Polymer Multiwalled Carbon Nanotube Research Articles

Investigation of fracture behavior and mechanical properties of epoxy composites supported with MWCNTs microscopically

Adding of a multi-walled carbon nanotubes (MWCNTs) to epoxy resin has shown promising results in improving fracture toughness in bulk epoxy and carbon fiber-reinforced epoxy composites (CFRP). using a hand layup proceeding followed by the so called vacuum bagging process method, carbon fiber-reinforced polymer multi-wall carbon nanotubes (MWCNTs) was added to an epoxy resin with a weight percentage mixing of 1% wt., 1.25% wt., and 1.5 % wt. MWCNTs. Furthermore, the specimen underwent analysis via Fourier-Transform Infrared (FTIR) spectroscopy, and X-ray Diffraction (XRD) spectroscopy, the composites were subjected to a microscopic examination using a Scanning Electron Microscope (SEM). FTIR and XRD verified the folding and unfolding of the polymer, in addition, the mechanical properties including tensile strength, bending stress, and impact behavior were investigated as well as the hardness test. The obtained results showed a significant improvement of about (40 %) in tensile strength, (53 %) in bending stress at 1 % wt. MWCNTs, and (70 %) percentage increment in the strength of Impact at 1.25 % wt. MWCNTs. And the gained hardness was about 40.5 HV which were compared with a reference substance named Carbon Fiber (CF) without any addition of nano materials. Carbon nanotubes have demonstrated their potential to enhance the mechanical properties of fiber-reinforced polymers, so this investigative study employs comprehensive characterization techniques, and demonstrates significant improvements in mechanical properties for the modified polymeric composite materials supported with nano materials.

In English

The possibilities to enhance the properties of nanostructured surfaces are evaluated on “polymer-multiwall carbon nanotube” composites. Influence of sp3 hybridization bonds is investigated in composites derived from polypropylene, polyamide-6, polyamide-12 and polyvinyl chloride after adding CNTs to polymers. IR absorption of “polymer-CNTs” films exceeds that of polymer by 10-103 times in the entire measured spectral range. In addition, two-polar IR absorption are measured on composites with negative components at spectral positions of “D-band” and “2D-band” of sp3 hybridization. In this case, the greater oscillation amplitudes of C-C, CH2 and CH3 bonds correspond to a higher absorption at the vibration frequencies γω(CН) and γω(CH2). Two-polar oscillations of absorption with a negative component in the spectral band ranges “D” and “2D” of sp3 hybridization in nanotubes have been measured for the composites. Frequencies of 2D-band correspond to the second order frequencies of D-band. The intensity of 2D band increases with an increase in the concentration of defects. The absorption of light increases when the frequencies of local oscillations of surface bonds in carbon nanotubes correspond to the frequencies of slotted modes along the boundary of the “nanotube polymer” (surface polaritons). Two-polar oscillations have an ultra-small half width 0.4–0.6 cm–1, which indicates a strong interaction of surface polaritons with photons. Vertically polarized light along carbon nanotubes and horizontally polarized light of D and 2D bands resulted in light beams splitting, two-photon interference and realization of the quantum Hong-Ou-Mandel effect.

In English

The possibilities to enhance the properties of nanostructured surfaces have been demonstrated on “polymer-multiwall carbon nanotubes” composites. Carbon nanotubes are among the most anisotropic materials known and have extremely high values of the Young modulus. Influence of sp 3 hybridization bonds on polymer crystallization and strengthening was investigated in composite films of polyethyleneimine, polyamide and polypropylene with multiwall carbon nanotubes. IR absorption maxima were measured after formation of composite “polyethyleneimine-carbon nanotubes” in the area of the sp 3 hybridization bonds at the frequency of primary amino groups of polyethyleneimine. High IR absorption at frequencies of sp 3 hybridization bonds of polypropylene, polyamide-6 with carbon nanotubes is determined by γ ω (CН) and γ ω (CH 2 ) vibrations as a result of the formation of C-C bonds in the polymer chains, which increases the crystallization of polymers and the strength of the composites. The IR absorption peak dependences on the carbon nanotube content at frequencies of sp 3 hybridization bonds are described by a 1D Gaussian curve for the diffusion equation in the electric field. Thus, the way to improve the strength properties of “polymer-CNTs” composites is the polymer crystallization as a result of the transformation of the C-C bonds in the polymer chains supported by the resonances of the primary amino groups, γ ω (CH) and γ ω (CH 2 ) in the electric field between the nanotubes and polymer matrix. Tensile strength for polyamide-6 composites at 0.25 % CNT increases 1.7 times and tensile deformation – 2.3 times.

