The Effect Of Ammonification On Double Diffusion Of PAN Solution And The Mechanism

The shape process of polyacrylonitrile is one of the key step to get the qualified PAN carbon fiber precursor. The traditional wet spinning usually conducts the 'core and shelil' structure.The shell is compact and the core is loose.This structure is not good for PAN carbon fiber. In the past, one of the methods to reduce the dis-heterogeneity situation is lifting up the concentration and low the temperature of coagulation.However, this method has its limit to control the 'core and shell'structure. Now, many researchers do the ammonification to make the fiber more homogeneous. It is an effective method, but how will this method effect the double diffusion speed and phase separation is not clear. Therefore, this thesis mainly studies the effect of ammoniation on the double diffusion and phase separation of polyacrylonitrile solution.Via the diffusion distance of the polymer solution to measure the diffusion speed by the aid of the mapping software and microscope. The effect shows that after ammonification the diffusion speed of PAN solution has lift up. By cloud point titration method, we draw the ternary phase diagrams. The ternary phase diagrams show that after ammonification the PAN solution needs more coagulation bath to get the phase separation point. During the phase separation process, the holes will reduce after ammonification. It is good for heterogeneity.Through the static contact angle, we found that high hydrophilicity will increase the double diffusion rate and slow down phase separation process. The gel permeation chromatography (GPC) and the conversion rate showed that ammonification degree of PAN solution has little relationship with polymerization process. UV spectrum and infrared spectrum test showed ammonification is the reaction between itaconic acid and ammonia. But this combination is unstable and can be destroyed by heating or violent oscillation.Finally, we think that the reason why the double diffusion velocity is faster and the phase separation process slows down is that the ammonium ions increase the hydrophilicity of macromolecules. But the combination of ammonium ions and the carboxyl groups in itaconic acid is not stable. This structure will be destroyed in the high temperature oscillation and 80 degrees high temperature water bath.