Improving Water‐Based Ink Adhesion on Commercial Polymers by Corona Treatment

ABSTRACT Polyolefins are widely employed as external skins for flexible packaging, yet their nonpolar, hydrophobic surfaces present challenges for high‐resolution, wear‐resistant printing. Converters have traditionally relied on surface treatments, such as corona treatment, to increase surface free energy (SFE) and promote compatibility with solvent‐based inks. While water‐based inks offer sustainability advantages and reduced volatile organic compound exposure over solvent‐based inks, their adhesion to polymer substrates is inconsistent and generally not robust. Industry guidelines suggest SFE differentials between ink and substrate are the only factor influencing adhesion; however, this factor may not completely describe the ink‐substrate interactions. The adhesion performance of water‐based inks was evaluated on polyethylene, ethylene acrylic acid copolymer, ethylene vinyl alcohol copolymer, and polyamide. Polymer films were examined pre‐ and post‐corona treatment to assess changes in surface energy, chemistry, and topography on ink printability and durability. To achieve acceptable print durability, these polymers all required corona treatment, leading to chemical and morphological modifications to the film surface. Results demonstrated that surface chemistry and topography are stronger indicators of water‐based ink adhesion than SFE alone. These findings establish a framework for optimizing the durability of water‐based inks on polyolefins and related substrates through targeted surface treatment strategies.