Surface modification of PET film via a large area atmospheric pressure plasma: An optical analysis of the plasma and surface characterization of the polymer film

This paper presents a comprehensive study of surface modification of polyethylene terephthalate film substrates to improve its adhesion properties using a large area atmospheric plasma. Different aspects of this study includes (1) analysis of the physical and chemical characteristics of the plasma (2) as well as the substrates, and (3) evaluation of adhesion of an acrylate based hard coating onto PET substrates. PET is chemically inert to most coatings, but atmospheric plasmas can modify the surface in a manner that is compatible with high throughput manufacturing. First, optical emission spectroscopy was employed to analyze the plasma in terms of its chemical composition as well as physical characteristics such as electron temperature and density. This section estimates electron temperature of 0.2-0.4 eV and density in the order of 1014-1015 cm− 3 for the studied plasmas. Second, various plasma gas mixtures with helium as the seed gas mixed with fraction of oxygen and/or nitrogen (0.5-1.1 v%) were used to carry out the surface treatment of the substrates at different exposure doses between 15 and 75 J cm− 2. Post-treatment characterization by XPS, AFM, and a goniometer show that the surface becomes enriched with oxygen, rougher, and more wetting depends on the power and composition of the plasma. Lastly, standard adhesion 180° T-peel tests indicated improved adhesion after treatment.