Carbon Nanotubes In Polymer Matrix Research Articles

Electrical conductivity of carbon nanotube/polypropylene composites prepared through microlayer extrusion technology

Abstract The morphological distribution of carbon nanotubes (CNTs) in polymer matrix has a crucial impact on the performance of CNT-filled polymer composites. A novel microlayer extrusion technology used in the dispersion and orientation of CNTs was proposed, and polypropylene (PP)/multiwalled CNT (MWCNT) composites with different numbers of layers were prepared with it. The MWCNT dispersion was investigated by scanning electron microscopy and Raman mapping method, and the MWCNT orientation was quantified by Raman spectroscopy. The influences of the dispersion and orientation of MWCNTs on the electrical conductivity and crystallization behavior of the composites were investigated. The results showed that the anisotropic conducting properties of the multilayered composites varied distinguishably with the increase of layer numbers and rotation speed. Furthermore, the degree of crystallinity of PP increased when the layer number increased from 1 to 729. All of these results suggest that with the increase of the layer numbers and the rotation speed, the dispersion and orientation of MWCNTs in PP matrix improve greatly. Overall, we provide an efficient and practical approach to control the dispersion and orientation of CNT in polymer matrix, which has a promising application prospect in the field of plastic processing.

Fast mass and charge transport through electrically aligned CNT/polymer nanocomposite membranes

This work represents the properties of electrically aligned carbon nanotubes (CNT)/polycarbonate (PC) nanocomposites towards the development of hydrogen gas separation membranes. A fraction (0.1 weight %) of CNTs synthesized by chemical vapour deposition method have been dispersed homogeneously throughout PC matrix by ultrasonication. The alignment of CNT in PC matrix has been accomplished by applying an external electric field of 1250 V/cm during solution casting. These nanocomposites have been studied by gas permeation, electrical, and dielectric constant measurements. Gas permeability measurements obtained here that electrically aligned nanocomposite membranes can be used as good hydrogen separating media. I–V characteristics and dielectric constant shows the enhancement in conductivity and permittivity of these nanocomposites. Overall experimental results exhibit here that alignment of CNTs in polymer matrix shows the dramatic improvement in mass and charge transport properties. Copyright © 2016 John Wiley & Sons, Ltd.

Mechanics of aligned carbon nanotube polymer matrix nanocomposites simulated via stochastic three-dimensional morphology

The promise of enhanced and tailored properties motivates the study of one-dimensional nanomaterials, especially aligned carbon nanotubes (A-CNTs), for the reinforcement of polymeric materials. While CNTs have remarkable theoretical properties, previous work on aligned CNT polymer matrix nanocomposites (A-PNCs) reported mechanical properties that are orders of magnitude lower than those predicted by rule of mixtures. This large difference primarily originates from the morphology of the CNTs, because the CNTs that comprise the A-PNCs have significant local curvature commonly referred to as waviness. Here we present a simulation framework capable of analyzing 105 wavy CNTs with realistic three-dimensional morphologies to quantify the impact of waviness on the effective elastic modulus contribution of wavy CNTs. The simulation results show that due to the low shear modulus of the reinforcing CNT ‘fibers’, and large () compliance contribution of the shear deformation mode, waviness reduces the effective stiffness contribution of the A-CNTs by two to three orders of magnitude. Also, the mechanical property predictions resulting from the simulation framework outperform those previously reported using finite element analysis since representative descriptions of the morphology are required to accurately predict properties of the A-PNCs. Further work to quantify the morphology of A-PNCs in three-dimensions, simulate their full non-isotropic constitutive relations, and predict their failure mechanisms is planned.

