Effect of stereosequences on crystallinity and properties of zone-drawn poly(vinyl alcohol) microfibrils

To effectively orient the molecular chains of novel syndiotactic poly(vinyl alcohol) (PVA) microfibrillar fiber (PVA fibril), a high-temperature zone- drawing method was adopted. The PVA fibrils were directly prepared from the saponification and in situ fibrillation without a spinning procedure. The maximum draw ratio of the PVA fibril increased with a decrease in the syndi otactic diad (r-diad) content, indicating that the deformability of WA mole cules was lowered in higher syndiotactic PVA. Degree of crystal orientation s up to 0.990 were achieved by stretching the PVA fibril with the r-diad co ntent of 65.1% and the original degree of crystal orientation of 0.902 at 2 50 degreesC close to its crystal melting temperature (T,). When the same dr aw ratio was applied to the fibrils, a higher crystal orientation was achie ved for the fibrils having higher syndiotacticity. Wide-angle X-ray data sh ow that the longitudinal crystal sizes of drawn PVA fibrils were larger in higher syndiotacticities. The degree of crystal orientation, crystallinity, T,, longitudinal crystal size, and tensile strength of the maximum drawn W A fibril with a r-diad content of 65.1% were 0.99, 0.97, 279 degreesC, 187 Angstrom, and 4.66 N/tex, respectively. (C) 2001 John Wiley & Sons, Inc.