Simultaneous Treatment of Both Sides of the Polymer with a Conical-Shaped Atmospheric Pressure Plasma Jet

Abstract

A conical-shaped atmospheric pressure plasma jet (CS-APPJ) was developed to overcome a standard limitation of APPJs, which is their small treatment area. The CS-APPJs increase the treatment area but use the same gas flow. In the present work, polypropylene samples were treated by CS-APPJ and characterized by scanning electron microscope (SEM), the contact angle, Fourier-transformed infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It was observed that the treatment co-occurs on the face directly in contact with the plasma and on the opposite face (OF) of the samples, i.e., no contact. However, the treatment changed the chemical composition on each side; the OF is rougher than the direct contact face (DCF), probably due to the oxygen groups in excess at the DCF and nitrogen in quantity at the OF. Although simultaneous treatment of both sides of the sample occurs for most atmospheric plasma treatments, this phenomenon is not explored in the literature.

Study of a Conical Plasma Jet with a Cloth-Covered Nozzle for Polymer Treatment

“…A series of WCA measurements were performed with a 5 mm spacing between the consecutive drops to obtain the treatment profile along the target’s long side, as shown in Figure 1 c. The top and bottom faces of each sample were measured. As noted in previous work [ 27 ], when applying a plasma jet to a thin dielectric sample, a secondary DBD-type discharge is generated between the sample bottom and the sample holder. Figure 7 depicts the water contact angle distributions for different gap values, while keeping an argon flow of 4.0 SLM.…”

“…As can be seen in Figure 7 , the plasma modification effect happened within the entire funnel geometrical area, as well as in its close vicinity. Also, as in [ 27 ], both sides of the samples were treated. Except for the big gap of 8 mm, which is discussed separately, within the funnel region, the bottom and top sides of the samples exhibit similarly wide plateau-like WCA distributions.…”

“…Therefore, the cloth cover allows for device operation with bigger gaps between the exit nozzle and the target. For instance, in previous works [ 26 , 27 ], where a similar device was operated without the cloth cover, plasma could not be excited at gaps bigger than 3 mm.…”

“…In previous work, we proposed a simple plasma jet system terminating with a conical horn exit, which can perform uniform surface modification over the entire area covered by the horn [ 26 ], without any target/jet manipulation. The device also has low power and moderate gas consumption (several L/min) and provides surface modification on both sides of planar polymer samples [ 27 ]. Moreover, 3D objects (like seeds or small samples) can be placed inside the funnel and treated on all sides simultaneously [ 26 , 27 ].…”

“…The device also has low power and moderate gas consumption (several L/min) and provides surface modification on both sides of planar polymer samples [ 27 ]. Moreover, 3D objects (like seeds or small samples) can be placed inside the funnel and treated on all sides simultaneously [ 26 , 27 ]. The beneficial properties of this jet device can be explained by the effective trapping of the reactive species inside the conical horn that can be achieved at very short (few mm) sample-to-horn exit distances and moderate gas flow rates [ 28 ].…”