Transparent nanocomposites with enhanced performances from poly(propylene carbonate) and silica

In this study, silica nanoparticles with a refractive index matching PPC and a diameter smaller than the visible light wavelength were chosen to prepare enhanced PPC/silica nanocomposites by a simple melt compounding method. The result exhibited all the nanocomposites possessed excellent transparency (about 90%), even in the nanocomposite with a silica content of 10 wt%. For PPC/silica nanocomposites, the percolation threshold was determined to be 7.5 wt% based on the dynamic rheological behavior and percolation theory. Moreover, the overall performance of the PPC-based nanocomposite with a silica content of 7.5% is the best. The optimal nanocomposite showed a Young's modulus of 3792 MPa, a yield strength of 46.5 MPa, a storage modulus of 3812 MPa and a highest temperature at maximum weight-loss rate (T_max, 309°C). These characteristics are very important for potential commodity applications of PPC.     

Preparation and characterization of novel polyethylene/carbon nanotubes nanocomposites with core–shell structure

Preparation of novel polyethylene/carbon nanotubes (CNTs) nanocomposites with core–shell structure was presented. The method involved in situ ethylene polymerization in which nanotube surface was treated with Grignard Agent, followed by reacting with active transition metal compound, TiCl₄. The multiwalled carbon nanotubes (MWCNTs) supported catalysts polymerize ethylene to form polymer nanocomposite. MWCNTs were homogeneously dispersed within polymer matrix, and as expected, the resultant nanocomposites featured core–shell structure which was confirmed by HRTEM. For the nanocomposite, the microscopic examination of the cryogenically fractured surface not only ensured a good distribution of carbon nano-particles in the PE matrix but also revealed the ductile-like fracture. The Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed for the study of covalent sidewall functionalization and chemical bonding environment of MWCNTs, also indicated effective immobilization of titanium catalyst on the MWCNTs surface. The crystalline properties, dielectric property and thermal stability of the nanocomposites were determined by WAXD, impedance analyzer and TGA. The dielectric result showed a slight decline of the dielectric constant of the nanocomposites with increase of the polymerization time, and lower dielectric loss was also observed.     

Study of alternating current impedance analysis and dielectric properties of carbon nanotube‐based polysulfone nanocomposites

Polysulfone (PSU)/multiwalled carbon nanotubes (MWCNTs) nanocomposites containing 0.5–3 wt% of MWCNTs were prepared by solution casting technique. To understand the dispersion behavior of MWCNTs inPSU matrix, high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM) were used. Electrical properties of nanocomposites were investigated by analyzing alternating current (AC) impedance spectra. The real part of complex impedance was decreased with increasing carbon nanotubes loading in the PSU matrix, which may be due to increase in conductive networks in the nanocomposite. The complex impedance Nyquist plots for PSU/MWCNTs nanocomposites were characterized by the appearance of a single semicircular arc, whose radii of curvature decreases with increasing MWCNTs loading. The polarization mechanism and the AC conduction mechanism were studied by designing equivalent circuit from impedance data. The dielectric response of PSU/MWCNTs nanocomposite was investigated over a wide range of frequency from 10 Hz to 10⁻⁶ Hz. Dielectric constant of PSU/MWCNTs nanocomposite was enhanced significantly from 2 to 6 × 10¹⁰ at 10 Hz when the addition of MWCNTs was increased from 0 to 3 wt%. The enhancement of dielectric property might be due to the interfacial polarization between carbon nanotubes and polysulfone. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Facile preparation and properties of polyvinylidene fluoride dielectric nanocomposites via phase morphology control and incorporation of multiwalled carbon nanotubes conductive fillers

