt%). Neat PLA and PLA with the other components were solvent‐cast in the form of films using chloroform as a solvent. Improvement in elongation at break and reduction in tensile strength suggested a plasticizing effect of both PEO and PEG on PLA. Thermal and infrared data revealed that the addition of PEO induced β crystals in PLA. Scanning electron micrographs indicated a porous surface morphology of the blends. PEO alone in PLA exhibited the best optical clarity with higher percentage crystallinity, while PEG incorporation in PLA/PEO resulted in superior barrier properties. Also, the stability of the blends under a wide range of pH means prospective implementation of the films in packaging of food and non‐food‐grade products. © 2018 Society of Chemical Industry     

Improving the properties of polylactic acid by blending with low molecular weight polylactic acid‐g‐natural rubber

The low molecular weight (M_w) polylactic acid‐g‐natural rubber (PLA‐g‐NR) was synthesized by grafting the maleated natural rubber (MNR) with low molecular weight PLA at a weight ratio of 1:1 in toluene at 80°C. Two types of MNR (MNR10 and MNR20) having anhydride moieties of 10 and 20 wt%, respectively, were prepared. The reaction was followed by IR analysis. Next, the obtained PLA‐g‐NR was blended with pristine PLA using a twin‐screw extruder at PLA to PLA‐g‐NR weight ratios of 90:10, 80:20, 70:30, and 60:40 followed by compression to obtain specimens for testing. In case of 10 wt% PLA‐g‐NR having MNR10, it was found that blending of PLA with PLA‐g‐NR resulted in a 200% improvement in impact strength and twofold percent elongation at break (flexibility). Further SEM analysis confirmed that PLA‐g‐NR was compatible with PLA matrix. In contrast, NR was present as disperse particles which exhibited poor adhesion to PLA. From these findings, it was also found that PLA‐g‐NR was capable of improving the properties of PLA more than NR due to the fact that it exhibited higher compatibility. POLYM. ENG. SCI., 54:2770–2776, 2014. © 2013 Society of Plastics Engineers     

Electrospun Fe2O3 nanotubes and Fe3O4 nanofibers by citric acid sol‐gel method

Citric acid‐based sol‐gel method has been used to synthesize metal oxides widely. Iron‐based one‐dimensional nanostructured materials, including Fe₂O₃ nanotubes and Fe₃O₄ nanofibers, have been successfully prepared by directly annealing electrospun citric acid‐based precursor fibers under different atmospheres in this study. Thermo‐gravimetric and differential thermal analyses were carried out from room temperature to 800°C under air and argon atmosphere, respectively. The results reveal the formation mechanisms for Fe₂O₃ nanotube and Fe₃O₄ nanofiber. Fe₂O₃ tubular structures with average inner diameter about 500 nm and wall thickness about 20 nm were obtained. Fe₃O₄ nanoparticles were self‐assembled along the one dimensional orientation to form Fe₃O₄ nanofibers with average diameter around 500 nm. The reflection losses as a function of frequency for the samples with 23 and 33 wt% Fe₃O₄ nanofibers in paraffin were examined. The frequency dependence of reflection losses under various matching thicknesses (2, 3, 4, 6 and 8 mm) was simulated. The as‐fabricated Fe₃O₄ nanofibers can be believed to be promising candidates as highly effective microwave absorbers.     

Polyaniline doped with α, ω‐alkanedisulfonic acids: preparation and characterization

The use of α, ω‐alkanedisulfonic acid, HO₃S(CH₂)_nSO₃H (n = 1, 4, 6 and 12), as a dopant for polyaniline (PANi) was investigated. This series of disulfonic acids with varying chain lengths were synthesized and used in the doping of PANi. The doped polymers showed conductivity in the range 10^?2 to 10^?1 S cm^?1. Thermal studies showed that the doped polymers, depending on the chain length of α,ω‐alkanedisulfonic acid, were stable up to ca 300 °C and the thermal stability decreased with increasing dopant chain length. The thermal stability of α,ω‐alkanedisulfonic acid‐doped PANi was higher than that of alkanesulfonic acid‐doped PANi which typically degrades around 250 °C, suggesting a moderately broader processing window for α,ω‐alkanedisulfonic acid‐doped PANi for blending with other thermoplastics. Copyright © 2012 Society of Chemical Industry     

