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Nanotubes

Ultem 1000 polyether-imide was mixed with three different carbon-based nanofillers in an attempt to increase thermal conductivity(TC) of the polymer. After initial mixing, the nanocomposites were extruded or processed via the Laboratory Mixing Molder process. High-resolution SEM revealed significant alignment of the nanofillers in the extruded samples. TC measurements were made both along and perpendicular to the direction of alignment of nanofillers as well as for unaligned samples. It was found that the largest improvement in TC was achieved in the case of aligned samples when the measurement was performed in the direction of alignment. Unaligned samples also showed a significant improvement in TC and could be useful in applications when it was not possible to align the nanofiller. Modification of multiwalled carbon nanotubes(MWCNTs) led to double the TC value compared with the composite containing unmodified MWCNTs. The improvements in TC did not, however, approach those expected on the basis of a rule of mixtures. This was probably due to poor phonon transfer through the matrix. 36 refs.

Nanocomposites of single walled or multiwall carbon nanotubes (5 wt%) with styrene-vinyl phenol copolymers (with vinyl phenol contents of 0, 10, 20, 30 and 40%) were prepared. Electrical conductivity and tensile tests indicated that the copolymer containing 20% vinyl phenol had the optimum dispersion of carbon nanotubes. FTIR results indicated that hydrogen bonding interactions occurred between the carbon nanotubes and the polymers and this interaction was greatest for the copolymer which contained 20% vinyl phenol. 11 refs.

Nanocomposites were fabricated from an unsaturated polyester resin and carbon nanotubes (vapour grown carbon fibres and vapour grown nanofibres) and their electrical conductivities and percolation behaviour investigated both experimentally and theoretically. The electrical conductivity of the nanocomposites was examined as a function of carbon nanotube volume fraction and the influence of aspect ratio and nanotube orientation on critical concentration in the percolating systems analysed using the excluded volume approach and Monte carlo simulations. 16 refs.

Single walled carbon nanotubes with good optical and electrochemical properties were solubilised in a polyimide and cast films and guided wave mode thin films fabricated therefrom. Absorption spectra and time-resolved bleaching spectra were obtained for these films and the photoresponsive behaviour of the films examined. 20 refs. (Polychar-14, World Forum on Advanced Materials, Nara City, Japan, April 17-21, 2006)

A review is presented on advances in carbon nanotube-reinforced polymer composites. Aspects covered include mechanical properties of the nanotubes, methods of composite manufacture, applications of in-situ polymerisation, electrospinning and layer-by-layer self-assembly. 36 refs.

Brief details are given of curing processes in carbon nanotube-reinforced epoxy resins to examine the formulation, characterisation and optimisation in the fabrication of the nanocomposite materials. Thermal characterisation, including thermal degradation and TG, was performed using DSC. 12 refs.

Details are given of the preparation of PETP/multi-walled carbon nanotube composites by in-situ polymerisation. The purification and functionalisation of the multi-walled carbon nanotubes were carried out to improve dispersion. The reaction between PETP and functionalised multi-walled carbon nanotubes was confirmed by examining rheological properties and SEM. Initial modulus and tensile strength of the composite films were measured. 12 refs.

Polylactic acids with various molecular weights were synthesised and reacted with -COCl groups, which had been introduced to carbon nanotubes using the grafting to technique. The morphology of the resulting carbon nanotubes was examined using TEM and SEM. Characterisation was also undertaken using GPC and TGA. 3 refs.

Details are given of the preparation of polyaminobenzoic acid grafted multi-walled carbon nanotubes via a Friedel-Crafts reaction. Surface and internal morphology of the carbon nanotubes was observed using SEM and TEM. FTIR and TGA were used to provide additional evidence of covalent bond between polyaminobenzoic acid and multi-walled carbon nanotubes and the contents of polymer in the product. 12 refs.

Single walled carbon nanotube was functionalised with pyrene derivatives grafted with linear alkyl chains of various length. The dielectric behaviour of the nanocomposite film of single walled carbon nanotube functionalised with pyrene derivative and epoxy resin in terms of the nanotube passivation is reported. Characterisation was undertaken using atomic force microscopy, TEM, FTIR, Raman spectroscopy, UV vis spectroscopy and dielectric measurements. 17 refs.

Use of polymer single crystals, called nano hybrid shish kebabs (NHSK) and based on either polyethylene or polyamide-6,6, for patterning the surface of carbon nanotubes with platinum or polypyrrole is described. Crystals were laid down from solution, and were visualised using field emission scanning electron microscopy. The NHSK decorate the carbon nanotube in a periodic fashion and are consistent in size. Potential modification of electron transport properties of the carbon nanotube was suggested. 6 refs.

Development of the interphase layer model as a continuum media with local cohesion and adhesion effects is described. The kinematics of continuum media, the formulation of governing equations and the statement of boundary conditions for multi-scale modelling of composite materials are discussed, and the prediction of mechanical properties of a polymeric matrix reinforced with nanoparticles, nanofibres or (carbon) nanotubes as a function of their size and dispersion is presented. 41 refs.

