Characterisation of poly(ethylene terephthalate) and cotton fibres after cold SF6 plasma treatment

Poly(ethylene terephthalate) (PET) and cotton fibres, treated in an appositely set up RF SF6 plasma reactor under different operating conditions, were characterised by XPS, EPR, DSC, XRD, ATR analyses, water contact angle and water droplet roll-off angle measurements. The ageing of plasma-treated samples was also investigated under different post-treatment conditions. Plasma treatment led to efficient implantation of fluorine atoms on the surface of both polymers; this resulted in water repellence without altering the bulk properties of the polymers. The radical species formed in the plasma-activated polymer surface were involved in its fluorination and in the subsequent uptake of atmospheric oxygen. Surface reorganisation of polymer segments, tending to reduce the interfacial energy between the polymer and the phase in contact with it, induced the surface modifications observed under ageing and in samples plasma-treated several times. An increase in the depth of the fluorinated layer, leading to outstanding stable hydrorepellence, was achieved by repeated SF6 plasma treatments, followed by surface rearrangements favoured by swelling.