Templated growth of polyaniline on exfoliated graphene nanoplatelets (GNP) and its thermoelectric properties

Polyaniline (PANi)/exfoliated graphene nanoplatelets (GNP) nanocomposites were prepared by in situ polymerization of aniline monomer in the presence of GNP for thermoelectric applications. PANi has a strong affinity for GNP due to π electron interactions, forming a uniform nanofibril coating. A paper-like nanocomposite was prepared by controlled vacuum filtration of an aqueous dispersion of PANi decorated GNP. The Seebeck coefficient of the resulting nanocomposite changes with initial concentration of aniline in the solution as well as the protonation of PANi, reaching as high as 33 μV/K for nanocomposites containing approximately 40 wt% of PANi and with a protonation ratio of 0.2. The presence of GNP improved the electrical conductivity of the nanocomposites to 59 S/cm. As a result, thermoelectric figure of merit ZT of the nanocomposites is 2 orders of magnitude higher than either of the constituents, exhibiting a significant synergistic effect.     

Microstructural and main mechanical properties of novalac based carbon–carbon composites as the pyrolysis heating rate

In this study, the effects of pyrolysis heating rate on microstructural and main mechanical properties of Novalac-based carbon/carbon composites were investigated by CHNS, optical microscope, FE-SEM, BET N₂ adsorption, XRD, Raman, FT-IR, wear analyzing, three-point bending test, tensile and Vickers micro-hardness tests. Firstly, PAN-derived carbon nanofibers (reinforcing agent) was synthesized using electrospinning followed by the functionalizing via the wet chemical oxidation to improve the strength of nanofiber bonding to the matrix of composites. Firstly, novalac resin (acting as a matrix), hexamethylenetetramine (hardener agent) and carbon nanofibers (reinforcing agent) were mixed and hot-pressed at 180 °C under the compression load of 40 kN to produce compressed CNFs-Novolac composites. Carbon/Carbon composites were obtained from the pyrolysis of CNFs-Novolac composites up to 1000 °C by the various heating rates under the compression press of 400 bar, finally. Structural and mechanical studies confirmed that the heating rates below or equal to 10 °C.min⁻¹ resulted in the production of low porosity (≤17%) carbon composite with high carbon content (>90 wt%), high fracture strength (≥270 MPa), high toughness (≥9 MPa m^1/2), high hardness (≥156 Hv), and low friction coefficient (<0.6).     

Flexible BaTiO3/SiC@PbTiO3/epoxy composite films with enhanced dielectric performance at high frequency

Flexible polymer composites with high dielectric constants and low dielectric losses at high frequencies are highly desired in microwave and RF applications. However, a high dielectric constant is often obtained at the expense of flexibility because a high loading of filler is needed. In this work, we synthesize a core-shell structured 1D filler by coating high-dielectric-constant PbTiO₃ onto the surface of low-thermal-expansion-coefficient SiC nanofibers, which are then incorporated into the epoxy matrix together with BaTiO₃ nanoparticles to form the multi-phase BaTiO₃/SiC@PbTiO₃/epoxy composite film. A high dielectric constant (35 at 100 Hz and 20 at 5 GHz) and a low dielectric loss (0.023 at 100 Hz and 0.13 at 5 GHz) are achieved as the filling content of SiC@PbTiO₃ and BaTiO₃ is 5.24 wt% and 80 wt%, respectively. Prediction models of the effective dielectric constant of polymer-based composites reveal that a continuous polarization network is constructed in the composites owing to the physical contact between BaTiO₃ and PbTiO₃. The construction of the multi-phase filler provides a feasible way to effectively adjust and improve the dielectric properties of polymer-based composite films.     