A novel PVDF dielectric nanocomposite was achieved by controlling phase morphology and incorporating conductive fillers simultaneously, and the mechanical, thermal, dielectric properties of the resultant dielectric nanocomposites were investigated. Mechanical analysis showed that incorporation of modified MWCNTs (MWCNTs-COOH) in the PVDF nanocomposites resulted in significant improvements on the tensile strength (T_s) and elasticity modulus (E_m). When the filler content was 12 wt%, the T_s of MWCNTs-COOH/PVDF could reach 64.6 MPa. XRD test showed that the addition of MWCNTs-COOH and MWCNTs promoted the formation of β-phase of PVDF. DMA analysis showed that the glass-transition temperature of the PVDF nanocomposites slightly increases on loading of original MWCNTs and this effect was more pronounced on loading MWCNTs-COOH. The dielectric property analysis showed that the original MWCNTs were more likely to form local conductive networks in the PVDF matrix, promoting the electron displacement polarization, and improving the dielectric constant. When the contents of MWCNTs was 12 wt%, the percolation threshold was obtained and the dielectric constant (ε′) reached 286, which was 36 times of pure PVDF. Our work provides a simple way to fabricate polymer blends with excellent dielectric performances, good mechanical properties as well as good processing capability but low cost. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48463.     

Synthesis and characterization of (Fe3O4/MWCNTs)/ epoxy nanocomposites

A sonochemical technique is used for in situ coating of iron oxide (Fe₃O₄) nanoparticles on outer surface of MWCNTs. These Fe₃O₄/MWCNTs were characterized using a high‐resolution transmission electron microscope (HRTEM), X‐ray diffraction, and thermogravimetric analysis. The as‐prepared Fe₃O₄/MWCNTs composite nanoparticles were further used as reinforcing fillers in epoxy‐based resin (Epon‐828). The nanocomposites of epoxy were prepared by infusion of (0.5 and 1.0 wt %) pristine MWCNTs and Fe₃O₄/MWCNTs composite nanoparticles. For comparison purposes, the neat epoxy resin was also prepared in the same procedure as the nanocomposites, only without nanoparticles. The thermal, mechanical, and morphological tests were carried out for neat and nanocomposites. The compression test results show that the highest improvements in compressive modulus (38%) and strength (8%) were observed for 0.5 wt % loading of Fe₃O₄/MWCNTs. HRTEM results show the uniform dispersion of Fe₃O₄/MWCNTs nanoparticles in epoxy when compared with the dispersion of MWCNTs. These Fe₃O₄/MWCNTs nanoparticles‐infused epoxy nanocomposite shows an increase in glass transition (T_g) temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Removal of toxic nitrate ions from drinking water using conducting polymer/MWCNTs nanocomposites

New application of conducting polymers as stable nanocomposites for nitrate ion exchange materials in water and wastewater treatment and for environmental protection is introduced in this work. The nanocomposites of multi-walled carbon nanotubes (MWCNTs) with different polymers such as: polyaniline (PANI), polypyrrole (PPY), poly(1,8-diaminonaphthalene) [P(1,8-DAN)] and poly(2-vinylpyridine) (P2VP) were synthesized with different dopants as effective and reusable nanocomposites for nitrate removal from drinking water. Nitrate anions at toxic concentrations were removed from water using ion exchange mechanism without any toxic byproducts. The obtained results demonstrate that effective ion exchange occurs between NO₃ ^? and Cl^?. There are some protonated heteroatoms in polymer chains that are bonded with anions of dopants and their counter ions in nanocomposites. These dopant anions on the =NH⁺– groups of polymers can be exchanged with NO₃ ^? in water. Adsorption of NO₃ ^? on polymer/MWCNTs nanocomposites showed dependency to some parameters. Different experimental parameters such as pH and temperature of the sample, polymers dopant, and the ratio of polymer to MWCNTs in nanocomposites affect the amount of nitrate removal. The highest removal efficiency was achieved at 1.20 g L^?1 of PANI/MWCNTs (3:1) nanocomposite, pH = 6.5 and ambient temperature. After five successive cycles of nitrate removal, this parameter was still up to 70 % compared to the first run (up to 80 %).     