Formation of carbon sp3 hybridization bonds in local electric fields of composites “polymer-CNT”

Carbon nanotubes are among the most anisotropic materials known and have extremely high values of Young's modulus. The possibilities to enhance the properties of nanostructured surfaces were demonstrated on “polymer-multiwall carbon nanotube” composites. Influence of sp < sup > 3 hybridization bonds on polymer crystallization and strengthening was investigated in composite films of polyethyleneimine, polypropylene and polyamide with multiwall carbon nanotubes. It was established that the effective way to enhance the strength properties of “polymer-multiwall carbon nanotube” composites is the composite crystallization and sp < sup > 3 C-C tetrahedrons organization between nanotubes supported by resonance γω(C?)? and γω(CH2) vibrations in the intrinsic electric field 6×10 3 V/cm between nanotube and polymer matrix. Tensile strength for polyamide-6 composites at 0.25% CNT increases 1.7 times and tensile deformation – 2.3 times.

Microwave flexible gas sensor based on polymer multi wall carbon nanotubes sensitive layer

This study presents the feasibility and the first real time results of microwave flexible gas sensor based on poly (3,4-ethylenedioxythiophene) polystyrene sulfonate – multi wall carbon nanotubes (PEDOT:PSS-MWCNTs) as sensitive material, deposited by inkjet printing technology. The sensor is suitable for wireless applications, it consists of two stub resonators on kapton in order to provide a differential detection. The final aim of this work is to develop a low cost communicating sensor which can be integrated into real time multi sensing platform dedicated to the applications requiring low power consumption and adaptable for the Internet of Things (IoT), in order to do the detection of harmful gases such as Volatile Organic Compounds (VOCs). Preliminary results have shown a large influence of ethanol concentration on the electrical properties of the passive resonators at radio-frequency range. These vapors have induced additional insertion losses and frequency shifts on the first resonant frequency mode around 0.65GHz. The sensor sensitivity to ethanol vapors exposition has been estimated to −642.9Hz/ppm and −7μdB/ppm for resonant frequency and insertion losses variations in differential mode, respectively, according to the values at 4min of exposure to 500, 1000 and 2000ppm. To deepen the study of the sensor, we have focused on the influence of ethanol on the conductivity of the sensitive layer, in terms of repeatability and sensitivity. We proposed a way of real-time reconstruction of the response by representing the difference of the insertion losses as well as the difference of frequencies calculated on the basis of the phase average value within a specified frequency range near the resonance. This lead to estimate a sensitivity of −9μdB/ppm and 648.1Hz/ppm, respectively, for ethanol concentrations ranging from 500ppm to 2000ppm at 10min of exposure.

Construction of a new electrochemical sensor based on molecular imprinting recognition sites on multiwall carbon nanotube surface for analysis of ceftazidime in real samples

In this paper a new electrochemical sensor based on molecularly imprinted polymer immobilized on multiwall carbon nanotube surface was introduced for determination of ceftazidime. The sensor was constructed via synthesis of a molecularly imprinted polymer on glassy carbon electrode which has been modified with carboxyl-functionalized multiwall carbon nanotubes. Then, for increasing the sensitivity of the sensor, Ag dendrites (AgDs) nanobranch was deposited on polymer electrochemically. The resulting imprinted polymer-multiwall carbon nanotube composite showed high sensitivity, excellent stability and good specific recognition behavior towards template molecule. The morphology of AgDs/MIP/c-MWCNT/GCE was investigated by field emission scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy in detail. Under the optimal experimental conditions, the current response of the imprinted sensor was linear to the concentration of ceftazidime in the range of 2–500 and 500–7000nM, with the limit of detection of 0.55nM (S/N=3). The proposed sensor has also been examined for recognition of ceftazidime quantitatively, in complicated matrices real samples.

Synthesis, spectroscopic and crystal structure of a new 2D coordination polymer of Ni(II) constructed by naphthalene-1,4-dicarboxylic acid; Nanomolar detection of fructose at a nano-structured Ni(II) coordination polymer multiwall carbon nanotube