New Evidence for a Quasi-Simultaneous Proton-Coupled Two-Electron Transfer and Direct Wiring for Glucose Oxidase Captured by the Carbon Nanotube–Polymer Matrix

Systematic cyclic voltammetry (CV) studies of glucose oxidase (GOx) and its cofactor, flavine adenine dinucleotide (FAD), almost similarly captured by the matrix of single-walled carbon nanotube and polymer complex, in turn, deposited on GC electrodes have been performed. The comparative analysis of kinetic data obtained for the FAD and GOx specimens treated through the same Marcus theory-based algorithmic procedure strongly suggests that the GOx species, notwithstanding the deeply buried position of FAD, mechanistically behave virtually in the same manner as isolated FADs (the operationally capable, nearly intact structure of GOx was confirmed by the catalytic activity vs glucose), strongly suggesting that FADs inside GOx are directly wired to the GC electrode, presumably, via almost direct contact of nanotubes with both FADs residing inside each GOx biomolecule (as basically suggested by Guiseppi-Elie, A.; et al. Nanotechnology 2002, 13, 559–564, and shortly supported by a number of valued researchers). Furthermore, the nonadiabatic, quasi-simultaneous two-proton-coupled two-electron transfer/exchange mechanism was concluded from further cross-analysis based on a generalized Marcus theory for the proton-coupled electron transfer (PCET), extra furnished by the first-time temperature-dependent CV studies and a subsequent Arrhenius treatment.

Micro‐contact reconstruction of adjacent carbon nanotubes in polymer matrix through annealing‐Induced relaxation of interfacial residual stress and strain

ABSTRACTThermoplastic polyurethane (TPU)/multi‐walled carbon nanotubes (CNT) nanocomposites were prepared by twin‐screw extrusion and micro injection molding. The electrical conductivity of micro injection molded polymer nanocomposites exhibits a low value and uneven distribution in the micromolded samples. Real‐time tracing of electrical conductivity was conducted to investigate the post thermal treatment on the electrical conductivity of microinjection molded composites. The results show that postmolding thermal treatment leads to a significant increase in the electrical conductivity by over three orders of magnitude for 5 wt % CNT‐filled TPU composites. In‐situ Transmission electron microscopy confirms the conductive CNT network does not change at the micron/sub‐micron scale during thermal treatment. TEM image analysis by a statistical method was used to determine the spatial distribution of CNT in the sample and showed that the average distance between adjacent CNT reduced slightly at the nanometer scale after postmolding thermal treatment. A new conductive mechanism is proposed to explain the enhancement of electrical conductivity after thermal treatment, i.e. micro‐contact reconstruction of adjacent CNT in the polymer matrix through annealing‐induced relaxation of interfacial residual stress and strain. Raman spectra and small angle X‐ray scattering curve of annealed samples provide supporting evidence for the proposed new conductive mechanism. The electron tunneling model was used to understand the effect of inter‐particle distance on the conductivity of polymer composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42416.

Mechanical material characterization of an embedded Carbon nanotube in polymer matrix by employing an equivalent fiber

Effective elastic properties for carbon nanotube reinforced composites are obtained through a variety of micromechanics techniques. An embedded carbon nanotube in a polymer matrix and its surrounding interphase is replaced with an equivalent fiber for predicting the mechanical properties of the carbon nanotube/polymer composite. The effects of an interphase layer between the nanotubes and the polymer matrix as result of effective interphase layer is investigated. A modeling analysis investigating the effect of the aspect ratio on the tubes reinforcement mechanism has been carried out. The variations of mechanical properties with tube reduce, interphase thickness and waviness is investigated. Furthermore in this work, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube Random Contact which explicitly accounts for the progressive reduction of the tubes effective aspect ratio as the filler content increases.

