Atmospheric Plasma Processing of Polymers in Helium-Water Vapor Dielectric Barrier Discharges

• Published in: Plasma processes and polymers Vol. 8; no. 7; pp. 631 - 639
• Main Authors: Rodriguez-Santiago, Victor, Bujanda, Andres A., Stein, Benjamin E., Pappas, Daphne D.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 22.07.2011; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: adhesion; Applied sciences; Atmospherics; Coating, metallization, dyeing; Contact angle; dielectric barrier discharge; Exact sciences and technology; Hydrophilicity; Machinery and processing; Plastics; Polyethylene terephthalates; Polyethylenes; Polymer industry, paints, wood; polymers; Polytetrafluoroethylenes; Surface energy; surface functionalization; Technology of polymers; water vapor plasma; X-ray photoelectron spectroscopy; Ethylene terephthalate polymer; Ultra high molecular weight ethylene polymer; Adhesivity; Molecular structure; Tetrafluoroethylene polymer; Plasma assisted processing; Processing time; Long term variation; adhesion; Experimental study; Property processing relationship; Surface treatment; Wettability; Polyurethane; surface functionalization; Surface properties; Structure modification; dielectric barrier discharge; polymers; water vapor plasma; Surface energy
• ISSN: 1612-8850; 1612-8869; 1612-8869
• DOI: 10.1002/ppap.201000186

In this study, the surfaces of ultrahigh molecular weight polyethylene (UHMWPE), poly(ethylene terephthalate) (PET), and polytetrafluoroethylene (PTFE) films were treated with a helium‐water vapor plasma at atmospheric pressure and room temperature. Surface changes related to hydrophilicity, chemical funtionalization, surface energy, and adhesive strength after plasma treatment were investigated using water contact angle (WCA) measurements, X‐ray photoelectron spectroscopy (XPS), and mechanical T‐peel tests. Results indicate increased surface energy accompanied with enhanced hydrophilicity. WCA decreased by 36, 50, and 16% for UHMWPE, PET, and PTFE, respectively, after only 0.4 s treatment. For UHMWPE, it is shown that the surface functionalization can be tailored depending on the plasma exposure time. Aging studies performed for these three polymers show the stability of the surface groups as indicated by a small increase in WCA values of plasma treated samples which can be attributed to cross‐linking of surface and subsurface polymer chains. XPS analysis of the surfaces show increased oxygen content via the formation of polar, hydroxyl‐based functional groups. Furthermore, major changes in the polymer structure of PET are observed, possibly due to the opening of the aromatic rings caused by the plasma energetic species. T‐peel test results show an 8, 7.5, and 400‐fold increase in peel strength for UHMWPE, PET, and PTFE, respectively. Most importantly, it is shown that water‐vapor based plasmas can be a promising, “green,” inexpensive route to promote the surface activation of polymers. The use of water vapor as a reactive gas for dielectric barrier discharges offers great advantages since it does not require vacuum equipment and it is readily available in its purified form. Not only water vapor plasma is proven in this work to be an efficient means of polymer surface modification and tailoring but it also expands the possibilities of its use in the formation of coatings using water‐soluble precursors coupled with activation and functionalization.