| Summary: | 博士 === 國立清華大學 === 化學工程學系所 === 106 === Using supercritical fluid CO2 as an efficient and green solvent in nanocomposite preparations is included in this dissertation. There are three chapters, which are organized as follows:
In Chapter 1, a detail description that introduces the basic principles, characteristics and technical classification of supercritical fluid, as well as the application of supercritical fluid and carbon dioxide expansion liquid in polymer material mixing process.
In chapter 2, a detailed description that introduces the matrix phase, reinforcing phase and interfacial phase of composite materials and the manufacturing technologies of composite materials.
In Chapter 3, the absorption of scCO2 weakens the entanglement of Epoxy chains. This increases the free volume of the Epoxy and decreases its viscosity, glass transition temperature, and surface tension. Thus the lower viscosity of Epoxy resin could help disperse GNPs (Graphene nanoplatelets) and MWCNTs (Multi-walled carbon nanotubes) uniformly in the Epoxy resin. The application of GNPs and MWCNTs had a remarkable synergetic effect on both the electrical conductivity and the thermal conductivity of Epoxy-NCFs (Nano carbon fillers) nanocomposites. The dispersion of the NCFs in the nanocomposite prepared with both the GNPs and MWCNTs was more uniform when using scCO2 mixing than it was when using either acetone mixing or subcritical CO2 mixing. When employing acetone mixing, residual organic solvent (acetone) was retained in the nanocomposite after post-heating treatment; no CO2 was detected, however, in the resulting nanocomposites prepared using scCO2 mixing, indicating the superiority of this proposed method. Our experiments reveal that scCO2 allows significant processing of an intractable, high viscosity polymer and improves the processability of Epoxy-GNPs-MWCNTs nanocomposites.
In Chapter 4, the optimum operating condition was used from the experiment of the chapter 3. VGCFs (vapor growth carbon fibers) and GNPs were dispersed in PMMA (Poly(methylmethacrylate)) matrix more uniformly to obtain PMMA-VGCFs-GNPs nanocomposites. Experiments show that supercritical CO2 mixing method compared to the NMP mixing method, the electrical and thermal conductivities of the nanocomposites both improved, relative to the values obtained after NMP mixing and for neat PMMA. In addition, the results of GC/MS confirmed that the supercritical CO2 drying method can effectively remove all the residual NMP in the composite material, compared with the subcritical CO2 drying method and vacuum drying method, the composite material will remain a certain amount of NMP, these will affect the composite material properties.
In Chapter 5, a summary of previous chapters was provided. With the encouraging results in this study, it is believed that applying green solvents compressed CO2 and manufacturing of polymer-NCFs manocomposoties could be very promising. It could also meet the purposes of process intensification, sustainable development and environmental protection.
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