ON THE RELATION BETWEEN COMPACTION AND MECHANICAL-PROPERTIES FOR ULTRAFILTRATION HOLLOW FIBERS

Only a few authors have measured the mechanical properties of hollow fibers in order to define the maximum.operating pressure at which no compaction occurs. Since the spinning conditions of hollow fibers introduce an anisotropy between radial and longitudinal properties, knowledge of the fiber-axis properties alone is not sufficient to define yield stress and maximum operating pressure. In this study, the fiber is considered to be a thick walled porous tube, and the Von Mises criterion is used to obtain an elastic mechanical pressure from a transverse compression test. A permeability test was used to evaluate the hydraulic limiting pressure beyond which flux decline becomes irreversible and compaction occurs. A good correlation was found between the calculated mechanical pressures and the experimental hydraulic limiting pressures.