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The use of controlled extension flows associated with processing with predominant shear flows can bring gains in the dispersive capacity of nanofillers during the processing of nanocomposites. In this work, we use a controlled flow device coupled to the matrix of a single-screw extruder to process PP matrix composites containing 0.5% and 2.5% (v/v) of MWCNT. The nanocomposites were evaluated by optical microscopy and oscillatory rheological analysis. The clusters size analysis showed that in PP/0.5MWCNT-el, 70.5% of all its clusters were below 1µm2 while its analog processed without the extensional flow showed 59.8% of its clusters below this value. The rheological analysis allowed to verify that the compositions processed with the presence of the extensional flow have their crossover frequencies shifted to lower values, that is, longer relaxation times corroborating that improved degrees of dispersion were achieved.

The combination of copper and dielectric materials have emerged as one of the most promising alternatives for the next generation of charge storage devices and microelectronic integrated circuits. In this work, copper nanowires (CuNW) were synthesized using a hard template technique, where copper was electrodeposited into and then liberated from porous alumina templates. Flexible nanofibers of poly(vinylidene fluoride)/copper nanowire (PVDF/CuNW) at different loadings were then obtained using the technique of electrospinning. SEM and TEM images showed that the CuNW had a straight, rigid structure with an average length and diameter of 1.5 µm and 30 nm, respectively. The morphological characterizations also revealed that the CuNW were embedded and aligned inside the nanofibers of PVDF, leading to an increase in the diameters of the generated electrospun nanofibers, e.g., 154 nm and 227 nm for pure PVDF and PVDF/CuNW (20 wt%), respectively. The polymorphic behavior of the PVDF/CuNW nanofibers was studied by FTIR and WAXD, confirming the positive impact of electrospinning on piezoelectric β phase formation of the PVDF matrix. Dielectric measurements indicated that the real permittivity of the mats of the nanofibers increased with CuNW loading. The ascending trend of the real permittivity with the filler content was ascribed to the formation of nanocapacitor structures, i.e., the copper conductive nanofillers acting as nanoelectrodes and the polymer matrix as nanodielectrics. Thus, the results of this study showed that the electrospun PVDF/CuNW nanofibers could be suitable in applications where flexible dielectric and piezoelectric materials are required.

Conductive nanostructures have emerged as the next generation of functional materials for electronic devices. In this work, electrospun nanofiber mats of polyamide 6/polyaniline (PA6/PAni), with high porosity and high surface area, coated with nitrogen-doped carbon nanotubes (N-CNTs) were developed. Employing the chemical vapor deposition technique, N-CNTs were synthesized at various temperatures, e.g., 650, 750, 850, and 950 °C. PA6 and PA6/PAni nanofiber mats were produced employing the electrospinning technique. The mats were then dipped in an aqueous suspension containing dispersed and stabilized N-CNTs. The results revealed that the presence of PAni enhanced the adsorption of N-CNTs on the surface of nanofiber mats, thereby improving their electrical conductivity. The highest conductivity was obtained when the mats were coated with N-CNT650. However, the impact of PAni on the conductivity was higher when the mats were coated with N-CNTs synthesized at higher temperatures, i.e., 10−12 S/cm for PA6/N-CNT950 and 10−5 S/cm for PA6/PAni/N-CNT950, an increase of seven orders of magnitude. It was concluded that the physical features and nitrogen content of N-CNTs had a significant impact on the electrical behavior of the developed mats. Furthermore, it was realized that the synergistic effect between PAni and N-CNT can be employed to build nanostructures with improved conductivity. Keywords: Carbon nanotubes, Nitrogen doping, Polyaniline, Electrospinning, Electrical conductivity