Experimental and theoretical dielectric studies of PVDF/PZT nanocomposite thin films

Poly(vinylidene fluoride)/lead zirconate titanate nanocomposite thin films (PVDF/PZT-NPs) were successfully prepared by mixing fine Pb(Zr_0.52,Ti_0.48)O₃ nanoparticles (PZT-NPs) into a PVDF solution under ultrasonication. The mixture was spin coated onto glass substrate and then cured at 110 °C. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used to characterize the structure and properties of the obtained thin-film nanocomposites. The dielectric properties of the PVDF/PZT-NPs were analyzed in detail with respect to frequency. In comparison with pure poly (vinylidene fluoride), the dielectric constant of the nanocomposite (15 vol.% PZT-NPs) was significantly increased, whereas the loss tangent was unchanged in the frequency range of 100 Hz to 30 MHz. The nanocomposites exhibited good dielectric stability over a wide frequency range. Different theoretical approaches were employed to predict the effective dielectric constants of the thin film nanocomposite systems, and the estimated results were compared with the experimental data.     

Fumed SiO2 nanoparticle reinforced biopolymer blend nanocomposites with high dielectric constant and low dielectric loss for flexible organic electronics

In the present study, fumed silica (SiO₂) nanoparticle reinforced poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) blend nanocomposite films were prepared via a simple solution‐blending technique. Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), X‐ray diffraction (XRD), and scanning electron microscopy (SEM) were employed to elucidate the successful incorporation of SiO₂ nanoparticles in the PVA/PVP blend matrix. A thermogravimetric analyzer was used to evaluate the thermal stability of the nanocomposites. The dielectric properties such as dielectric constant (?) and dielectric loss (tan δ) of the PVA/PVP/SiO₂ nanocomposite films were evaluated in the broadband frequency range of 10^?2 Hz to 20 MHz and for temperatures in the range 40–150 °C. The FTIR and UV–vis spectroscopy results implied the presence of hydrogen bonding interaction between SiO₂ and the PVA/PVP blend matrix. The XRD and SEM results revealed that SiO₂ nanoparticles were uniformly dispersed in the PVA/PVP blend matrix. The dielectric property analysis revealed that the dielectric constant values of the nanocomposites are higher than those of PVA/PVP blends. The maximum dielectric constant and the dielectric loss were 125 (10^?2 Hz, 150 °C) and 1.1 (10^?2 Hz, 70 °C), respectively, for PVA/PVP/SiO₂ nanocomposites with 25 wt % SiO₂ content. These results enable the preparation of dielectric nanocomposites using a facile solution‐casting method that exhibit the desirable dielectric performance for flexible organic electronics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44427.     

Radiation resistant metal decorated MWCNTs/PMMA nanocomposite films with enhanced thermomechanical properties

UV/O₃ radiation and chemical resistant nanocomposite films of functionalized/metal decorated multiwall carbon nanotubes (MWCNTs) with polymethylmethacrylate (PMMA) are synthesized. Silver nanoparticles are decorated on the surface of UV/O₃ functionalized MWCNTs by both reduction and in situ growth from AgNO₃ aqueous solution. Microscopic studies reflect the better dispersion of UV/O₃ functionalized/silver decorated MWCNTs in polymer matrix contributing in enhancement of thermal stability, thermomechanical strength, glass transition temperatures, and thermal conductivity of nanocomposites even at 0.25 wt% MWCNTs additions. The thermal stability of nanocomposite film (0.25 wt% loading), prepared by using a surfactant (Sodium dodecyl sulfate) is increased to about 27°C while the thermomechanical properties are raised up to 76% at 100°C. Thermal and thermomechanical behavior of pre‐ and post‐UV/O₃ irradiated nanocomposite films are compared with neat polymer. The results reveal that UV/O₃ functionalized MWCNTs can effectively disperse the radiation and have a dramatic reinforcement effect on the nature of the degradation of PMMA matrix. POLYM. COMPOS., 36:969–978, 2014. © 2014 Society of Plastics Engineers     

N-type silk fibroin/TiO2 nanocomposite transparent films: electrical and optical properties

