Xueli Wu

Preparation and characterization of polyamide composites with modified graphite powders

Although Graphite powders (GPs) are used widely as fillers to improve the electrical, thermal and mechanical properties of polymers, their poor affinity with polymers has limited their industrial applications in many fields. In the present work, GPs were modified by a proposed chemical method to improve their affinity with polyamide 6 (PA6). The GPs was first oxidized with hydrogen peroxide (GPs-OH) and then modified with hexmethylene diisocryanate (GPs-NH2). The X-ray photoelectron spectroscopy (XPS), elemental analysis, thermogravimetric analysis (TGA), X-ray diffraction (XRD) and electrical properties results proved the successful modification of GPs by the proposed method. The composites of GPs and PA6 (GPs/PA), GPs-OH and PA6 (GPs-OH/PA) and GPs-NH2 and PA6 (GPs-NH2/PA) were prepared via the twin-screw extruding and injection molding processes. The scanning electron microscopy (SEM) images and the optical microscopy images of composites showed good compatibility between modified GPs and PA6. The test results of tensile strength and bending strength suggested that the modified GPs can enhance the mechanical properties of PA6, which will increase its application in various fields.

Nano-cladding of natural microcrystalline cellulose with conducting polymer: preparation, characterization, and application in energy storage

This study demonstrates the possibility to coat individual fibers of natural microcrystalline cellulose with polypyrrole using in situ chemical polymerization to obtain an electrically conducting continuous high charge storage capability composite with a nano-cladding structure. By manipulating the ordered nano-cladding nanostructure, conducting nanocomposites were achieved and outstanding electrical conductivity, as high as 48.7 S cm−1, was obtained with the feeding mass ratio of sisal microcrystalline cellulose SMC : Py = 3 : 7. X-ray photoelectron spectroscopy (XPS) results showed that with the increase in SMC content, doping level of PPy in the composite increased. It was found that the PPy nanoparticles deposited on the surface of the SMC and connected to form a continuous cladding. The as-prepared SMC/PPy nanocomposites demonstrated a mass-specific capacitance (Cs) of 367 F g−1 at a 0.2 A g−1 current density in the supercapacitor application. Moreover, SMC/PPy electrode retained about 87.5% of the initial Cs after 1000 cycles, and about 57.8% of Cs when the current density increased five times. This study provides a straightforward method to utilize the renewable resource sisal microcrystalline cellulose to obtain a conducting composite, which could be applied in sensors, flexible electrodes, and flexible displays. It also opens a new field of potential applications of micrometre-scale natural microcrystalline cellulose.

Polystyrene grafted carbon black synthesis via in situ solution radical polymerization in ionic liquid

DENKA BLACK/polystyrene nanocomposites (DB/PS) were successfully prepared through a facile strategy. Some of the styrene molecules were grafted and polymerized onto the surface of the DB via the in situ free radical addition process in ionic liquid, and others self-polymerized and coated on the polystyrene grafted DB. The ionic liquid improves the grafting percentage because of its high viscosity. The electrical properties of polymer composites before and after the grafting were measured. It was found that the electrical conductivity of the DB/PS composites decreased with increasing amounts of monomer styrene and initiator 2, 2′-azobis (isobutyronitrile) (AIBN). The microstructure, morphology and thermal properties of the composites were characterized by Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The results proved that the polystyrene had been successfully grafted onto the DB surface.