In situ synthesis of cabbage like polyaniline@hydroquinone nanocomposites and electrochemical capacitance investigations

A Cabbage like polyaniline@hydroquinone composite microsphere was synthesized using in situ polymerization and the electrochemical performance was investigated. The core template, p‐benzoquinone, is demonstrated working as an oxidizing agent for the in situ polymerization of PANI, and to be reduced to 1, 4‐hydroquinone after reaction. The morphology and microstructure of samples were examined by field emission scanning electron microscopy, transmission electron microscope, X‐ray photoelectron spectrometer, thermo gravimetric, and Fourier transform infrared spectra. The cyclic voltammetry, impedance and galvanostatic charge/discharge analysis demonstrates that PANI contributes electronic conductive channels for hydroquinone, and hydroquinone works as a pseudocapacitance component. The prepared PANI@hydroquinone nanocomposite exhibits brilliant electrochemical properties of a specific capacitance of 126.0 F g^?1 at a scan rate of 5 mV s^?1 and enhanced stability of about 85.1% of initial capacitance retained after 500 cycles scanning at a current density of 1 A g^?1. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42290.     

Flexible papers derived from polypyrrole deposited cellulose nanofibers for enhanced electromagnetic interference shielding in gigahertz frequencies

An array of highly conductive, lightweight and flexible cellulose nanopapers as effective attenuators of electromagnetic radiations within 8.2–12.4 GHz (X band) were formulated via in situ polymerization of pyrrole monomers on to cellulose nanofibers (CNFs). It is quite obvious that the free hydroxyl groups on the surface of CNFs facilitate the formation of intense intermolecular hydrogen bonding with PPy which is envisaged for its excellent electromagnetic shielding performance with an average shielding effectiveness of ca. –22 dB (>99% attenuation) at 8.2 GHz for a paper having 1 mm thickness. The fabricated papers displayed a predominant absorption mechanism (ca. 89%) rather than reflection (ca. 11%) for efficiently attenuating electromagnetic radiations, which has a considerable importance in the modern telecommunication sector. Thus, the designed PPy/CNF papers would replace the conventional metal-based shields and pave way for the development of green microwave attenuators functioning via a strong absorption mechanism. The PPy/CNF nanopapers exhibited a DC conductivity of 0.21 S/cm, a prime requisite for the development of highly efficient electromagnetic shields. Undoubtedly, such nanopapers can be employed in wide range of applications such as electrodes for supercapacitors and other freestanding flexible paper-based devices.     

In situ fabrication of polyaniline‐silver nanocomposites using soft template of sodium alginate

Polyaniline (PANI)‐Ag nanocomposites were synthesized by in situ chemical polymerization approach using ammonium persulfate and silver nitrate as oxidant. Characterizations of nanocomposites were done by ultraviolet–visible ( UV–vis), Fourier transform infrared (FTIR), X‐ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy (TEM). UV–vis, XRD and FTIR analysis established the formation of PANI/Ag nanocomposites and face‐centered‐cubic phase of silver. PANInanofibers were of average diameter ～ 30 nm and several micrometers in length. Morphological analysis showed that the spherical‐shaped silver nanoparticles decorate the surface of PANI nanofibers. Silver nanoparticles of average diameter ～ 5–10 nm were observed on the TEM images for the PANI‐Ag nanocomposites. Such type of PANI‐Ag nanocomposites can be used as bistable switches as well as memory devices. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Highly filled multilayer thermoplastic/graphene conducting composite structures with high strength and thermal stability for electromagnetic interference shielding applications

Polyvinyl chloride (PVC)/graphene and poly(methyl methacrylate) (PMMA)/graphene nanocomposites were made by solution casting technique with graphene weight fractions of 1, 5, 10, 15, and 20%. Multilayer structures of the composites were made by hot compression technique to study their electromagnetic interference shielding effectiveness (EMI SE). Tensile strength, hardness, and storage modulus of the nanocomposites were studied in relation with graphene weight fraction. There has been a substantial increase in the electrical conductivity and EMI SE of the composites with 15–20% filler loading. Differential thermal analysis of the composites shows improved thermal stability with an increase in graphene loading. PMMA/graphene composites have better thermal stability, whereas PVC/graphene composites have superior mechanical properties. About 2 mm thick multilayer structures of PMMA/graphene and PVC/graphene composites show a maximum EMI SE of 21 dB and 31 dB, respectively, in the X band at 20 wt % graphene loading. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47792.     