Hybrids of Mg–Al-layered double hydroxide and multiwalled carbon nanotube as a reinforcing filler in the l-phenylalanine-based polymer nanocomposites

In this study, hybrid nanofiller based on acid functionalized multiwalled carbon nanotube (CNT) and Mg–Al-layered double hydroxide (LDH) was used as reinforcing agent in the preparation of the amino acid containing polymer nanocomposites. LDH–CNT nanofillers were prepared in aqueous solution by ultrasonic irradiation in one-step. An optically active poly(amide-imide) (PAI) was prepared under green condition using molten tetra-n-butylammonium bromide. PAI/LDH–CNT nanocomposites containing 2, 4, and 8 mass% of LDH–CNT were prepared by ultrasonic method, and the structure and morphology of the obtained hybrid compounds were characterized by different techniques. The homogeneous dispersion of nanofillers in the PAI matrix was observed by field emission scanning electron microscopy and transmission electron microscopy. The obtained results revealed a coexistence of exfoliated and intercalated modified LDH–CNT in polymer matrix. Strong combination of the above nanofillers with the PAI matrix provided an efficient thermal improvement for the resulted nanocomposites.

Covalent incorporation of aminated carbon nanotubes into epoxy resin network

In order to expand applied field of epoxy resin, its mechanical properties have to be improved. Carbon nanotube (CNT) is regarded as an exceptional toughening agent for polymers. However, poor dispersion quality of CNT in polymer matrix and weak interfacial force between them commonly lead to low reinforcing efficiency. This article presented a study on the mechanical properties of epoxy composite reinforced with aminated CNT (CNT-NH2). The amination of CNT was achieved via a wet chemical procedure using 1,6-diaminohexane (DAH) as amine source. Fourier transform infrared spectroscopy, zeta potential test, and thermogravimetric analysis were employed to investigate the as-prepared CNT-NH2. The results show that DAH has been successfully grafted onto the surface of CNT. Scanning electron microscopic images show that CNT-NH2 is homogenously dispersed in epoxy matrix. Mechanical properties tests suggest that the tensile strength and fracture toughness of the obtained CNT-NH2/epoxy composite are all enhanced compared with cured pure epoxy resin. The tensile strength and fracture toughness of the as-prepared CNT-NH2/epoxy composite with 0.8 wt% CNT-NH2 show 42% and 95% improvement, respectively. These results indicate that CNT-NH2 is a promising toughening agent for enhancing the mechanical properties of epoxy resin.

Study of structural morphology, thermal degradation and surface charge decay in PU + PSF + CNTs polymer hybrid nanocomposite

Abstract Polyurethane (PU)/Polysulfone (PSF)/Multi Wall Carbon Nanotubes (CNTs) hybrid nanocomposite films were prepared by solution grown method with different wt% of functionalized CNTs. The structural and thermal properties of PU, PSF and PU + PSF + CNTs nanocomposite films were studied by various techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), FTIR and TGA/DTG. The dispersion of CNTs in polymer was studied by SEM spectra, which indicates the presence of CNTs on the surface of the polymeric material. XRD results show the increases of crystallinity with different weight percentage of CNTs in polymer matrix. FTIR spectra reveal the position of different chemical bonds in pure and hybrid nanocomposite films. TGA and DTG show that the thermal stability of hybrid nanocomposite is better than PU and PSF due to reinforcement of CNTs in PU–PSF matrix. Surface charge decay study represents the charge stability in hybrid nanocomposite is due the localization of charge carriers in deeper traps.

Investigation of the structure of multiwall carbon nanotubes in polymer matrix

In the last ten years carbon nanotube composites are in the focus of the researchers. Concentration series were prepared using carbon nanotube containing master blend by IDMX mixer. In the experiments polypropylene, polycarbonate and ABS polymers were used as matrix materials. The prepared materials were characterised by scanning electron microscopy. The carbon nanotubes can be seen on the fractured surfaces. We did not find any sign of agglomerates in the materials. The nanocomposites were investigated by LP-FTIR method. The specimens were irradiated with 1 W for 1 minute by CO2 laser. The polymer matrix was burnt or charred by the CO2 laser; the structure of the carbon nanotubes in the matrix was studied. The carbon nanotubes create a physical network in the polymers we used.

