Electrical and rheological properties of MWCNT/polycarbonate nanocomposites

The electrical and rheological percolation behaviors of polycarbonate/multiwall carbon nanotube nanocomposites were investigated. To determine the effects of surface functionalization on a carbon nanotube surface, poly(styrene-co-acrylonitrile) (SAN)-grafted multiwall carbon nanotubes were prepared using surface-initiated atom transfer radical polymerization. The amount of grafted SAN was controlled by changing the polymerization time and was characterized using TGA. FT-IR and TEM were used to characterize the surface of the functionalized carbon nanotubes. The rheological and electrical percolation behaviors of the SAN-grafted multiwall carbon nanotube/polycarbonate nanocomposites were compared to those of pristine multiwall carbon nanotubes, where the effects were shown to increase with increasing SAN content. The results are attributed to the compatibility of SAN with polycarbonates, which induced uniform dispersion of the functionalized carbon nanotubes. Uniform dispersion was also confirmed by evaluating a tensile-fractured nanocomposite specimen.     

Synthesis and characterization of multiwalled carbon nanotubes‐polymethyl methacrylate composites prepared by in situ polymerization method

Multiwalled carbon nanotubes‐polymethyl methacrylate composites (MWCNT‐PMMA) were prepared by an in situ polymerization method. The effect of nanotube content and their surface functionalization on the mechanical properties of the resulting nanocomposites was investigated. The use of only 1.8 wt% functionalized tubes improved flexural modulus by about 43% and flexural strength by about 60%. In situ polymerization using functionalized tubes improved interfacial bonding strength due to a chemical interaction between carbon nanotubes and the growing PMMA, which resulted in improved load transfer mechanism. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Polymeric nanocomposite films from functionalized vs suspended single-walled carbon nanotubes

The reported work was to demonstrate that the defect-derived photoluminescence in functionalized single-walled carbon nanotubes could be exploited in probing the dispersion of these nanotubes in polymeric nanocomposites because the luminescence emissions are sensitive to the degree of nanotube bundling and surface modification. The polyimide-SWNT nanocomposite thin films obtained from nanotubes with and without functionalization were compared. The spectroscopic results suggest that despite a similar visual appearance in the two kinds of films, the nanotube dispersion must be significantly better in the film with functionalized nanotubes, as reflected by the strong photoluminescence. In fact, the nanotubes embedded in polymer matrix that can be readily characterized by Raman spectroscopy are non-luminescent, while those that are difficult for Raman are strongly luminescent. Therefore, Raman and photoluminescence serve as complementary tools in the investigation of nanocomposites concerning the nanotube dispersion-related properties.     

Polyaniline–Carbon Nanotube Composites: Preparation Methods,Properties, and Applications

Synthesis of polyaniline and hybrid carbon nanotube reinforced polyaniline nanocomposites by various methods has discussed in this review. Different routes used for functionalization of carbon nanotube have been reported. The electrical, mechanical, and thermal properties of polyaniline/carbon nanotube nanocomposites are also discussed. The dispersion of functionalized carbon nanotube, filler concentration, and their alignment in the interior of polyaniline matrix affect their morphology. Furthermore, article focussed upon the various morphologies of polyaniline and polyaniline/carbon nanotube nanocomposites obtained with different methods along with electrical conductivity. Possible applications of polyaniline/carbon nanotube nanocomposites in the areas of actuators, sensors, electromagnetic interference shielding have also discussed.     

Double‐wall carbon nanotube‐reinforced polyester nanocomposites: Improved dispersion and mechanical properties

Double‐walled carbon nanotube (DWCNT)‐reinforced polyester nanocomposites were prepared and tested to characterize their mechanical properties. The DWCNTs were functionalized to improve their dispersion within the polyester matrix. The improvement in the mechanical properties shows that the functionalized DWCNTs have better distribution within, and good adhesion with, the polyester matrix. A comparison of the mechanical properties of nanocomposites reinforced by functionalized and nonfunctionalized DWCNTs confirms that the functionalization leads to substantially improved composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Covalent addition of diethyltoluenediamines onto carbon nanotubes for composite application

Diethyltoluenediamines (DETDA) was grafted to single‐walled carbon nanotubes (SWNTs) through diazonium‐based addition for improving dispersion and interfacial bonding in SWNT/epoxy nanocomposites. Characterization results of Fourier Transformed Infrared spectroscopy and Raman spectroscopy validated covalent bonding between DETDA and carbon nanotubes. The degree of functionalization was about 4% based on thermo‐gravimetric analysis. Interfacial bonding strength was computed in the presence of chemical bonding and the computation results indicated that the interfacial shear strength in the presence of functionalized carbon nanotubes was significantly enhanced. The experimental test revealed that the tensile strength of nanocomposites was enhanced about 23% and Young's modulus about 25%, with 0.5 wt% loading of functionalized‐nanotubes. These considerable improvements further verified the load‐transfer enhancement in the functionalized‐SWNTs/epoxy nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

