Influence of two‐stage drawing conditions on ultradrawing behavior of gel films of ultrahigh‐molecular‐weight polyethylene and low‐molecular‐weight polyethylene blends

Abstract The influence of two‐stage drawing conditions on the ultradrawing behavior of the gel films of ultrahigh‐molecular‐weight polyethylene/low‐molecular‐weight polyethylene blends is reported in this article. The critical draw ratios (λ c ) of the gel films prepared near their critical concentrations were found to depend significantly on the draw ratio attained in the first drawing stage ( D 1 r ) and on the temperature utilized in the second drawing stage ( T sec ). After drawing the gel films to a fixed draw ratio in the first drawing stage, each two‐stage drawn gel film was made to exhibit a maximum λ c (λ c max ) by drawing the drawn gel film at its corresponding optimum T sec . In addition, the optimum T sec was found to increase significantly with the D 1 r value of the drawn gel films. It is worth noting, on the other hand, that the λ c max of two‐stage drawn gel films increased consistently with an increasing D 1 r until its value reached an optimum value of 160. These results clearly suggest that, as T sec and D 1 r are increased to their optimum values, the λ c max of the two‐stage drawn gel films can be improved further so as to be higher than those of the corresponding one‐stage drawn gel films. These interesting phenomena were investigated in terms of reduced viscosities of the solutions and by an analysis of the thermal, birefringence, and tensile properties of the drawn gel films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1890–1901, 2001