Spinning of the solutions of poly(vinyl alcohol)/NaCl/H2O systems and their fiber properties

The NaCl/water solutions of commercial poly(vinyl alcohol) (a-PVA) with the degrees of polymerization and saponification of 1730 and 99.39%, respectively were gel-spun into methanol (–30°C) and then the removed NaCl dry-filaments were drawn at 200°C. The draw ratio showed the maximum at NaCl concentration C _N = 3 wt% (polymer concentration C _P = 150 kg/m³). The Young's modulus and strength at break were 95 and 6 GPa ( = 19). In the case of DMSO system (C _P = 170 kg/m³), the Young's modulus was 52 GPa ( = 25) and the strength at break was 3.3 GPa. Under a polarized microscope, the fine lateral structure was observed for the DMSO system, but not for the NaCl system, that is, the smooth structure was recognized. The smooth structure, like a Netlon packing net for oranges, might be considered to result in heightening of mechanical properties.