Different Radial Modification Profiles Observed on APPJ-Treated Polypropylene Surfaces according to the Distance between Plasma Outlet and Target

Abstract

The plasma jet transfer technique relies on a conductive wire at floating potential, which, upon entering in contact with a primary discharge, is capable of igniting a small plasma plume at the distal end of a long flexible plastic tube. In this work, two different long tube configurations were employed for the surface modification of polypropylene (PP) samples using argon as the working gas. One of the jet configurations has a thin copper (Cu) wire, which was installed inside the long tube. In the other configuration, the floating electrode is a metallic mesh placed between two plastic tubes in a coaxial arrangement. In the first case, the tip of the Cu wire is in direct contact with the working gas at the plasma outlet, whereas, in the second, the inner plastic tube provides an additional dielectric barrier that prevents the conductor from being in contact with the gas. Water contact angle (WCA) measurements on treated PP samples revealed that different surface modification radial profiles are formed when the distance (d) between the plasma outlet and target is changed. Moreover, it was found that the highest WCA reduction does not always occur at the point where the plasma impinges the surface of the material, especially when the d value is small. Through X-ray photoelectron spectroscopy (XPS) analysis, it was confirmed that the WCA values are directly linked to the oxygen-functional groups formed on the PP surfaces after the plasma treatment. An analysis of the WCA measurements along the surface, as well as their temporal evolution, together with the XPS data, suggest that, when the treatment is performed at small d values, the plasma jet removes some functional groups at the point where the plasma hits the surface, thus leading to peculiar WCA profiles.

Adhesion Properties and Stability of Non-Polar Polymers Treated by Air Atmospheric-Pressure Plasma

“…These factors include treatment parameters, polymer class, chemical structure, presence of functional groups, degree of oxidation in terms of intrinsically structurally bonded oxygen, crystallinity, and surface polarity. Among the many classes of polymers, those that lack functional groups and exhibit a high hydrophobic character, such as polyolefins, can provide a consistent representation of the surface treatment outcomes in a given experimental configuration and of the extent of surface recovery [19][20][21][22][23][24][25][26][27].…”

Plasma electrode dielectric barrier discharge: development, characterization and preliminary assessment for large surface decontamination

“…Yet, the substrate area altered by a single plasma jet is typically limited to a few cm 2 [9,10]. Moreover, within the plasma-treated surface the degree of material modi cation/decontamination is not uniform, being more intense at the center (where the plasma jet hits the target) and less pronounced at the edges [11]. As shown in [12] by using proper shielding gas the plasma-modi ed area can be further extended by ~ 20%, but this gain is at the expense of introducing new components and increasing the system complexity.…”

Plasma Electrode Dielectric Barrier Discharge: Development, Characterization and Preliminary Assessment for Large Surface Decontamination

“…Yet, the substrate area altered by a single plasma jet is typically limited to a few cm 2 [9,10]. Moreover, within the plasma-treated surface the degree of material modification/decontamination is not uniform, being more intense at the center (where the plasma jet hits the target) and less pronounced at the edges [11]. As shown in [12] by using proper shielding gas the plasma-modified area can be further extended by ~20% , but this gain is at the expense of introducing new components and increasing the system complexity.…”