Preparation Of Polyimide/TiO₂ Composite Fibers And Their Structure And Properties

The environmental problems is more prominent with the rapid development of the industrialization process, especially the serious air pollution, which cause frequent haze weather, resulting in serious harm to human’s health. Air pollution mainly refers to emissions of high temperature flue gas from industrial, thus controlling the emissions of flue gas from industrial, is an important way to improve the atmospheric environment. Bag filter dust with high efficiency in capturing dust, which can effectively capture the dust from the high temperature flue gas, basically achieving zero emissions, is the main means to control air pollution. The core of the bag filter dust technology is the high temperature resistant filter material, which is using to prepare high temperature resistant filter bag. Among them, polyimide fiber high temperature filtration materials are widely used in cement plants,chemical plants, steel mills, and other fields because of their excellent mechanical properties, thermal stability, resistance to light radiation and so on.Recently, environmental protection has become more important, put forward the higher request of bag-type dust collector. In general, most of the high temperature dust filter bag is mainly used to capture dust, not having purification effect of degrading toxic gas such as dioxin. It is urgent to develop a kind of high temperature filter bag ,which not only can degrade toxic gases, but also can capture dust. Titanium dioxide, as a semiconductor photocatalysis material, shows the great application in the aspect of photocatalysis, owing to their excellent photocatalytic properties, chemical stability, corrosion resistance to light, no secondary pollution.In this paper, through the introduction of titanium dioxide on the surface of polyimide fiber, the prepared composite fibers not only maintains the fiber thermal stability but also owns ultraviolet catalytic properties, achieving material multifunction. The main work is as follows:First of all, with commodity polyimide fiber as the matrix and titanium sulfate as titanium salt, prepare titanium dioxide/polyimide composite fibers by the method of ion exchange, and examines the ion exchange time and titanium sulfate concentration on the influence of the composite fiber morphology. The test results show that the content of titanium dioxide on the fiber is less, extension of the ion exchange time and increase titanium sulfate concentration has no effect on increasing the content of titanium dioxide. The study result indicated that Ti4+ valence state is too high.Then we choose titanyl sulfate to substitute titanium sulfate as the titanium salt, using the same method preparing the titanium dioxide/polyimide composite fiber, the microstructure shows that the titanium dioxide have been generated on the surface of PI fiber, but the content of TiO2 was too low, so anatase characteristic peak can not be detected.To improve the content of Ti02, by the method of ion exchange combined with in-situ precipitation method, titanium dioxide content may be increased with the cyclic ion-exchange and precipitation process . By XRD testing, the characteristic peaks of anatase titanium dioxide was detected. With methyl orange as the degradation products, the degradation rate of methyl orange can achieve 100% after 6h of ultraviolet light catalysis , which show that polyimide/Ti02 composite fiber has good photocatalytic performance.The degradation temperature of PI/composite is about 550 ℃, keeping the thermal stability of the polyimide fiber.