Drawn gel films of blends of ultrahigh-molecular-weight polyethylenes and low-molecular-weight short-chain branched polyethylene

A critical concentration was found for different compositions of UHMWPE/SBPE solutions, at which the concentration dependence of the reduced viscosity changes from low to high power. The critical concentration (C-c) is shifted to a higher value with increasing amount of SBPE in the UHMWPE/SBPE gel. The birefringence of the drawn films suggests that the degree of orientation of UHMWPE molecules along the drawing direction increases with the draw ratio. The increased orientation of UHMWPE improves the tensile strength and moduli of the drawn films. The draw ratios of gel films prepared from each blend of UHMWPE and SBPE exhibits a maximum value when the samples were prepared at concentrations close to their critical concentration. On the other hand, the maximum draw ratio obtained for gel films prepared near their C-c decreases significantly at higher weight ratios of SBPE to UHMWPE. In contrast, the gel films with less than 2 wt.-% of SBPE in UHMWPE yield a higher maximum draw ratio than the sample prepared from pure UHMWPE gel. Possible mechanisms accounting for this behavior are proposed.