Study On The Properties Of The Precursor Sol Of Continuous Mullite Fiber And Its Effect On The Gel Fiber Formation By Dry-Spinning Method

With the development of high-tech industries and increasing demands for materials, the research of mechanical materials applied in high-temperature oxidizing environment has became an important direction since the twenties century. Continuous mullite fiber, a kind of super-light heat-resisting insulation material, which exists in the form of mullite minicrystals in the structure, possesses excellent strength, modulus, heat resistance, creep resistance and thermal shock resistance, especially the excellent mechanical property in high-temperature oxidizing environment compared with other inorganic fibers. These excellent properties make it have extensive application prospect in the flied of adiabatic and composite materials.In this paper, using water as disperse medium, aluminum nitrate (AN), aluminum isopropoxide (AIP) and tetraethoxysilane (TEOS) as raw materials, polyvinylpyrrolidone (PVP) as modifier, the homogeneous and steady precursor sol of mullite fiber was synthesized through hydrolysis and condensation reactions. The effect of material ratios on the spinnability of the precursor sol was analyzed, and the microstructure of the synthesized mullite precursor sol was also systematically investigated by FT-IR and laser particle size analyzer of light dispersion. The homogeneous was composed of many uniform nanoparticles (10-20nm). The additives of PVP and HNO3 exert great influences on the properties of the precursor sol, the particle size and the distribution of the sol particles become larger and wider respectively with the addition of PVP , while HNO3 does on the contrary. It is found that the flow behavior of the precursor sol changes to non-Newton flow when relative aging time equals to 0.9 and PVP has a great effect on the spinnability of the precursor sol.According to Chambon-Winter (CW) criterion, the gel points of specific systems were determined by studying the dynamic rheological properties. The influences of PVP, aging temperature on the gelation time were also observed. Through the measurements of laser particle size analyzer, TEM and viscometer, the process of sol-gel transition was studied. It is also found the sol-gel transition temperature is between 40℃and 45℃adopted the testing methods of viscosity and DSC.Continuous mullite fiber was attained through dry-spinning method. Effects of different aging conditions and solid content on the fiber formation were studied. Continuous mullite fiber can be attained when the solid content is about 55%.