Hybrid polyaniline–TiO2 nanocomposite Langmuir–Blodgett thin films: Self‐assembly and their characterization

Polyaniline (PANi)–titanium dioxide (TiO₂) nanocomposite materials were prepared by chemical polymerization of aniline doped with TiO₂ nanoparticles. Surface pressure–area (π‐A) isotherms of these nanocomposites show phase transformations in the monolayer during compression process. Multiple isotherms indicate that the monolayer of the nanocomposite material can retain its configuration during compression‐expansion cycles. Langmuir–Blodgett thin films of PANi–TiO₂ nanocomposite were deposited on the quartz and indium tin oxide coated conducting glass substrates. Fourier transfer infrared spectroscopy and UV–visible spectroscopy study indicates the presence of TiO₂ in PANi, whereas X‐ray Diffraction study confirmed the anatase phase of TiO₂ and particle size (～nm) of PANi–TiO₂. The morphology of Langmuir–Blodgett films of these nanocomposites was also characterized by atomic force microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41386.     

Melt spinning of conductive textile fibers with hybridized graphite nanoplatelets and carbon black filler

In this study, two different carbon fillers: carbon black (CB) and graphite nanoplatelets (GNP) are studied as conductive fillers for the preparation of conductive polypropylene (PP) nanocomposites. In order to obtain a homogenous dispersion of GNP, GNP/PP composites were prepared by two different methods: solid state mixing (SSM) and traditional melt mixing (MM). The result shows that MM is more efficient in the dispersion of GNP particles compared to SSM method. PP nanocomposites containing only one conductive filler and two fillers were prepared at different filler concentrations. Based on the analysis of electrical and rheological properties of the prepared nanocomposites, it shows that a hybridized composite with equal amounts of GNP and CB has favorable processing properties. Conductive fibers with a core/sheath structure were produced on a bicomponent melt spinning line. The core materials of these fibers are the hybridized GNP/CB/PP nanocomposite and the sheath is pure polyamide. It was found that GNPs were separated during melt and cold drawing which results in the decrease of conductivity. However, the conductivity could partly be restored by the heat treatment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2579–2587, 2013     

Electromagnetic interference shielding effects of polyaniline-coated multi-wall carbon nanotubes/maghemite nanocomposites

Highly conductive nanocomposites were prepared by in situ polymerization of polyaniline (PANi) and multi-walled carbon nanotubes (MWCNTs) as electromagnetic interference shielding materials. γ-Fe₂O₃ nanoparticles were also incorporated in the nanocomposites to improve the ferromagnetic properties. SEM and TEM images showed the uniformly coated PANi on the surface of MWCNTs and γ-Fe₂O₃. XRD peaks also confirmed the presence of MWCNT and γ-Fe₂O₃ in the nanocomposites. The nanocomposites showed significant improvement in permittivity, permeability, and electromagnetic interference shielding efficiency due to the conductive effect of MWCNTs and the magnetic effect of γ-Fe₂O₃. The electromagnetic interference shielding efficiency of nanocomposites increased up to 34.1 dB due to the synergetic effect of reflection and absorption of electromagnetic interference by MWCNTs and γ-Fe₂O₃ additives.     

Spectral and electrochemical studies on blends of polyaniline and cellulose esters

Blends of chemically prepared polyaniline emeraldine base (PANi) with cellulose esters were studied as films by UV–visible spectroscopy and cyclic voltammetry. The cellulose esters used were acetate, propionate, acetate butyrate, and acetate hydrogen phthalate. Films were prepared by casting from N‐methylpyrrolidone or formic acid, and the effect of doping by acids on their spectral and electrochemical properties was studied. Similar behavior was observed with the acetate, propionate, or acetate butyrate, with spectral changes on adding acid due to protonation of the PANi. In agreement with previous studies, kinetic measurements on PANi in a cellulose acetate matrix shows a relatively slow spectral change on protonation. In contrast, with cellulose acetate hydrogen phthalate (CAHP), no changes were observed on adding acid, and it is suggested that the hydrogen phthalate group acts as proton donor. This was mirrored by the cyclic voltammetry behavior in hydrochloric acid solution. Electrochemical studies on films of PANi/CAHP blends in different relative proportions in sulfuric acid solution show a marked dependence on the solvent used for casting, with higher currents and better electrical conductivity being observed in films prepared from N‐methylpyrrolidone. This is shown to be due to the presence of PANi particles in the films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2182–2188, 2002     

