Formation of cobalt sulfide layers on polyamide 6 by sorption–diffusion method using solutions of dodecathionic acid, H2S12O6

Abstract

The processes of obtaining layers of cobalt sulfides CoxSy by the sorption–diffusion method on polyamide 6 (PA) using solutions of dodecathionic acid, H2S12O6, as precursors of sulfur are studied. The concentration of sorbed sulfur (from ~50 to ~300 µmol · cm–3) increases with the increase of the duration of treatment (up to 6 h) and temperature (20–40 °C) of precursor solution. Cobalt sulfide layers are formed on the surface of polyamide after the treatment of sulfurized polymer with Co(II) salt solution. The concentration of cobalt in the layer increases with the increase of initial sulfurization duration and a different concentration of cobalt (24–28 µmol · cm–3) in PA at each temperature is reached. XRD spectra of polyamide films treated for different time with solutions of dodecathionic acid and then with Co(II) salt solution confirmed the formation of cobalt sulfide layers on the surface of polyamide: five phases of cobalt sulfides – CoS, Co3S4, Co6S5, Co9S8 and CoS2 were found in the films on the polyamide surface. The morphology of modified films characterised by SEM and AFM showed a spongy structure formed by the network of plate-like crystallites.