Study Of Molding Mechanism And Dynamics Simulation Along The Dry-Spinning Process Of Continuous Mullite Fiber

Continuous mullite fiber is a new type of high-tech inorganic fiber which has the excellent performance as high-strength, high-modulus, high-temperature resistance particularly in high-temperature conditions,widely used in aerospace, military and civilian high-tech fields. However, the domestic mullite fiber are almost staple fiber, and the continuous mullite fiber which has more outstanding performance has not been industrialized. The suitable molding conditions and spinning mechanism were seeked in this paper to make up for this gap.In this paper, with water as the solvent, tetraethyl orthosilicate (TEOS) as silicon source, isopropanol aluminium (AIP) and aluminum nitrate (AN) as aluminium source, the steady mullite precursor sol was formed through hydrolysis and condensation reaction, and then the precursor sol was spun into the continuous mullite fiber by dry-spinning machine.First, the molding mechanism was studied among the parameters including spinning temperature (extrusion temperature, tube and drying temperature), component’s condition, winding speed, solvent evaporation and fibre diameter. The results showed that during the spinneret temperatures between 44℃and 90℃, the as-spun fiber had a good spinning performance. The tube were divided into 3 parts as the top, mid-range and the end in order to describing the fiber molding more exactly. The top temperature played a key role. If its temperature was too high, the fiber was aways broken because the over-lost sovent would remain cracks and defects inside of fiber which could hardly calcined by bridge; the contrary, low evaporation solution was also a disadvantage to fiber molding. The weight percentage of solvent remains would be cut down while fiber diameter increased; and the charecterastic of as-spun fiber would change better fast but worse soon while winding speed increased.Secondly, the additive’s effect on spinning temperature, components conditions, as-spun fiber diameter, solvent evaporation, winding speed by dry spinning polyvinyl pyrrolidone (PVP) , Polyvinyl alcohol (PVA) modified mullite precursor sol were discussed. The results showed that additives could positively impact the precursor sol spinning molding conditions. When their adding was 3-8%, the spinning performance of the precursor sol would be improved and the internal structure of as-spun fiber was no change. And the additives can lubricate the as-spun fiber surface by its water-keeping characteristic. The structure and properties of as-spun fibers were test by XRD, IR, SEM, etc. The result showed that the as-spun fiber has characterastics as the smooth surface, small diameter, homogeneous structure, good flexibility and 1,000 meters continuous spinning ability.Finally, the solvent diffusion kinetics model simulation was built on the base theories of Newton fluid and Constitutive equations, using Matlab software to simulate the solvent evaporation situation during dry spinning process. Analyzed solvent diffusion process from the parallel and vertical axial directions. In parallel axial direction, the weight percentage of solvent remains changes at three stages, the convection and the flash were the key factor. In vertical axial direction, the weight percentage of solvent remains changes at two stages, convection and diffusion were the key factores.