High-performance polymer/nanodiamond composites: synthesis and properties

Conjugated polymer/nanodiamond nanocomposites have been known as high-performance materials due to improved physical properties relative to conventional composites. In this attempt, novel conjugated polymer/nanodiamond nanocomposites were successfully prepared by in situ oxidative polymerization. Physical characteristics of the resultant nanocomposites were explored using Fourier transform infrared spectroscopy, field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscope, differential scanning calorimeter, thermogravimetric analysis and X-ray diffraction spectroscopy. Structural analysis revealed the oxidative polymerization of various matrices [polyaniline (PANi), polypyrrole (PPy), polythiophene (PTh) and polyazopyridine (PAP)] over the surface of functionalized (F-NDs) and non-functionalized nanodiamonds (NF-NDs) thus ensuing NF-NDs/PAP/PANi/PPy, F-NDs/PAP/PANi/PPy, NF-NDs/PANi/PPy/PTh and F-NDs/PANi/PPy/PTh nanocomposites. FESEM images depicted the fibrillar morphology of resulting nanocomposites with granular arrangement of nanofiller in matrix. Thermal analysis results showed that the functionalized F-NDs/PAP/PANi/PPy hybrid had higher value of 10 % weight loss around 489 °C relative to F-NDs/PANi/PPy/PTh with T₁₀ at 471 °C. The glass transition temperature was found to be 99 and 105 °C for NF-NDs/PANi/PPy/PTh and F-NDs/PANi/PPy/PTh, respectively. On the other hand, NF-NDS/PAP/PANi/PPy and F-NDs/PAP/PANi/PPy showed higher T _g’_s of 109 and 118 °C. The conductivity of NF-NDs/PAP/PANi/PPy was 3.8 Scm^?1 and improved with the functionalized filler loading in F-NDs/PAP/PANi/PPy up to 5.4 Scm^?1, while NF-NDs/PANi/PPy/PTh and F-NDs/PANi/PPy/PTh had relatively lower values around 2.9 and 3.7 Scm^?1, respectively. New conducting nanocomposites may act as useful contenders in significant industrial applications such as polymer Li-ion battery.     

Polypropylene-elastomer (TPO) nanocomposites: 1. Morphology

PP/PP-g-MA/MMT/elastomer nanocomposites were prepared in a twin-screw extruder at fixed 30 wt% elastomer and 0-7 wt% MMT content. The ratio of maleated polypropylene, PP-g-MA and organoclay was maintained at 1. Elastomer particle size and shape in the presence of MMT were evaluated for three different molecular weight grades of polypropylene (PP) and five different ethylene-co-octene elastomers (EOR) with different melt flow index (MFI) and octene contents. The MMT particles are located exclusively in the PP phase in the PP/PP-g-MA/MMT/EOR nanocomposites as seen from TEM images. Injection molded nanocomposite samples show significant decreases in elastomer particle size and increases in elastomer aspect ratio and particle density compared to as-extruded or pelletized samples. The elastomer particle size decreased significantly with increased MMT content and the molecular weight of PP. Low molecular weight PP based nanocomposite showed a greater reduction in elastomer particle size compared to medium and high molecular weight PP based nanocomposites. Elastomers having MFI in the range of 0.5-1.0 gave minimum elastomer particle sizes in the PP/PP-g-MA/MMT/EOR nanocomposite. The elastomer particles were deformed during injection molding leading to an increase in their aspect ratio. The nanocomposites containing high octene content elastomer gave smaller elastomer particle size and higher elastomer aspect ratios compared to nanocomposites containing low octene content elastomer.     

