RbstractThis review provides valuable information about the general characteristics, processing conditions and physical properties of carbon nanotube buckypaper (BP) and its polymer composites. Vacuum filtration is the most common technique used for manufacturing BP, since the carbon nanotubes are dispersed in aqueous solution with the aid of surfactant. Previous works have reported that mechanical properties of BP prepared by vacuum filtration technique are relatively weak. On the other hand, the incorporation of polymer materials in those nanostructures revealed a significant improvement in their mechanical behavior, since the impregnation between matrix and BP is optimized. Electrical conductivity of BP/polymer composites can reach values as high as 2000 S/m, which are several orders of magnitude greater than traditional CNT/polymer composites. Also, BP can improve remarkably the thermal stability of polymer matrices, opening new perspectives to use this material in fire retardant applications.

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The non-isothermal thermogravimetric methods have been used extensively for the determination of kinetic parameters in polymers. The poly (ether ketones) are used as matrix in advanced high performance composites due its high thermal stability, excellent environmental performance and superior mechanical properties. In this work, the non-isothermal decomposition kinetics of the polymer poly (ether ether ketone) (PEEK) was evaluated in nitrogen and synthetic air atmospheres, using the Flynn-Wall-Ozawa and Coats Redfern models. The results showed that the necessary time for the material decomposes in 5% is approximately 216 years if it is submitted to temperatures of 350 °C in nitrogen atmosphere. On the other hand, if the material is submitted to air atmosphere, this decomposition time drops to about 1,05 years in the same temperature and for the same conversion rate. The decomposition kinetics study by Coats Redfern showed that the D3 mechanism (three-dimensional diffusion (Jander equation)) had better adjustment to the decomposition kinetics of the material in nitrogen atmosphere, while in synthetic air the R1 mechanism (phase boundary controlled reaction (one-dimensional movement)) has better adjustment to the decomposition kinetics of the material.

Polyacrylonitrile (PAN) was solubilized in N,N-dimethyl formamide (DMF) and the electrospinning process has been employed to obtain PAN nanofibers (PF). Multiwalled carbon nanotubes (MWCNT) were dispersed with the aid of Triton X-100 surfactant and subsequently centrifugated. Buckypapers (BP/PF) were prepared by vacuum filtration procedure of MWCNT suspension supernatant stacking four PF layers over a nylon membrane. The PF removal was carried out by immersing the BP/PF system in DMF and removal periods of 10 and 30 min were evaluated. Scanning electron microscopy (SEM) has not shown any PAN residue in the MWCNT network resulting in highly porous BP. However, by Fourier transform infrared spectroscopy (FT-IR) a PAN band was found around of 2243 cm−1 corresponding to nitrile group (C≡N). Besides, PAN leftover was evidenced by thermogravimetric analysis (TGA), high-resolution transmission electron microscopy (HR-TEM), electrical characterization through four-point probe, nitrogen adsorption at 77 K, and X-ray diffraction (XRD).

Polycarbonate (PC)/acrylonitrile‐butadiene‐styrene copolymer (ABS) blend‐based multi‐wall carbon nanotubes (MWCNT) nanocomposites is an attractive alternative for the manufacture of electronics housing as it can have the mechanical and electromagnetic properties required for this application. The preferred location of MWCNT in PC/ABS blend is an important parameter to obtain better mechanical and electromagnetic properties. In this way, three different blending protocols (BP) were used to obtain PC/ABS/maleic anhydride‐grafted ABS (ABS‐g‐MAH) (85/10/5) blend‐based MWCNT nanocomposites with the addition of 0.5 and 1 wt% of MWCNT in a twin‐screw extruder. Specimens were evaluated by thermal (thermogravimetric analysis—TGA and differential scanning calorimetry—DSC), mechanical (Izod impact strength and tensile tests), dynamic mechanical analysis (DMA), electrical, and rheological properties, which were correlated with the nanocomposites morphology evaluated by high‐resolution scanning electron microscopy. The BP associated with the addition of a compatibilizer agent influenced the MWCNT distribution and location in the polymeric matrix. The one‐step extrusion process results in MWCNT mostly at the interface of the PC/ABS blend and agglomerates, leading to lower mechanical and thermal properties. The BP in which a PC/MWCNT masterbatch was first prepared and then diluted in ABS and ABS‐g‐MAH achieves the higher mechanical properties, increasing Young's modulus and the ultimate tensile strength. The third BP in which MWCNT was added in a second step in the blend already processed resulted in a homogeneous dispersion of MWCNT on both phases and a lower electrical resistivity.

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The thermal degradation of the polyamide 6,6 (abbreviated henceforth as PA 6,6) reinforced with different concentrations of carbon nanotubes (CNTs) was investigated by means of thermal analysis. In this study, the nanostructured composites were produced using 0.1, 0.5 and 1.0 wt% of CNT. X-ray diffraction analyses were performed in order to evaluate the crystallographic properties of nanostructured composite. The degradation kinetics of PA 6,6/CNT nanostructured composites were measured by thermogravimetric analysis at different heating rates under nitrogen flow. TGA experiments were performed to elucidate the thermal behavior and supply the data that characterize the degradation kinetic. The degradation parameter kinetics was determined using the Ozawa-Wall-Flynn (O-W-F) methods, which do not require knowledge of the reaction mechanism. In this work, the results show that the addition of CNT up to the amount of 0.5 wt% increases the thermal stability of PA 6,6.

ResumoNeste trabalho o comportamento de cristalização e a condutividade elétrica de compósitos nanoestruturados de poli(sulfeto de fenileno) reforçado com nanotubos de carbono de paredes múltiplas obtidos através da técnica de mistura em fusão foram estudados. A incorporação do nanoreforço na matriz polimérica foi responsável por um aumento da cristalinidade devido ao fenômeno de nucleação heterogênea. A condutividade elétrica do PPS apresentou um aumento de 11 ordens de magnitude quando 2,0 m/m% de MWCNT foram adicionados a matriz polimérica. Além disso, o limite de percolação elétrica encontrado para este sistema foi de 1,4 m/m% de MWCNT, revelando a formação de uma rede condutiva tridimensional no interior da matriz polimérica. Palavras-chave: PPS, MWCNT, cristalização, propriedades elétricas, limite de percolação elétrica. AbstractIn this work, the crystallization behavior and electrical conductivity of multiwalled carbon nanotubes reinforced poly (phenylene sulfide) nanostructured composites obtained by melt mixing were investigated. The incorporation of nanofiller in polymeric matrix was responsible for an increase in crystallinity due heterogeneous nucleation phenomenon. The electrical conductivity of PPS showed an increase by 11 orders of magnitude when 2.0 wt% of MWCNT was considered. Moreover, the electrical percolation threshold found on this system was 1.4 wt%, suggesting the formation of three-dimensional conductive network within the polymeric matrix.