Nitrogen-doped carbon nanotubes (N-CNTs) were synthesized at various temperatures ranging from 650 to 950 °C, at 100 °C intervals, by chemical vapor deposition technique (CVD). The synthesized N-CNTs were employed as modifiers of glassy carbon paste electrodes (GCPE), which were further used as electrochemical sensors for the determination of dopamine (DA) and epinephrine (EP), two important catecholamines that display biological roles as neurotransmitters and hormones. The results revealed that electrodes modified with the N-CNTs synthesized at 650 °C (GCPE/N-CNT650) and 950 °C (GCPE/N-CNT950) presented better electrocatalytic activities and sensing capabilities than the others (GCPE/N-CNT750 and GCPE/N-CNT850). N-CNT950 had the highest graphitization and the highest powder conductivity, whereas N-CNT650 had the lowest graphitization and the lowest powder conductivity. However, both N-CNT950 and N-CNT650 had the highest nitrogen contents, 3.5 and 3.8 at.%, respectively, which probably enhanced their number of electroactive sites to interact with DA and EP molecules. This result is of high significance, because the use of the lowest temperature (650 °C) in the CVD process, yielded N-CNTs with improved electrocatalytic activity and less energy consumption during CVD.

Electrical conductive nanostructures made of nanofibers of poly (amide 6) (PA6) with carboxyl functionalized multiwall carbon nanotubes (MWCNTCOOH) and anchored MWCNTCOOH were produced. The nanotubes were surface activated with carboxyl groups, dispersed in formic acid and added to a formic acid solution of PA6. The mixture was electrospun by applying a voltage of 30 kV; afterwards, the nanofiber's mats were immersed in an aqueous dispersion of MWCNTCOOH containing a nonionic surfactant. The chemical structure, morphology, thermal stability, and electrical conductivity of the nanostructures were evaluated by UV spectroscopy, scanning (SEM), and transmission electron microscopy (TEM), thermal gravimetric analyses (TGA) and volumetric conductivity measurements. The efficiency of the functionalization was confirmed by the UV peaks in the range between 220 and 250 nm (corresponding to a carbonyl group conjugated with a carbon-carbon double bond). SEM and TEM micrographs showed the pullout of the MWCNTCOOH from the nanofibers and the formation of a stable, percolated, and anchored MWCNTCOOH network on the nanofibers due to the anchoring of the MWCNTCOOH from the surfactant solution on the MWCNTCOOH of the nanofibers. The coated nanostructures had higher thermal stability and higher electrical conductivity than the noncoated ones, showing the efficiency of this simple procedure. POLYM. ENG. SCI., 55:1263–1272, 2015. © 2015 Society of Plastics Engineers

BiFeO

© 2015 AIP Publishing LLC.The search for new biomaterials in the bone reconstitution field is growing continuously as humane life expectation and bone fractures increase. For this purpose, composite materials with biodegradable polymers and hydroxyapatite (HA) have been used. A composite material formed by a film, nanofibers and HA has been made. Both, the films and the non-woven mats of nanofibers were formed by nanocomposites made of butylene adipate-co-terephthalate (PBAT) and HA. The techniques used to produce the films and nanofibers were spin coating and electrospinning, respectively. The composite production and morphology were evaluated. The composite showed an adequate morphology and fibers size to be used as scaffold for cell growth.

In this work, nanocomposites based on the triblock copolymer polystyrene-b-polyisoprene-b-polystyrene (SIS) thermoplastic elastomer filled with multiwall carbon nanotubes (MWCNT) were obtained by melt mixing. The nanocomposites were characterized by oscillatory rheometry, electrical resistivity, small angle x-ray scattering (SAXS) and transmission electron microscopy (TEM). The results showed that both, rheological and electrical percolation were achieved at MWCNT loadings between 1-3 vol.%. Rheological tests revealed that the insertion of MWCNT into SIS significantly enhanced the process of relaxation of SIS blocks. Resistivity measurements revealed that conductive nanocomposites were obtained at MWCNT loadings ~1.6 vol.%. The electrical resistivity decreased eleven orders of magnitude from neat SIS to SIS/ 5 vol.% MWCNT. Finally, SAXS and TEM showed that the melt mixing process and the presence of MWCNT hampered the self-assembly of SIS into well-ordered domains.