A comparison of gas-phase methods of modifying polymer surfaces

Abstract

Oxidation is the most common surface modification of polymers. This paper presents a comparison of five gas-phase surface oxidation processes: corona discharge, flame, remote air plasma, ozone, and combined UV/ozone treatments. Well-characterized biaxially oriented films of polypropylene and poly(ethylene terephthalate) were treated by each of the five techniques. The surface-treated films were then analyzed by X-ray photoelectron spectroscopy (XPS or ESCA), contact-angle measurements, and Fourier-transform IR (FTIR) spectroscopy.Corona, flame, and remote-plasma processes rapidly oxidize polymer surfaces, attaining XPS O/C atomic ratios on polypropylene of greater than 0.10 in less than 0.5 s. In contrast, the various UV/ozone treatments require orders of magnitude greater exposure time to reach the same levels of surface oxidation. While corona treatment and flame treatment are well known as efficient means of oxidizing polymer surfaces, the ability of plasma treatments to rapidly oxidize polymers is not as widely appreciated.Of the treatments studied, flame treatment appears to be the 'shallowest'; that is, the oxygen incorporated by the treatment is most concentrated near the outer surface of the film. Corona and plasma treatments appear to penetrate somewhat deeper into the polymers. At the other extreme, the UV/ozone treatments reach farther into the bulk of the polymers.

Surface characterization and ageing of ultraviolet-ozone-treated polymers using atomic force microscopy and x-ray photoelectron spectroscopy

“…>10 nm). Other studies 6 have shown that UVO treatment of polymers penetrates much deeper (up to 1 µm has been suggested) than the more surface-specific plasma and corona oxidative modifications.…”

“…Previous surface modification methods that have been applied to polymers have included chromic acid, 4 corona, 5 flame, 6 * Correspondence to: R. H. Bradley, Materials Surfaces and Interfaces Group, School of Applied Sciences, The Robert Gordon University, St Andrew Street, Aberdeen AB25 1HG, UK.…”

Nanoparticle-coated separators for lithium-ion batteries with advanced electrochemical performance

“…However, the contact angle increases upon aging and reverts to its original value after about one week, due to delocalization of the charged groups and reorganization of the surface. 22,23 The silica nanoparticles with a mean diameter of 18 nm used in this study were functionalized using N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride and, thus, they are densely covered by quaternary ammonium groups. By virtue of their surface charge, the nanoparticles form stable dispersions in water showing no tendency for aggregation in a wide pH range, as confirmed by light scattering.…”

Mapping physicochemical surface modifications of flame-treated polypropylene

“…However, it has been demonstrated that, during flame treatment, the concentration of O is very low relative to the concentration of OH and the other active species, which explains the lack of LMWOM [37]. This, in turn, is the main reason why flame-treated PP is more stable than corona-treated PP as a function of storage time under ambient conditions [19,22,39].…”

“…Nevertheless, the great potential involved in the flame treatment was underexploited until 1980s [16], when remarkable innovations at both the technical (e.g., the introduction of the polarized flame) and the safety level renewed interest in this method. Correspondingly, the acquisition of new powerful techniques such as optical contact angle (OCA) [17], atomic force microscopy (AFM) [18], and X-ray photoelectron spectroscopy (XPS) [19][20][21] prompted a fervid scientific activity, as demonstrated by the number of scientific papers in this area [16,[22][23][24]. At the present time, interest toward flame treatment relies mainly on the innovations expected in many areas for the next years.…”