Argon and nitrogen plasma modified polypropylene: Surface characterization along with the optical emission results

This study focuses on the surface modifications of polypropylene using a capacitively coupled radio frequency gas discharge system. Improvements on the polymer surface properties are investigated for the case of argon and nitrogen plasmas at different radio frequency input power values. Higher number of reactions and their repetitions are expected by the charged particles at higher input power setting. On the other hand, the optical emission intensity does not change linearly with increasing RF input power. In addition to the optical emission spectroscopy, all chemical changes and formation of new functional groups are investigated using a Fourier transform infrared-attenuated total reflection spectrometer. Different reactions are observed for argon and nitrogen plasmas due to their ionization energies and their response to the polymer material. Changes in the surface morphologies are measured using a scanning electron microscope. Formed structures with different sizes and shapes are observed on the surfaces. Furthermore, it is observed that the originally hydrophobic type polypropylene surface is changed to a hydrophilic type after the plasma modification. Wettability of the surface is characterized by measuring the water contact angle. These changes due to the plasma exposure are discussed in detail for various discharge parameters