Hydrophobic functionalization of cellulosic substrate by tetrafluoroethane dielectric barrier discharge plasma at atmospheric pressure.

Hydrophobic functionalization of cellulosic fabric (viscose) was carried out using helium/tetrafluoroethane (He/ TFE) plasma, a commercially available fluorocarbon gas, at the atmospheric pressure. By selecting suitable plasma parameters, He/TFE plasma was produced and maintained in glow state so that the various fragments of TFE in plasma zone could react covalently with the cellulose. After the plasma treatment, the highly hydrophilic cellulosic fabric turned into superhydrophobic fabric with a water absorbency time of >> 60 min, a water contact angle of 153 degrees and a water rolling angle of 5 degrees. The functionalization was found to be wash durable to 25 laundry cycles. From the analyses of species present in plasma zone by optical emission spectroscopy (OES), gas chromatography-mass spectrometry (GC-MS), and the chemical nature of the functionalized substrate by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS), a possible mechanism involved in the reaction of TFE fragments with cellulose macromolecule was arrived at. Further, it could be inferred that the modification took place only at the surface of the fibres at the nanometre level. The study postulates that it is possible to elucidate reactions undergoing in plasma zone and to control them to achieve desirable modification of substrates.