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The interface between nanofillers and elastomers is one of the most important factors to determine the performance of elastomer nanocomposites. In this study, for the first time, we developed a method to quantitatively characterize the interfacial layer thickness of carbon nanotubes (CNTs)/Natural rubber (NR) composites by using peak force quantitative nanomechanical mapping (PF-QNM) technique of atomic force microscopy (AFM). We obtained the modulus and adhesion distribution of the composites, and selected those CNTs close to the sample surface, where the CNTs show lower adhesion for the accurate characterization of the interfacial thickness. Then, we characterized the thickness of interfacial layer according to the gradient change in Young’s modulus. The results show that the average interfacial thickness of CNTs/NR composites is about 9 nm, similar with that in carbon black (CB)/elastomer composite (10 nm) reported in previous study, indicating the good interfacial interaction between CNTs and NR matrix. The average interfacial thickness of the modified CNTs/NR composites is about 17.4 nm, indicating the stronger interfacial interaction. The “Payne effect” and mechanical properties of these nanocomposites were also examined, and the results were consistent well with the AFM PF-QNM results. This study provides a new method to quantitative characterize the interface between filler and elastomer matrix at nanoscale resolution. [ABSTRACT FROM AUTHOR]

We prepared hydrogenated butadiene-acrylonitrile (HNBR) elastomer composites with random orientations of carbon nanotubes (CNTs) and aligned CNTs, denoted by random composites and aligned composites, respectively, by means of a simple mechanical blending method. The CNTs were dispersed uniformly in the HNBR matrix in both types of composites. Interestingly, at CNT contents of 1-2.5 vol%, the dielectric loss (tan δ) of the aligned composites increases slightly, and the dielectric constant ( ε′) of aligned composites increases largely with the increasing content of CNTs, whereas both the tan δ and the ε′ of the random composites increase largely with the increasing content of CNTs. As a result, a high ε′ (5000 at 1000 Hz) and a low tan δ (0.42 at 1000 Hz) were obtained in the aligned composite with a CNT content of 2.5 vol%, whereas a high ε′ and a high tan δ were obtained in the random composites. The relationship between the microstructure and dielectric properties was qualitatively analyzed by means of the percolation theory and intercluster polarization model. The mechanism for the achievement of high ε′ and low tan δ for dielectric composites was discussed. This study provides a guide to design microstructure that yields composites with improved dielectric properties. [ABSTRACT FROM AUTHOR]

Previous studies using molecular simulation indicated that carbon nanotubes (CNTs) can act as nanosprings to adjust the viscoelasticity of elastomer composites. In this study, we prepared elastomer composites with both high elasticity and conductivity for the first time using carbon nanotubes array (CNTA) as nanosprings. A special CNTA bundle prepared by electrostatic self-assembly was directly blended with the polymethylvinylsiloxane (PMVS) matrix. The results indicated that these CNTAs were well dissociated into many single CNTs with almost no change in length in the PMVS matrix with low viscosity during mechanical shearing, and exhibited a nanospring effect. The CNTA composites exhibited not only higher conductivity and electromagnetic shielding effectiveness but also higher elasticity than the commonly used conductive carbon black composites at the same filler content. This study indicated that high performance conductive elastomer composites can be obtained by using special CNTAs as nanosprings. [ABSTRACT FROM AUTHOR]

In this study, the early stage of interfacial crystallisation behaviour of low molecular weight polyethylene (PE) and isotactic polypropylene (iPP) oligomer on the surface of carbon nanotubes (CNTs) with different diameters, chiralities and topography structures was studied using MD simulations. We started to simulate the effect of CNTs chirality and diameter on PE molecular chain orientation, and then the effect of CNTs topography structure on PE and iPP molecular chain orientation was investigated. Finally, some experiments were carried out to prove the simulated results. Our study shows that for CNTs with a diameter comparable with the radius of gyration (Rg) of a polymer chain, an easy orientation of PE chains along CNTs axis is observed for all the systems of the CNTs with different chiralities due to a geometric confinement effect. For CNTs with a much larger diameter, multiple orientation of PE chains is induced on its surface due to the lattice matching between graphite lattice and PE molecular chains. In this case, the chirality of CNTs dominates the orientation of graphite lattice, which determines the orientation of PE chains arrangement on CNTs surface. More importantly, it was found that the groove structure formed by CNT bundles is very useful for the stabilisation of polymer chain, and thus facilitates the orientation of molecular chain along the long axis of CNTs. As a result, a novel nanohybrid shish–kebab (NHSK) structure with CNTs acting as central shish while polymer lamellae as kebab can be successfully obtained for both PE with zigzag conformation and iPP with helical conformation. This simulation result was well supported by the experimental observation. Our study could provide not only a deep understanding of the origin of the polymer chain orientation on CNTs surface but also the guidance for the preparation of polymer/CNTs nanocomposites with novel NHSK structure. [ABSTRACT FROM PUBLISHER]

