Kinetic Study On Precipitation Polymerization Of Acrylonitrile Initiated By Anionic Initiators

As an important precursor to producing carbon fiber, the configuration of polyacry lonitrile (PAN) is the key to enhance not only the tensile strength but also the modulus of the final carbon fiber. It is convience to initiate the acrylonitrile by anionic initiator than other metholds for normal experiment. We took the dibutylmagnesium as the main initiator and the triethylaluminium as the assisting initiator to obtain high isotactic PAN. High isotactic PAN samples was prepared by using several monomer concentrations (0.288-0.496mol/L), initiator concentrations (0.00568-0.01135mol/L) and different polymerization times (15-60min). The kinetic model was proposed from the sub-micro process of precipitation polymerization. A kinetic equation was then deduced by using the concept of total ways of the primary precipitate aggregates F[V]. The final first-order kinetic equation: ln[1/(1-a)]=kt where a represented conversion rate and t polymerization time was based on Taylor series expansion of F[P] and the relation between F[P] and precipitation amount. ln[1/(1-a)]and polymerization time(t) had a linear relationship which proved the first-order kinetic equation was in good agreement with the experiment date. The reaction rate constant k was decreased with the concentration of monomer increased. It suggested that the initiator was diluted by monomer which made the total ways of the primary precipitate aggregates decreased and then k decreased. On the contrary, k increased as the concentration of initiator increased. However, the reaction orders with respect to monomer and initiator were both found to be 1.0 in the acrylonitrile's precipitation polymerization. The kinetic equation of the precipitation polymerization was Rp=ko[M]1.0[I]1.0.In order to obtain the novo spinning solution of high isotactic polyacrylonitrile, we took the methyl acrylate (MA) as the second monomer to reinforce the properties of homo PAN. The peak of 1730cm-1 in FT-IR suggested MA attend the copolymerization and could be found in the polymer chain while the spectrum of 13C-NMR proved the MA did not change the stereoregularity of PAN. We obtain the reactivity ratio between AN and MA by using the K-T methold to fit the data of the element analysis that r1=0.875, r2= 1.147. Since the r1·r2≈1, AN-MA is ideal copolymerization.It is not enough to emprove the strength and modulus of carbon fiber just by changing the structure of the spinning solution. So we paid much attention on one of the most important procesure of CF's manufacturing which is called high pressurized steam drawing. We pointed out that adding a magnetic force water level controlling can make the steam happening equipment safer and a hygrometer may hepe us to get the saturated steam. In addition the rust among the steam can be removed by filtration made by copper. Finally, we designed a new high pressurized steam drawing machine which contains lots of mazes by combining the effects of drawing rate, velocity and preserving time.