Comparison of SF6 and CF4 Plasma Treatment for Surface Hydrophobization of PET Polymer

Abstract

The fluorination of the polymer polyethylene terephthalate in plasma created from SF6 or CF4 gas at various pressures was investigated. The surface was analysed by X-ray photoelectron spectroscopy and water contact angle measurements, whereas the plasma was characterized by optical emission spectroscopy. The extent of the polymer surface fluorination was dependent on the pressure. Up to a threshold pressure, the amount of fluorine on the polymer surface and the surface hydrophobicity were similar, which was explained by the full dissociation of the SF6 and CF4 gases, leading to high concentrations of fluorine radicals in the plasma and thus causing the saturation of the polymer surface with fluorine functional groups. Above the threshold pressure, the amount of fluorine on the polymer surface significantly decreased, whereas the oxygen concentration increased, leading to the formation of the hydrophilic surface. This effect, which was more pronounced for the SF6 plasma, was explained by the electronegativity of both gases.

Simple Fabrication of Transparent, Colorless, and Self-Disinfecting Polyethylene Terephthalate Film via Cold Plasma Treatment

“…The F 1s and C 1s peaks were fitted to optimized Gaussian-Lorentz functions using the peak-fitting program, AVANTAGE (Thermo Fisher Scientific, Waltham, MA, USA). For the C 1s spectra, the sub-peak at 291.2 eV was assigned to carbon fluoride (CF 2 ) [29], and for the F 1s spectra, the sub-peaks at 688.1 and 686.5 eV were attributed to absorbed-fluorine atoms (a-F) and CF 2 , respectively [30]. Hence, it is supposed that a-F and CF 2 were newly generated on the outer surface of the PET film during the CF 4 plasma treatment.…”

Surface Modification to Improve Properties of Materials

“…Several fluorine-containing gases dissociate to F atoms under plasma conditions, but the surface finish depends on the type of the precursor. Resnik et al [43] compared plasma treatment of polyethylene terephthalate using two gases and reveal effects that have not been observed before. The treatment of this polymer with plasma sustained both in tetrafluoromethane and sulfur hexafluoride revealed a high concentration of fluorine in the surface layer probed by X-ray photoelectron spectroscopy (XPS) only up to a certain pressure.…”

Plasma Treatment of Poly(ethylene terephthalate) Films and Chitosan Deposition: DC- vs. AC-Discharge

“…Among a number of methods of surface modification, plasma treatment is a well-known and highly effective technique to achieve the required surface properties without application of additional chemical reagents, which is especially desirable for modification of materials being developed for biomedical application [5][6][7][8]. Another significant benefit of plasma treatment relies on the possibility to vary the material's surface characteristics, namely chemical structure, morphology, hydrophilicity and surface charge by changing a number of plasma-processing parameters, i.e., discharge type, duration and nature of working gas [9][10][11][12]. The majority of these processing conditions are easily adapted, but discharge type is mainly determined by equipment and, thus, should be carefully chosen in advance.…”