This paper highlights the effect of different concentrations of titanium dioxide (TiO₂) nanoparticles on the electrical and optical properties of silk fibroin (SF). TiO₂ based SF nanocomposite films were prepared using the solvent casting method. Uniform dispersion and agglomeration of nanoparticles, in nanocomposite films, were observed by field emission SEM. The conductivity of pure SF and nanocomposite films was determined by a four-point probe and the TiO₂ nanoparticles were found to bring high conductivity to the nanocomposite films. Dielectric strength improved with the addition of nanoparticles to the SF matrix. Dielectric constant and capacitance of the pure SF and nanocomposite films were measured using an LCR meter, which showed a 10-fold enhancement on the addition of nanoparticles in SF. A very unusual property, i.e. negative resistance, was observed during LCR meter analysis for the nanocomposite films for a particular range of frequency (200–550 kHz), voltage (1 V) and current (0.5–1.5 μA). TiO₂ nanoparticles changed the semiconducting behavior of the SF films from p-type to n-type as measured by the Hall effect experiment. The optical properties of pure SF and nanocomposite films were measured using a UV–visible spectrophotometer. The increased concentration of nanoparticles in the SF has effectively enhanced the absorbing coefficient, refractive index and percentage transmittance and reduced the bandgap energy. These SF/TiO₂ nanocomposite films have shown the potential to be used as dielectric and high refractive index material for optoelectronics applications. © 2021 Society of Industrial Chemistry.     

Structure and properties of multi‐walled carbon nanotubes/polyethylene nanocomposites synthesized by in situ polymerization with supported Cp2ZrCl2 catalyst

Multi‐walled carbon nanotubes (MWCNTs)/polyethylene (PE) nanocomposites were prepared via in situ polymerization with MWCNTs supported Bis‐ (cyclopentadienyl) zirconium dichloride (Cp₂ZrCl₂) catalyst. X‐ray photoelectron spectroscopy (XPS) and field emission scanning electron microscope (FESEM) results implied that Cp₂ZrCl₂ catalyst was immobilized in the surface of the MWCNTs supports via a bridge of methylaluminoxane (MAO). The efficient dispersion of MWCNTs in PE matrix and the strong compressive forces associated with PE on the MWCNTs were demonstrated by means of transmission electron microscope (TEM), FESEM and Raman spectra. With introducing 0.2 wt% MWCNTs, both the tensile strength and elongation of MWCNTs/PE nanocomposite were improved by factors of 1.6 (from 29 to 45 MPa) and 1.5 (from 909% to 1360%) comparing with the pure PE, respectively. Morphology observation of fractured surface revealed that the PE firmly adhered to the nanotubes, which was responsible for the significant improvement of the mechanical properties of nanocomposites. Thermal stabilities of the nanocomposites were significantly improved. In addition, the MWCNTs/PE nanocomposites showed very high ultraviolet (UV) shielding property, which could increase photooxidative stability of the PE. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Structure and dielectric properties of polyimide/silica nanocomposite nanofoam prepared by solid‐state foaming

In this article, polyimide (PI)/silica nanocomposite nanofoams were prepared by solid‐state foaming using supercritical CO₂ as foaming agent. To control the cell size and morphology of the PI/silica foam, the silica nanoparticles as nucleating agent were in situ formation from TEOS via sol‐gel process, which make the silica nanoparticles homogeneously dispersed in PI matrix. The resulting PI/silica nanocomposite nanofoams were characterized by scanning electron microscopy (SEM), the image analysis system attached to the SEM and dielectric properties measurements. In PI/silica nanocomposite nanofoams, one type of novel morphology was shown that each cell contained one silica nanoparticle and many smaller holes about 20–50 nm uniformly located in the cell wall. This special structure could visually prove that the nucleation sites during foaming were formed on the surface of nucleating agents. Compared with those of neat PI foam, the cell size of PI/silica nanocomposite nanofoams was smaller and its distribution was narrower. The dielectric constant of PI/silica nanocomposite nanofoams was decreased because of the incorporation of the air voids into the PI/silica nanofoams. While the porosity of PI/silica nanocomposite nanofoam film was 0.45, the dielectric constant of the film (at 1 MHz) was reduced from 3.8 to about 2.6. Furthermore, the dielectric constant of PI/silica nanofoam films remained stable across the frequency range of 1×10²～1×10⁷ H_Z. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42355.     