Polyaniline nanofibers for In situ MAO‐catalyzed polymerization of ethylene

In this work electro‐conductive polyaniline nanofibers (PAni‐nanofibers) were prepared via interfacial methodology. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations revealed that the synthesized PAni‐nanofibers present high aspect ratio with an average diameter of 80 nm, while they exhibit high conductivity (DC conductivity values: 4.19 ± 0.21 S cm^?1). After specific treatment to remove moisture and remaining trapped HCl from PAni‐nanofibers, it was possible to prepare promising polyethylene (PE)/PAni composites by in situ polymerization of ethylene using bis(cyclopentadienyl) zirconium(IV) dichloride (Cp₂ZrCl₂) and methylaluminoxane (MAO) as catalytic system. More precisely, various contents of PAni‐nanofibers (from 0.2 to 7 wt %) were successfully incorporated in the in situ produced PE/PAni nanocomposites. PAni‐nanofibers were found to affect significantly the crystallization of the polyolefinic matrix while preserving its thermal stability. Preliminary measurements of electric properties showed PAni‐nanofibres are able to bring electro‐conductive properties to the in situ polymerized PE/PAni composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41197.     

The role of the interphase on the shear induced failure of multiwall carbon nanotubes reinforced epoxy nanocomposites

Multiwall Carbon Nanotubes (MWCNT) with an elevated aspect ratio were chemically functionalized with amines and two types of epoxide groups. Thermogravimetric analysis and Fourier Transform‐Infrared Spectroscopy (FTIR) analysis corroborated that the functionalization degree was substantial (up to 30 wt %) and the presence of a covalent bond with the MWCNT. The functionalized MWCNT (f‐CNT) were incorporated into an epoxy matrix after its dispersion in the diglycidyl ether of bisphenol A (DGEBA) precursor. To induce a shear failure mode, a short‐beam (SB) experimental setup was implemented. The SB shear strength (SBSS) proved that the functionalization had a strong influence on its value. For the case of pristine CNT, a neutral effect was obtained. A strong detrimental effect (?17.2% ± 9.5) was measured for the amine type f‐CNT and a positive effect (up to 10.9% ± 8.9) was measured of the epoxide type f‐CNT. Fractographic analysis of each formulation was correlated with SBSS performance, proving that the surface texture of the fractured samples was strongly correlated to its value. Furthermore, dynamic mechanical analysis proved that the damping factor and the crosslink molecular weight were correlated with the SBSS performance. A lower full width at half maximum of the damping factor was associated to an improvement of SBSS. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41364.     

Polyaniline nanocomposites with negative permittivity

In this review, the fundamentals of negative permittivity are critically discussed. Current research on polyaniline and its nanocomposites with negative permittivity are presented in detail. The reasons why these unique materials show negative permittivity are analyzed. This knowledge will be useful for future metacomposite design and manufacturing. These polymeric materials with negative permittivity are envisioned to create next‐generation left‐hand media for cloaking, subwavelength imaging, stealth, and invisibility applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2238–2244, 2013     

Preparation of fine Ni particles and their shielding effectiveness for electromagnetic interference

Fine Ni particles with sphere‐like architecture were synthesized via a wet chemical route in distilled water. The resulting fine Ni particles and/or commercial microsized Ni particles were then added to a mixed resin solution to fabricate resin‐based conductive composites. The shielding effectiveness (SE) of the resultant conductive composites for electromagnetic interference was measured as a function of nickel mass fraction. The results indicated that the SE values of the two kinds of Ni‐containing resin‐based composites increased with increasing loading of Ni filler. Moreover, the fine Ni particles, in the absence of any protective agents, were liable to aggregate for the sake of decreasing surface energy, which could be well avoided by ultrasonic disposal. The resin‐based conductive composites containing a low concentration (33.3 wt %) of the ultrasonically disposed fine Ni particles recorded an SE value as much as above 22 dB in a frequency range of 130 MHz to 1.5 GHz, which could not be realized for the composites filled with microsized nickel particles unless the mass fraction of the Ni filler in this case was as high as 50.0 wt %. In other words, the ultrasonically disposed fine Ni particles could be used as efficient lightweight filler for shielding of electromagnetic interference. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synergistic effects of carbon nanotubes and exfoliated graphite nanoplatelets for electromagnetic interference shielding and soundproofing

