Variations in surface and electrical properties of polytetrafluoroethylene film after plasma-induced grafting of acrylic acid

摘要

Polytetrafluoroethylene(PTFE) film was graftpolymerized with acrylic acid(AAc) via a low-temperature plasma technique.The effect of plasma treatment parameters(radio-frequency power and treatment time) on the spin number of free radicals in PTFE film was examined.Attenuated total reflection Fourier transform infrared(ATR-FTIR)spectroscopy,X-ray photoelectron spectroscopy,scanning electron microscopy,and atomic force microscopy were employed to characterize the chemical structure,surface composition,and microstructure of the original PTFE and PTFE-g-PAAc films,respectively,in order to verify the successful graft polymerization of AAc onto a PTFE film surface.Thermogravimetric analysis illustrated that the thermal stability of bulk PTFE film remains unchanged after graft modification.Water contact angle measurements confirmed that the hydrophilicity of PTFE-g-PAAc film was effectively improved as compared to the original PTFE film.The dielectric constant(ε_r) of PTFE-g-PAAc(GD =218 μg/cm^2) film remained invariable,compared to that of the unmodified PTFE film.Nevertheless,the dielectric loss(tanδ) of PTFE film increased considerably,from 0.0002(GD = 0μg/cm^2) to 0.0073(GD = 218 μg/cm^2),which might be due to the increase in surface polarity and moisture resulting from AAc graft modification.In addition,the surface electrical resistance(R_s) of PTFE film decreased slightly,from 131.89(GD = 0 μg/cm^2) to 110.28 Ω cm^2(GD = 218μg/cm^2) after surface modification,but still retained its inherent high impedance.