Syndiotacticity-rich ultrahigh molecular-weight poly(vinyl alcohol) film. I. Determination of optimum polymer concentration by zone-drawing method infilm preparation

A new method using a simple zone-drawing technique has been suggested for d etermining the optimum initial concentration of a polymer solution that has suitable macromolecular entanglements. This method was developed to replac e the incorrect inherent viscosity-measuring method for syndiotacticity-ric h (syndiotactic diad content of 63.4%) ultrahigh molecular-weight (number-a verage degree of polymerization of 12,300) (UHMW) poly(vinyl alcohol) (PVA) solution. Syndiotacticity-rich UHMW PVA. films were prepared from dimethyl sulfoxide (DMSO) solutions with different initial concentrations: of 0.1, 0.2, 0.3, 0.4, and 0.5 g/dL. In order to investigate the drawing behavior o f the syndiotacticity-rich UHMW PVA films with different solution concentra tions, the films were drawn under various zone-drawing conditions. Through a series of experiments, it was discovered that the initial concentration o f PVA solution in DMSO caused significant changes in the draw ratio of the syndiotacticity-rich UHMW PVA film. That is, the one-step and maximum zone draw ratios of the film at an initial concentration of 0.3 g/dL exhibited i ts maximum values and gradually decreased at higher or lower concentrations . Thus, it was disclosed that the initial concentration of 0.3 g/dL is the optimum polymer concentration to produce a maximum draw ratio in this work. Based on the above results, it may be concluded that the optimum concentra tion of the initial PVA solution can be determined directly by measuring th e zone draw ratio. The draw ratio, birefringence, crystallinity, degree of crystal orientation, tensile strength, and tensile modulus of the maximum d rawn PVA film were 32.9, 0.0449, 0.61, 0.991, 1.91, and 46.2 GPa, respectiv ely. (C) 2000 John Wiley & Sons, Inc.