Study On Preparation And Property Of NanoTiO₂/POPAN Composite Material

The preparation of polyacrylonitrile was carried out by solution polymerization method, using acrylonitrile as monomer and azobisisobutyronitrile as the initiator and dimethyl sulfoxide as solven. Then nano-TiO2/PAN composite materials were prepared by ultrasonic blending method. Nano-TiO2/PAN composite materials were heat treated, light and heat co treated in the air. The relative rates of cyclization of PAN were calculated by the changes of strength of peaks in FTIR. The effects of time and temperature on relative rates of cyclization of PAN during pre-oxidative process of TiO2/PAN composite materials were investigated. TiO2/POPAN composite materials were characterized by Scanning electron microscopy (SEM), X-ray diffraction(XRD), Thermogravimetry-differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy(FTIR),UV-visible diffuse reflectance spectro scopy(UV-Vis DRS). It is found that TiO2distributed on the surface of polyacrylonitrile. XRD showed the decrease of intensity of diffraction peak which respected the crystal surface of-C≡N in large molecules. The oxidative cyclization reaction was carried out, and disorder degree of PAN increased. TG-DTA results showed that the cyclization reaction of TiO2/PAN composite materials needed higher temperature than PAN. FT-IR spectra of TiO2/POPAN composites showed the decrease of strength of the peak at2243cm"1which belonging to-C≡N and new bands appear at1590and810cm-1belonging to-C≡N-and-C=C-H of aromatic ring. The formations of aromatic rings were carried out during the pre-oxidative process of TiO2/PAN composite materials, with dehydrogenation and cyclization reactions. DRS results showed that the visible light absorption strength of TiO2/POPAN composite films is higher than that of TiO2/PAN composite films.In the conditions of heat treatment, light and heat co treatment, the relative rates of cyclization of PAN in TiO2/POPAN composite materials were calculated by the changes of strength of peaks. The rates of cyclization and absorbance in visible light region of TiO2/POPAN composite materials increased with the increasement of treatment temperature and reaction time. The exists of TiO2restrained cyclization reaction of PAN in the conditions of heat treatment, However TiO2promoted pre-oxidative stabilization process of PAN in the conditions of light and heat co treatment. The dynamics of cyclization reaction in pre-oxidative process were researched. In the conditions of heat treatment, the order of reaction of PAN cyclization reaction was3, the activation energy was obtained as81.2kJ/mol; the order of reaction of TiO2/POPAN composite material cyclization reaction was4, the activation energy was obtained as90.2kJ/mol. In the conditions of light and heat co treatment, the order of reaction of PAN cyclization reaction was2, the activation energy was obtained as78.8kJ/mol; the order of reaction of TiO2/POPAN composite material cyclization reaction was3, the activation energy was obtained as72.2kJ/mol.