Effect of radiation and thermal treatment on structural and transport parameters for cellulose regenerated membranes

Modifications caused by different types of ionizing radiation and thermal treatment on transport, chemical and structural parameters of polymeric (regenerated cellulose) membranes have been studied. Particularly, the effect of different types of radiation (ultraviolet light (UV) and ionising radiation (Ir) with different doses) and heating at 60 8C on transport and electrical parameters for a cellophane membrane has been considered by determining salt permeability and electrical resistance for the different samples. These parameters were obtained from salt diffusion and impedance spectroscopy (IS) measurements with the membranes in contact with NaCl solutions at different concentrations. Chemical surface and structural modifications of the polymer matrix due to the treatments have also been determined by X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (ATR mode). Results obtained from infrared spectroscopy seem to indicate that ionising radiation modifies the proportion of OH links, which is related to the dose of irradiation. XPS analysis only shows small differences in the atomic concentration and shape of the C 1s spectra. On the other hand, an increase of salt permeability for heated and UV-treated membranes was obtained, while this parameter decreases in the case of irradiated membranes. This result could be related to a change in the packing of the polymer chains, which results in an increase of the fractional void volume in the case of heat- and UV-treated membranes and the opposite effect for the irradiated ones; for these latter, a correlation between the irradiation dose and the decrease in permeability values was also obtained. IS results show a decrease in the electrical resistance of all treated samples. This fact can be due to the most open structure of heated and UV-treated samples, previously indicated; however, due to the closer structure assumed for the irradiated sample, this point might be related to the presence of free radicals in agreement with ATR results.