Comparison of dielectric barrier discharge and atmospheric pressure glow discharge for surface modification of PET film

Non-equilibrium plasmas under atmospheric pressure are of great interest in polymer surface processing because of their convenience, effectiveness and low cost. In the present work polyethylene terephthalate (PET) film surface is modified using the non-equilibrium plasma generated by the atmospheric pressure glow discharge (APGD) and dielectric barrier discharge (DBD) in ambient air. The differences in discharge characteristics between APGD and DBD are shown by measurement of their electrical discharge parameters and observation of light-emission phenomena. The effects of APGD and DBD on PET surface modification are studied by comparing their surface properties, which are characterized by contact angle measurement, X-ray photoelectron spectroscopy (XPS) and scanning electronic microscopy (SEM). It is found that the APGD is quite homogeneous and stable in the whole gas gap, which differs from the filamentary micro-discharge of the DBD. It is concluded that the APGD and DBD treatments modify the PET surface in both morphology and composition, but APGD is more effective in PET surface modification than DBD as it can modify the surface more uniformly and make the contact angle decline to a lower level.