Polypropylene/carbon nanotube/exfoliated graphite nanoplatelet (PP/CNT/xGnP) composites have been fabricated to evaluate their electromagnetic interference shielding effectiveness (EMI SE) and soundproofing. An EMI SE of 36.5 dB at 1250 MHz was measured for the 80/10/10 wt % PP/CNT/xGnP composite; its sound transmission loss was more than 5 dB higher than that for pure PP at low frequencies (520–640 Hz). These results indicate simultaneous EMI SE and soundproofing. Transmission electron microscopy was used to study the microstructure and to probe synergetic effects between the CNTs and xGnPs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3947–3951, 2013     

In situ preparation of cyclohexanone formaldehyde resin/layered silicate nanocomposites

In this study, in situ modified cyclohexanone formaldehyde resin (CFR) was prepared from clay (montmorillonite) and polydimethylsiloxane with diamine chain ends [α,ω‐diamine poly(dimethyl siloxane) (DA.PDMS)] in the presence of a base catalyst. Different clay contents (from 0.5 to 3 wt %) were used to produce clay‐modified nanocomposite ketonic resins [layered clay (LC)–CFR] and clay‐ and DA.PDMS‐modified nanocomposite ketonic resins (DA.PDMS–LC–CFR). The polymeric nanocomposite material prepared by this method was directly synthesized in one step. These nanocomposites were confirmed from X‐ray diffraction to have a layered structure with a folded or penetrated CFR, and they were further characterized via Fourier transform infrared spectroscopy–attenuated total reflectance and NMR spectroscopy. The thermal properties of all of the resins were studied with differential scanning calorimetry and thermogravimetric analysis. All of the resins showed higher thermal stability than their precursor CFR resin. The obtained samples were also characterized morphologically by scanning electron microscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39918.     

Preparation of highly thermally conducting polyamide 6/graphite composites via low‐temperature in situ expansion

Highly thermally conducting polyamide 6 (PA6) composites with high loadings of low‐temperature expandable graphite (LTEG) were prepared by an in situ exfoliation melting process, and the thermal conductivity of the composites was measured by a hot‐disk method. A two‐point method was applied to evaluate the electrical conductivity of the composites with various graphite loadings, and the thermal percolation was observed in the vicinity of the electrical percolation threshold concentration. Dynamic rheology analysis was used to define the geometric change caused by the interconnection of the in situ exfoliated graphite flakes. X‐ray diffraction measurement confirmed that the exfoliation of LTEG was crucial to the overall thermal conductivity of the composites. Dynamic mechanical analysis revealed that the incorporation of LTEG significantly improved the damping properties of PA6. Thermogravimetric analysis and differential scanning calorimetry measurements were applied to study the thermal properties of the investigated PA6/LTEG composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39596.     

Studies on the electromagnetic interference shielding effectiveness of metallized PVAc‐AgNO3/PET conductive films

A metal chelate polymer (MCP) of PVAc‐AgNO₃ was prepared by adding AgNO₃ salts into the PVAc matrix and was coated on to PET substrate to form PVAc‐AgNO₃/PET films. These films were then treated with NaBH₄ aqueous solution to become the reduced metallized conductive films (RMCF) of PVAc‐AgNO₃/PET. The electromagnetic interference shielding effectiveness (EMI/SE) and the characteristics of these films were investigated. The SE value was measured by the far‐field transmission line method. The surface resistivity (Rs) of RMCF with a AgNO₃ content of 15 wt % was found to be below 5 Ω/sq, and the SE value exceeded 20 dB over the frequency range 50–900 MHz. The Rs of RMCF with a AgNO₃ content of 30 wt % was less than 1 Ω/sq, and the SE value even reached 33 dB at 550–650 MHz. It was confirmed by X‐ray and scanning electronmicroscope (SEM) analysis that the conducting network, as formed by closely deposited silver atoms on the reduced coating surface, was the dominant pathway for effective electron propagation that contributed to the excellent conductivity of these RMCF (PVAc‐AgNO₃/PET). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 270–273, 2004     

Quantification of carbon nanotube dispersion and its correlation with mechanical and thermal properties of epoxy nanocomposites