聚异戊二烯/单壁碳纳米管复合材料的合成和性能研究

采用稀土催化剂利用原位聚合的方法,把聚异戊二烯接枝到单壁碳纳米管表面,制备了聚异戊二烯(PIp)/单壁碳纳米管(SWNT)复合材料。扫描电镜(SEM)被用来表征聚异戊二烯-接枝-SWNTs样品,显示相当均匀的聚合物出现在单个的或几束碳纳米管上。碳纳米管同聚异戊二烯的良好相容性提高了复合材料的玻璃化温度。大比表面积的碳纳米管和聚异戊二烯基质材料的较强的相互作用是聚异戊二烯纳米/碳纳米管复合材料具有独特性质原因。     

Flammability properties of polymer nanocomposites with single-walled carbon nanotubes: effects of nanotube dispersion and concentration

The effects of the dispersion and concentration of single walled carbon nanotube (SWNT) on the flammability of polymer/SWNT nanocomposites were investigated. The polymer matrix was poly (methyl methacrylate) (PMMA) and the SWNT were dispersed using a phase separation (‘coagulation’) method. Dispersion of SWNTs in these nanocomposites was characterized by optical microscopy on a micrometer scale. Flammability properties were measured with a cone calorimeter in air and a gasification device in a nitrogen atmosphere. In the case where the nanotubes were relatively well-dispersed, a nanotube containing network structured layer was formed without any major cracks or openings during the burning tests and covered the entire sample surface of the nanocomposite. However, nanocomposites having a poor nanotube dispersion or a low concentration of the nanotubes (0.2% by mass or less) formed numerous black discrete islands with vigorous bubbling occurring between these islands. Importantly, the peak heat release rate of the nanocomposite that formed the network layer is about a half of those, which formed the discrete islands. It is proposed that the formation of the discrete islands is due to localized accumulation of the nanotubes as a result of fluid convection accompanying bubble formation and rise of the bubbles to the surface through the molten sample layer and bursting of the bubbles at the surface. The network layer acts as a heat shield to slow the thermal degradation of PMMA.     

Amino functionalization of multiwalled carbon nanotubes by gamma ray irradiation and its epoxy composites

In this paper, γ‐ray radiation technique was utilized to simply functionalize multi‐walled carbon nanotube (MWCNT) with amino groups. The successful amino functionalization of MWCNTs (MWCNTs‐Am) was proven and the physicochemical properties of MWCNTs before and after radiation grafting modifications were characterized using FT‐IR, X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results indicated that the γ‐ray radiation had the visible effects on the surface properties of MWCNTs. The effects of various functionalized MWCNTs on morphological, thermal, and mechanical properties of an epoxy‐based nanocomposite system were investigated. Utilizing in situ polymerization, 1 wt% loading of MWCNT was used to prepare epoxy‐based nanocomposites. Compared to the neat epoxy system, nanocomposites prepared with MWCNT‐Am showed 13.0% increase in tensile strength, 20.0% increase in tensile modulus, and 24.1% increase in thermal decomposition temperature. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

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.     

Synthesis and properties of water soluble single‐walled carbon nanotube graft ionic polyacetylene nanocomposites

Water‐soluble single‐walled carbon nanotube‐polyacetylene [SWNT‐PA, SWNT‐P(2EPy‐MeTf)] nanocomposites have been synthesized by using the surface initiated “grafting‐from” method. The FT‐IR spectra confirmed the formation of an amide bond between the functionalized SWNTs and the initiator, 4‐(2‐Aminoethyl) pyridine, to polymerize N‐Methyl‐2‐ethynlypyridinium triflate (2EPy‐MeTf). UV‐vis spectroscopy indicated that the degree of polymerization of P(2EPy‐MeTf) in the SWNT‐polyacetylene composites is 15, based on the Lewis‐Calvin equation. The SWNT‐polyacetylene composites have been characterized by TGA, AFM, and TEM. From TGA analysis, the loading of SWNTs in the SWNT grafted ionic polyacetylenes is estimated to be 22%. AFM and TEM images clearly showed that the nanotube is wrapped with the PA. The SWNT‐polyacetylene composites displayed high water solubility (8 mg/ml). The room temperature electrical conductivity of the doped SWNT‐polyacetylene composites was found to be in the range of 10⁻³ to 10⁻⁴ S/cm, an order of magnitude of increase over neat P(2EPy‐MeTf) and a two order of magnitude increase over Dendrimer‐polyacetylen composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Crystallization behavior of nylon 11/montmorillonite nanocomposites under annealing

