Plasma-modified interfaces between polypropylene films and vacuum roll-to-roll coated thin barrier layers

The interface between polypropylene (PP) films and vacuum roll-to-roll coatings was modified using various plasma pretreatments. Smoothing of the polymer surface by plasma treatment before vacuum coating decreased the O2 permeability of the material. O2 plasmas improved the unpolar PP surface by producing oxygen groups which formed chemical bonds to vacuum coated Al and improved the adhesion of Al barrier films. The electrons, ions, and UV radiation also present in the O2 plasma weakened the cohesive strength of the polymer by inner chain scissions. These results suggest that the atomic oxygen of the plasma should dominate the pretreatment processes.