Effect of MW Radiation on Thin-Film Polymer Membranes

Abstract

To improve physical-chemical properties of thin-film membranes from nylon and nylon membranes with a surface layer of polystyrene (PS), nylon-PS, the processing of the latter was carried out with microwave radiation (microwave) at a frequency of 2450 MHz and a power of 300 W in air. As a result of exposure to microwave radiation, changes were found in the mass of the membranes depending on the processing time for nylon membranes, up to 0.34% and, for nylon-PS membranes, up to 0.67%. The results of scanning electron microscopy showed the formation of melted and compacted areas on the membrane surface. An increase in the hydrophilicity and specific performance of membranes as a result of treatment with microwave radiation has been established. A decrease in the roughness of the surface layer of membranes and changes in the structure of the nylon-PS membrane were revealed according to the results of scanning electron microscopy. Changes in the supramolecular structure of the nylon-PS membrane were confirmed by the results of Fourier-transform infrared spectroscopy: a shift of the base of the absorption band to characteristic vibrations of the C–H bond of the phenyl group of polystyrene has been detected. The phenyl groups in the polymer macro-molecule interfere with crystallization of polystyrene and a displacement of the peak base indicates structural changes in the macromolecule, which leads to an increase in the degree of crystallinity of PS. Under the influence of microwave radiation in PS, the orientation of the phenyl group changes: it is located, alternating, on opposite sides of the main chain, which contributes to an increase in the number of crystallization centers, streamlining the structure. An increase in the intensity of the absorption bands of the IR spectra after the treatment of the nylon membrane with microwave radiation is associated with the destruction of the defective regions of the surface layer of the membrane.