Water permeability of poly(ethylene) terephthalate track membranes modified in plasma

The properties of poly(ethylene) terephthalate track membranes (PET TM) subjected to effect of plasma of the RFdischarge in air have been investigated. The influence of conditions of a plasma treatment on the surface properties and hydrodynamic characteristics of the membranes has been studied. It has been found that the effect of the air plasma on the membranes studied results in a formation of asymmetric track membranes with a higher flow rate; the structure and chemical composition of their superficial layer are changed. It was shown that the presence of the modified layer on the membrane surface caused changing in their hydrodynamic characteristics — the water permeability of the membranes, processed in plasma, in a greater degree depends upon pH of a filtered solution.

Summarizing the obtained results, we can make the following conclusions. The effect of the plasma of the RF-discharge in air on poly(ethylene) terephthalate track membranes leads to the formation of asymmetric track membranes with increased productivity, the structure and chemical structure of the surface layer of which are modified. The availability of the modified layer on the membrane surface causes changing a lot of the PET TM properties. Thus, increasing the contents of carboxyl groups in the surface layer of membranes results in an increase of the degree of their hydrophilicity. Development of erosion of the surface of membranes and their hydrophilization stipulate increase of wettability of PET TM, whose value depends upon the intensity of the discharge and the duration of its effect. Increasing the density of the negative charge of the pore surface causes a more significant change of the value of water permeability in time that results in decreasing the growth rate of the filtrate volume. Increase of the conformation mobility of macromolecules of the surface layer leads to changing the hydrodynamic characteristics of membranes — the water permeability of the modified membranes in comparison with the source membrane in a greater degree depends upon the pH of the filtered solution. The conformation mobility of macromolecules of the surface layer of membranes depends on the pH value of the filtered solution — the greatest stability is observed in solutions with low pH values. Acknowledgment The authors are grateful to M.V. Aristarkhova, I.V. Blonskaya and O.L. Orelovich for their help in realization of a number of experiments and preparation of the report.