Preparation of Polyetherimide Nanocomposites with Improved Thermal, Mechanical and Dielectric Properties

Summary Thermoplastic polyetherimide (PEI)-SiO₂ nanocomposites were prepared from a soluble PEI, which was synthesized from m-phenylenediamine and bisphenol A dianhydride, in combination with tetraethoxysilane solution via a novel sol-gel process. A coupling agent was used to enhance the compatibility between PEI and silica. This approach was compared with PEI-clay nanocomposite in which montmorillonite was modified with ammonium salts of 12-aminododecanoic acid using an intercalation polymerization. The size and dispersion of the silica or clay in the PEI nanocomposites were analyzed by X-ray diffractometer and scanning electron microscopy. It was found that the sol-gel process offered a fine interconnected or co-continuous phase, whereas the clay remained dispersed in nanocomposites. Though the thermal properties of PEI-clay nanocomposites were improved over pristine PEI, physical testing showed that the films become brittle as the organoclay content increased to over 2%. The thermal stability and mechanical properties of the PEI/silica nanocomposites prepared by sol-gel process were improved with silica content up to 10%. The onset decomposition temperatures were 550–600 °C. The dielectric constant decreased with increasing amounts of silica. At higher silica contents, the mechanical properties were reduced as a result of the phase separation.     

The effect of silica nanoparticles and carbon nanotubes on the toughness of a thermosetting epoxy polymer

Silica nanoparticles and multiwalled carbon nanotubes (MWCNTs) have been incorporated into an anhydride‐cured epoxy resin to form “hybrid” nanocomposites. A good dispersion of the silica nanoparticles was found to occur, even at relatively high concentrations of the nanoparticles. However, in contrast, the MWCNTs were not so well dispersed but relatively agglomerated. The glass transition temperature of the epoxy polymer was 145°C and was not significantly affected by the addition of the silica nanoparticles or the MWCNTs. The Young's modulus was increased by the addition of the silica nanoparticles, but the addition of up to 0.18 wt % MWCNTs had no further significant effect. The addition of both MWCNTs and silica nanoparticles led to a significant improvement in the fracture toughness of these polymeric nanocomposites. For example, the fracture toughness was increased from 0.69 MPam^1/2 for the unmodified epoxy polymer to 1.03 MPam^1/2 for the hybrid nanocomposite containing both 0.18 wt % MWCNTs and 6.0 wt % silica nanoparticles; the fracture energy was also increased from 133 to 204 J/m². The mechanisms responsible for the enhancements in the measured toughness were identified by observing the fracture surfaces using field‐emission gun scanning electron microscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Cure behavior and thermal stability analysis of multiwalled carbon nanotube/epoxy resin nanocomposites

As‐received multiwalled carbon nanotubes (MWCNTs) were first treated by a 3 : 1 (v/v) mixture of concentrated H₂SO₄/HNO₃ and further functionalized by ethylenediamine/dicyclohexylcarbodiimide/tetrahydrofuran solution. MWCNT/epoxy nanocomposites were prepared. Their cure behaviors were investigated by dynamic differential scanning calorimetry. Quantitative analysis of the activation energy as a function of the degree of curing was carried out by the Flynn‐Wall‐Ozawa method. The fitted multiple regression equations for values of the activation energy of different systems were obtained. MWCNTs have the retardation effect on the cure reaction of epoxy resin, while the functional groups on the surface of amine‐modified MWCNTs could accelerate the cure reactions. Thermal stability was studied by thermogravimetric analysis. The filling of amine‐modified MWCNTs is beneficial to lower the cure activation energy and improve thermal stability of the nanocomposite. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of poly(acrylonitrile-co-methylmethacrylate) nanocomposites reinforced by functionalized multiwalled carbon nanotubes

