Search

A green approach to the synthesis and morphological control of high performance polyimides and their nanohybrid shish-kebabs in glycerol through reaction-induced crystallization of nylon-salt-type monomers was reported. Crystalline polyimide nanoplates can be observed by direct polycondensation of pyromellitic acid with various kinds of aliphatic or aromatic diamines. With the existence of carbon nanotubes, the polyimides can be successfully decorated on the surface of CNTs through a reaction-induced hetero-epitaxial crystallization process, and resulted in novel polyimide/CNT nanohybrid shish-kebabs (NHSKs) structures. The morphologies of the NHSKs can be fine-tuned through changing the concentration of monomers or the reaction temperature, especially through the introduction of dynamic imine chemistry, the formation process of NHSKs can be attributed to a soft epitaxy mechanism. Thus a green approach for the synthesis of high performance polyimides and their CNT based nanohybrid structures was explored, which should be of great value for their applications in high performance reinforced nanocomposites. [ABSTRACT FROM AUTHOR]

ABSTRACT Graphene oxide (GO) and carbon nanotubes (CNTs) and their compound were introduced into semicrystalline poly( l-lactide) (PLLA) to prepare the corresponding binary and/or ternary nanocomposites, respectively. The dispersion states of nanofillers in different nanocomposites were investigated using UV-Vis spectroscopy, scanning electron microscopy (SEM) and rheological measurement. The results showed that when GO and CNTs were simultaneously present in the PLLA matrix, good dispersion states of both GO and CNTs could be achieved and the ternary nanocomposites exhibited percolated network structure. The effects of different nanofillers on the crystallization behavior of PLLA matrix were comparatively investigated under the different crystallization conditions including melt crystallization process (nonisothermal and isothermal crystallization from the melt) and cold crystallization (crystallization occurring from an amorphous state during the annealing process). The results showed that GO and CNTs exhibited apparent synergistic effects in improving crystallization ability and enhancing crystallinity of PLLA matrix. Study on the thermal stability of nanocomposites showed that the presence of nanofillers greatly improved the thermal stability of PLLA matrix. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40143. [ABSTRACT FROM AUTHOR]

As a part of serial work about tuning the selective location of carbon nanotubes (CNTs) in immiscible polymer blends, this work reports the effects of component polarity and viscosity ratio between components on the selective location of CNTs and the resultant electrical resistivity of the nanocomposites. To achieve the research aim, maleic anhydride (MA) was grafted onto poly( l -lactide) (PLLA) main chain through a reactive compounding processing. After that, different contents of CNTs were incorporated into blends of high density polyethylene (HDPE) and PLLA (or PLLA-g-MA). The morphologies of the ternary nanocomposites and the selective location of CNTs in the nanocomposites were characterized using scanning electron microscope (SEM) and transmission electron microscope (TEM). The microstructure of nanocomposites and the dispersion of CNTs were further proved by rheological measurement. Finally, the electrical resistivity of nanocomposites containing different CNT contents was measured. The results showed that through increasing the polarity of PLLA and decreasing the melt viscosity, CNTs were kinetically trapped at the blend interface region. Consequently, largely decreased percolation threshold was achieved for the PLLA-g-MA/HDPE/CNT nanocomposites. The morphological changes as well as the rheological properties were also comparatively analyzed. [ABSTRACT FROM AUTHOR]

Abstract: In this work, different contents of the organoclay (0.05–0.25wt%) were introduced into the polycarbonate/poly(vinylidene fluoride)/carbon nanotube (PC/PVDF/CNT) blend composites by diluting the master batches of the PC/organoclay and the PVDF/CNT through melt-compounding in an internal mixer. In the blend composites, the weight fraction ratio between PC and PVDF was maintained at 40/60, and the content of the CNTs was varied from 0.1 to 0.5wt%. The morphologies of the blend composites and the dispersion states of the nanofillers were characterized using scanning electron microscope and transmission electron microscope. Differential scanning calorimetry was used to investigate the crystallization behaviors of different blend composites so that the selective localization of the CNTs could be proved further. The results showed that with the presence of the CNTs and/or the organoclay, the blend composites showed the apparent morphological change from a typical sea-island structure to the quasi-cocontinuous structure. Specifically, at the organoclay content of 0.1wt%, most of the CNTs selectively located at the blend interface. The electrical resistivity was measured and the results showed that organoclay showed apparent influence on the electrical resistivity of the blend composites. Namely, the volume resistivity decreased with increasing organoclay content until a minimum value was achieved, then it increased gradually with further increasing organoclay content. Specifically, all the blend composites exhibited the minimum electrical resistivity at the 0.1wt% organoclay. Furthermore, a very small percolation threshold of the CNTs (0.06wt%) was achieved in this work, which was attributed to the selective localization of the CNTs at the blend interface. [Copyright &y& Elsevier]