Enhancing Mechanical Properties of Gel-Spun Polyvinyl Alcohol Fibers by Iodine Doping

High strength polyvinyl alcohol (PVA) fibers with a conventional degree of polymerization of 1500 were prepared by doping iodine with PVA spinning solution. The iodine-doped PVA (I-PVA) aqueous solution was extruded into cold methanol that provides dark purple PVA-iodine complex gel fibers. Only a small amount of iodine was required to enhance drawability and molecular orientation by reducing the interaction between PVA chains. An increase of ca. 10% in the maximum draw ratio of the doped fibers compared with that of undoped PVA translated into values for the tensile strength, 2.2 Giga-Pascal (GPa), and initial modulus (47 GPa) that were more than 30% higher than those of the neat PVA fiber. Easier chain slippage of molecules in the amorphous segments of the I-PVA fiber during drawing leads to increased orientation in these segments, which is believed to be the source of the improvements in mechanical properties. POLYM. ENG. SCI., 51:647-653, 2011. (C) 2010 Society of Plastics Engineers