One new 2D coordination polymer of Ni(II) namely [Ni2(ndc)2(DMSO)4(H2O)] n , where ndc = naphthalene-1,4-dicarboxylic acid and DMSO = dimethyl sulfoxide, has been synthesized and characterized by elemental analysis, spectral (IR, UV–Vis), thermal (TG/DTG) analysis and single-crystal X-ray diffraction. This coordination polymer possesses a 2D layer structure constructed from dinuclear nickel(II) building blocks in which two crystallographically independent Ni2+ ions are bridged by ndc2− ligands and water molecule. The ndc2− ligands adopt μ3 bridging modes, linking the metal centers into a two-dimensional coordination network. The two independent NiII cations are surrounded by dimethyl sulfoxide and naphthalene-1,4-dicarboxylate molecules in a distorted octahedron geometry. In the crystal structures of Ni(II) coordination polymer, there are non-classical hydrogen bonding arrangements and C–H∙∙∙π stacking interactions. Electrochemical behavior of [Ni2(ndc)2(DMSO)4(H2O)] n , (Ni-NDA) on the surface of carbon nanotubes (CNTs)/glassy carbon electrode (GCE) was described. The surface structure of the sensor was characterized by scanning electron microscopy (SEM). Oxidation of fructose on the surface of modified electrode was investigated with cyclic voltammetry and electrochemical impedance spectroscopy (EIS) and the results showed that the Ni-NDA/CNTs film displays excellent electrochemical catalytic activities toward fructose oxidation.

Flexible polymer-multiwall carbon nanotubes composite developed by in situ polymerization technique

Mechanically robust and flexible polymer-multiwall carbon nanotubes (MWCNT) composites are developed by in situ polymerization technique, where MWCNT are embedded in nontoxic, bio-compatible acryl amide-based polymer matrix. The addition of glycerol in the composite imparts required flexibility and a further addition of poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) shows significant improvements in tensile modulus, strength, and toughness compared to the polymer matrix. The composite is characterized by Scanning electron microscopy, Raman spectroscopy Attenuated total reflectance Fourier Transform infrared spectroscopy. At optimized conditions; the composite forms a heterojunction diode with n-Silicon having an electronic rectification ratio of 2.11 at ±1 V and a further addition of conducting polymer PEDOT: PSS in the composite enhances the electronic current rectification to 13.63 at ±1 V, with the turn on voltage of the device at 0.35 V. POLYM. COMPOS., 37:2860–2870, 2016. © 2015 Society of Plastics Engineers

Carboxylated or aminated polyaniline-multiwalled carbon nanotubes nanohybrids for immobilization of cellobiose dehydrogenase on gold electrodes.

Polymer-multiwalled carbon nanotube (MWCNT) nanohybrids, which differ in surface charge have been synthesized to study the bioelectrocatalysis of adsorbed cellobiose dehydrogenase (CDH) from Phanerochaete sordida on gold electrodes. To obtain negatively charged nanohybrids, poly(3-amino-4-methoxybenzoic acid-co-aniline) (P(AMB-A)) was covalently linked to the surface of MWCNTs while modification with p-phenylenediamine (PDA) converted the COOH-groups to positively charged amino groups. Fourier transform infrared spectroscopy (FTIR) measurements verified the p-phenylenediamine (PDA) modification of the polymer-CNT nanohybrids. The positively charged nanohybrid MWCNT-P(AMB-A)-PDA promoted direct electron transfer (DET) of CDH to the electrode and bioelectrocatalysis of lactose was observed. Amperometric measurements gave an electrochemical response with KMapp = 8.89 mM and a current density of 410 nA/cm2 (15 mM lactose). The catalytic response was tested at pH 3.5 and 4.5. Interference by ascorbic acid was not observed. The study proves that DET between the MWCNT-P(AMB-A)-PDA nanohybrids and CDH is efficient and allows the sensorial detection of lactose.

Removal of anionic azo dyes from aqueous solution using magnetic polymer multi-wall carbon nanotube nanocomposite as adsorbent

An adsorbent of magnetic polymer multi-wall carbon nanotube (MPMWCNT) nanocomposite was synthesized, which was composed of multi-wall carbon nanotubes, poly(1-glycidyl-3-methylimidazolium chloride) (ionic liquid-based polyether) and ferroferric oxide. The properties of MPMWCNT were investigated by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. The adsorptive capacity of MPMWCNT was examined using anionic azo dyes of orange II, sunset yellow FCF and amaranth as adsorbates. The effect of pH value was investigated and the adsorption kinetics and isotherms were also studied. It was found that a low pH value favors the adsorption of those anionic azo dyes and the adsorption kinetics and isotherms were well fitted by a pseudo second-order model and Langmuir model, respectively. The introduction of ionic liquid-based polyether and ferroferric oxide moieties into the multi-wall carbon nanotubes brings significant improvements in the adsorption and separation performance.