Synthesis of cellulose/reduced graphene oxide/polyaniline nanocomposite and its properties

A series of conductive nanocomposites cellulose/reduced graphene oxide/polyaniline (cellulose/RGO/PANi) were synthesized via in situ oxidative polymerization of aniline on cellulose/RGO with different RGO loading to study the effect of RGO on the properties of nanocomposites. The results showed that when RGO is inserted into cellulose/PANi structure, its thermal stability and conductivity are increased. So that adding of only 0.3 wt% RGO into the cellulose/PANi structure, its conductivity is increased from 1.1 × 1 10^?1 to 5.2 × 110^?1 S/cm. Scanning electron microscopy results showed that the PANi nanoparticles are formed a continuous spherical shape over the cellulose/RGO template; this increases the thermal stability of nanocomposite.     

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.     

Preparation of silver nanoparticles using chitosan suspensions

Silver/chitosan nanocomposites were prepared by using basic chitosan suspension as a stabilizer and as a reductant in the absence of other chemicals. The size and distribution of the resulting nanocomposite were strongly dependent on the concentration of chitosan and sodium hydroxide. UV-vis spectra and analytical electron microscopy (AEM) revealed the presence of silver/chitosan nanocomposites. In addition, Ag nanoparticles were obtained by annealing silver/composites at 600 °C. These nanoparticles were characterized by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectrometry (EDS). The FESEM indicated that the size of a majority of the Ag nanoparticles ranged between 10 and 150 nm. A change in the nanoparticles to porous-like nanostructures was observed when the composite feeding amount was increased, the annealing time prolonged, and the reaction temperature elevated.     

Facile hydrothermal synthesis and optical limiting properties of TiO2-reduced graphene oxide nanocomposites

TiO₂/reduced graphene oxide (RGO) nanocomposites Gx (RGO titania nanocomposite, x grams tetrabutyl titanate per 0.03 g RGO, x = 0.25, 0.50, 1.00) were prepared by a hydrothermal method: graphene oxide was reduced to RGO in a 2:1 water:ethanol mixture in the presence of varying quantities of tetrabutyl titanate, which deposited as TiO₂ on the RGO sheets. The nanocomposites were characterized by a combination of Fourier transform infrared spectroscopy, diffuse reflectance ultraviolet–visible spectroscopy, photoluminescence spectroscopy, Raman spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy studies. The nanocomposite G0.25 exhibits enhanced nonlinear optical properties compared to its individual components, which is ascribed to a combination of mechanisms. The role of defects and electron/energy transfer in the optical limiting performance of G0.25 was clarified with the help of Raman and photoluminescence spectroscopies. Intensity-dependent switching between reverse saturable absorption and saturable absorption behavior was observed with the G0.50 nanocomposite.     

Conductivity and anticorrosion performance of polyaniline/zinc composites: Investigation of zinc particle size and distribution effect

Polyaniline/zinc composites and nanocomposites were prepared using solution mixing method. Zinc (Zn) particles with an average particle size of 60 μm and zinc nanoparticles with an average particle size of 35 nm were used as fillers in polyaniline (PANI) matrix. Films and coatings of PANI/Zn composites and nanocomposites were prepared by the solution casting method. Electrical conductivity and anticorrosion properties of PANI/Zn composite and nanocomposite films and coatings with different zinc loadings were evaluated. According to the results, electrical conductivity and anticorrosion performances of both PANI/Zn composites and nanocomposites were increased by increasing the zinc loading. Also results showed that the PANI/Zn nanocomposite films and coatings have better electrical conductivity and corrosion protection effect on iron coupons compared to that of PANI/Zn composite.     

