Investigation of Surface Free Energy for PTFE Polymer by Bipolar Argon Plasma Treatment

The low ion energy argon plasma was used for surface modification of Poly tetra fluoroethylene (PTFE) polymer. The plasma was generated between two plane metal electrode by using 50 kHz bipolar power supply. The plasma treated surface was characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The sur-face free energy (SFE) of plasma treated surface was calculated from contact angle measurement. SFE increases from 33.39 mJ/m2 to 41.40 mJ/m2 with the increase in plasma treatment time and the corresponding contact angle changed from 76 ˚ to 60˚. XPS study shows that F/C ratio change from 1.8 (untreated) to 1.3 (treated) and O/C ratio changes from 0.094 (untreated) to 0.148 (treated). The XPS analysis shows that both F1s and the C1s spectra for PTFE are marginally modified by plasma treatment. AFM study shows that the average surface roughness (Ra) increased from 8.5 nm to 22.8 nm after plasma treatment. Vicker’s micro hardness of the film increases upon plasma treatment. The increase in SFE after plasma treatment is attributed to the functionalization of the polymer surface with hydrophilic groups as supported from the above observations