Iron(III) 1,4-bis(2-ethylhexyl)sulphosuccinate (AOT) was prepared by the reaction of ferric chloride with sodium AOT and fabricated into fibres by manual drawing and electrospinning. Long fibres of polypyrrole (PPy) were prepared by vapour deposition of pyrrole onto the FeAOT fibres. This technique was extended to the synthesis of composite fibres of PPy and multiwalled carbon nanotubes (MWCNT). The PPy and PPy/MWCNT fibres showed a nanoporous morphology, a conductivity of 10 -1 5 S/cm, and tensile strengths of 12-43 MPa. 28 refs.

Nanocomposites of poly(ethylene terephthalate) (PET) reinforced with multiwall carbon nanotubes (MWCNTs) were prepared by melt compounding in a twin-screw extruder. The MWCNTs acted as nucleating agents, enhancing the crystallisation of PET by heterogeneous nucleation. The incorporation of a small quantity of MWCNTs improved the thermal stability of the PET/MWCNT nanocomposites. The mechanical properties of the PET/MWCNT nanocomposites improved even in the presence of small amounts of MWCNTs and the rheological properties of the nanocomposites showed a significant dependence on the MWCNT. Loading with MWCNTs intensified the shear-thinning behaviour of the molten nanocomposites. The storage modulus and loss modulus of the PET/MWCNT nanocomposites increased with increasing frequency, and this increment was more pronounced at lower frequencies. At higher MWCNT contents, dominant nanotube-nanotube interactions led to the formation of interconnected or network-like structures of MWCNTs in the nanocomposites. 21 refs.

Multiwalled carbon nanotube/epoxy composites are prepared and the thermal, electrical and morphological properties characterised. Most of the nanotubes are found to be well dispersed although some aggregation is observed. Electrical properties, Tg and dielectric constant all increase with the formation of composites. However, the effects on thermal conductivity and thermal expansion are insignificant. 44 refs.

Multiwalled carbon nanotubes (MWCNT) were grafted with polystyrene by in situ nitroxide mediated radical polymerisation in the presence of TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyl) functionalised MWCNT, which was synthesised by the reaction between 4-hydroxyl-TEMPO (HO-TEMPO) and carbonyl chloride groups on the MWCNT. Although the controllability of the polymerisation was not high, highly soluble grafted MWCNTs were indeed obtained, indicating that the graft polymerisation was efficient. The resulting polystyrene grafted MWCNTs were easily defunctionalised at room temperature using 3-chloroperoxybenzioc acid. TEM, SEM, and TGA were employed to determine the structure, morphology, and the grafting quantities of the resulting products. 41 refs.

In this letter, the sandwich-like single-walled carbon nanotube (SWNT) paper/polyetheretherketone (PEEK) composites were successfully prepared by using a hot-compress method. Based on SEM observation, it was found that the PEEK macromolecules could diffuse into the voids of SWNT paper and were able to form very good bonding to the nanotube bundles, which ensure effective stress transfer between two phases. Some typical problems in preparing conventional carbon nanotube/polymer composites, e.g. the difficulty to obtain well-dispersed high-loading nanotubes into polymer matrices, were successfully overcome. Moreover, the compact networks of SWNTs were not destroyed at the appropriate processing condition. Correspondingly, the resulting composite (with one layer of SWNT paper) exhibited about 40% increased in Young's modulus and 4% enhanced in failure strength when comparing with that of neat PEEK, respectively. According to rule-of-mixtures of the special sandwich-like structure, the estimated Young's modulus can reach up to about 8GPa, which was nearly three times of that of neat matrix. Moreover, the surface electric conductivity and thermal conductivity of the PEEK films were also increased after the addition of SWNT paper. The preliminary results suggest that the SWNT paper has great potential for being used to reinforce polymers. 18 refs.

This paper investigates some mechanical and rheological properties of low density polyethylene (LDPE) composites reinforced by multi-walled carbon nanotubes (MWNTs). It was found that the Young's modulus and tensile strength of the composites can increase by 89% and 56%, respectively, when the nanotube loading reaches 10wt%. The curving and coiling of MWNTs play an important role in the enhancement of the composite modulus. It was also found that the materials experience a fluid-solid transition at the composition of 4.8wt%, beyond which a continuous MWNT network forms throughout the matrix and in turn promotes the reinforcement of the MWNTs. 45 refs.

Spurred by the discovery of carbon nanotubes in 1991 and the subsequent nanotechnology revolution, there has been a marked increase in the volume of scientific and engineering literature dealing with various aspects of the vibratory behaviour of carbon nanotubes and their composites in the last few years. This paper is an attempt to present a coherent yet concise review of as many of these publications as possible. The major topics covered in this review are modelling and simulation of vibrating nanotubes, studies of nanomechanical resonators and oscillators, the use of vibration measurements to characterize nanotube mechanical properties, nanotube augmentation of dynamic structural properties of composites, vibrations of nanotube-based sensors and actuators, sonication of nanotube-reinforced polymer resins, Raman scattering from nanotubes, and high frequency wave-nanotube interactions. Summaries of both theoretical and experimental studies are included, along with key conclusions and recommendations from these studies. 246 refs. Copyright (c) 2006 Elsevier Ltd.

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