Deposition of a PMMA coating with an atmospheric pressure plasma jet

Atmospheric pressure plasma jet polymerization of methyl methacrylate (MMA) was performed in order to deposit a PMMA-like coating on ultrahigh molecular weight polyethylene (UHMWPE). This study is a first step in the transfer from MMA plasma polymerization experiments previously performed in a dielectric barrier discharge (DBD) reactor to a newly designed atmospheric pressure plasma jet. In this novel plasma setup, the substrate is not directly exposed to the plasma region, but placed in the plasma jet afterglow. The effect of several plasma jet process parameters on the coating properties was investigated using different surface characterization techniques such as XPS, FTIR, AFM, and OPS. Results show that the stationary deposition of PMMA-like thin films results in a radial gradient in surface chemistry, surface morphology, and coating thickness. Additionally, the coating properties were found to significantly depend on the monomer-containing gas flow rate. This observation is also confirmed by CFD modeling, which shows that the monomer-containing gas flow rate strongly influences the gas flow pattern of the plasma afterglow and therefore the final properties of the deposited PMMA-like film.