Spinning process variables and polymer solution effects in the die-swell phenomenon during hollow fiber membranes formation

During hollow fiber spinning many variables are involved whose effects are still not completely clear. However, its understanding is of great interest because the control of these variables may originate membranes with the de sired morphologies and physical properties. In this work, the phase inversi on process induced by the immersion precipitation technique was applied to prepare hollow fibers membranes. It was verified that some of the variables involved, can promote a visco-elastic polymer solution expansion, called d ie-swell phenomenon, which is undesired since it may lead to low reproducib ility of the permeation properties. The effects of the distance between spi nneret and precipitation bath, the bore liquid composition, and the polymer solution composition were analyzed and discussed in order to avoid this ph enomenon. According to the results, it was verified that the parameters inv estigated might promote a delay precipitation, which restrained the visco-e lastic expansion.