Eval membranes for blood dialysis

Abstract

Both dry‐ and wet‐process were employed for preparing membrane of ethylene‐vinylalcohol copolymer (EVAL) for blood dialysis. Asymmetric and symmetric, dense or porous membranes were prepared by the dry‐process. The relationship between the structure of membranes and the experimental variables is explained by using a solubility curve model. This model predicts the membrane structure successfully under various conditions, including the change of temperature of the environment, the solvent system and the temperature of polymer solution. For wet‐processes, the casting solutions were coagulated in a precipitation bath (water). Three different structures were obtained: finger type, sponge type and particle‐bonded type. The cloud point experiment and the polymer segment motion help to understand and control the membrane structure. Some properties of the EVAL membrane for blood dialysis are shown. It is comparable with or better than the commercialized one. This study may prove useful in determing the controlling parameters for the preparation of membranes from other polymers.

Equilibrium phase behavior of the membrane forming water-DMSO-EVAL copolymer system

“…Later, Sakurada et al reported that using EVAL membrane in hemodialysis, efficient nonanticoagulant hemodialysis for renal failure patients was achieved [11]. Recently, EVAL copolymer membrane has attracted plenty of research interest in multiple fields of biomedical science [12][13][14][15][16][17][18][19]. In this current research, the isothermal phase behavior of EVAL in mixtures of dimethylsulfoxide (DMSO) and water (nonsolvent) was investigated for the temperature range between 25°C and 85°C.…”

“…Since EVAL copolymet is a crystalline polymer [20,21], it is rather difficult to determine the liquid-liquid demixing phase envelop using cloud point data (the composition at which the turbidity changes) along. In a previous publication [12], cloud points measured by a titration method were given for water-DMSO-EVAL system at room temperature for a wide concentration range. These data differ somewhat from the present experimental results.…”

Preparation of ethylene vinylalcohol copolymer membranes suitable for ligand coupling in affinity separation

“…Young and co-workers [15][16][17][18][19][20][21][22] have performed the most extensive study on the preparation of porous EVAL-membranes. In order to obtain a better understanding of the different membrane formation processes taking place, they investigated the thermodynamic (phase diagrams) and kinetic (onset of demixing) properties for the non-solvent/DMSO/EVAL system.…”

“…The membranes were assumed to form by homogeneous nucleation and growth of the polymer particles over the entire cross-section. If a weak non-solvent with a lower affinity to DMSO, such as 2-propanol or 1-octanol, was used instead of water, delayed conditions and particulate structure could be obtained without DMSO addition in the coagulation bath [5,17,22]. Symmetric particulate membranes obtained by precipitation in a coagulation bath containing a weak non-solvent or a sufficient amount of DSMO, displayed higher pure water fluxes in the range of 90-140 l/(h m 2 bar) [16] but suffer, however, from brittleness.…”