Surface modification of polymer surfaces: atmospheric plasma versus vacuumplasma treatments

An atmospheric pressure non-equilibrium plasma (APNEP) has been developed i n the UK by EA Technology Ltd and is currently being investigated in collab oration with the University of Surrey. The main focus is the use of atmosph eric pressure plasmas to modify the surfaces of commercially important poly mers including polyolefins, poly(ethylene terephthalate) and poly(methyl me thacrylate). These surface modifications include surface cleaning and degre asing, oxidation, reduction, grafting, cross-linking (carbonization), etchi ng and deposition. When trying to achieve targeted surface engineering, it is vital to gain an understanding of the mechanisms that cause these effect s, for example, surface functionalization, adhesion promotion or multi-laye r deposition. Hence comparisons between vacuum plasma treated surfaces have also been sought with a view to using the extensive vacuum plasma literatu re to gain further insight. In this paper, we will introduce the APNEP and compare the key characteristics of the plasma with those of traditional vac uum plasma systems before highlighting some of the surface modifications th at can be achieved by using atmospheric plasma. Data from the analysis of t reated polymers (by spectroscopy, microscopy and surface energy studies) an d from direct measurements of the plasma and afterglow will be presented. F inally, our current understanding of the processes involved will be given, particularly those that are important in downstream surface treatments whic h take place remote from the plasma source.