Gel-spinning of partially saponificated poly(vinyl alcohol)

DMSO/water (80/20 volume ratio) solutions of commercial poly(vinyl alcohol)s (a-PVA99, a-PVA88) with degrees of saponification of 99.3 and 88 mol % were gel-spun into methanol (−20 and −70°C). The dry filaments obtained were drawn at 200°C (a-PVA99) and 150–180°C (a-PVA88). The maximum draw ratio and Young's modulus were 26 and 34 GPa for a-PVA99 and 21 and 24 GPa for a-PVA88 (drawing temperature: 160°C). So, at first, the dry filaments obtained for a-PVA88 were drawn at 150–180°C until 10 times their original length. Moreover, the predrawn a-PVA88 filaments were perfectly saponificated under fixing at the both ends and then the filaments were redrawn at 200°C. The maximum draw ratio and Young's modulus for the filaments (a-PVA88→99) predrawn at 150°C were 28 and 39 GPa, respectively. The a-PVA88→99 filaments had two melting peaks (228 and 236°C).