GEL SPINNING OF SYNDIOTACTICITY-RICH POLY(VINYL ALCOHOL)

Syndiotacticity-rich poly(vinyl alcohol)s (s-PVA) of high degrees of polymerization (DP = 7900, 12600) were prepared from poly(vinyl trifluoroacetate)s obtained by bulk-polymerization at 40-degrees-C with 2,2'-azobis(2,4-dimethyl-valeronitrile) as the initiator. Gel filaments of the s-PVAs were prepared by extruding into cold methanol (-20-degrees-C) the solution in water-dimethyl sulfoxide (20 : 80, volume ratio) (polymer concentration, 3.5 g/dl; diameter of a nozzle, 0.8 mm). The maximum draw ratio of the filaments was about 14 at 230-degrees-C. The fibers, obtained by drawing 12 times the gel filaments of s-PVA with DP-7900, showed the highest tensile modulus of 30 GPa, strength at break of 1.9 GPa, crystallinity of 70%, and birefringence of 5.0 x 10(-2). Crystallinity up to 30% is considered to interfere with high drawing of the gel filaments. The fibers prepared from the gel filaments of commercial atactic PVA with DP = 17900 under the same conditions and elongated 13 times at 220-degrees-C showed Young's modulus and the tensile strength of 18 GPa and 1.3 GPa, respectively.