Carbon nanotube embedded poly 1,5-diaminonapthalene modified pyrolytic graphite sensor for the determination of sulfacetamide in pharmaceutical formulations

An electrochemically conductive single-walled carbon nanotube (SWCNT) embedded poly 1,5-diaminonapthalene (DAN) modified sensor has been developed for the determination of sulfacetamide (SFA). The surface morphology of the modified sensor has been characterized by FE-SEM, which revealed good dispersion of the carbon nanotube in polymer matrix. SFA was quantified using square wave voltammetry in phosphate buffer of pH 7.2, which acted as supporting electrolyte during analysis. The modified sensor exhibited an effective catalytic response towards the oxidation of SFA with excellent reproducibility and stability. The peak current of SFA was found to be linear in the concentration range of 0.005-1.5 mM and detection limit and sensitivity of 0.11 μM (S/N=3) and 23.977 µA mM(-1), respectively were observed. The analytical utility of method was checked by determining the SFA in various pharmacological dosage forms. The results obtained from the voltammetry were validated by comparing the results with those obtained from HPLC. The proposed method is sensitive, simple, rapid and reliable and is useful for the routine analysis of SFA in pharmaceutical laboratories.

Synthesis and gas-sensing properties of phenylhydrazine-functionalized single wall carbon nanotubes in polymer matrix

Abstract Gas sensor material was prepared by encapsulation of functionalized single-walled carbon nanotubes (SWCNT) into a gas-permeable polymer poly(1-trimethylsilyl-1-propyne) (PTMSP). A phenylhydrazino group was used for the functionalization of SWCNTs to improve their solubility and compatibility with polymers. Syntheses were carried out in aqueous surfactant solutions and in pure phenylhydrazine without surfactant. Two different temperatures (24 and 50°C) and two surfactants (sodium dodecyl sulfate and tricaprylmethylammonium chloride — Aliquat®336) were compared. Functionalized SWCNTs were characterized by X-ray photoelectron (XPS), Raman and Fourier transform infrared (FTIR) spectroscopy. Analyses showed that the synthesis at higher temperature in pure phenylhydrazine resulted in the highest functionalization yield. Phenylhydrazine itself proved to be a good solvent for SWCNTs. The functionalized nanotubes were soluble in organic solvents that under the same conditions were appropriate solvents for polymers. The sensitivity of functionalized SWCNT-PTMSP thin film composite to NO2 gas at room temperature was significantly higher than that of the similar sensor material containing the pristine SWCNTs.

Development and characterization of MWNTs/Chitosan biocomposite fiber

The Preparation of conductive biocomposite fiber through Carbon nanotubes (CNTs) incorporation into biopolymer matrixes has stimulated much interest for bio-implant applications. The present study focuses on development and characterization of biocomposite fiber composed of chitosan (CHT) as a biopolymer and multiwall carbon nanotubes (MWNTs) as a conductive filler. In term of processing, the most important challenge is to prepare a highly stable dispersion of MWNTs in biopolymer matrix. The hydrodynamic diameter distribution of CNTs in acetic acid solution acquired by dynamic light scattering (DLS).Results demonstrate the supreme stability of CNTs dispersion which is extremely essential for homogenous distribution of CNT in polymeric matrix. Rheological properties of the spinning solution have also been investigated to adjust the viscosity for fiber processing step. A range of viscosity between 2000–8000 cP, has been recorded in different CNT loading. The scanning electron microscopy (SEM) images of the surface and cross sectional area of the fibers reveal the formation of nano-pores after MWNT addition. The tensile strength show a maximum increase of about 33.65 % compared to bare CHT. Also, the measurement of four probe electrical conductivity for different MWNTs loading shows a maximum conductivity of 0.107 S/cm at percolation threshold of 2.89 wt%.

