Influence of Surface Modified MWCNTs on the Mechanical, Electrical and Thermal Properties of Polyimide Nanocomposites

Polyamic acid, the precursor of polyimide, was used for the preparation of polyimide/multiwalled carbon nanotubes (MWCNTs) nanocomposite films by solvent casting technique. In order to enhance the chemical compatibility between polyimide matrix and MWCNTs, the latter was surface modified by incorporating acidic and amide groups by chemical treatment with nitric acid and octadecylamine (C₁₈H₃₉N), respectively. While the amide-MWCNT/polyimide composite shows higher mechanical properties at low loadings (<3 wt%), the acid-MWCNT/polyimide composites perform better at higher loadings (5 wt%). The tensile strength (TS) and the Young’s modulus (YM) values of the acid-MWCNT/polyimide composites at 5 wt% MWCNT loadings was 151 and 3360 MPa, respectively, an improvement of 54% in TS and 35% in YM over the neat polyimide film (TS = 98 MPa; YM = 2492 MPa). These MWCNT-reinforced composites show remarkable improvement in terms of thermal stability as compared to that for pure polyimide film. The electrical conductivity of 5 wt% acid modified MWCNTs/polyimide nanocomposites improved to 0.94 S cm ⁻¹ (6.67 × 10 ⁻¹⁸ S cm⁻¹ for pure polyimide) the maximum achieved so far for MWCNT-polyimide composites.     

Electrical conductivity of spark plasma sintered Al2O3–SiC and Al2O3-carbon nanotube nanocomposites

The electrical conductivity of alumina-silicon carbide (Al₂O₃–SiC) and alumina-multiwalled carbon nanotube (Al₂O₃-MWCNT) nanocomposites prepared by sonication and ball milling and then consolidated by spark plasma sintering (SPS) is reported. The effects of the nanophase (SiC and MWCNTs) and SPS processing temperature on the densification, microstructure, and functional properties were studied. The microstructure of the fabricated nanocomposites was investigated using field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The phase evolution was determined using X-ray diffraction (XRD). The room-temperature direct current (DC) electrical conductivity of the monolithic alumina and nanocomposites was determined using the four-point probe technique. The EDS mapping results showed a homogenous distribution of the nanophases (SiC and MWCNTs) in the corresponding alumina matrix. The room-temperature DC electrical conductivity of monolithic alumina was measured to be 6.78 × 10⁻¹⁰ S/m, while the maximum electrical conductivities of the alumina-10 wt%SiC and alumina-2wt%MWCNT samples were 2.65 × 10⁻⁵ S/m and 101.118 S/m, respectively. The electrical conductivity increased with increasing nanophase concentration and SPS temperature. The mechanism of electrical conduction and the disparity in the electrical performance of the two investigated nanocomposite systems (alumina-SiC and alumina-MWCNT) are clearly described.     

Dispersions of carbon nanotubes in sulfonated poly[bis(benzimidazobenzisoquinolinones)] and their proton-conducting composite membranes

A sulfonated poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI) possessing a conjugated pyridinone ring was shown to be effective for dispersing multiwalled carbon nanotubes (MWCNTs) in DMSO. The dispersions in which the SPBIBI to MWCNTs mass ratio was 4:1 demonstrated the highest MWCNTs concentrations, i.e., 1.5-2.0 mg mL⁻¹, and were found to be stable for more than six months at room temperature. Through casting of these dispersions, MWCNTs/SPBIBI composite membranes were successfully fabricated on substrates as proton exchange membranes for fuel cell applications and showed no signs of macroscopic aggregation. The properties of composite membranes were investigated, and it was found that the homogeneous dispersion of the MWCNTs in the SPBIBI matrix altered the morphology structures of the composite membranes, which lead to the formation of more regular and smaller cluster-like ion domains. As a result, and in comparison to a pristine SPBIBI membrane, the composite membranes displayed more significant proton conductivities, especially at low relative humidity, without sacrificing other excellent properties, such as thermal, dimensional and oxidative stabilities. For instance, the composite membranes with an MWCNTs content only of 0.5 wt% exhibited proton conductivities of 0.021 S cm⁻¹ at 50 RH% and 70 °C, a value almost fourfold as high as that of the pristine SPBIBI membranes under identical conditions (0.005 S cm⁻¹). The result was comparable to Nafion 117 (0.021 S cm⁻¹). The homogenous dispersion of the MWCNTs and the efficient enhancement the SPBIBI performance were attributed to the π-π interaction between the pyridinone ring and the sidewalls of the MWCNTs which changed the morphological structure of composite membranes as revealed by TEM. A combination of a low methanol crossover with excellent thermo-oxidative and water stabilities indicated that the SPBIBI composite membranes were good candidate materials for proton exchange membranes in fuel cell applications.     