Polyacrylonitrile-co-poly(methylmethacrylate)/multiwalled carbon nanotubes (PAN-co-PMMA/MWCNTs) nanocomposites were synthesized by an in situ emulsifier-free polymerization method with variable percentages of functionalized carbon nanotube (f-MWCNT). MWCNTs were functionalized with concentrated H₂SO₄ and HNO₃ with a continuous sonication process. Chemical interaction of f-MWCNT with the copolymer was studied by UV-visible spectroscopy. Fourier transform infrared spectroscopy proved the interaction of f-MWCNT with the PAN-co-PMMA copolymer matrix. The structural interaction of f-MWCNT with copolymer matrix was investigated by X-ray diffraction study. The dispersion and morphology of the f-MWCNT in the copolymer matrix were studied by scanning electron microscopy and high-resolution transmission electron microscopy. It was noticed that the f-MWCNTs were uniformly dispersed within the copolymer matrix. The thermal property of the PAN-co-PMMA/f-MWCNT nanocomposite was analyzed by thermogravimetric analysis. It was noticed that the thermal stability of the PAN-co-PMMA/f-MWCNT nanocomposite was more than that of the virgin copolymer matrix. When the electrical conductivity property of the synthesized nanocomposite was measured, it was noticed that the better dispersion of f-MWCNT in the non-conductive PAN-co-PMMA copolymer matrix made the PAN-co-PMMA/f-MWCNT nanocomposites conductive. From the measurement of gas barrier properties of synthesized nanocomposites, it was assumed that the well-dispersed f-MWCNT in the copolymer matrix creates the huddles for penetration of oxygen gas. It was noticed that the oxygen permeability of the PAN-co-PMMA/f-MWCNT nanocomposite was reduced by five times as compared to that of the neat PAN-co-PMMA copolymer matrix. The PAN-co-PMMA/f-MWCNT nanocomposites with higher thermal stability and reduced oxygen permeability properties may be suitable for application as conducting packaging materials.     

Dielectric,thermal and mechanical properties of hybrid PMMA/RGO/Fe2O3 nanocomposites fabricated by in-situ polymerization

Currently, the organic-inorganic hybrid materials have gained tremendous importance due to their unique applications in different technological fields. In this connection, the chemical synthesis of poly(methyl methacrylate) (PMMA) and its binary and ternary nanocomposites by in-situ bulk polymerization with various percentages of reduced graphene oxide (RGO) and hematite nanoparticles (Fe₂O₃ NPs) is presented. Dielectric properties of binary and ternary nanocomposites are investigated in the frequency range of 25 Hz-1 MHz for each composition. Ternary nanocomposite of PMMA with RGO:Fe₂O₃ NPs (2:2 wt%) exhibits a substantial enhancement of the dielectric constant up to ≈308 and suppressed dielectric loss of 0.12 at 25 Hz. Appearance of three types of interfaces in ternary PMMA nanocomposites accounts for the superior dielectric properties due to the accumulation of greater number of charges at the interfaces as compared to the binary nanocomposites with only one interface. The same optimized ternary PMMA nanocomposite shows a remarkable improvement in the thermal conductivity (2.04 W/mK), which is attributed to the formation of efficient thermal conducting pathways contributed by the synergic reduction in thermal resistance of both RGO and Fe₂O₃ NPs (2:2 wt%) relative to the binary nanocomposites PMMA/2 wt% RGO (1.04 W/mK) and PMMA/2 wt% Fe₂O₃ (0.98 W/mK). Thus, ternary nanocomposites prove to be the excellent candidates for thermal management applications. Furthermore, a comparison of the mechanical strength and thermal stability for all the binary and ternary nanocomposites is presented. In the last section, respective precursors and optimized binary and ternary nanocomposites are characterized by XRD, FTIR and SEM which reveal the strong interaction of respective nanofillers into PMMA matrix.     

