Preparation And Characterization Of Vinylidene Chloride Copolymer/Inorganic Nanoparticle Composites And Porous Carbons

Porous carbons exhibt a lot of pores, great specific surface area, good physical and chemical stability and heat-resistance, and can be used in the environemtnal protection, industrial catalyst, new energy devices and so on. The common porous carbons maily contain micro-pores, which restricts its application in the treatment of waste water containing giant molecules and super capacitors using organic electrolytes with great molecular size. Thus, a noval method was proposed in this thesis to prepare porous carbons with mirco- and meso- pores, and greater specific surface area and porosity. Vinylidene chloride polymers were used as the carbon precursor and the micro-pores would be formed directly during the carbonization process. Inorganic nanoparticles incorporated acted as templates would form the meso-pores.Firstly, vinylidene chloride-methyl acrylate (VDC-MA) copolymer was used as carbon precursor, and nanometer hydrotalcite (nano-HT) with primary particle size of 20-50nm as template. VDC-MA copolymer/nano-HT composite were prepared by in-situ suspension polymerization, and porous carbons were obtained by high-temperature carbonization of the VDC-MA copolymer/nano-HT composites and removing of inorganic particles. The structure of composites and the resultant porous carbons were characterized by electron microscopy, infrared spectrometer, thermogravimeric analysis, X-ray diffraction, and N2 adsorption/desorption analysis. It was found that VDC-MA copolymer paticles became irregular as HT added in suspension polymerization. HT particles were dispersed in the VDC copolymer matrix in the nanometer size when the weight fraction of HT was≤15.84wt%. The thermal stability of VDC-MA copolymers were improved as HT incorporated, while the themal degradation mechanism of VDC-MA coplymer was not varied. Furthermore, influences of the carbonization temperature and HT content on the pore structure of the resultant porous carbons were studied. The results showed that the porous carbons had large porosity and large specific surface area when the carbonization temperature was 800℃. The carbon prepared from the composite with 8.43wt% HT had a specific surface area of about 1000 m2/g, a narrow pore size distribution with average pore size of about 2nm, and meso-porosity degree of 26.5%. Secondly, the aqueous dispersion of nano-silica (particle size of 10-15nm) were used to prepare VDC-MA copolymer/nano-silica composite particles by in-situ emulsion polymerization, and the porous carbons were prepared by carbonization of compsite particles and removal of silica by HF etching. The morphology of composite particles, and the influences of silica content on the pore structure, microcrystalline structure and morphology of porous carbons were investigated. The results showed that silica template could be completely removed after HF etching. The meso-pores within the carbon materials were mainly originated from the silica particles. The obtained porous carbons exhibited IV type absorption behavior with hysteresis loops, indicating the presence of meso-pores. VDC copolymers could completely carbonized, and the resultant porous carbon had a stable structure, a narrow meso-pore size distribution, a large specific surface area, pore volume and meso-porosity degree, when the carbonization temperature was 800℃. With the increase of silica content in composite particles, the average pore size, meso-pore volume and the meso-porosity degree of the carbons increased. The carbons prepared from the compsoite particles with 11.86wt%,22.68wt%, and 35.29wt% silica exhibited specific surface areas up to 1000-1500 m2/g, average pore sizes of 3.1nm, 3.7nm and 5.3nm, and meso-porosity degrees of 49.5%,63.6%, and 82.2%, respectively. TEM and SEM micrographs showed that the obtained carbons had well-developed pore structure and a lot of meso-pores with narrow pore size distributions, indicating the significant effect of silica in forming of meso-pores.The above results illustrated that the proposed inorganic templeting method using VDC-MA copolymers as the carbon precursor, was a useful way to prepare carbons with micro- and meso- pores, due to the combination of the formation of micro-pores by the thermal degradation of VDC copolymer and the formation of meso-pores by removal of inorganic nano-particles.