An experimental study is carried out to quantitatively assess the dispersion quality of carbon nanotubes (CNTs) in epoxy matrix as a function of CNT variant and weight fraction. To this end, two weight fractions (0.05% and 0.25%) of as-grown, oxidized, and functionalized CNTs are used to process CNT/epoxy nanocomposites. Scanning electron microscopy, X-ray diffraction, and Fourier transform infrared analysis of different variants of CNTs are used to establish the efficiency of purification route. While the relative change in mechanical properties is investigated through tensile and micro-hardness testing, thermal conductivity of different nanocomposites is measured to characterize the effect of CNT addition on the average thermal properties of epoxy. Later on, a quantitative analysis is carried out to establish the relationship between the observed improvements in average composite properties with the dispersion quality of CNTs in epoxy. It is shown that carboxylic (-COOH) functionalization reduces the average CNT agglomerate size and thus ensures better dispersion of CNTs in epoxy even at higher CNT weight fraction. The improved dispersion leads to enhanced interfacial interaction at the CNT/epoxy interface and hence provides higher relative improvement in nanocomposite properties compared to the samples prepared using as-grown and oxidized CNTs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48879.     

Enhanced impact resistance and electromagnetic interference shielding of carbon nanotubes films composites

High reliability and high-performance electromagnetic interference (EMI) shielding polymeric composite was fabricated by introducing carbon nanotube films (CNT_f) into an epoxy (EP) matrix as mechanical and EMI shielding reinforcement simultaneously. According to the computed tomography (CT) detection recorded by a high-speed camera, CNT_f exhibited excellent mechanical behavior and good energy absorption. While being introduced into laminated EP composite, the CNT_f enhanced both the mechanical performance and EMI shielding performance. The damage mechanism of CNT_f/EP was studied by CT detection of the impact process, indicating that the CNT_f absorbed the impact energy by improving the delamination resistance. Additionally, the multilayered CNT_f can trap and attenuate the entered electromagnetic microwaves by repeated adsorption, reflection, and scattering in the composite, resulting in excellent EMI shielding performance. Consequently, the energy absorption and the total shielding effectiveness of the CNT_f/EP reached to 4.58 × 10⁻³ J and 52.31 dB, respectively. Therefore, we demonstrated that the CNT_f was an ideal functional reinforcement for mechanically strong and high-performance EMI shielding polymeric composites and the CNT_f reinforced EP composite is promising in practical EMI-shielding applications.     

In situ polymerization of bio‐based thermosetting polyurethane/graphene oxide nanocomposites

Novel bio‐based polyurethane/graphene oxide (GO) nanocomposites have been successfully synthesized from biorenewable epoxidized soybean‐castor oil fatty acid‐based polyols with considerable improvement in mechanical and thermal properties. The GO was synthesized via a modified pressurized oxidation method, and was investigated using Raman spectra, AFM and XPS, respectively. The toughening mechanism of GO in the bio‐based polyurethane matrix was explored. The elongation at break and toughness of polyurethane were increased by 1.3 and 0.8 times with incorporation of 0.4 wt % GO, respectively. However, insignificant changes in both mechanical strength and modulus were observed by adding GO. The results from thermal analysis indicated that the GO acts as new secondary soft segments in the polyurethane which lead to a considerable decrease in the glass transition temperature and crosslink density. The SEM morphology of the fracture surface after tensile testing showed a considerable aggregation of graphene oxide at concentrations above 0.4 wt %. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41751.     

Ultrasonic characterization of conductive epoxy resin/polyaniline composites

This study presents the ultrasonic characterization of conductive epoxy resin (ER)/polyaniline (PANI) composites. The prepared PANI is mixed with ER matrix at weight percentages of 5%, 10%, and 15% for preparing the ER/PANI composites. The effects of PANI amount on the mechanical properties of ER/PANI composites are investigated by ultrasonic pulse‐echo‐overlap method. Also, electrical conductivity, ultrasonic wave velocity and ultrasonic micro‐hardness values of ER/PANI composites are correlated. Experimental results show that there is an excellent correlation between ultrasonic micro‐hardness and ultrasonic shear wave velocity. Also, the results of ultrasonic velocities and elastic constants values illustrate that the appropriate combination ratio is 95 : 5 for ER and PANI in ER/PANI composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42748.     

