ISSN:
0142-2421
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Physics
Notes:
This paper describes the effects that a low-power plasma (〈1 W) has on the chemistry, topography and surface energy of polyethylene (PE) film. The gases used for treating the film were air and nitrogen. The plasma cell was attached directly to the preparation chamber of an x-ray photoelectron spectrometer, enabling the immediate effects of the plasma on the chemical nature of the films to be monitored. Significant amounts of chemical functionality were introduced onto the surface using both plasmas even after a few seconds of treatment. Carbon/oxygen functionality dominates surfaces treated with an air plasma. Nitrogen plasma treatment, as expected, introduced amines, imines and amides. Exposing the treated surfaces to air results in oxygen adsorption, the amount of oxygen pick-up being time dependent. This ageing of the treated polymer films is thought to occur via two processes: short-term hydrolysis of the amines and gradual oxidation of the polymer chain itself.The topographical changes were studied using atomic force microscopy, which was performed after the films had been exposed to air. Both plasmas caused the polymer surface to roughen, with nitrogen plasma treatment having a more pronounced effect. The surface energy of the film was increased from 37 dyn cm-1 (untreated) to 47 and 46 dyn cm-1 after 20 s of exposure to air and nitrogen plasmas, respectively. After 1 min of treatment, the polar surface energy component of the film treated with a nitrogen plasma (12 dyn cm-1) was much higher than that treated with an air plasma (7 dyn cm-1). This is supported by the XPS results in that the concentration of chemical groups introduced onto the surface after nitrogen plasma treatment was greater than that for air.The greater changes in polymer surface properties observed for nitrogen plasma treatment were not reflected in the values obtained for the level of polymer/metal adhesion. Only air plasma-treated samples showed significant improvement in the adhesion between polyethylene and aluminium and we conclude that the presence of oxygen-containing functional groups plays a major role in this improvement.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/sia.740230508
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