Exfoliated nylon 11/montmorillonite (MMT) nanocomposites were prepared via in situ polymerization by the dispersion of organically modified MMT in 11‐aminoundecanoic acid monomer. The polymorphic behavior of the nylon 11/MMT nanocomposites was investigated with X‐ray diffraction, transmission electron microscopy, and Fourier transform infrared with attenuated total reflectance. MMT induced and stabilized the δ‐crystalline form of nylon 11. The crystal structure of nylon 11 was transformed from a hexagonal δ‐form structure to a triclinic α‐form structure during the annealing process. Meanwhile, the hydrogen bonds in the nanocomposites also exhibited some differences from neat nylon 11 after annealing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5483–5489, 2006     

Non-isothermal crystallization of in situ polymerized poly(ε-caprolactone) functionalized-SWNT nanocomposites

The non-isothermal crystallization behavior of three in situ polymerized, partially tethered poly(ε-caprolactone) with functionalized single walled carbon nanotube (SWNT) nanocomposites are examined using differential scanning calorimetry and corroborated using small and wide angle X-ray scattering. While the nanotubes are strong nucleators of the crystals of poly(ε-caprolactone) and dramatically accelerate the crystallization of the polymer, they do not alter the unit-cell, the melting temperature and the fractional crystallinity of the polymer crystals.     

Electrical conductivity and oxygen permeability of polyacrylonitrile/multiwalled carbon nanotubes composites

Polyacrylonitrile (PAN)/Multiwalled carbon nanotube (MWCNT) nanocomposites were prepared by nonconventional ultrasonic‐assisted emulsifier free emulsion polymerization technique with variable percentage of functionalized carbon nanotube. PAN/MWCNT nanocomposites were characterized by ultraviolet‐visible (UV‐visible) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The result from UV‐visible suggested that the functionalized MWCNT had interfacial interaction with PAN matrices. The surface morphology of functionalized MWCNT and PAN/MWCNT nanocomposites were studied by scanning electron microscopy (SEM). Electrical properties of PAN/MWCNT nanocomposites were measured and the result indicated that the conductivity increased with increasing concentration of MWCNTs. The oxygen permeability of PAN/MWCNT nanocomposites gradually increased with increase of MWCNT concentration, the result which was in agreement with the vertical alignment ofMWCNT in SEM. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Polyaniline / carbon nanotube composites: starting with phenylamino functionalized carbon nanotubes

Summary Composites of carbon a nanotube with polymers are a developing and interesting area of research. The dispersion of the nanotube in polymer matrices is an important factor while making its nanocomposites. Even though in-situ polymerization approach offers a better approach for synthesizing homogeneous polymer nanotube composites, the dispersion of the nanotubes in the monomer solution is a problem. In this article we report a new chemical method for dispersing nanotubes in monomer and the preparation of uniform tubular composite of polyaniline (PANI) and multiwalled carbon nanotube (MWNT). For this the oxidized multiwalled nanotube (o-MWNT) was functionalized with p-phenylenediamine, which gave phenylamine functional groups on the surface. This functionalization helped to disperse the nanotubes in acidic solution. The in-situ polymerization of aniline in the presence of these well dispersed nanotubes gave a new tubular composite of carbon nanotube having an ordered uniform encapsulation of doped polyaniline. The phenylamine functional groups on the surface were grown into polyaniline chain so that the composite contains polyaniline functionalized CNT and they were no more an impurity in the final nanocomposite. The microscopic and structural properties of this composite were compared with that of a composite prepared under identical condition using o-MWNT.     

Microstructure and mechanical properties of carbon nanotube reinforced cementitious composites developed using a novel dispersion technique

The present paper reports the first attempt of developing carbon nanotube (CNT) reinforced cement composites through a short dispersion route using Pluronic F-127 as a novel dispersing agent. Optimum concentrations of Pluronic for various types of CNT were determined, and the influences of Pluronic and CNT on the microstructure and mechanical properties of cementitious composites were thoroughly investigated. Pluronic with optimized defoamer concentration significantly improved the bulk density and mechanical properties of cement mortar. Further, dispersion of 0.1% single walled nanotube (SWNT) improved flexural modulus of mortar by 72% and flexural and compressive strengths by 7% and 19%, respectively after 28 days of hydration. Flexural and compressive strengths with functionalized SWNT increased with the hydration period up to 17% and 23% after 56 days, respectively. All CNT reinforced samples exhibited significantly higher stiffness, fracture energy and ductility as compared to plain mortar and composite samples prepared using a common surfactant.     

