The draw ratio (DR) is an important parameter in the process of spinning hollow fiber membranes, by which their separation and performance characteristics can be controlled over a wide range of values. For the first time, a method for determining the DR using a roller movable in the vertical direction is described, which makes it possible to establish the ratio of the dope extrusion linear flow rate to the take-up speed. In the course of the work, polysulfone hollow-fiber membranes were obtained at various DR values. The influence of the draw ratio on the morphology and geometric and gas transport properties of the resulting polysulfone hollow fiber membranes has been examined.

The spinning solution properties (viscosity, chemical composition) can be varied depending on the method of its preparation. These variations might cause changes in the thermodynamics and kinetics of the phase separation process during the membrane formation. In this work, the influence of various modes of spinning solution preparation on the morphology, geometric and gas transport properties of the resulting polysulfone (PSf) hollow fiber membranes was investigated. The differences in methods of solution preparation were the temperature and time of stirring. It was found that with the transition to the lower-temperature stirring of the spinning solution the outer diameter and wall thickness of the fiber increase, and the thickness of the selective layer decreases. The highest ideal selectivity values are observed with the solution stirring for 5 hours at temperature 120 °С (3.1 for pair He/CO2). The maximum values of the gas permeability are achieved in the mode of the solution stirring for 24 hours at temperature 50 °C (P/l (He) = 201 m3/( m2∙h∙atm); P/l (CO2) = 83 m3/( m2∙h∙atm)).

A new method of electroprometry has been proposed that allows continuous investigation of extended sections of a hollow fiber membrane. Samples of polysulfone hollow fiber membranes with different porous structures were obtained: finger-shaped and spongy. These membranes were examined on a laboratory electroprometric apparatus with continuous scanning along the length of the hollow fiber membrane sample at a high voltage of 15 kV. Defects were detected in these hollow fiber membranes by the proposed method of electroporometry, the nature of which was then investigated using scanning electron microscopy. A correlation was found between the size of the detected defect and the magnitude of the corona discharge current signal: the larger the defect, the greater the absolute value of the current. It is shown that the proposed method can be effectively used as an express method to study the homogeneity of the porous structure of hollow fiber membranes in extended areas with geometrical localization of possible defects.