(715a) Effect of Shear and Elongation On Polymer Morphology in Hollow Fiber Spinning

Polymeric hollow-fiber membranes provide immense energy savings over traditional separation methods, but little is understood about how the morphology and functionality of such membranes formed from precursor polymer solutions (membrane dopes) are affected by the complex flow processes encountered during wet-spinning. In this study, we report results showing that the microstructure of a membrane dope and the morphology of the fibers depend on the flow conditions (elongation and shear) and shear history prior to phase separation in a non-solvent bath.

The experimental methods used for this work include small-angle light scattering under shear (RheoSALS), videomicroscopy of phase separation during fiber formation from carefully designed microfluidic channels, and various characterizations of the spun fibers (e.g. electron microscopy and polarized attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR)).

The data presented in this talk shows a clear correlation between shear and elongation immediately prior to phase separation and fiber morphology. The work presented can be used to provide new guidelines for evaluation of membrane dopes and spinning conditions in a simple laboratory set-up before engaging in pilot-scale spinning experiments that are much more labor intensive and require significantly more material than the microfluidic experiments.