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

Poly(ethylene terephthalate) (PET) and cotton fibres, treated in an apposit ely 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 sa mples was also investigated under different post-treatment conditions. Plas ma treatment led to efficient implantation of fluorine atoms on the surface of both polymers; this resulted in water repellence without altering the b ulk properties of the polymers. The radical species formed in the plasma-ac tivated polymer surface were involved in its fluorination and in the subseq uent uptake of atmospheric oxygen. Surface reorganisation of polymer segmen ts, tending to reduce the interfacial energy between the polymer and the ph ase in contact with it, induced the surface modifications observed under ag eing and in samples plasma-treated several times. An increase in the depth of the fluorinated layer, leading to outstanding stable hydrorepellence, wa s achieved by repeated SF6 plasma treatments, followed by surface rearrange ments favoured by swelling.