Surface modification of polymer surfaces: atmosphericplasma versus vacuum plasma treatments

Abstract

An atmospheric pressure non-equilibrium plasma (APNEP) has beendeveloped in the UK by EA Technology Ltd and is currently beinginvestigated in collaboration with the University of Surrey. The mainfocus is the use of atmospheric pressure plasmas to modify the surfaces ofcommercially important polymers including polyolefins, poly(ethyleneterephthalate) and poly(methyl methacrylate). These surface modificationsinclude surface cleaning and degreasing, oxidation, reduction, grafting,cross-linking (carbonization), etching and deposition. When trying toachieve targeted surface engineering, it is vital to gain an understandingof the mechanisms that cause these effects, for example, surfacefunctionalization, adhesion promotion or multi-layer deposition. Hencecomparisons between vacuum plasma treated surfaces have also been soughtwith a view to using the extensive vacuum plasma literature to gainfurther insight. In this paper, we will introduce the APNEP and comparethe key characteristics of the plasma with those of traditional vacuumplasma systems before highlighting some of the surface modifications thatcan be achieved by using atmospheric plasma. Data from the analysis oftreated polymers (by spectroscopy, microscopy and surface energy studies)and from direct measurements of the plasma and afterglow will bepresented. Finally, our current understanding of the processes involvedwill be given, particularly those that are important in downstream surfacetreatments which take place remote from the plasma source.