Synthesis of pyrene‐capped polystyrene for dispersion of pristine single‐walled carbon nanotubes

Pyrene‐capped polystyrene (PyPS) with various molecular weights (M?_n) was synthesized through the anionic polymerization method and characterized using UV, Fourier transform infrared and NMR spectroscopy and gel permeation chromatography. The polymers were then used for non‐covalent functionalization of pristine single‐walled carbon nanotubes (SWNTs). The functionalization efficiency was assessed by measuring the SWNT dispersibility in chloroform. In the presence of PyPS, the dispersibility can be as high as 372.5 mg L^?1, and the dispersions containing more than 1.25 mg mL^?1 of PyPS are very stable with no solid deposits observed after being centrifuged at 5000 rpm for 15 min. Once the PyPS concentration is converted to the molar concentration of the pyrene unit and the dispersibility redefined as nanotube content per molar pyrene unit, the renewed dispersibility is found to be independent of M?_n of PyPS within the detected M?_n range. For a certain PyPS polymer, however, both nanotube dispersibility and dispersion stability are strongly dependent on the PyPS concentration. These results suggest that PyPS may be used as an excellent dispersant for subsequent preparation of polystyrene/SWNT composites. Copyright © 2011 Society of Chemical Industry     

Functionalized Multi-Walled Carbon Nanotubes with Vitamin C Structures: Characterization and Fabrication of Thiazole Containing Poly(amide–imide)-based Composites

The functionalization of multi-walled carbon nanotubes by ascorbic acid (vitamin C) was carried out. Then, functionalized multi-walled carbon nanotubes were dispersed throughout a poly(amide–imide) matrix by ex situ technique with 5, 10, and 15% loading by weight. The composite hybrid films were prepared by a solvent casting method. It was found that the functionalization of multi-walled carbon nanotubes could improve their dispersion and interfacial adhesion to the poly(amide–imide) matrix as proved by field emission scanning and transmission electron microscopy techniques. The modulus, tensile strength, and the thermal stability of the composites were improved in spite of excellent multi-walled carbon nanotube dispersion in the matrix.     

In situ polymerization of polyamide 66 nanocomposites utilizing interfacial polycondensation. III. Co‐synthesis of silica nanocomposites via sol–gel chemistry

In situ co‐synthesis of nylon 66 (PA66)‐silica nanocomposites can be accomplished through sol–gel chemistry conducted simultaneously with the nylon polymerization. Unfunctionalized silica nanocomposites and bonded silica nanocomposites wherein the inorganic silica phase chemically couples to the nylon polymer through a functionalized silane are generated via the simultaneous initiation of synthesis reactions in the inorganic and organic species. The effects of agitation and water‐to‐silane molar ratio on the courses of the inorganic and organic reactions and the generated silica morphology in the resulting nanocomposites are investigated using the tools of Brookfield Viscometer, Fourier transform infrared spectroscopy, and transmission electron microscopy. Dynamic mechanical analysis confirms the mechanical reinforcement of the various nanocomposites in relation to their silica content and network morphology. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Effect of modified single‐wall carbon nanotubes on mechanical and morphological properties of thermoplastic elastomer nanocomposites based on (polyamide 6)/(acrylonitrile butadiene rubber)

Thermoplastic elastomer nanocomposites based on acrylonitrile butadiene rubber (NBR) and polyamide 6 (PA6), with acid functionalized single‐wall carbon nanotubes (SWNT), were prepared via a direct melt‐mixing process in an internal mixer. The influence of SWNT content (0, 0.5, 1, 1.5) on morphological properties of PA6/NBR with different ratios (80/20, 70/30, 60/40) were then investigated. Characterization of nanocomposites was conducted by using transmission electron microscopy, scanning electron microscopy, differential scanning calorimetry, and mechanical properties. Scanning electron microscopy micrographs proved the droplet‐matrix blend morphology in which the size of NBR droplets decreased as the SWNT loading increased, suggesting dispersion of SWNT in the PA6 phase. It was further proved by transmission electron microscopy images, showing homogenous dispersion of SWNT in the PA6 phase. Differential scanning calorimetry results showed a slightly reduced percentage of crystallinity in samples containing SWNT. The mechanical properties of nanocomposites indicated an enhancement in tensile strength, modulus, and hardness on increasing SWNT content. J. VINYL ADDIT. TECHNOL., 22:336–341, 2016. © 2014 Society of Plastics Engineers