Nanohybrid shish kebab (NHSK) structure, in which fibrous carbon nanotubes (CNTs) act as shish, while polymer lamellae as kebab, is of particular interest both scientifically and technologically. In this work, two types of CNTs with the same diameter range and different topography structure, namely multiwalled carbon nanotubes (MWNTs) with a relatively smooth surface and double-walled carbon nanotubes (DWNTs) bundles with a groove structure, were used to induce polyethylene (PE) crystallization for the formation of NHSK. For PE/MWNTs system, NHSK was formed only at a relatively low crystallization temperature (Tc), and PE lamellae are not completely perpendicular to the long axis of MWNTs. However, for PE/DWNTs bundles system, NHSK could be obtained even at a much higher Tc, and almost all the PE lamellae are perpendicular to CNTs long axis, due to the unique "groove structure" formed by DWNTs bundles. The enhanced nucleation ability and the facilitated lamellae orientation by using DWNTs bundles are not only of great crystallography interest but also are very important for functional design in nanodevice applications. [ABSTRACT FROM AUTHOR]

In our previous work, the formation of a nanohybrid shish kebab (NHSK) structure was successfully achieved in helical polymer systems promoted by using single-walled carbon nanotube (CNT) bundles with a unique 'groove structure', which is of great crystallographic interest. To further investigate the effect of surface groove structure of CNT bundles on the formation of NHSK structure in helical polymer systems, in the work reported here double-walled carbon nanotube (DWNT) fibers with bundle structure were used as nucleating agents and orientation templates for poly( L-lactide) (PLLA) crystallization. A fine NHSK structure with controlled lateral size and period of kebabs was successfully obtained under various experimental conditions by using DWNT bundles. This could be due to the geometric confinement effect of the surface groove structure of the DWNT bundles, which could facilitate the orientation of PLLA chains along the DWNT axis and the lateral formation of a stable nucleus. Our work suggests an efficient method for the functionalization of CNTs with biocompatible PLLA, which may have some potential applications in biomedical areas. In addition, it is demonstrated that the formation of NHSK structure can effectively improve the physical bonding between PLLA and nanotubes, thus significantly improving the mechanical properties of PLLA/CNT nanocomposite fibers. Copyright © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Dielectric elastomer (DE) composites have attracted much attention owing to their potential applications such as flexible electronics, energy storage, artificial muscles and sensors. The underlying mechanism to improve the electromechanical performance of DE is believed to be the interfacial polarization between fillers and matrix. Thus, understanding the interfacial polarization mechanism is a key to design and produce high performance DE composites. Despite of extensive works on studying the effect of fillers on interfacial polarization, the role of molecular polarity of matrix is still lacking. Thus, in this study, we prepared three kinds of carbon nanotubes (CNTs)/hydrogenated nitrile butadiene rubber (HNBR) DE composites with different molecular polarity of HNBR as the matrices and a special kind of aligned CNTs as the high dielectric constant (ε′) fillers to study the role of molecular polarity of HNBR on interfacial polarization and dielectric properties of the composites. These composites exhibit the similar dispersion and filler network of CNTs in matrices, which is a precondition of this study. Interestingly, at the same content of CNTs (higher than the percolation threshold), the ε′ of these composites largely increases with the enhancement of the molecular polarity of HNBR, whereas the ε′ of these pure HNBR matrices is very close. An equivalent circuit was then established to quantitatively analyze the interfacial polarization mechanism, and it fits well with the experiment data. This study demonstrates for the first time that the higher molecular polarity of matrix leads to the stronger interfacial polarization and thus results in higher ε′ of the composites. [ABSTRACT FROM AUTHOR]

To solve the poor interface between aramid fiber and rubber, this paper studies a method of constructing nanostructures on the fiber surface. First, functional groups such as hydroxyl and amino groups were introduced onto aramid fiber through the Michael addition of tannic acid and polyethyleneimine. Then, the modified aramid fiber was impregnated in the aramid nanofiber/carbon nanotube aqueous dispersion to prepare a surface-coated fiber. The fibers and surface nanostructures were characterized by scanning electron microscopy, transmission electron microscope, Raman spectroscopy, X-ray photoelectron spectroscopy, thermalgravimetric analysis, and H pull-out tests in detail. The results show that the H pull-out force of the coated fiber is increased by 126.4% compared with the original aramid fiber, which is due to the good mechanical interlocking at the interface of the composites. In addition, carbon nanotubes could form a conductive path through mutual entanglement and overlap on the surface of aramid fiber, which also gives the function of real-time monitoring of deformation of the composites. [Display omitted] [ABSTRACT FROM AUTHOR]