Empirical Investigation of the Wettability and Printability of Plasma-Treated Polymer Film Substrates for Flexible Packaging Applications in Lagos

Surface modification of polymer films by plasma treatment is widely used to enhance substrate wettability and printability, critical for achieving durable ink adhesion and print quality in flexible packaging applications. This study empirically investigates the effect of low-pressure oxygen plasma treatment conditions on the wettability and printability of polyethylene and oriented polypropylene films used in flexible packaging production in Lagos State, South West Nigeria. Treatment parameters of plasma power at 50, 100, and 150 W, treatment duration at 15, 30, and 60 seconds, and oxygen flow rate at 10, 20, and 30 sccm were varied in a Box-Behnken experimental design. Surface energy and its polar and dispersive components were calculated from contact angle measurements with multiple test liquids. Printability was assessed by ink adhesion test using cross-cut tape method, ink spread measurement, and print density homogeneity after flexographic printing with solvent-based inks. Ageing of surface activation at ambient conditions was monitored over 14 days. Results demonstrate that surface energy increased from 31 to 52 mJ/m2 for polyethylene and from 35 to 58 mJ/m2 for oriented polypropylene under optimal plasma conditions. Ink adhesion improved from grade 3B to 5B following plasma treatment, achieving maximum tape adhesion classification. Polar component of surface energy was the primary driver of ink adhesion performance rather than total surface energy. Surface activation decayed by 35 percent over 14 days of ambient storage, indicating the need for controlled treatment-to-print intervals. Optimal plasma conditions were 100 W power, 30 seconds duration, and 20 sccm oxygen flow. The study provides validated surface treatment specifications for flexible packaging print operations in South West Nigeria. Keywords: plasma treatment, polymer film, wettability, printability, flexible packaging