Nanocomposite films of poly(vinylidene fluoride) filled with polyvinylpyrrolidone‐coated multiwalled carbon nanotubes: Enhancement of β‐polymorph formation and tensile properties

To improve interactions between carbon nanotubes (CNTs) and poly(vinylidene fluoride) (PVDF) matrix, multiwalled CNTs (MWCNTs) were successfully coated with amphiphilic polyvinylpyrrolidone (PVP) using an ultrasonication treatment performed in aqueous solution. It was found that PVP chains could be attached noncovalently onto the nanotubes' surface, enabling a stable dispersion of MWCNTs in both water and N,N‐dimethylformamide. PVP‐coated MWCNTs/PVDF nanocomposite films were prepared by a solution casting method. The strong specific dipolar interaction between the PVP's carbonyl group (C?O) and the PVDF's fluorine group C?F₂ results in high compatibility between PVP and PVDF, helping PVP‐coated MWCNTs to be homogenously dispersed within PVDF. Fourier transform infrared and X‐ray diffraction characterization revealed that the as‐prepared nanocomposite PVDF films exhibit a purely β‐polymorph even at a very low content of PVP‐wrapped MWCNTs (0.1 wt%) while this phase is totally absent in the corresponding unmodified MWCNTs/PVDF nanocomposites. A possible mechanism of β‐phase formation in PVP‐coated MWCNTs/PVDF nanocomposites has been discussed. Furthermore, the tensile properties of PVDF nanocomposites as function of the content in PVP‐coated MWCNTs were also studied. Results shows that the addition of 2.0 wt% of PVP‐coated MWCNTs lead to a 168% increase in Young's modulus and a 120% in tensile strength. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Highly-efficient electromagnetic interference shielding and microwave dielectric behavior of a (Bi2O3 + B2O3)-doped MWCNT/BaTiO3 ceramic nanocomposite

Microwave dielectric properties along with electromagnetic interference shielding effectiveness (EMI SE) of a multi-walled carbon nanotube (MWCNT)/barium titanate (BaTiO₃) nanocomposite are investigated in this paper. Appropriate amount of sintering additive (Bi₂O₃ +?B₂O₃) was doped into some nanocomposites to reduce the sintering temperatures. The dielectric properties of the nanocomposites with various MWCNT and sintering additive contents were evaluated at different microwave frequency ranges. It was found that the incorporation of optimized amount of (Bi₂O₃ +?B₂O₃) can give rise to significantly good dielectric properties. Results also indicated that incorporation of 6?wt% (Bi₂O₃ +?B₂O₃) into 1.5?mm-thick nanocomposite containing 8?wt% MWCNT led to an EMI SE greater than 28?dB, suggesting this novel nanocomposite as a promising candidate for microwave absorption and electromagnetic interference applications.     

Solvent-Free One-Pot Synthesis of high performance silica/epoxy nanocomposites

High performance silanized silica/epoxy nanocomposites were prepared through mixing epoxy, tetraethyl orthosilicate (TEOS), (3-aminopropyl)trimethoxysilane (APTMS) and ammonia solution at 50 °C. This all-in-one “Solvent-Free One-Pot Synthesis” results in nanocomposites with uniform dispersion of oval shaped silica nanoparticles and strong adhesion between silica and epoxy matrix. The influence of the synthesis conditions, such as molar ratio of NH₃:TEOS, aging time, curing process and silica content on the thermal mechanical properties of nanocomposites were studied. The silanized silica/epoxy nanocomposite prepared in this study exhibits better thermal mechanical property in comparison with neat epoxy, non-functionalized silica/epoxy and commercialized silica/epoxy systems. The prepared nanocomposite with 3 wt% silanized silica exhibits 20%, 17% and 6% improvements on flexural, tensile and storage modulus over those of neat epoxy, respectively.