Effect of Polymer Viscosities on the Fiber Structure and Membrane Properties of Polypropylene/Polyethylene Bicomponent Hollow Fibers.

Polypropylene (PP) / Polyethylene (PE) bicomponent microporous hollow fiber membranes were prepared through the bicomponent melt spinning and drawing processes. Fibers of hollow shape were firstly prepared through the melt spinning process by introducing the air into the core part of the fiber cross-section. Annealing and drawing processes were applied to thus prepared fibers to furnish the membrane properties to the fibers. In this study, high and low molecular weight PP, HMwPP and LMwPP, were used. Viscosity of HMwPP was higher than that of PE, while viscosity of LMwPP was lower than that of PE. In the case of LMwPP/PE fibers, birefringence of PE component increased with take-up velocity and birefringence of LMwPP component was lower than that of PE component at all attainable take-up velocities. In HMwPP/PE fibers, birefringence of both components increased with take-up velocity at low take-up velocities. Birefringence of HMwPP component increased continuously with further increase of take-up velocity, however that of PE component decreased significantly at the take-up velocity higher than 1 km/min. In this region, birefringence of HMwPP component in HMwPP/PE bicomponent hollow fibers was much higher than that of LMwPP component in LMwPP/PE hollow fibers. Hollow fiber membrane which was prepared by annealing and drawing of HMwPP/PE hollow fibers showed 10 times higher air transmission rate than that of LMwPP/PE fibers. In addition, air transmission rate increased with an increase in the HMwPP composition. These results indicate that the structure of PP component in the as-spun fiber undertake a crucial role on membrane properties in PP/PE bicomponent hollow fiber membrane. [ABSTRACT FROM AUTHOR]