Morphology and physical properties of polyacrylonitrile fibers spun from a spinning dope with or without zinc chloride

Abstract

All commercial PAN homopolymers are generally manufactured by the radical polymerization of acrylonitrile(AN) in solvent with an initiator. PAN has the strong intermolecular dipolar bonds between the nitrile groups on adjacent polymer chains, and thus it has a much higher melting temperature (317$^\circ$C) than the general purpose polymers such as polyethylene(PE), polypropylene(PP), and polyvinylchloride(PVC). The solvent of PAN must have the functional groups that disrupt the strong dipolar bonds. Dimethylformamide(DMF), dimethysulfoxide(DMSO), and dimethyl acetamide(DMAc) can be used as a solvent. PAN homopolymer was prepared in the conventional was by the radical polymerization of AN in DMF solution with azobisisobutyronirile(AIBN). The molecular weight and polydispersity index were about $4\times10^5$ and 2.16, respectively. PAN fibers are generally manufactured by a wet spinning, a dry-jet wet spinning, or a dry spinning. The most successful techique among them is the dry-jet wet spinning because PAN fibers produced by this techique have better mechanical properties. $ZnCl_2$ was added to a spinning dope in order to improve the mechanical properties of PAN fibers and the addition effect was analyzed. When the amount of $ZnCl_2$ was 0.01, 0.02, 0.05, and 0.10 mole $ZnCl_2$ per mole AN units, the residual amount of $Zn^{+2}$ in PAN fiber was $6.5\times10^{-4}$, $6.8\times10^{-4}$, $7.6\times10^{-3}$, and $9.3\times10^{-3}$ wt\%, respectively. As the residual amount of $Zn^{+2}$ increased, the maximum degradation temperature(DTmax) dropped to a lower one because the residual $Zn^{+2}$ accelerated the thermal degradation of PAN fibers. The complexations between the CN groups and $Zn^{+2}$ were investigated using a Raman and Infraed Spectroscopy. Any shifts in the wavenumber $\nu_{CN}$ for CN stretching were not observed for all experiments. It was understood that the complex of CN group and $Zn^{+2}$ could be neglected because the amount of $ZnCl_2$ added to ...