SBS nanocomposites as toughening agent for polypropylene

The toughening of polypropylene [PP] with styrene–butadiene–styrene rubber [SBS]/montmorillonite [MMT] nanocomposites was investigated with respect to morphological, thermal, and mechanical properties. The MMT/SBS nanocomposites were prepared in an internal mixer, using an epoxidized SBS [SBSe] to investigate its effect as a compatibilizer. The MMT/SBS nanocomposite was added to PP up to 10 wt%, aiming at material toughening. Transmission electron microscopy (TEM) revealed MMT induced dispersed-phase reductions when compared to typical PP/SBS blends. In addition, changes in the PP crystallization process were observed in the presence of the nanocomposite. Surprisingly, the use of nanofiller, combined with SBSe compatibilizer agent, increased the PP impact strength by about 60%, with no reduction in the tensile module.     

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.     

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

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

Multifunctional high‐density polyethylene nanocomposites produced by incorporation of exfoliated graphene nanoplatelets 2: Crystallization,thermal and electrical properties

This research investigates the effect of exfoliated graphene nanoplatelets (GNP) on the crystallization behavior, thermal conductivity, and electrical conductivity of high‐density polyethylene (HDPE)/GNP nanocomposites. HDPE/GNP nanocomposites were fabricated by melt blending followed with injection molding. Results indicate that GNP is a good nucleating agent at low loading levels and as a result can significantly increase crystallization temperature and crystallinity of HDPE. At high GNP loadings, however, the close proximity of GNP particles retards the crystallization process. The thermal stability and thermal conductivity of HDPE/GNP nanocomposites were found to be significantly enhanced as a function of GNP concentration owing to the excellent thermal properties of GNP. Finally, the high percolation threshold of HDPE/GNP nanocomposites (∼10–15 vol%), prepared by melt blending and injection molding was successfully reduced to around 5 vol% of GNP loading by employing a novel compounding method, solid‐state ball milling. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Exploring interfacial interactions,dielectric, ferroelectric and piezoelectric properties of ultrahigh molecular weight polyethylene/graphene oxide nanocomposites

Graphene oxide (GO) incorporated ultra-high molecular weight polyethylene (UHMWPE) nanocomposites were prepared by encapsulating GO by UHMWPE in an aqueous media via high-shear mixing, which were subsequently dried and compression molded. Morphological characterizations via scanning electron microscopy revealed the intercalation of UHMWPE chains in the graphitic stacks corresponding to GO. Further, dielectric permittivity of UHMWPE/GO nanocomposite of 1 wt% GO showed a drastic increase (~61) as compared to pure UHMWPE (~2) due to an enhanced interfacial polarization. A significantly higher value of remnant polarization (~10 nC/cm²) and coercive field (~3 kV/cm) was observed in UHMWPE/GO nanocomposite of 1 wt% GO, which showed a strong hysteresis loop of polarization versus electric field plot as compared to pure UHMWPE, which displayed a very weak hysteresis loop. The piezoelectric coefficient (d₃₃) of ~9.5 pm/V was estimated in UHMWPE/GO nanocomposite of 1 wt% GO via piezoresponse force microscopy. Nanocomposite sensor devices were also fabricated and piezoelectric output voltage of ~6 V was recorded in UHMWPE/GO nanocomposite of 1 wt% of GO. We report here for the first time the unique ferroelectric and piezoelectric properties displayed by UHMWPE/GO nanocomposites.     

Carbon nanohorn and graphene nanoplate based polystyrene nanocomposites for superior electromagnetic interference shielding applications

In this article is reported the preparation of carbon nanohorn (CNH)/graphene nanoplates (GNP)/polystyrene (PS) nanocomposites through in‐situ bulk polymerization of styrene monomer in the presence of CNH, followed by the addition of suspension polymerized GNP/PS bead during polymerization of styrene, as next‐generation multifunctional material for high electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) applications. Morphological analysis revealed selective dispersion of CNH in bulk polymerized PS matrix, where GNP/PS beads were randomly distributed. The formation of continuous CNH–CNH conductive path and GNP–CNH–GNP or CNH–GNP–CNH conductive network throughout the PS matrix at exceptionally low loading of CNH (1.0 wt %) and GNP (0.15 wt %) leads to high electrical conductivity (6.24 × 10^?2 S cm^?1) and EMI SE ～(?24.83 dB) when the nanocomposites was prepared in the presence of 75 wt % GNP/PS bead. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42803.     

