Surface modification of biaxially oriented polypropylene (BOPP) film using acrylic acid-corona treatment: Part I. Properties and characterization of treated films

In this work, the acrylic acid (AAc)-corona discharge was carried out on biaxially oriented polypropylene (BOPP) films by introducing AAc vapor into the corona region of a normal corona treater. Three different corona energies of 15.3, 38.2 and 76.4 kJ/m2 were studied. Surface properties of treated films were compared with those of air-corona treated films prepared with the same corona energies. The change in chemical composition on the film surface was characterized by curve-fitting of the ATR-FTIR spectra. The wettability of treated films, before and after aging in different environments, was observed by water contact angle and surface free energy. The surface morphology of air- and AAc-corona treated films was investigated using SEM and AFM techniques. Adhesion of the treated films to some other substrate was determined with the T-peeling test. It was found that the hydrophilicity of all treated films increased with increasing corona energy. AAc-corona treated films showed greater wettability than did the air-corona treated films and could retain the surface hydrophilicity for more than 90 days of aging under ambient conditions. The surface morphology of BOPP films changed after corona treatment into a globular structure. The AAc-corona treated films showed rougher surfaces due to surface oxidation and polymer formation, whereas, air-corona treated films displayed a similar structure but of smaller size due to the formation of low molecular weight oxidized materials (LMWOM) arising from the degradation of BOPP films. AAc-corona treated films showed greater peel strength than did the air-corona treated films.