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Vertically oriented bamboo-like nitrogen-containing carbon nanotube (CNT) arrays were grown on an alumina (Al 2 O 3 ) substrate by the injection chemical vapor deposition (CVD) process using ethanol as a carbon source and ethylenediamine as a nitrogen source. The substrate is a sintered Al 2 O 3 plate with a rough surface consisting of polycrystalline Al 2 O 3 micro-grains. The concentration of ferrocene in ethanol played a major role in the growth of CNT arrays. Aligned multi-walled CNT arrays were obtained under optimized catalyst concentrations (0.015 g/ml) and growth temperature (900 °C) with the height of the arrays attaining 160 μm after the growth for 1 h. The growth of CNT occurred predominately between 30 and 40 min and ceased growth beyond 60 min. X-ray photoelectronic spectrum detects the incorporation of nitrogen atoms in the CNTs with an atomic ratio of 1.2%. The present study indicates that it is possible to grow high quality carbon nanotube arrays over a cheap alumina substrate of a rough surface. more...

The molecular weight of ethylene- block - co -polypropylene (co-PP) was adjusted by reactive extrusion with the incorporation of dicumyl peroxide (DCP), and the effect of molecular weight on the crystallization behavior, crystal morphology, and fracture behavior was investigated. It was found that, with increasing DCP content, the molecular weight (MW) decreased and the polydispersity ( M w / M n ) slightly decreased. After modification, the number of spherulites with obscure boundaries increased, and the size of the spherulites was more even due to increasing amount of grafting and micro-cross-linking structures, generated in co-PP degradation, which were acting as nucleating agents. Evaluated by essential work of fracture method, the specific essential work of fracture, w e , was found to be strongly dependent on the molecular weight, especially, on the number average molecular weight ( M n ) linearly, while the specific non-essential work of fracture, βw p , was enhanced with decreasing z-average molecular weight ( M z ), probably owing to the reduction of ultra-high molecular weight component in degraded co-PP. more...

Large area of vertically aligned bamboo-structured carbon nanotubes (CNTs) films was grown on quartz substrates by the injection CVD reactions using a double injection regime involving separate injection of a hydrocarbon liquid and a promoter. Excellent arrays of all bamboo carbon nanotubes were obtained using ethanol as the carbon source by this reaction design. Arrays of the bamboo nanotubes were obtained also using toluene and pyridine in replace of ethanol as the carbon source. A high growth rate of the film which is double of that reported earlier, was obtained by controlling the ratio of ethanol and ethylenediamine, with the film thickness attained 160 μm after the growth for 20 min. We found that ethylenediamine played a key role in the formation of the bamboo structures. When a single injection was used in absence of ethylenediamine, the reaction could still yield the arrays of nanotubes which, however, of the normal tubule structures rather than the bamboos structures. The fine structures of the bamboo nanotubes changed with the sort of the carbon source, the carrying gases and the synthesis temperatures. The present double injection CVD reactions allow the use of mutually insoluble hydrocarbons and promoters, avoiding the possible reactions among the reactants, and, more importantly, provides the feasible control over the nanotube arrays from the tubule to the bamboo structures. more...

Melamine–formaldehyde (MF) resin microcapsules containing decabromodiphenyl ether (DBDPO) with better thermal stability were successfully prepared by in situ polymerization, DBDPO being the core material and MF resins being the wall materials. Chemical structure of the prepared microcapsules was characterized by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Morphologies and thermal properties were also investigated by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), respectively. The results indicated that MF microcapsules with DBDPO particles prepared in this study showed better thermal stability, and could be used as effective flame retardant even for the resins which should be processed at temperatures higher than 350 °C. more...

