Moisture Barrier Properties of Silicone Rubber Surface Layers Fluorinated at Different Temperatures

In this study, direct fluorination is used to modify the surface of silicone rubber. Moisture barrier properties of the SIR surface layers fluorinated at different temperatures are evaluated by moisture absorption experiments at a temperature of 30 or 60°C and at a relative humidity of 75 or 97%. Physicochemical characteristics of the fluorinated SIR surface layers are investigated on the basis of ATR-IR, XPS and SEM techniques. The moisture absorption measurements show that the fluorinated surface layer has a distinct moisture barrier to the entry of water into the interior of SIR at each humidity and temperature condition, and a close association of the barrier properties with fluorination temperature or physicochemical characteristics of the fluorinated layer. The barrier is particularly significant for such a surface layer fluorinated at a lower temperature, which has higher fluorine content and compactness although a small thickness, compared to the surface layer fluorinated at higher temperatures. In addition, fitting analysis of the experimental data further shows a lower apparent diffusivity of the surface fluorinated samples than the unfluorinated sample.