Photo-induced electron transfer in a pyrenylcarbazole containing polymer–multiwalled carbon nanotube composite

A polymer incorporated with a pyrenylcarbazole pendant poly(12-(3-(pyren-1-yl)-carbazol-9-yl)dodecyl methacrylate, denoted as PCP) was synthesized and applied in the functionalization of multi-walled carbon nanotubes (MWCNTs) by noncovalent π–π interaction. The PCP–MWCNT hybrids were isolated and characterized by SEM, TEM, and UV-visible absorption and emission spectroscopies. The strong interaction between PCP and the MWCNT in a 1,1,2,2-tetrachloroethane (TCE) solution was studied. It demonstrated an effective quenching effect on emission from PCP by the MWCNTs. DFT calculations showed electron delocalization between the pyrene and carbazole moieties. The LUMO of PCP is mainly located on the pyrene moiety while the LUMO + 1 is predominantly positioned on the carbazole moiety. Femtosecond transient absorption (TA) experiments determined the characteristic TA peaks of the excited states, which have contributions from both the pyrene and carbazole moieties. The excited state lifetime of the polymer PCP was measured to be 659 ps and the photo-excited electrons were injected into the MWCNTs very effectively on a time scale of 420 fs.

A highly electrically conductive polymer–multiwalled carbon nanotube nanocomposite membrane

Electrically conductive polymeric ultrafiltration membranes were fabricated by pressure filtering a thin layer of poly(vinyl alcohol) – cross-linked with carboxylated multiwalled carbon nanotubes (CNTs) and succinic acid – onto a support membrane. The effect of the degree of cross-linking and that of CNT concentration on the performance of these membranes was evaluated. These membranes demonstrated high pure water flux with good particle separation, high electrical conductivity, low polymer crystallinity, and low surface tensions. Membranes formed with 20 min cross-linking curing times and 20 w/% CNT concentration showed electrical resistivity as low as 2.8×10 −4 Ω m (conductivities as high as 3.6×10 3 S/m), pure water flux of 1440 L/m 2 h at pressures of 550 kPa, and triple-point initial contact angles as low as 40° with high hysteresis. ▸ Fabrication of a novel PVA–CNT–COOH self-supporting membrane. ▸ Membrane exhibits very high electrical conductivity as high as 3.6×10 3 S/m. ▸ Membranes show good UF properties including high flux and surface hydrophilicity. ▸ Water flux and MWCO can be tailored by altering CNT content and curing time.

Nanomechanical Properties of Teflon Amorphous Fluoropolymer -MWCNT Bilayer Films

ABSTRACTTeflon amorphous fluoropolymer (TAF) multi-walled carbon nanotube (MWCNT) suspensions have the potential for creating conductive coatings on insulating films for numerous applications. However, there are few studies on polymer MWCNT suspension properties and even fewer that use Teflon. To define mechanical and electrical property relationships, bilayer films of TAF-MWCNT were created with differing concentrations of MWCNTs. Nanoindentation revealed that addition of 8 wt% MWCNTs to TAF increased the elastic modulus by about 25% and hardness by about 15%. Conducting indentation showed 8 wt% MWCNT films exhibit uniform stable conductance once indentation depth exceeds several hundred nanometers. Films with lower concentrations of CNTs were insulating. The two techniques provide a unique description of structure property relationships in this suspension film system.

Properties of microinjection molding of polymer multiwalled carbon nanotube conducting composites

AbstractThe effects of processing conditions on the microstructure and properties of polypropylene/multiwalled carbon nanotube (PP/MWCNT) and polycarbonate/multiwalled carbon nanotube (PC/MWCNT) composites were studied. Samples of various MWCNT loadings were prepared by diluting commercial masterbatches. Different processing conditions were then used to systematically change the degree of nanotube alignment, from random to highly aligned. The crystallinity of the PP/MWCNT nanocomposites was found to go through a maximum as a function of nanotube content while the overall rate of crystallization increased. For the highly sheared microinjected PP/MWCNT samples well oriented crystals were formed. Electrical conductivity of the nanocomposites was improved by the presence of the crystalline structure; however, the high degree of nanotube alignment in the microparts resulted in a significant increase in the electrical percolation threshold. The PP nanocomposites exhibited mechanical properties significantly enhanced by nanotube loading; this effect was small in the case of the PC nanocomposites. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Molecularly imprinted-multiwall carbon nanotube paste electrode as a biosensor for voltammetric detection of rutin

A new molecularly imprinted polymer–multiwall carbon nanotube paste electrode (MIP–MWNPE) was prepared as a voltammetric sensor for rutin. The electrochemical behavior of rutin at the surface of the modified electrode was studied using cyclic voltammetry (CV) and square wave voltammetry (SWV). Under the optimized conditions, the oxidation peak current of rutin showed two linear dynamic ranges (0.08–1.4 μM and 2.0–160.0 μM) with a detection limit of 0.05 μM, using square wave voltammetric method. The RSD% for 5.0 and 10.0 μM determination of rutin were 2.7% and 2.9%, respectively. The kinetic parameters such as electron transfer coefficient (α) and charge transfer rate constant (ks/s−1) were also determined using the electrochemical approach. The modified electrode showed good sensitivity, special selectivity, and stability for rutin analysis. It was successfully applied for the determination of rutin in real samples such as urine and pharmaceutical formulation with satisfactory results.