The effects of the draw temperature and the strain rate on the tensile deformation of polyamide 6 (PA6) were investigated using three PA6 samples with different initial shapes and physical dimensions. It is observed that the special double yielding phenomenon is indeed present in PA6, provided that certain temperature and strain rate are given, as well as the appropriate initial structure. The results also show that the dependence of the first yield stress on temperature is nearly linear while on strain-rate is logarithmic. The temperature and strain-rate sensitivity change at the draw temperature in the vicinity of the glass transition temperature of PA6. The double yielding of PA6 is not only the combination of two thermally activated rate processes depending on temperature and strain rate, but also associated with the initial structure of samples. The yielding manner for PA6 seems to be determined by the synergetic effect of both the deformation of amorphous and crystalline phases. Thus some special structure involving the crystalline and amorphous phases should come into being in PA6 exhibiting double yielding. Especially the important role of inter- and intra-link should be taken into account. The theory of partial melting–recrystallization cannot account fully for the double yielding of PA6. more...

Poly (vinyl chloride) (PVC)/ethylene-vinyl acetate copolymer (EVA) blends were prepared to investigate the effect of EVA content on the phase morphology and fracture behaviour, evaluated by means of the essential work of fracture method (EWF). The results clearly showed the prominent influence of phase transformation on fracture toughness of the blends. At low EVA content ( more...

A complex double yielding behavior is observed in the engineering stress–strain curves of injection molded specimens of polyamide 6 (PA6) under tensile loading, and a simple method is put forward to judge the apparentness of the double yielding process. By thermal treatment, the effect of the crystallinity level on the double yielding behavior is studied in some detail. The results show that the second yield stress becomes larger than the first after the thermal treatment, which is contrary to the case without thermal treatment. With the annealing time decreasing and the annealing temperature increasing, the percentage crystallinity becomes higher, and the second yield point is much more apparent with a decrease of crystallinity of the specimens. A possible crystallinity window may exist in double yielding behavior of PA6 material. These results indirectly show that the second yield point is not only associated with the deformation of the crystalline region. more...

A novel in situ microfiber reinforced blend (MRB) based on poly(ethylene terephthalate) (PET) and polyethylene (PE) was prepared by extrusion-hot stretching-quenching process, and was compatibilized with ethylene vinyl acetate copolymer (EVA) in the presence of the transesterification reaction catalyst, dibutyltin oxide (DBTO). The effects of compatibilization on the essential work of fracture parameters in PET/PE MRB were examined. It is found that the specific essential work of fracture (we) and the specific non-essential work of fracture (wp) were significantly increased, when adding 1 and 2.5 phr of EVA to PET/PE MRB and it was further increased with the addition of 0.5 phr of DBTO as the catalyst of the transesterification reaction. The fracture surfaces study by scanning electron microscope (SEM) further proved that EVA is a successful compatibilizer for PET/PP blend. The morphology study of the blends shows that the well-defined fibers with the diameter of several microns were generated in situ during melt extrusion-hot stretch-quenching processing. more...

This article dealt with the tensile properties of in-situ microfiber-reinforced composite (MRC) based on poly(ethylene terephthalate) (PET) and polyethylene (PE). The MRC was prepared through slit die extrusion and hot-stretching, followed by injection molding at the processing temperature of PE matrix, far below the melting temperature of PET in order to maintain the formed microfibers. As expected, the tensile modulus and strength of PET/PE MRC can be significantly elevated at some composition. On the other hand, the reinforcement is heavily dominated by PET concentration; neither low nor high PET content was desirable for reinforcement. Results from elongation tests showed that the ultimate elongation between the samples with mincrofiers and spherical particles at some PET concentrations was extremely different, which was illustrated by the model proposed in which great slippage between the particles and the matrix occurred for the system with spherical particles, whereas there was no slippage between the microfibers and the matrix for MRC. more...

This article introduced the morphologies of in situ microfiber reinforced composite (MRC) based on poly(ethylene terephthalate) (PET) and polyethylene (PE). The PET/PE MRC was prepared through slit-die extrusion and hot-stretching, followed injection molding at the processing temperature of PE matrix, far below the melting temperature of PET in order to maintain the microfibers. Morphological observation indicated that the PET microfibers could be achieved by the way used in this study, and the microfiber characteristics, such as diameter, diameter distribution, were mainly dominated by PET content at a fixed hot-stretching ratio (HSR) of 19.17. Increasing the PET content the fiber diameter became bigger and the diameter distribution wider, but the minimum fiber diameter always remained constant. more...