Study On Solution Polymerization Of Acrylonitrile With High Viscosity

The quality of carbon fiber precursor plays a key role in preparing high-performance carbon fibers, but the quality of carbon fiber precursor lies on the character of PAN spinning solution.In this AN/IA copolymerization system, AIBN and DMSO were used as initiator and solvent, respectively. By increasing the concentration (20wt% and 25wt%) and the conversion(>90%) of the monomers, high viscosity was obtained to meet the demand in the spinning process. It’s indicated that, with the same proportion of the initiator and the same ratio of two monomers, the conversion didn’t depend on total initial monomer concentration; in high convention system, the value of viscosity was less than 40Pas while the total monomer concentration was under 20wt%; once the concentration was more than 20wt%, the viscosity would increase substantially, and that would lead to the difficulty in heat and mass transfer. When the total concentration and conversion were 25wt% and 85% respectively, the viscosity met the demand. The total concentration had little influence on the molecular weight and its distribution. These researches would make a contribution to the batch polymerization on how to choose appropriate total monomer concentration and conversion.Meanwhile, based on radical polymerization mechanism, we analysed the apparent kinetics of the PAN copolymerization system, built mathematical model between conversion (x) and reaction time (t), and then we fitted the data to obtain the model parameters. The x-t model demonstrated that conversion was only dependent on the initial initiator concentration, not the initial total monomer concentration. By calculating the x-t model and thermal equilibrium of the batch polymerization, we got the relationship of the heat of polymerization (Q) and reaction time (t), which could provide the foundation for temperature control and stir type in the batch polymerization.We researched the copolymers by using elemental analysis testing and differential scanning calorimeter (DSC). It’s found that most of IA comonomers enter into the copolymerization early, but the mole fraction of IA comonomers constitute to copolymers become smaller with the reaction going on. And that, shortening the reaction time and increasing total monomer concentration ratio can reduce the pre-oxidation initial temperature, and effectively reduce the heat release in process.