High Molecular Weight Polyacrylonitrile For High-performance Carbon Fiber: Study On Solution Copolymerization Of Acrylonitrile

High quality PAN precursor plays a key role in the preparation of high-performance carbon fiber, and PAN resins with high molecular weight can improve the preoxidation during the preparation of high quality PAN-based carbon fiber. In order to prepare this kind of polymer, the copolymerizations of AN were carried out in dimethyl sulfoxide at low temperature using a new initiator and a novel comonomer.Firstly, we studied the solution copolymerization of AN and IA using AIBN as initiatior in DMSO. Orthogonal design method was employed to investigate the effect of the polymerization temperature, the concentrations of the initiator and the comonomers on the molecular weight and the conversions of the comonomers. The copolymers were characterized by FT-IR, NMR and GPC. The results showed that a low polymerization temperature, a low feeding ratio of the initiator, and a high concentration of the comonomer would all benefit in increasing the molecular weight of the copolymer, and the concentration of the initiator was the most important factor to affect the molecular weight of the copolymer, and thus the optimized formula was achieved.Next, we investigated the copolymerization of AN and IA using ABVN as an initiatior at low temperature, and the polymerization rate at 35℃was obtained. The results showed that the molecular weight of the copolymer using ABVN as initiator was higher than that using AIBN; however, the polymerization rate was slower, and the conversions of the comonomers were lower. Kinetics equation of the copolymerization system at 35℃determined to be Rp= K[I]0.594[M]1.655.Finally, we performed the copolymerization of AN andβ-monobutyl itaconate using ABVN as initiatior at low temperature. The introduction ofβ-monobutyl itaconate into the system will increase the diffusion coefficient of the preoxidation to decrease skin-core structure. We compared two different comonomers for the copolymerization and the results showed that the molecular weight of PAN homopolymer was higher than that of the copolymer, and the molecular weight and the conversion of the comonomer usingβ-monobutyl itaconate as comonomer were both higher than those using IA as comonomer. The reactivity ratio of AN/β-MBI copolymerization system calculated by Fineman-Ross method was 0.799 for AN and 0.863 forβ-MBI, respectively. They were both clode to 1, which were beneficial to be equally distributed of macromolecular chains and cyclization. They were all in favor of improving the mechanical properties of carbon fiber.