Effect of BOPET film surface treatments on adhesion performance of biodegradable coatings for packaging applications

This study aims to verify the effectiveness of a biodegradable PLA coating on biaxially oriented poly ethylene terephthalate (BOPET) films substrates in order to develop a biodegradable sealant layer for improving the functional properties of polyester films. In particular, this work focuses on the evaluation of different surface treated BOPET films to understand the effect of typical polyester substrate treatments on the adhesion of the PLA coating. At this purpose the film's surface properties and topography have been characterized respectively by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and by atomic force microscopy (AFM); while their surface tension has been analyzed by contact angle tests. Furthermore, the PLA coating adhesion to different BOPET webs has been assessed by delamination tests and dynamical mechanical analysis. In addition, to evaluate the optical properties haze and transparency measures have been performed. It was found that corona treatment proves to be more effective in increasing surface energy and roughness of substrate with respect to a chemical treatment. The coating adhesion to corona treated BOPET was higher compared to the neat and the chemical treated BOPET films. Improvement in adhesion of PLA on corona treated BOPET was interpreted on the basis of surface oxidation due to the electrical discharge as showed by AFM and ATR-FTIR analyses. Indeed the increase of both contact surface and functional groups able to form hydrogen bonds and other molecular interactions, allow to a better interface interaction between the two layers. (C) 2015 Elsevier Ltd. All rights reserved