Improvement of surface hydrophobicity on silicone rubber modified by CF₄ radio frequency capacitively coupled plasma

Abstract

In order to improve the surface hydrophobicity, silicone rubber (SIR) samples were exposed to CF₄ radio frequency (RF) capacitively coupled plasma (CCP). Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrum and X-ray photoelectron spectroscopy (XPS) were used to observe the variation of the functional groups of the modified SIR. Static contact angle (SCA) was employed to estimate the change of hydrophobicity of the modified SIR. The surface energy of SIR is reduced largely from 27.37 mJ/m² of original SIR sample to 2.94 mJ/m² of SIR sample treated by CF₄ CCP modification at RF power of 200 W for a treatment time of 5 min. According to the XPS, ATR-FTIR and surface energy analysis, it is suggested that the improvement of hydrophobicity on the modified SIR surface is mainly ascribed to the decrease of surface energy, which is caused by the cooperation of the fluosilicic structure of Si-F or Si-F₂ and the fluoric groups of C-CF_n induced by the methyl replacement reaction and residual methyl groups of SIR surface.

Keywords

surface hydrophobicity / silicone rubber / radio frequency capacitively coupled plasma / static contact angle

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