Etching Processes of Polytetrafluoroethylene Surfaces Exposed to He and He–O₂ Atmospheric Post-discharges

Abstract

A comparative study of polytetrafluoroethylene (PTFE) surfaces treated by the post-discharge of He and He-O2 plasmas at atmospheric pressure is presented. The characterization of treated PTFE surfaces and the species involved in the surface modification are related. In pure He plasmas, no significant change of the surface has been observed by X-ray photoelectron spectroscopy (XPS), dynamic water contact angles (dWCA) and atomic force microscopy (AFM), in spite of important mass losses recorded. According to these observations, a layer-by-layer physical etching without any preferential orientation is proposed, where the highly energetic helium metastables are the main species responsible for the scission of −(CF2)n− chains. In He−O2 plasmas, as the density of helium metastables decreases as a function of the oxygen flow rate, the treatment leads to fewer species ejected from the PTFE surfaces (in agreement with mass loss measurements and the detection of fluorinated species onto aluminum foil). However, the dWCA and AFM measurements show an increase in the hydrophobicity and the roughness of the surface. The observed alveolar structures are assumed to be caused by an anisotropic etching where the oxygen atoms etch mainly the amorphous phase.

Competitive and synergistic effects between excimer VUV radiation and O radicals on the etching mechanisms of polyethylene and fluoropolymer surfaces treated by an atmospheric He–O2post-discharge

“…In figures 6 and 7, we show wide survey spectra and narrow-region spectra for HDPE and PVDF; some of the other peaks have been published previously [10,35]. In table 1, the grey columns show the relative atomic compositions and the white columns the relative distribution in the functions detected on the various polymer surfaces (HDPE, PVF, PVDF, PTFE, FEP and PFA) but also on the aluminum foils placed closed to these surfaces during the plasma treatments.…”

Preparation of a Super Hydrophilic Polytetrafluoroethylene Surface Using a Gaseous Ammonia-Water Low-Temperature Plasma

“…Plasma treatment is widely used for this purpose since it allows surface modification without changing the bulk properties of the material [2]. A number of studies concerning the plasma modification of polymer surfaces have already been published [3][4][5][6][7][8][9][10]. Recently, the surface modification of PTFE by plasma treatment using a mixture of gases has attracted a great deal of attention [4][5][6][7], and argon and ammonia plasmas have been shown to be very efficient at modifying PTFE surfaces [1,9,10].…”

A Spectroscopic Study on Argon-Ammonia Water Gaseous Plasma Super-hydrophilizing Polytetrafluoroethylene

“…So far, we have found that a lowtemperature plasma formed from a mixture of gaseous argon, ammonia and water was very effective at rendering the normally inert polytetrafluoroethylene (PTFE) surface super hydrophilic [1]. The surface modification of PTFE by plasma treatment using a mixture of gases has attracted a great deal of attention [3][4][5][6]. Adding water vapor to an argon/ammonia plasma was observed to dramatically decrease the water contact angle (WCA) on PTFE and to eventually generate super hydrophilic surfaces on PTFE films with WCA less than 4° [1].…”