115 放電分散を用いたCNT分散樹脂の機械的特性

Carbon nanotubes (CNTs) are highly expected as a reinforcement material for polymer composites because of their excellent mechanical properties. However, it is difficult to disperse CNTs in polymer matrix because CNTs tend to aggregate by Van der Waals force. In this study, CNT/epoxy composite was prepared using discharge dispersion method which is completely different from the conventional methods. Micro shock waves caused by discharge disperse CNTs, and furthermore, electrostatic repulsion decreases the reaggregation of CNTs. This discharge dispersion method is able to disperse CNTs in a short time and requires no special chemical agents. The dispersion state was observed using digital microscope and mechanical properties were studied by flexural tests. Although monodispersed CNTs were observed, CNT aggregates of ten-plus micro meter were also observed. The flexural modulus was increased by CNT dispersion. Compared to 0.00 wt %, flexural modulus was increased about 34 % when CNT content was 0.01 wt %.

Interface effects on the viscoelastic characteristics of carbon nanotube polymer matrix composites

It is generally known that load transfer from the polymer matrix to carbon nanotubes (CNTs) can be greatly hindered due to the pristine CNT surface condition. This imperfect condition can have a profound influence on the effectiveness of CNT reinforcement. In order to address this issue in the context of viscoelastic response, an effective medium theory is first presented, and then applied to study the effect of interfacial sliding on the time-dependent creep, stress relaxation, strain-rate sensitivity, and storage and loss moduli of a multi-walled CNT/polypropylene nanocomposite. We show that, without accounting for the imperfect load transfer at the interface, the predicted creep compliances are too stiff, but with the introduction of a weakened interface, the measured creep curves at various CNT loading can be well captured. Both stress relaxation and stress–strain relations are also found to greatly depend on the interface condition. Under low-frequency harmonic loading our calculations also reveal that the interface condition is further weakened and that a larger interface sliding parameter is required to reflect the measured storage and tangent moduli. We conclude that the viscoelastic characteristics of a CNT nanocomposite are very sensitive to the interface condition, and that continued improvement in surface functionalization is necessary to realize the full potential of CNT reinforcement.

Alignments of Carbon Nanotubes in Polymer Matrix: A Raman Perspective

Carbon nanotubes are highly anisotropic due to their high aspect ratio, therefore it is very important to align them in CNT/polymer composites. The extent of alignment can be easily studied by Raman spectroscopy. Carbon nanotubes are aligned perpendicular and parallel to the polymer film by application of an external magnetic field in polyvinyl butyral (PVB). FT-IR spectra of these films suggest that there is no chemical reaction between CNT and polyvinyl butyral, but the decrease in the G band intensity of carbon nanotubes in Raman spectra suggests that the tangential site of carbon nanotubes faces the surface of the polymer film, indicating the alignment of the carbon nanotubes in a CNT/polymer composite.

Dispersion and Performance Properties of Carbon Nanotubes (CNTs) Based Polymer Composites: A Review

Carbon nanotubes (CNTs) based polymer composites have variety of engineering applications (electromagnetic shielding, antistatic coatings, high-strength low-density corrosion-resistant components, lightweight energy storage and many more); due to their excellent mechanical, electrical, chemical, magnetic, etc. properties. In the polymer nanocomposites CNTs are dispersed in the polymeric matrix. However the dispersion may be uniform or may not be uniform. The biggest challenge is the effective dispersion of individual CNTs in the polymer matrices, as CNTs tends to form clusters and bundles due to strong van der Waals’ forces of attraction. The aggregated structure continue until physical (Mechanical) or chemical modification (Encapsulation/surface modification) of CNTs. Few modification methods such as vigorous mixing of the polymers damages CNTs structure, and may hinder their properties. But these problems can be overcome by mechanical or chemical modification of CNTs surfaces. In the chemical modification, the modifier or the long tail surfactant may encapsulate and/or partially wrap the CNTs surfaces. In this review, recent work on CNTs based polymer nanocomposite is carried out with few modifiers/encapsulating agents. Incorporation of CNTs in polymer matrix changes the performance properties such as tensile strength, tensile modulus, elongation at break, toughness, Dynamic mechanical thermal analysis (DMTA), etc. The phase morphology of the composite materials throws light on the properties of CNTs based polymer nanocomposite. Moreover phase morphology may be directly correlated with the behavior of the material, hence reviewed here through transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Furthermore review is also carried out on the non-isothermal crystallization (DSC) and rheology of CNTs polymer nanocomposite.