Mesoporous electroactive silver doped calcium borosilicates: Structural,antibacterial and myogenic potential relationship of improved bio-ceramics

In this work improved electroactive mesoporous Ag-doped bio-ceramics for medical usages are developed, examining their structural, electrical, in-vitro bioactivity, cell cultures and antibacterial properties against various classical pathogenic bacteria. Ag-containing mesoporous bio-ceramics (MBCs): xmol%Ag₂O - (100-x)[45.8CaO-8.4B₂O₃-45.8SiO₂] where x = 2, 5, 7.5 and 10 were synthesized through a sol-gel method. The small angle X-ray scattering and electron microscopy studies reveal the embedment of silver nanoparticles in the samples. Existence of silver as Ag⁺/Ag⁰ forms in the samples is confirmed by X-ray photoelectron spectroscopy. The N₂ adsorption-desorption analysis evidence the mesoporous structure of the samples. The electrical conductivity of samples increases from 5.4 x 10^?8 S cm^?1 for x = 2 to 1.9 x 10^?6 S cm^?1 for x = 7.5 and then decreases to 0.9 x 10^?6 S cm^?1 for x = 10 at 110 °C. In vitro bioactivity studies revealed that Ag-containing MBCs hold the bone-like hydroxyapatite formation after immersion in human blood plasma like-solution such as Dulbecco's Modi?ed Eagle's Medium. The antibacterial effect of samples against pathogenic bacteria (S. aureus, E. coli, P. monas aeruginosa, and B. cereus) increases with Ag concentration (x = 7.5) and then decreases with Ag content (x = 10). Antibacterial effect is greater for the sample with high electrical conductivity. The cell culture studies evidence not considerable cytotoxic effects for Ag-containing MBCs. Finally, the C2C12 myoblast cell culture studies reveal the significant cell growths and differentiation (myogenesis) for high electrical conducting Ag-containing MBCs.     

High density electron emission source based on carbon nanotubes for industrial applications

Vertically aligned multi-walled carbon nanotubes (MWCNTs) have been grown by Catalyzed-Chemical Vapour Deposition (C-CVD) both on bare doped silicon and thin TiN film on silicon, using iron and nickel as catalyst, respectively. The aim is the development of high density and stable cold emission sources for industrial applications. Field emission characteristics of MWCNTs have been evaluated, obtaining current densities up to 150 mA/cm² at applied electrical field of 6 V/µm. Emission measurements have been performed which prove a medium-term stability. Structural and morphological characterization of MWCNTs has been carried out by SEM and Raman spectroscopy.     

Synthesis and characterization of polyazomethine conducting polymers and oligomers

Conjugated polyazomethine polymers were prepared from the polycondensation of terephthalaldehyde with 4,4′-thiodianiline, and 4,4-thiodibenzaldehyde with 4,4′-thiodianiline, 4,4′-phenylenediamine and benzidine. The polymers showed good stability in air and were soluble in many organic solvents. The electrical conductivities of the undoped and doped (H₂SO₄ and I₂) polymers were studied. Doping the polymers markedly increased their conductivities from 10^?8 ? 10^?11 S cm^?1 (dielectric region) to 10^?3 ? 10^?5 S cm^?1 (semiconducting region). The polymers were characterized by IR spectroscopy, elemental analyses, viscosity measurements and X-ray diffraction. Furthermore, polyazomethine oligomers were prepared and a comparative study of the physical properties of the oligomers and their corresponding polymers was performed. The electrical behavior of the oligomers was studied. It was found that oligomers with a minimum of eight aromatic (Ar) rings gave almost the same electrical conductivities as long-chain polymers.     

Thermosetting polyurethane multiwalled carbon nanotube composites

Thermosetting polyurethane (PU) multi‐walled carbon nanotube (MWCNT) nanocomposites at loadings up to 1 wt % were prepared via an addition polymerization reaction. The morphology of the nanocomposites and degree of dispersion of the MWCNTs was studied using a combination of scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and wide angle X‐ray diffraction (WAXD), and revealed the nanotubes to be highly dispersed in the PU matrix. Addition of just 0.1 wt % MWCNTs resulted in significant enhancements in stiffness, strength and toughness. Increases in Young's modulus, % elongation at break and ultimate tensile strength of 561, 302 and 397% were measured for the nanocomposites compared to the unfilled PU. The effect of the MWCNTs on the modulus of the PU was evaluated using the Rule of Mixtures, Krenchel and Halpin‐Tsai models. Only the Halpin‐Tsai model applied to high aspect ratio nanotubes was in good agreement with the modulus values determined experimentally. Strong interfacial shear stress was found between PU chains and nanotubes, up to 439 MPa, calculated using a modified Kelly‐Tyson model. Evidence for strong interfacial interactions was obtained from the Raman spectra of both the precursor materials and nanocomposites. When the MWCNTs were added to the isophorone diisocyanate an up‐shift of 14 cm^?1 and on average 40 cm^?1 was obtained for the position of the carbon‐hydrogen (C? H) out‐of plane bending (766 cm^?1) and isocyanate symmetric stretch (1420 cm^?1) modes respectively. Moreover, an up‐shift of 24 cm^?1 was recorded for the nanotube tangential mode (G‐band) for the 1.0 wt % nanocomposite because of the compressive forces of the PU matrix acting on the MWCNTs. The dynamic mechanical (DMA) properties of the PU thermoset and the nanocomposites were measured as a function of temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Ultralight conducting polymer/carbon nanotube composite aerogels

By embedding carbon nanotubes into poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT–PSS) supermolecular hydrogels in the presence of a very small amount of polyvinyl alcohol (PVA), we have presented the fabrication of ultralight conducting polymer/carbon nanotube composite aerogels with the apparent density of 0.04–0.07 g/cm³ made by supercritical CO₂ drying of as-made composite hydrogel precursors. The carbon nanotubes employed here are directly applicable to pristine (MWCNTs) or acid treated (c-MWCNTs) multi-wall nanotubes. Infra-red spectroscopy is used to confirm that PVA used for stabilizing nanotubes during the synthesis of hydrogel precursors has been completely removed by solvent exchange before supercritical CO₂ drying. The morphology and textural properties of the resultant composite aerogels are investigated by scanning electron microscopy, nitrogen adsorption/desorption, and X-ray powder diffraction tests. The thermal stability, together with electrical conductivities, of the resulting composite aerogels is revealed by the thermal gravitational analysis as well as conductivity tests. The results show that embedding of either MWCNTs or c-MWCNTs into PEDOT–PSS aerogel matrix can significantly enhance the specific surface areas (280–400 m²/g), the thermal stability and electrical conductivities (1.2–6.9 × 10⁻² S/cm) of the resulting composite aerogels.     

Synthesis of Ga-doped Li7La3Zr2O12 solid electrolyte with high Li+ ion conductivity

Garnet-type Li₇La₃Zr₂O₁₂ (LLZO) Li⁺ ion solid electrolyte is a promising candidate for next generation high-safety solid-state batteries. Ga-doped LLZO exhibits excellent Li⁺ ion conductivity, higher than 1 × 10^?3 S cm^?1. In this research, the doping amount of Ga, the calcination temperature of Ga-LLZO primary powders, the sintering conditions and the evolution of grains are explored to demonstrate the optimum parameters to obtain a highly conductive ceramics reproducibly via conventional solid-state reaction methods under ambient air sintering atmosphere. Cubic LLZO phase is obtained for Li_6.4Ga_0.2La₃Zr₂O₁₂ powder calcined at low temperature 850 °C. In addition, ceramic pellets sintered at 1100 °C for 320 min using this powder have relative densities higher than 94% and conductivities higher than 1.2 × 10^?3 S cm^?1 at 25 °C.     

Using graphene networks to build SiC(rGO,Gx) bulk ceramics from polymeric precursors

Unique properties of graphene open new opportunities for preparing composites with favorable functional capabilities. Herein, an ingenious synthesis route via re-pyrolysis process of ball-milling-induced SiC(rGO, Gx)_p fillers/polycarbosilane-vinyltriethoxysilane-graphene oxide (PCS-VTES-GO, PVG) precursors blends is proposed to obtain structural-functional integrated SiC(rGO, Gx) bulk polymer-derived ceramics (PDCs). The introduction of SiC(rGO, Gx)_p provides favorable moldability, ceramic yield and linear shrinkage. Attractively, graphene networks with more free-moving electrical-charge carriers and wider phonon-channel prominently enhance electrical and thermal conductivities of products. Particularly, SiC(rGO, G_20%) bulk PDCs generated at 1300 °C own satisfactory ceramic yield (90.74%), linear shrinkage (5.00%), fracture toughness (2.07 MPa m^1/2), bending strength (35.37 MPa), electrical conductivity (25.72 S cm^?1) and thermal conductivity (6.72 W m^?1·K^?1), realizing outstanding values to the best of our knowledge. This fabrication method favors mass production of larger-sized PDCs and possess potential emerging uses.     

Preparation and thermal properties of multiwalled carbon nanotube/polybenzoxazine nanocomposites

In this study, we prepared nanocomposites comprising multiwalled carbon nanotubes (MWCNTs) and polybenzoxazine (PBZ). The MWCNTs were purified through microwave digestion to remove most of the amorphous carbon and metal impurities. After purification, MWCNTs were treated with H₂SO₄/HNO₃ (3 : 1) to introduce hydroxyl and carboxyl groups onto their surfaces. Raman spectroscopy revealed the percentage of nanotube content improved after prolonged microwave treatment, as evidenced by the decrease in the ratio of the D (1328 cm^?1) and G (1583 cm^?1) bands. For the untreated MWCNTs, the I_D/I_G ratio was 0.56. After microwave treatment for 40 min, the value decreased to 0.29, indicating that the percentage of nanotube content improved. Dynamic mechanical analyses (DMAs) revealed that the storage moduli and the T_gs of the MWCNTs/PBZ nanocomposites were higher than that of the pristine PBZ. This is due to the nanometer‐scale MWCNTs restricting the motion of the macromolecular chains in the nanocomposites. Transmission electron microscopy (TEM) image revealed that the MWCNTs were well dispersed within the PBZ matrix on the nanoscale when the MWCNT content was less than 2.0 phr. The coefficient of thermal expansion (CTE) of the nanocomposites decreased on increasing the MWCNTs content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Enhanced electrical conductivity of nylon 6 composite using polyaniline-coated multi-walled carbon nanotubes as additives

Aggregation in polymer composites is one of the major obstacles in the carbon nanotubes (CNTs) applications. Authentic CNTs are known to have very good electrical conductivity and mechanical strengths. Surface functionalization can avoid aggregation and help dispersion of CNTs, but reduces CNT’s electrical conductivities and mechanical strengths dramatically. It needs a good way to resolve the above dilemma situation; i.e., poor dispersion-good conductivity vs. good dispersion-poor conductivity. Herein, we demonstrate that in-situ polymerized polyaniline (PANI)-coated CNTs have good polymer matrix compatibility, and are superior electrically conductive fillers to nylon 6 composites. In this report, multi-walled CNTs (MWCNTs) were surface-modified with poly(acrylic acids) (PAA), followed by further coating with PANI. The electrical conductivity of (PANI-MWCNTs)-nylon 6 composite thin film was increased from 10⁻¹² to 7.3 × 10⁻⁵ S/cm in the presence of 1 wt% PANI-coated MWCNTs prepared by physical mixing of PANI and PAA-grafted MWCNTs. When in-situ polymerized PANI-coated MWCNTs were added, the electrical conductivity of MWCNTs-nylon 6 composite was further enhanced by 3 orders to be 3.4 × 10⁻² S/cm at the same 1 wt% loading of MWCNTs. Both Fourier-transformed infrared and uv-visible absorption spectra indicate that there exist very strong site-specific charge transfer interactions between the quinoid rings of PANI and MWCNTs, which results in the superior electrical conductivity of MWCNT-nylon 6 composite.     

Effect of the crystalline layer on the electrical behaviour of 17.7Li2O·5.2ZrO2·68.1SiO2·9.0Al2O3 glass ceramic monoliths

Li₂O–ZrO₂–SiO₂–Al₂O₃ (LZSA) glass ceramic systems are usually obtained from powder technology to obtain materials with a low thermal expansion coefficient (CTE). However, in these cases, there is a high residual porosity. An alternative to reduce the porosity involves the production of monoliths. Nevertheless, there is still a lack of crystallisation kinetics and the final properties of glass ceramic monoliths are affected such as electrical properties. This study aims to evaluate the electrical behaviour as function of the crystalline layer thickness formed on the monolith surface of a 17.7Li₂O·5.2ZrO₂·68.1SiO₂·9.0Al₂O₃ (molar basis) glass ceramic LZSA composition. Monoliths thermally treated at 750, 800, and 850 °C were chosen to evaluate based on the range of the crystalline layer growth. Electrochemical impedance spectroscopy was used for the electrical characterisation of LZSA glass and the glass ceramics. The resistivity increased with increasing thermal treatment temperature due to the formation of lithium-based crystalline phases. The electrical conductivity at 25 °C of the glass ceramic thermally treated at 850 °C decreased to 1.4 × 10^?13 S cm^?1 from 8.7 × 10^?11 S cm^?1 for LZSA glass. Based on the electrical behaviour, monoliths thermally treated at 850 °C can be considered potential for dielectric industrial applications.     

Polypyrrole nanocoatings of poly(styrene-co-methacrylic acid) particles

In this study the properties of polypyrrole (PPy) nanocoating over poly(styrene-co-methacrylic acid) (PS-MAA) particles were investigated. Monodisperse PS-MAA templates were obtained by free surfactant emulsion polymerization. The addition of methacrylic acid into the monomer feed mixture reduced particle size, ionic charge and hydrophobicity of the template surface. Correlations between template sizes and compositions, PPy confinement (granularity, shell size, etc.) and electrical conductivity, σ, are discussed. After dissolving the PPy/PS-MAA composites in tetrahydrofurane, PPy void spheres are obtained proving the core-shell nature of the coated particles. Bare styrene templates show densely packed PPy coatings and electrical conductivities near 7 S cm⁻¹ at high PPy loadings; on the contrary, at the same PPy mass percentage, the richer methacrylic acid particles show low packed PPy grains and conductivities that fall to 0.8 S cm⁻¹. In core-shell particles the PPy mass per unit area, Γ, is the key parameter which determines the insulator-conductor transition for any particle size. The conductivity values of PPy/PS-MAA composites follow a percolation law: σ∝t(Γ−Γc), with a critical threshold Γ_c=(0.262 ± 0.002)×10⁻⁶ g cm⁻². The critical exponent obtained t = 1.98 ± 0.07 agrees with the predicted value t = 2.0 for three-dimensional lattices of random resistors.     

Improving the electrical conductivity of ethylene 1‐octene copolymer/cyclic olefin copolymer immiscible blends by interfacial localization of MWCNTs

The localization of multiwall carbon nanotubes (MWCNTs) in the immiscible blends of ethylene–1‐octene copolymer (EOC) and cyclic olefin copolymer (COC) with the sea–island morphology and electrical conductivity of resulting nanocomposites were investigated. Depending on the feeding orders, as the MWCNTs were located in the COC droplet, the electrical conductivity was obtained as high as 5.71 × 10^?7 S/cm, while the MWCNTs were located in EOC/COC interface, the electrical conductivity increased significantly up to 1.72 × 10^?2 S/cm. The improved electrical conductivity in EOE/COC/MWCNTs nanocomposite is attributed to the interfacial localization of MWCNTs which is resulted from thermodynamic affinity of MWCNTs to COC, as well as an interconnected structure via deformed and swelled COC droplets. Thermodynamic affinity of MWCNTs to COC and established interconnected structure are confirmed by rheological characterization, microscopic observations, dynamic mechanical analysis, and electrical conductivity measurements. Therefore, as a result of selective localization of MWCNTs and well‐designed phase morphology, lower rheological and especially electrical percolation thresholds could be obtained in the ternary nanocomposites compared to the binary systems. POLYM. ENG. SCI., 59:447–456, 2019. © 2018 Society of Plastics Engineers     

Studies on a novel anion‐exchange membrane based on chitosan and ionized organic compounds with multiwalled carbon nanotubes for alkaline fuel cells

In this work, a novel hydroxyl‐anion‐conducting membrane composed of chitosan (CTS), an ionized organic compound ([QAIM]OH), and hydroxylated multiwalled carbon nanotubes (MWCNTs‐OH) has been fabricated through a blending‐casting method assisted by a glutaraldehyde (GA) crosslinking process that can improve the mechanical properties of the membrane effectively. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy revealed that [QAIM]OH and MWCNTs‐OH were successfully introduced into the CTS matrix. A chemical crosslinking reaction between CTS and GA could be confirmed by FTIR, X‐ray photoelectron spectroscopy, and contact angle tests. By tuning the mass fraction of [QAIM]OH and MWCNTs‐OH in the membrane, the maximum OH^? conductivity (5.66 × 10^?3 S cm^?1 at room temperature) could be achieved for the composition CTS:[QAIM]OH (1:0.75 in mass) blend doped with 3% MWCNTs‐OH. At a current density of 59.9 mA cm^?2, a membrane electrode assembly fabricated with the CTS/[QAIM]OH/ MWCNTs‐OH membrane (1:0.5/3%) achieved a power density of 31.6 mW cm^?2 in a H₂/O₂ system at room temperature. Under the condition of intermediate temperature (100–140 °C) without water, the conductivities of the membranes increased with increasing temperature and the amount of [QAIM]OH, which acted as an ionic liquid in the membrane, indicating that the ionic transport behaviors could still be occurring. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46323.     

Preparation and characterization of poly(ethylene glycol)/organo-vermiculite nanocomposite polymer electrolytes

Vermiculite (VMT) was readily intercalated by hexadecyl trimethyl ammonium bromide to yield organo-vermiculite (OVMT), which was confirmed by X-ray diffraction measurement and Fourier transform infrared spectroscopy. Poly(ethylene glycol)/organo-vermiculite (PEG/OVMT) nanocomposites were prepared by using the direct melt intercalation method, and its intercalation state was confirmed by transmission electron microscope. Thereafter, a lithium salt was dissolved in the PEG/OVMT nanocomposites to prepare composite polymer electrolytes. The highest conductivity was 2.1 × 10⁻⁵ S cm⁻¹ at room temperature, which was obtained by AC impedance analysis when the amount of OVMT based on PEG was 1 wt%.     

Surface modification of MWCNT and its influence on properties of paraffin/MWCNT nanocomposites as phase change material

Multiwalled carbon nanotubes (MWCNTs) were modified by an organo-silane in order to improve their dispersion state and stability in paraffin wax. A family of paraffin-based phase change material (PCM) composites filled with MWCNTs was prepared with different loadings (0, 0.1, 0.5, and 1 wt%) of pristine MWCNTs and organo-silane modified MWCNTs (Si-MWCNT). Structural analyses were performed by means of Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and rheological studies using temperature sweeps. Moreover, phase change transition temperatures and heat of fusion as well as thermal and electrical conductivities of the developed PCM nanocomposites were determined. The SEM micrographs and FTIR absorption bands appearing at approximately 1038 and 1112 cm⁻¹ confirmed the silane modification. Differential scanning calorimetery (DSC) results indicate that the presence of Si-MWCNTs leads to slightly favorable enhancement in the energy storage capacity at the maximum loading. It was also shown that the thermal conductivity of the PCM nanocomposites, in both solid and liquid phases, increased with increasing the MWCNT content independent of the kind of MWCNTs by up to about 30% at the maximum loading of MWCNTs. In addition, the modification of MWCNTs made the samples completely electrically nonconductive, and the electrical surface resistivity of the PCMs containing pristine MWCNTs decreased with increasing MWCNTs loading. Furthermore, the rheological assessment under consecutive cyclic phase change demonstrated that the samples containing modified MWCNTs are more stable compared to the PCM containing pristine MWCNTs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48428.     

Influence of nanoscale NiO on magnetic and electrochemical behavior of PVDF-based polymer nanocomposites

New poly(vinylidene fluoride) (PVDF)/NiO-based polymer nanocomposites were prepared by phase inversion method, using dimethyl formamide as solvent and deionized water as non-solvent. The structure and porous morphology of the membranes were studied by field emission scanning electron microscopy. The presence of NiO resulted in overall decrease in porosity and crystallinity of the nanocomposite membranes. Using electrochemical impedance spectroscopy, a maximum ionic conductivity of 1.08 × 10⁻³ S cm⁻¹ was obtained for PVDF membrane with 1 wt% content of NiO. The good efficiency of conductivity observed in the membrane was explained on the basis of decrease in crystallinity and movement of charge carriers in NiO structure. The magnetization of nanocomposite membranes gradually increased with increase in NiO content.     

Reduction of percolation threshold through double percolation in melt‐blended polycarbonate/acrylonitrile butadiene styrene/multiwall carbon nanotubes elastomer nanocomposites

We demonstrate a method that involves melt blending of polycarbonate (PC) and melt‐blended acrylonitrile butadiene styrene (ABS) with multiwall carbon nanotubes (MWCNTs) to prepare electrically conducting PC/MWCNT nanocomposites at significantly low MWCNT loading. The partial solubility of ABS in PC led to a selective dispersion of the MWCNTs in the ABS phase after melt‐blending PC and ABS. Thus, a sudden rise in electrical conductivity (∼10⁸ orders of magnitude) of the nanocomposites was found at 0.328 vol% of MWCNT, which was explained in terms of double percolation phenomena. By optimizing the ratio of PC and the ABS–MWCNT mixture, an electrical conductivity of 5.58 × 10⁻⁵ and 7.23 × 10⁻³ S cm⁻¹ was achieved in the nanocomposites with MWCNT loading as low as 0.458 and 1.188 vol%, respectively. Transmission electron microscopy revealed a good dispersion and distribution of the MWCNTs in the ABS phase, leading to the formation of continuous MWCNT network structure throughout the matrix even at very low MWCNT loading. Storage modulus and thermal stability of the PC were also increased by the presence of a small amount of MWCNTs in the nanocomposites.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers