Practical approach in surface modification of biaxially oriented polypropylene films for gravure printability

• Published in: Applied surface science Vol. 314; pp. 331 - 340
• Main Authors: Nuntapichedkul, Boonchai, Tantayanon, Supawan, Laohhasurayotin, Kritapas
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 30.09.2014; Elsevier
• Subjects: Adhesion; BOPP; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Contact; Contact angle; Copolymers; Corona treatment; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Gravure; Grooves; Ink; Physics; Polypropylenes; Printing; Surface free energy; BOPP; Corona treatment; Surface free energy; Ink; Surface treatments; Free energy; Surface energy
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2014.06.032

•Gravure printability on BOPP film with small groove size has been improved using corona treatment associated with propylene–ethylene copolymer.•Low-molecular-weight oxidized materials on the BOPP film surface were formed mainly as ester and aldehyde from ethylene units.•Printability of magenta and cyan inks on the treated BOPP surface was correlated more with the interfacial tension between inks and substrate than Wa and S.•The reported technique is industrially scalable. Biaxially oriented polypropylene (BOPP) film is one of the most popularly used materials for the gravure printing process in flexible packaging industry. The skin layers of BOPP film were associated with 3–6 weight % of propylene–ethylene copolymer. These films were completely biaxial-oriented by sequential stretching process after which the film surfaces were subjected to corona treatment integrated in the production line. The FT-IR results exhibited that polar functional groups as carbonyl molecules were established on the corona-treated BOPP film. The contact angles of these BOPP films were measured; the surface free energies (SFE) were then calculated. AFM topographical images also agreed well with the SFE which increased as the contents of propylene–ethylene copolymer increased. An approximated 20% increased SFE was obtained for the BOPP film that was associated with 6% propylene–ethylene copolymer. The printing quality on BOPP films was tested by light microscope which confirmed that the chromatic resolution of the printed images improved down to even more smaller groove sizes, 10 or 5 dot%. This improvement was also examined and found to correspond well with the interfacial tensions and work of adhesion between the inks and the modified BOPP films.