Antibacterial electrospun chitosan/poly(vinyl alcohol) nanofibers containing silver nitrate and titanium dioxide

Chitosan/poly(vinyl alcohol) (PVA) nanofibers with antibacterial activity were prepared by the electrospinning of a chitosan/PVA solution with a small amount of silver nitrate (AgNO₃) and titanium dioxide (TiO₂). Nanofibers with diameters of 270–360 nm were obtained. The yield of low‐viscosity chitosan (LCS)/PVA nanofibers was higher than that of high‐viscosity chitosan (HCS)/PVA, and the water content of the HCS/PVA nanofibers and the LCS/PVA nanofibers were 430 and 390%, respectively. The nanofibers developed in this study exhibited antibacterial activities of 99 and 98% against Staphylococcus aureus and Escherichia coli, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Enhanced mechanical and thermal properties of graphene nanoplatelets-reinforced polyamide11/poly(lactic acid) nanocomposites

The present paper aims to obtain a sustainable nanocomposite by using bio-based polyamide 11 and biodegradable poly (lactic acid) blend as matrix and graphene nanoplatelets (GNP) as nanofiller. GNP was incorporated in the PA11/PLA blend matrix in the ratio of 0.5-1-3-5-10 wt% through the twin-screw extruder. The crystallinity of PA11 in the blend, which was 12.9%, increased with the inclusion of GNP, and the highest crystallinity value was observed at 20% for the 1GNP sample. The crystallinity of PLA in the blend, which was 2.3%, increased to 4.6% with 5 wt% GNP addition. The inclusion of GNP to PA11/PLA improved the thermal degradation temperatures and increase the char residue. Also, increments were observed for storage modulus, loss modulus, and glass transition temperature of the matrix with the inclusion of GNP. The addition of GNP caused the tensile strength of the matrix to increase first and then decrease at higher amounts due to the agglomerations. 0.5–1 wt% GNP increased tensile strength by 10% and 5%, respectively. Increasing the amount of GNP to 10 wt% led to a sharp decrease in tensile strength by 24%. Overall, GNP is a suitable nanofiller to enhance the thermal and mechanical features of the PA11/PLA blend.     

MgFe1.98O4 – BaFe12O19 magneto-dielectric composites based ferrite resonator antenna for super-high frequency applications

The structural, morphological, and wideband electromagnetic response of (1-x) MgFe_1.98O₄ + x BaFe₁₂O₁₉ composites with x = 20, 40, 60, and 80 wt percent (wt%) were investigated. The composites' sintering temperature was optimised to be 1250 °C for 2 h. The phase purity and independent existence of the end members in the composites were verified using XRD, Raman and FTIR spectroscopy. The microstructures of the sintered composites indicate the effect of grain growth on the density and grain packing efficiency. The relative permittivity of the composites is in the 9–11 range, while the relative permeability is between 1.4 and 2.8. The increase in BaFe₁₂O₁₉ concentration from 20 to 80 wt% resulted in a dilution effect in permeability and enhanced saturation magnetization and coercive field strength. The composites with 20–80 wt% BaFe₁₂O₁₉ possess a characteristic impedance ranging from 0.55 to 0.38 and a miniaturisation factor ranging from 5.16 to 3.82 at 900 MHz. The composites containing 20 and 40 wt% BaFe₁₂O₁₉ exhibited appreciable miniaturisation factors of 5.16 and 5.24, respectively, with characteristic impedances of 0.55 and 0.47. Furthermore, these composites have low magnetic and dielectric losses of the order of 10^?1 and 10^?3, respectively, making them suitable candidates for resonator antenna applications. A magneto-dielectric resonator antenna using the composite comprising 40 wt% BaFe₁₂O₁₉, with a density greater than 95%, was designed, simulated and fabricated. The fabricated magneto-dielectric resonator antenna resonated at a frequency of 14.7 GHz, with a significantly low return loss of ?44 dB and wide impedance bandwidth of 1.44 GHz, suggesting the application potential of the dual-ferrite composite in the Ku-band frequency range.