Study On Preparation And Properties Of Carbon Nanotube Fluids

Carbon nanotubes (CNTs), a novel one-dimensional carbon nanomaterial, undoubtedly occupy a unique position among advanced materials due to their novel structure, excellent electrical conductivity and mechanical properties. Unfortunately, due to high surface free energy, CNTs will be aggregated easily. This will limit the applications of CNTs. Regarding the chemistry of CNTs, sinnificant work has focused on their surface functionalization with the aim of enhancing dispersibility with polymers, and designing novel derivatives with even more complex behavior. In general, the chemical functionalization of CNTs take place either via covalent grafting to the graphitic surface, structural defects, and end cups of the tubes, through molecular stacking(p stacking)on the walls, or by wrapping of the tubes with polymers.In each case, functionalized CNTs exhibit solidlike behavior in the absence of solvents and do not undergo any macroscopic solid-to-liquid transition. Recently, we have developed a series of functionalized CNTs that exhibit liquidlike behavior in the absence of a diluent or solvent. The solventless carbon nanotubes fluids are synthesized by attaching a corona of flexible chains onto CNTs. The carbon nanotubes fluids possess flow properties (viscosities and diffusivities) that are remarkably similar to those of simple molecular liquids, specific properties (e.g., refractive index, viscosity, conductivity, magnetism) that are difficult or impossible to achieve with molecular-based fluids. Unlike simple liquids, however, they do not possess a measurable vapor pressure. And it undergoes a solid-to-liquid transition at low temperatures. At the same time, the carbon nanotube fluids were introduced into PA11 to produce CNTs/PA11 composites via melt blend. The structure of composites was observed with scanning electron microscope, and it was found that CNTs had a uniform dispersion and orientation in PA11.The rheological behaviors of CNTs/PA11 composites was studied by using torque rheometer.The main results obtained in this paper are shown as follows.1. Oxidation action on the surface of CNTs can produce some hydroxyl groups. The oxidation action rule of several oxidizers-potassium permanganate, Fenton reagent and mixed acid, from aspects of category, dosage and oxidation condition were studied. By FTIR,XPS testing and suchlike technologies, we analyzed the structure of the hydroxyl group qualitatively and quantitatively ,and found out the key technique to control the quantity of hydroxyl group on the surface.2. Through O-Si, organic positive hydronium was bonded on the surface of carbon nanotubes. We studied the action mechanism between silicone alkyl of the organic positive hydronium and hydroxyl of the CNTs and try to find out the method to purify the reaction products. And finally, found out the optimal action concentration, time, temperature and medium type as well as the key technology of purifying.3. The CNTs fluids with multiple ether links was prepared by ion-exchange between CNTs (with organic positive hydronium) and sodium sulfonate nonylphenol polyoxyethylene. The optimum reaction conditions were confirmed. And CNTs fluids were characterized by FTIR, TG, low-temperature DSC and shear modulus testing.4. The carbon nanotube fluids were introduced into PA11 to produce CNTs/PA11 composites via melt blend. The structure of composites was observed with scanning electron microscope, and it was found that CNTs had a uniform dispersion and orientation in PA11.The rheological behaviors of CNTs/PA11 composites was studied by using torque rheometer.