Facile synthesis of novel Pt–Ru@PPy–MWNT electrocatalysts for direct methanol fuel cells

Pt–Ru@polymer–multiwall carbon nanotubes (MWNT) composites were successfully prepared as electrocatalysts by loading Pt–Ru nanoparticles onto the surface of polymer coated-MWNT. Polymers such as poly(β-caprolactone), poly(maleic anhydride), and poly(pyrrole). Polymer coating on the surface of MWNT was performed by in situ polymerization of the respective monomer in the presence of MWNT. Pt–Ru nanoparticles were deposited onto polymer–MWNT composite by the reduction of the metal ions (Pt 4+ and Ru 3+) using γ-irradiation. Thus, Pt–Ru@polymer–MWNT catalysts were obtained. The Pt–Ru@polymer–MWNT catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD) and elemental analysis for morphology, size and composition, respectively. The polymer was found to be coated to a thickness of 5–35 nm over the surface of MWNT. TEM images of the Pt–Ru@polymer–MWNT composite indicates that Pt–Ru alloy nanoparticles are more dispersed on the surface of polymer–MWNT composites as compared to the surface of pristine MWNT. The surface of polymer–MWNT is changed to hydrophilic as compared to the hydrophobic surface of pristine MWNT. The catalytic efficiency of Pt–Ru@polymer–MWNT catalyst was examined for the oxidation of carbon monoxide (CO) and methanol. The electrodes fabricated with Pt–Ru@PPy–MWNT and Pt–Ru@PMA–MWNT show enhanced activity for the electro-oxidation of methanol over the Pt–Ru@PCL–MWNT electrode. Also, results from stripping voltammetry for the adsorbed CO at Pt–Ru@polymer–MWNT catalyst electrodes inform that CO oxidation is energetically favorable at these electrodes. Thus, Pt–Ru@polymer–MWNT catalysts are suited for the electrode assembly in direct methanol fuel cells.

Electrical and Optical Properties of Conducting Poly(3-hexylthiophene)/Multi-walled Carbon Nanotube System

Polymer multi-wall carbon nanotube (MWNT) composites were prepared and characterized as part of an effort to develop polymeric materials with improved combinations of properties for potential use in solar cell applications. Multi-walled carbon nanotube (MWNT) poly(3-hexylthiophene) nanocomposites were synthesized by in situ polymerization of monomers in the presence of different amounts of MWNTs. A process is reported to efficiently disperse multi-walled carbon nanotube (MWNT) bundles in a semiconducting polymer matrix. A uniform dispersion of the nanotubes in the polymer matrix was obtained. Characterization of the nanocomposites and the effects of MWNT concentration and dispersion on the structural, optical and electrical properties were discussed. FTIR and Raman spectroscopic investigations of nanocomposites indicate that the polymer is wrapped on the nanotubes, taking up a rigid orientation through π-π stacking. The Hall voltage measurement is followed to monitor carrier concentrations and mobilities, instead of the device fabrication and hole mobility measurements.

High Performance Nanotube‐Reinforced Plastics: Understanding the Mechanism of Strength Increase

AbstractPolymer–multiwalled carbon nanotube composite films were fabricated using two types of polymer matrices, namely poly(vinyl alcohol), (PVA) and chlorinated polypropylene. In the first case, the PVA was observed to form a crystalline coating around the nanotubes, maximising interfacial stress transfer. In the second case the interface was engineered by covalently attaching chlorinated polypropylene chains to the nanotubes, again resulting in large stress transfer. Increases in Young's modulus, tensile strength, and toughness of × 3.7, × 4.3, and × 1.7, respectively were observed for the PVA‐based materials at less than 1 wt.‐% nanotubes. Similarily for the polypropylene‐based composites, increases in Young's modulus, tensile strength and toughness of × 3.1, × 3.9, and × 4.4, respectively, were observed at equivalent nanotube loading levels. In addition, a model to describe composite strength was derived. This model shows that the tensile strength increases in proportion to the thickness of the interface region. This suggests that composite strength can be optimized by maximising the thickness of the crystalline coating or the thickness of the interfacial volume partially occupied by functional groups.