One-pot preparation and continuous spinning of carbon nanotube/poly(p-phenylene benzobisoxazole) copolymer fibers

Poly(p-phenylene benzobisoxazole) (PBO) fibers are some of the strongest organic polymer fibers, however, even stronger fibers can be made using carbon nanotubes (CNTs). In the present study, the copolymerization of functionalized CNTs with PBO was successfully carried out by one-pot in situ polycondensation in polyphosphoric acid. Pristine CNTs were first oxidized to CNT–COOH and then modified by 4,6-diaminoresorcinol (DAR) or PBO trimer (DAR–TA–DAR) to improve the reactivity, solubility, dispersivity, and interfacial adhesion of CNTs in polymer matrix. Functionalized CNTs were further covalently incorporated with PBO through in situ polymerization. The chemical structure and morphology of functionalized CNTs and CNT–PBO copolymers were well characterized for confirming the formation of covalent bond between CNTs and PBO. Moreover, continuous CNT–PBO copolymer fibers have been fabricated using a dry-jet wet-spinning technique. The structure and morphology of CNT–PBO copolymer fibers have been characterized and their mechanical and thermal properties have been investigated. The tensile modulus, tensile strength, and thermal stability of CNT–PBO copolymer fibers have been improved. The improvement in PBO molecular chain packing order, the good dispersion and high alignment of CNTs in the PBO matrix, and the covalent bonding at the CNT–PBO interface have been suggested as the main reasons for the performance improvement of PBO.

Sulfonated carbon nanotubes/sulfonated poly(ether sulfone ether ketone ketone) composites for polymer electrolyte membranes

AbstractA series of composite membranes consisting of sulfonated carbon nanotubes (sCNTs) and sulfonated poly(ether sulfone ether ketone ketone) were successfully fabricated via the solution casting method. The chemical structure, as well as the long‐term stability of the sCNTs in different solvents, was investigated by Fourier transform infrared (FTIR) analysis and solubility experiment, respectively. The morphology, tensile strength, proton conductivity, and methanol permeability of the composite membranes were also investigated. The scanning electron microscope (SEM) observation indicated the good dispersion of the carbon nanotubes in polymer matrix as well as the strong interfacial bonding between the sulfonated poly(ether sulfone ether ketone ketone) (SPESEKK) matrix and sCNTs. The addition of either pristine carbon nanotubes or modified carbon nanotubes significantly enhanced the tensile strength of the SPESEKK membrane. The proton conductivity of the SPESEKK membrane increased while the methanol permeability decreased as the sCNTs content increased, showing a strong interaction between the modified nanotubes and SPESEKK. Copyright © 2010 John Wiley & Sons, Ltd.

Microscopic and Spectroscopic Investigation of Poly(3-hexylthiophene) Interaction with Carbon Nanotubes

The inclusion of carbon nanotubes in polymer matrix has been proposed to enhance the polymer’s physical and electrical properties. In this study, microscopic and spectroscopic techniques are used to investigate the interaction between poly(3-hexylthiophene) (P3HT) and nanotubes and the reciprocal modification of physical properties. The presence of P3HT-covered nanotubes dispersed in the polymer matrix has been observed by atomic force microscopy and transmission electron microscopy. Then, the modification of P3HT optical properties due to nanotube inclusion has been evidenced with spectroscopic techniques like absorption and Raman spectroscopy. The study is completed with detailed nanoscale analysis by scanning probe techniques. The ordered self assembly of polymer adhering on the nanotube is unveiled by showing an example of helical wrapping of P3HT. Scanning tunneling spectroscopy study provides information on the electronic structure of nanotube-polymer assembly, revealing the charge transfer from P3HT to the nanotube.