Emission Spectroscopy of Pulsed Powered Microplasma for Surface Treatment of PEN Film

Microplasma can be found in many applications. The technology is used also for surface treatment of polymers. The process of surface treatment by microplasma is environmental friendly and could be realized at low cost due to the relatively low discharge voltage (around 1 kV) even under atmospheric pressure and small size of power supply and reactor. This paper presents the surface treatment by microplasma of PEN (polyethylene naphthalate) film using Ar gas and mixtures of Ar with N₂ and O₂. Microplasma process was analyzed by emission spectroscopy method. An experimental Marx generator with MOSFET switches was used as a pulsed high voltage power supply. The emission spectra were measured by an ICCD camera, a spectrometer, and a photomultiplier tube. Surface wettability of PEN film was confirmed measuring contact angle before and after the microplasma surface treatment. It was observed that contact angle of PEN film was decreased especially with O₂/Ar mixture. Analysis by X-ray photoelectron spectrometer (XPS) showed the decrease of C1s, which correspond to C-H bond. Emission spectrum of microplasma discharge in Ar/N₂ mixture showed Ar peaks, OH peaks, N₂ second positive band system peaks (N₂ SPS) and N₂ first positive band system peaks (N₂ FPS) and a decrease in peaks intensities of ArI and OH for microplasma discharge in O₂/Ar mixture. Lifetime emission signals for N₂ SPS for the microplasma discharge in 0.25% N₂ in Ar was around 1 μs. The calculation of microplasma rotational and electron temperatures show low rotational and high electron temperature.