Synchronization of thermal properties and constituents in Nanocomposite: Manufacturing,characterization, adjustable properties

This is critical to maintain better thermal properties, especially thermal conductivity as well as low particle content along with organized particle dispersion in polymer nanocomposites. Thus, this study is designed to develop a nanocomposite containing a constant reinforcing load of binary particles (carbon and alumina) in the binary matrix of polypropylene (PP)/poly ethylene-co-vinyl acetate (EVA). The samples were prepared through the melt blending and hot pressing technique. Compared to pure PP/EVA matrix, the nanocomposites showed a shift in Fourier-transform infrared spectroscopy peak and absorption intensity, which proves better interaction of nanoparticles with the matrix. The Scanning Electron Microscopy analysis showed the nanocomposite having carbon (C) and alumina (A) relative ratio 2:3 offered even structure with better distribution of nanoparticles compared to other nanocomposites. Also, Differential scanning calorimetry and Thermogravimetric analysis revealed that alumina-rich binary nanoparticles reinforced composites offer an efficient improvement in thermal behavior. Moreover, the nanocomposite containing high alumina relative ratio (C: A = 2:3) gives a sharp shift in thermal conductivity of 1.57 W/m-k from 1.2 W/m-k of carbon-rich nanocomposite (C: A = 3:2) and 0.16 W/m-k of pure PP/EVA. However, these relative properties emphasize the important role of this nanocomposite as a programmable thermal material.     

Enhancing the electrical conductivity of carbon black/graphite nanoplatelets: Poly(ethylene‐butyl acrylate) composites by melt extrusion

The influence of processing parameters such as screw geometry, temperature profile, and screw speed on the electrical properties of hybrid composites consisting of graphite nanoplatelets and carbon black in ethyl butyl acrylate was studied. Two different screws were used to compound the hybrid composites at two different temperatures and two different screw speeds. A beneficial effect was noted with regard to the electrical properties when adding nanoplatelets to the filler system. The cause could be a synergistic effect due to the difference in particle shape of the two fillers. Lower percolation thresholds were obtained with the conventional screw due to less breakage of the graphite nanoplatelets compared to the barrier screw. No significant changes of the electrical properties were observed when changing the temperature profiles or the screw speeds. Furthermore, the melt viscosity of the compounds was not appreciably affected at the rather low filler contents used here. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42897.     

The effects of modified zinc oxide nanoparticles on the mechanical/thermal properties of epoxy resin

Characterized by its strength, durability, and thermal properties, epoxy resin has been widely used as an adhesive, paint, and coating in many applications in the aerospace, civil and automotive industries. Despite this, the thermoset polymer resin has been known for its brittleness and low fracture resistance. This study focuses on the reinforcement of an epoxy resin system (diglycidyl ether of bisphenol A) with zinc oxide (ZnO) nanoparticles in their pristine form and a further modified form. The modification took place in two ways: coating with polydopamine (PDA) and covalently functionalizing them with (3-aminopropyl)triethoxysilane (APTES) and (3-glycidoxypropyl)trimethoxysilane (GPTMS). Therefore, four different types of nanoparticles were used: pristine ZnO, ZnO/PDA, ZnO/GPTMS, and ZnO/APTES aiming to improve the interfacial bonding between the polymeric matrix and the reinforcement. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy, and scanning electron microscopy characterization and imaging techniques were used to prove that the ZnO nanoparticles were successfully modified prior to manufacturing the epoxy composites. While tensile testing showed that using pristine ZnO increases the composite's strength by 32.14%, the fracture toughness of the resin was improved by 9.40% when reinforced with ZnO functionalized with APTES. TGA showed that the addition of functionalized nanoparticles increases the material's degradation temperature by at most 7.31 ± 4.9°C using ZnO/APTES. Differential scanning calorimetry and dynamic mechanical analysis testing proved that the addition of any type of nanoparticles increases the resin's glass transition temperature by as much as 7.83°C (ZnO/APTES).     

Effect of unfunctionalized and HNO3‐functionalized MWCNT on the mechanical and electrical performances of PEMFC bipolar plates

This study aims at developing lightweight and high performance electrically conductive nanocomposites for proton exchange membrane fuel cell (PEMFC) bipolar plates (BPPs). These composites were made from an optimized co‐continuous mixture of Polyethylene terephthalate (PET) and polyvinylidene fluoride (PVDF) reinforced with highly conductive carbon additives composed of carbon black (CB) and synthetic graphite (GR). Multiwall carbon nanotubes (MWCNT) were functionalized then used to improve BPPs electrical conductivity and their mechanical properties, such as flexural and impact strengths. It was observed that the best BPP prototype was obtained using nitric acid (HNO₃)‐functionalized MWCNT. The latter led to the smothest BPP surface, the lowest through‐plane resitivity (0.12 Ω cm) and the highest impact and flexural strengths. These results are attributed to the improved dispersion of the functionalized MWCNT, a result of their best compatibilization with the (PET/PVDF) polymeric phase. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43624.