Surface Wettability and Surface Structure of Remote O_2 Plasma Treated Poly(Tetrafluoroethylene)

The surface wettability and surface structure of poly(tetrafluoroethylene)(PTFE) treated with remote O2 plasma were studied.The contact angles of the samples were measured and the critical surface tensions γC were determined on the basis of the Zisman's plots.The values of the surface free energy γS,and its dispersion force γdS,dipole force γpS,and hydrogen bonding force γhS were evaluated by the extended Fowkes equation.In addition,the analysis was performed on the relation of the distribution of reactive species in remote O2 plasma and the surface free energy.The results show that the surface wettability of remote O2 plasma treated PTFE is determined only by the polar force(γpS+γhS),especially by theγhS.A mixed atmosphere constituted by all reactive species or super pure and high free radicals concentration in remote O2plasma facilitates the increase of polar force(γpS+γhS),but the surface free energy is mainly influenced by the concentration of charged particles.X-ray photoelectron spectroscopy(XPS) indicates that the C—F bonds on the PTFE surface are broken by the O2 plasma treatment,and then the C—O and C=O are yielded effectively,leading to a higher surface wettability.