Effect of lattice structure evolution and stacking fault energy on the properties of Cu–ZrO2/GNP nanocomposites

A hybrid nanocomposite comprising nanosized ZrO₂ and graphene nanoplatelet (GNP)-reinforced Cu matrix was synthesised via powder metallurgy. The influence of sintering temperature and GNP content on the electrical and mechanical behaviour of the Cu–ZrO₂/GNP nanocomposite was investigated. The ZrO₂ concentration was fixed at 10% for all the composites. Upon increasing the GNP concentration up to 0.5%, a significant improvement was observed in the compressive strength, microhardness, and electrical conductivity of the composite. Furthermore, the properties were significantly improved by increasing the sintering temperature from 900 to 1000 °C. The compressive strength, hardness, and electrical conductivity of Cu–10%ZrO₂/0.5%GNP were higher than those of the Cu–ZrO₂ nanocomposite by 60, 21, and 23.8%, respectively. This improvement in the mechanical properties is because of the decrease in the crystallite size and dislocation spacing, which increases the dislocation density, thereby increasing the impedance towards dislocation movement. The lower stacking fault energy of the hybrid nanocomposites enables easier electron transfer within and between the Cu grains, resulting in an improved electrical conductivity. The enhancement in strength and electrical conductivity were aided by the GNPs and ZrO₂ nanoparticles that were dispersed widely in the Cu matrix.     

Mechanical performance of re‐extruded and aged graphene/polypropylene nanocomposites

In the present research polypropylene/expanded graphite (PP/ExpG) and polypropylene/graphene nanoplatelet (PP/GNP) composites were prepared by melt blending and their morphology and tensile properties were investigated. Although both reinforcements improved the elastic modulus of PP, PP/GNP composite presented better dispersion of the nanofiller in the polymer matrix and it was selected for further re‐extrusion and ageing experiments. The re‐extrusion affected the content of crystal phases of PP in pure PP and in its nanocomposite with GNP and increased their elastic modulus. The ageing of one and five times re‐extruded PP caused an increase of the β‐crystal phase and the formation of voids in the cross‐section. GNPs seem to protect the PP matrix from ageing as in Fourier transform IR spectra of PP/GNP nanocomposite, both one and five times extruded, the peak corresponding to carbonyl degradation products of PP was barely visible. The tensile properties of aged nanocomposites, one and five times re‐extruded, were similar to those of the corresponding non‐aged composites, whereas in aged PP the tensile strength and strain decreased significantly compared to non‐aged PP. The anti‐ageing effect of graphene can prolong the life of the PP matrix. © 2017 Society of Chemical Industry     

Dispersion optimization of exfoliated graphene nanoplatelet in polyetherimide nanocomposites: Extrusion,precoating, and solid state ball milling

Polyetherimide (PEId) nanocomposites reinforced with exfoliated graphite (graphene) nanoplatelets (GNP) were fabricated by various processing methods to achieve good dispersion including: melt‐extrusion, precoating, solid state ball milling (SSBM) as well as combinations of these methods. As a result of the precoating approach, the electrical conductivity is greatly increased with a percolation threshold as low as 2 wt% as compared to 10 wt% for melt‐extrusion, with the cost of lower mechanical properties. SSBM was investigated as an alternative process to enhance dispersion, adhesion and to reduce GNP size. High electrical conductivity and improved modulus were achieved by this approach. Further improvements to the mechanical properties could be made by combining the extrusion and SSBM approaches. Examination of the nanocomposite morphology explains the effect of these combined compounding approaches on GNP particle dispersion and their relation to the improved GNP/PEId nanocomposite performance. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers